I have a 95 GTX 657 that lasted 10 years strong on the motor and finally it gave up. Before the rebuild it was beggining to smoke more so I figured it was getting tired but as long as I can remember it always smoked a lot and I am the original owner. The shop i took the ski to told me that the rear piston had come apart. He did a full rebuild (supposedly) and it ran Awesome for about 8 hours of run time in summer of 06. Then it lost power and finally wouldnt start. I pulled the plugs to find no compression in the rear cylinder. The summer was done.... took it to the shop and he pulled the head to find the new piston in the rear damaged, (top pf the piston and ring land broken, top ring all mangled). motor received two new pistons and jugs were sent to L.A. Sleeve for machining. I got the ski back at memorial day in 07 and stuffed it in the water and it ran super ..... for an hour...... summer was done again...... took it back to the shop wanting the problem fixed whatever it may be. They guy died in a rhino accident about two months ago and I picked up the ski from his house from his wife.. the ski had not been back apart it was just collecting dirt... so now I took it apart to find the rear piston scored, fron piston clean with no visible signs of damage wrist pin bearings look great rods have zero up and down play but are within tolerance for side to side play. rear cylinder appeared to be dry and the front appeared to be lubricated. Im guessing that I have an oiling problem to the rear cylinder. The pistons are marked 663 which im guessing is the over bore size. I am going to rebuild the upper end myself but I dont want the same thing happening again! Can someone please shed some light for me? Is there a known oiling problem on this motor and if so what causes it? Also I'm not very familiar with how the oil mixes with tthe fuel if its thrown up with the rotary valve or is there an injector that could be clogged. Maybe I need to rebuild the oil pump? What should I check for? Should I just rebuild it and then premix the fuel? Thanks for any help I can Get....
95 GTX 657 Rear Cylinder keeps going out
- Thread starter KeonaJane
- Start date
- Status
robin savell lloyd
Active Member
read this post it talks about your rear cylinder probelm. scroll down till you see alot of typeing. then start reading you will find some good info on your subject. post title is "does anyone know if this is true or maybe just like to start a debate"
by robin savell lloyd
by robin savell lloyd
robin savell lloyd
Active Member
ABOUT REAR CYLINDER PISTON SEIZURE by the technicians of Group K
Every technician that has any pwc experience has seen it. The engine whose rear piston has scored (seized) for no diagnosable reason (while the other piston(s) look perfect). subsequent teardown inspections out rule airleaks, fuel and coolant blocks, oil, ignition, etc. At Group K we believe that "nothing" happens for no apparent reason. However in the last decade of working on pwc engines, we have seen numerous seized rear pistons that we could not account for. This document makes an effort to account for an awful lot of the ones we've seen.
SOME IMPORTANT EXPERIENCES -- Among Sea Doo race engine builders, richer jetting in the rear cylinder (to avert piston seizure)has been standard fare from the 580 cc days. We remember speaking with some of those technicians about the apparent need for "uneven jetting". They all told us that identical front and rear jetting in their Rotaxes was a near guaranteed rear piston seizure. We argued that none of our 650 Waverunners or Kawasaki SS twins had ever required uneven jetting. We felt certain that they had some other technical problem that they were overlooking. We continued to believe that, until the day we started testing our first Yamaha 701 Raider.
Our Sleeper kit development for the 701 Raider was relatively uneventful. However when we installed the Coffman pipe that drove rpms to 7100 (from the stock 6400), we began to experience a rash of scored rear pistons. We realized that we were probably facing the same gremlin that our Sea Doo pals had been living with for years. We were bound and determined that we would be the guys that would solve the problem. We believed that we would show that uneven jetting would not be needed. We then experimented with milder compression, retarded timing, richer overall jetting, dual cooling with additional flow for the rear cylinder...and plenty more. Three weeks, and a dozen seized rear pistons later, we finally had a strong running format that could run wide open for almost a full minute...before it seized piston number 13. We finally broke down and put one size larger main jet in the rear carb. With this richer jet, the machine still accelerated strong, and reached peak rpm quickly. We ran it full speed for over 15 miles...we couldn't make it seize (or foul a plug). In fact, to our surprise, later tear downs would show not even the slightest visual signs of over richness or fouling. Shortly there after, we repeated this same frustrating scenario with the (then new) Yamaha 1100 triples. Only the rear cylinder desired richer jetting.
Armed with this experience, we revisited our earlier model stand up and runabout dual carb engine kits. Remarkably, none showed the need for uneven jetting. Even more remarkable was that an identically modified 701 Raider motor, mounted in a stand up hull, did not require richer rear cylinder jetting. The stand up, with the Raider motor could run wide open all day long on "parallel" jetting. When that same motor, with it's parallel jetting, was then installed into a Raider hull...immediate rear piston seizure.
As all this went on, we realized we were creating far more questions than answers. For the meantime, we simply accepted our experiences at face value, and used parallel jetting when we could...uneven jetting when we had to.
During the beginning of our development on the 782 Laydown Rave motors, we immediately started to experience rear cylinder scoring (that was staved off by richer rear carb jetting). At that same time, we were lucky enough to be having a conversation about this problem with Ross Liberty of Factory Pipe Products. They were in the process of developing their pipe for the Laydown Rave in their newly completed dyno facility. This dyno, and it's instrumentation, can tell "everything" that's happening while the engine is under load. Ross mentioned that they too were chasing the "richer rear cylinder" gremlin. He said that they had eliminated every imaginable variable, and no matter what they did, the combustion chamber temperatures were never identical under full load. He said they suspected something related to the crankshaft twisting. He suspected that this twisting was affecting the "sameness" of ignition timing. We suspect that he is correct.
CRANKSHAFT TORSIONING "The Gremlin" -- This suggestion, by Factory Pipe, is what we consider to be the true cause of the countless scored pistons we saw during our own tests. To understand it, one must first understand the difference between twisting and torsioning. Crankshaft twisting refers to a crank that has been rotationally jolted so hard that one of the press fit connections rotates out of index...and stays that way. When a crankshaft "twists", there is large and immediate loss in power that comes along with a noticeable vibration. When a crankshaft "torsions", there is a momentary rotational springing action...nothing comes out of index, there is no vibration, there is no noticeable power loss. A welded crank cannot "twist", but it can still "torsion". The total amount of "torsioning" that takes place depends on the length and rigidity of the crankshaft. The longer and less beefy...the worse the torsioning. What we now refer to it as "crankshaft torsioning" (not twisting)... works like this :
The front cylinder on all pwcs is the cylinder closest to the ignition rotor. The amount of torsioning that can take place between the ignition flywheel and the front crank pin is nearly non-existent. However, structurally speaking, the rear crank pin is much "farther away" from the ignition flywheel. When the pump (at speed) suddenly hooks up on some smooth water, the front cylinder and the ignition flywheel have enough rotational momentum to torsion the crankshaft over it's entire length. As this happens, the flywheel and front cylinder can actually get 2 to 3 degrees of rotation ahead of the rear cylinder. As this 2 to 3 degree torsioning rotation takes place, the front cylinder is still getting perfectly timed ignition sparks. However the rear cylinder is lagging slightly behind when it gets it's ignition spark. This means that the rear cylinder is firing 2 to 3 degrees more advanced than the front cylinder. Furthermore, this advanced timing is happening at the worst imaginable time...at high loads and high rpms. As any engine builder can tell you, running 3 degrees too much high rpm advance on a race engine is a guaranteed way to seize (or hole) a piston.
While we don't have any iron clad proof that these presumed effects of crankshaft torsioning are an absolute fact, we feel that have enough hands on experiences and supporting information to consider it "a very probable truth". Until some one with more insight and experience can come up with a more probable truth...we'll consider crankshaft torsioning to be a reality.
WHY IS THIS SUCH A PROBLEM "ALL OF A SUDDEN" ? -- Because late model pwcs have more power, more hull weight, and better turning abilities than ever before. All these features load the drive train harder, and increase the likelihood of crankshaft torsioning. Remember, the first machines to consistently experience this were the 580 Sea Doos. While those old 580s may not be considered muscle boats, their engines generated lots of power per cc, the pumps hooked up great, and the hull could hold turns at full speed. The early runabouts from the other makers could do none of those things...hence they never loaded the crank hard enough to induce torsioning. In this same vane, high output stand-up boats are so lightweight, and so hard to keep hooked up, that crank torsioning could barely take place. That's why our old "parallel jetted" 701 Raider engine lived in the standup hull, yet seized the rear piston in the runabout hull. The weight and constant hook up of the larger Raider hull loaded the crank harder than any stand up hull ever could.
The apparent effects of crankshaft torsioning are likely among the reasons that Rotax made such a quantum leap in crankshaft "beefiness" for their 782 cc Laydown Rave engines.
OTHER SUPPORTING INFORMATION -- Perhaps foremost in this area is the current trends among the boat makers themselves. The '96 ZXi 1100 ignition automatically retards the timing to the rear cylinder after engine temperatures increase beyond a specified level. The '96 Yamaha Blaster II ignition fires 2 degrees retarded at all times, and the rear combustion chamber has considerably less compression than the front. All the 1997 701 models, from Yamaha, also have this "staggered" compression arrangement.
We also suspect that crankshaft torsioning was a consideration for the new reed valve 950 Rotax engine. The rotary valve Rotax crankshafts are, by far, the longest of the 2 cylinder pwc cranks. This length is needed to accommodate the rotary valve diameter and related hardware. A 950 rotary valve twin would need even more length, if the necessary larger rotary valve disc were used. A 950 rotary valve engine with 135 hp, and the large GSX hull, would have certainly experienced unprecedented crank torsioning. The reed valve design would result in a much shorter and stiffer crank, not to mention reduced lower end total length and weight.
Every technician that has any pwc experience has seen it. The engine whose rear piston has scored (seized) for no diagnosable reason (while the other piston(s) look perfect). subsequent teardown inspections out rule airleaks, fuel and coolant blocks, oil, ignition, etc. At Group K we believe that "nothing" happens for no apparent reason. However in the last decade of working on pwc engines, we have seen numerous seized rear pistons that we could not account for. This document makes an effort to account for an awful lot of the ones we've seen.
SOME IMPORTANT EXPERIENCES -- Among Sea Doo race engine builders, richer jetting in the rear cylinder (to avert piston seizure)has been standard fare from the 580 cc days. We remember speaking with some of those technicians about the apparent need for "uneven jetting". They all told us that identical front and rear jetting in their Rotaxes was a near guaranteed rear piston seizure. We argued that none of our 650 Waverunners or Kawasaki SS twins had ever required uneven jetting. We felt certain that they had some other technical problem that they were overlooking. We continued to believe that, until the day we started testing our first Yamaha 701 Raider.
Our Sleeper kit development for the 701 Raider was relatively uneventful. However when we installed the Coffman pipe that drove rpms to 7100 (from the stock 6400), we began to experience a rash of scored rear pistons. We realized that we were probably facing the same gremlin that our Sea Doo pals had been living with for years. We were bound and determined that we would be the guys that would solve the problem. We believed that we would show that uneven jetting would not be needed. We then experimented with milder compression, retarded timing, richer overall jetting, dual cooling with additional flow for the rear cylinder...and plenty more. Three weeks, and a dozen seized rear pistons later, we finally had a strong running format that could run wide open for almost a full minute...before it seized piston number 13. We finally broke down and put one size larger main jet in the rear carb. With this richer jet, the machine still accelerated strong, and reached peak rpm quickly. We ran it full speed for over 15 miles...we couldn't make it seize (or foul a plug). In fact, to our surprise, later tear downs would show not even the slightest visual signs of over richness or fouling. Shortly there after, we repeated this same frustrating scenario with the (then new) Yamaha 1100 triples. Only the rear cylinder desired richer jetting.
Armed with this experience, we revisited our earlier model stand up and runabout dual carb engine kits. Remarkably, none showed the need for uneven jetting. Even more remarkable was that an identically modified 701 Raider motor, mounted in a stand up hull, did not require richer rear cylinder jetting. The stand up, with the Raider motor could run wide open all day long on "parallel" jetting. When that same motor, with it's parallel jetting, was then installed into a Raider hull...immediate rear piston seizure.
As all this went on, we realized we were creating far more questions than answers. For the meantime, we simply accepted our experiences at face value, and used parallel jetting when we could...uneven jetting when we had to.
During the beginning of our development on the 782 Laydown Rave motors, we immediately started to experience rear cylinder scoring (that was staved off by richer rear carb jetting). At that same time, we were lucky enough to be having a conversation about this problem with Ross Liberty of Factory Pipe Products. They were in the process of developing their pipe for the Laydown Rave in their newly completed dyno facility. This dyno, and it's instrumentation, can tell "everything" that's happening while the engine is under load. Ross mentioned that they too were chasing the "richer rear cylinder" gremlin. He said that they had eliminated every imaginable variable, and no matter what they did, the combustion chamber temperatures were never identical under full load. He said they suspected something related to the crankshaft twisting. He suspected that this twisting was affecting the "sameness" of ignition timing. We suspect that he is correct.
CRANKSHAFT TORSIONING "The Gremlin" -- This suggestion, by Factory Pipe, is what we consider to be the true cause of the countless scored pistons we saw during our own tests. To understand it, one must first understand the difference between twisting and torsioning. Crankshaft twisting refers to a crank that has been rotationally jolted so hard that one of the press fit connections rotates out of index...and stays that way. When a crankshaft "twists", there is large and immediate loss in power that comes along with a noticeable vibration. When a crankshaft "torsions", there is a momentary rotational springing action...nothing comes out of index, there is no vibration, there is no noticeable power loss. A welded crank cannot "twist", but it can still "torsion". The total amount of "torsioning" that takes place depends on the length and rigidity of the crankshaft. The longer and less beefy...the worse the torsioning. What we now refer to it as "crankshaft torsioning" (not twisting)... works like this :
The front cylinder on all pwcs is the cylinder closest to the ignition rotor. The amount of torsioning that can take place between the ignition flywheel and the front crank pin is nearly non-existent. However, structurally speaking, the rear crank pin is much "farther away" from the ignition flywheel. When the pump (at speed) suddenly hooks up on some smooth water, the front cylinder and the ignition flywheel have enough rotational momentum to torsion the crankshaft over it's entire length. As this happens, the flywheel and front cylinder can actually get 2 to 3 degrees of rotation ahead of the rear cylinder. As this 2 to 3 degree torsioning rotation takes place, the front cylinder is still getting perfectly timed ignition sparks. However the rear cylinder is lagging slightly behind when it gets it's ignition spark. This means that the rear cylinder is firing 2 to 3 degrees more advanced than the front cylinder. Furthermore, this advanced timing is happening at the worst imaginable time...at high loads and high rpms. As any engine builder can tell you, running 3 degrees too much high rpm advance on a race engine is a guaranteed way to seize (or hole) a piston.
While we don't have any iron clad proof that these presumed effects of crankshaft torsioning are an absolute fact, we feel that have enough hands on experiences and supporting information to consider it "a very probable truth". Until some one with more insight and experience can come up with a more probable truth...we'll consider crankshaft torsioning to be a reality.
WHY IS THIS SUCH A PROBLEM "ALL OF A SUDDEN" ? -- Because late model pwcs have more power, more hull weight, and better turning abilities than ever before. All these features load the drive train harder, and increase the likelihood of crankshaft torsioning. Remember, the first machines to consistently experience this were the 580 Sea Doos. While those old 580s may not be considered muscle boats, their engines generated lots of power per cc, the pumps hooked up great, and the hull could hold turns at full speed. The early runabouts from the other makers could do none of those things...hence they never loaded the crank hard enough to induce torsioning. In this same vane, high output stand-up boats are so lightweight, and so hard to keep hooked up, that crank torsioning could barely take place. That's why our old "parallel jetted" 701 Raider engine lived in the standup hull, yet seized the rear piston in the runabout hull. The weight and constant hook up of the larger Raider hull loaded the crank harder than any stand up hull ever could.
The apparent effects of crankshaft torsioning are likely among the reasons that Rotax made such a quantum leap in crankshaft "beefiness" for their 782 cc Laydown Rave engines.
OTHER SUPPORTING INFORMATION -- Perhaps foremost in this area is the current trends among the boat makers themselves. The '96 ZXi 1100 ignition automatically retards the timing to the rear cylinder after engine temperatures increase beyond a specified level. The '96 Yamaha Blaster II ignition fires 2 degrees retarded at all times, and the rear combustion chamber has considerably less compression than the front. All the 1997 701 models, from Yamaha, also have this "staggered" compression arrangement.
We also suspect that crankshaft torsioning was a consideration for the new reed valve 950 Rotax engine. The rotary valve Rotax crankshafts are, by far, the longest of the 2 cylinder pwc cranks. This length is needed to accommodate the rotary valve diameter and related hardware. A 950 rotary valve twin would need even more length, if the necessary larger rotary valve disc were used. A 950 rotary valve engine with 135 hp, and the large GSX hull, would have certainly experienced unprecedented crank torsioning. The reed valve design would result in a much shorter and stiffer crank, not to mention reduced lower end total length and weight.
robin savell lloyd
Active Member
part 2 WHAT CAN YOU DO ABOUT TORSIONING -- In a nut shell, anything that will reduce the combustion chamber temperature of the rear cylinder. For many engines, running slightly richer rear cylinder jetting is enough. Others, with a more serious temperature problem need the richer jetting "and" lower rear cylinder compression. Our testing, earlier this year, showed lower rear cylinder compression to offer no appreciable loss in overall power, along with a significant reduction in rear cylinder combustion chamber temperatures. As a result, many 1996 Group K engine sets have been prepared with slightly staggered compression ratios. (It bears noting that crank torsioning is a much bigger issue for modified pump gas engines than engines running on race gas. Our testing showed that many engines kits would overheat the rear cylinder on pump gas, yet have much more even temperatures on 110 octane race gas. However $4 - $5 a gallon gasoline is a very expensive solution.)
Of course, slightly retarding the ignition timing of the rear cylinder would seem to be the smartest solution. However the electronics of such a device are somewhat expensive and complex for an aftermarket approach. We are made to understand that MSD (the Texas ignition makers) manufactured a few Yamaha total loss racing ignitions, for one of the larger teams, that had an additional "plus or minus 6 degree" adjustment plate for the rear cylinder pickup. We suspect these plates were used to slightly retard the rear cylinder firing of some "tour" engines that were dancing on the edge of the reliability envelope.
In fourth coming year models, some boat makers may choose to drive the ignition off the back of the crankshaft. A design like this could be effective, but it would turn the rear area of the engine into "a very busy place". However pwc engine compartments, as a whole, are certain to become "busier places" anyway.
In time, we believe that all the boat makers will come up with their own special way of dealing this problem on their stock boats. With each new years machines making more power and more hook up, the phenomenon of crankshaft torsioning on high performance pwcs will have to be dealt with som
Of course, slightly retarding the ignition timing of the rear cylinder would seem to be the smartest solution. However the electronics of such a device are somewhat expensive and complex for an aftermarket approach. We are made to understand that MSD (the Texas ignition makers) manufactured a few Yamaha total loss racing ignitions, for one of the larger teams, that had an additional "plus or minus 6 degree" adjustment plate for the rear cylinder pickup. We suspect these plates were used to slightly retard the rear cylinder firing of some "tour" engines that were dancing on the edge of the reliability envelope.
In fourth coming year models, some boat makers may choose to drive the ignition off the back of the crankshaft. A design like this could be effective, but it would turn the rear area of the engine into "a very busy place". However pwc engine compartments, as a whole, are certain to become "busier places" anyway.
In time, we believe that all the boat makers will come up with their own special way of dealing this problem on their stock boats. With each new years machines making more power and more hook up, the phenomenon of crankshaft torsioning on high performance pwcs will have to be dealt with som
Rear cylinder....
Welcome Keona Jane!....your in the right place. It seems you know a little more about your engine than you give yourself credit for. I agree with you about your system. Are you still on the oil injection system? and if so, have you ever done a volume test on the oil pump? Before this problem with losing the pto piston, were the carbs removed for a rebuild? If so, was the alignment checked on the linkage? With this problem limited to the pto cylinder, did you check the injection line to that cylinder for blockage?
There are several things you may need to check if you decide to re-do this motor again. The oil pump is on the front of the engine and is supplied by one hose, about 3/8" diameter, with 2 smaller hoses, about 1/8, going to the back side of each carb. The lines are actually connected at the bottom of the rotary plate.
Another issue is the type of oil you are using. The Rotax engine requires a non NMMA, non TCW-3, low ash oil. Most members use the synthetic blend. You cannot use the standard, off the shelf 2-cycle oil in these engines. If you can't buy the Sea-Doo blend, then Quick Silver sells both mineral and synthetic blends of this oil standard in Wal-Mart (read the label because they sell several types. It will list that it is compatable on the back label). If you dont know what type of oil is in it now, synthetic or mineral, then you'll need to do a complete oil change.
For an engine this old, I'd do away with oil injection and go premix with a 50:1 ratio. Relying on the oil injection pump at this age isn't too smart, unless your a mechanic who tinkers on this thing all the time, inspecting it. I have a 97 model 787cc and my hands are always in it.
One more option. You can start fresh by ordering a new OEM remanafactured 657cc engine that comes with a 1 year no fault warranty for $745..........
You have a lot of options here to go over. If you like, I can send you some links where you can go over the prices for doing this work. Whether you just want to buy a new top end, or motor......I can help. With the oiling in the mag cylinder good, I'd think you have a clogged pto oiling line, or a broken one. Good luck and let me know how you come out. Any more questions, just give a shout!...................:cheers:
Welcome Keona Jane!....your in the right place. It seems you know a little more about your engine than you give yourself credit for. I agree with you about your system. Are you still on the oil injection system? and if so, have you ever done a volume test on the oil pump? Before this problem with losing the pto piston, were the carbs removed for a rebuild? If so, was the alignment checked on the linkage? With this problem limited to the pto cylinder, did you check the injection line to that cylinder for blockage?
There are several things you may need to check if you decide to re-do this motor again. The oil pump is on the front of the engine and is supplied by one hose, about 3/8" diameter, with 2 smaller hoses, about 1/8, going to the back side of each carb. The lines are actually connected at the bottom of the rotary plate.
Another issue is the type of oil you are using. The Rotax engine requires a non NMMA, non TCW-3, low ash oil. Most members use the synthetic blend. You cannot use the standard, off the shelf 2-cycle oil in these engines. If you can't buy the Sea-Doo blend, then Quick Silver sells both mineral and synthetic blends of this oil standard in Wal-Mart (read the label because they sell several types. It will list that it is compatable on the back label). If you dont know what type of oil is in it now, synthetic or mineral, then you'll need to do a complete oil change.
For an engine this old, I'd do away with oil injection and go premix with a 50:1 ratio. Relying on the oil injection pump at this age isn't too smart, unless your a mechanic who tinkers on this thing all the time, inspecting it. I have a 97 model 787cc and my hands are always in it.
One more option. You can start fresh by ordering a new OEM remanafactured 657cc engine that comes with a 1 year no fault warranty for $745..........
You have a lot of options here to go over. If you like, I can send you some links where you can go over the prices for doing this work. Whether you just want to buy a new top end, or motor......I can help. With the oiling in the mag cylinder good, I'd think you have a clogged pto oiling line, or a broken one. Good luck and let me know how you come out. Any more questions, just give a shout!...................:cheers:
Last edited by a moderator:
rear cylinder
Thanks to both of you for the replies. After reading the crank torsioning thread I got somewhat discouraged for even wanting to go deep and rebuild this thing but the kids love it and insist I fix it and not sell it so I'm stuck with one of two options. I have not done an oil pump volume test and the carbs were not removoed for rebuild or anything else prior to the initial engine damage. the first six years it ran great then the final four years before blowing up i could only get a good full day out of the plugs before they would foul out and the smoke at an idle was getting worse once you took of it went away and ran great. If you let it idle for extended periods (trying to wait for a spot on the dock or beach) it would foul the plugs and start rough.
I'm debating on doing the rebuild because im concerned about the crank now. I dont mind doing the work and the jug is not damaged so I can have it cleaned up. I pulled the pistons and they are marked 663M07850 which I discovered are .50 over wiseco pistons. So I know this guy put good parts in it. Original seadoo gaskets were used and it appears that the oil filter from the tank to the pump is new as well. So now the debate is do I rebuild the upper half and eliminate the injection system and worry that the crank is distorting, or do I spemd the 750 for a rebuild and drop it and go?
If I go with the wiseco pistons again Im assuming about a 400 dollar upper end rebuild once the dust settles. I'd love to save the money but its not woth 350 for the headaches and heartaches of losing this ski for another summer. I have others for them to ride but this is the jewel. Besides now I'm on a quest! By the way, seadoosnipe, you mentioned that the two lines going to the carbs from the pump are injector lines?? I have not taken it down to that point but I will assume that the lines inject oil into the bore of each carb? if so how can I clean out or blow out these lines? and secondly how do I run a volume test on the oil pump. Thanks for all the help. By the way I will say, with my head down of course, that I had been using the cheaper tcw3 nmma oil. come to think of it I had been using a valvoline PWC oil for a long time and then I bought the Wal mart bottles of marine tech 2 oil about a year before the first grenade. It seemed to work okay but like I said , after the first rebuild the smoking at an idle went away with that rebuild. I dont know exactly what the builder did and naturally I cant ask him anymore.
Thanks to both of you for the replies. After reading the crank torsioning thread I got somewhat discouraged for even wanting to go deep and rebuild this thing but the kids love it and insist I fix it and not sell it so I'm stuck with one of two options. I have not done an oil pump volume test and the carbs were not removoed for rebuild or anything else prior to the initial engine damage. the first six years it ran great then the final four years before blowing up i could only get a good full day out of the plugs before they would foul out and the smoke at an idle was getting worse once you took of it went away and ran great. If you let it idle for extended periods (trying to wait for a spot on the dock or beach) it would foul the plugs and start rough.
I'm debating on doing the rebuild because im concerned about the crank now. I dont mind doing the work and the jug is not damaged so I can have it cleaned up. I pulled the pistons and they are marked 663M07850 which I discovered are .50 over wiseco pistons. So I know this guy put good parts in it. Original seadoo gaskets were used and it appears that the oil filter from the tank to the pump is new as well. So now the debate is do I rebuild the upper half and eliminate the injection system and worry that the crank is distorting, or do I spemd the 750 for a rebuild and drop it and go?
If I go with the wiseco pistons again Im assuming about a 400 dollar upper end rebuild once the dust settles. I'd love to save the money but its not woth 350 for the headaches and heartaches of losing this ski for another summer. I have others for them to ride but this is the jewel. Besides now I'm on a quest! By the way, seadoosnipe, you mentioned that the two lines going to the carbs from the pump are injector lines?? I have not taken it down to that point but I will assume that the lines inject oil into the bore of each carb? if so how can I clean out or blow out these lines? and secondly how do I run a volume test on the oil pump. Thanks for all the help. By the way I will say, with my head down of course, that I had been using the cheaper tcw3 nmma oil. come to think of it I had been using a valvoline PWC oil for a long time and then I bought the Wal mart bottles of marine tech 2 oil about a year before the first grenade. It seemed to work okay but like I said , after the first rebuild the smoking at an idle went away with that rebuild. I dont know exactly what the builder did and naturally I cant ask him anymore.
Oil requirements....
You just named your culprit.....the wrong oils. Although the Rotax engine is a 2-cycle engine, it's operation is very different and highly depends on that low ash, NON NMMA, NON TCW-3 type oil. This is the obvious cause of your damage, I already feel that in my bones. Oil requirments are very stringent in the proper operation of this engine. It must have a low ash oil to work properly. Both carbs have two different size jets in them to off set some of the issues in the posts made by Robin. The oil injection lines are directly behind the carbs, mounted under the bottom of the rotary plate.
You can do this to check them, but when you put them back on, you'll need to make sure they have been purged of all air.
On the front of the pto cover, you'll see the oil pump. It has a cable hooked to it that goes to the carbs. There are two allen head screws that hold it on. Take them out. With the two screws removed, you'll be able to remove the pump. Look at how the injection lines are connected to the pump. With the age of the lines, you may want to replace them anyway, unless your gonna go to premix. When taking out the pump, work the small lines either off the pump where they connect to it, or from the injection at the rotary valve and slide them out from under the carbs. Then, try and work the pump over to the side by the tank. When you pull the pump, the teflon gear shaft may remain in the magneto shaft, pull it out. That's what drives the pump. It's white in color.
With this all exposed, get a cup or can and put those two small lines into it for letting the oil drain into. Then, take a drill motor, hook it up to the shaft of the oil pump and set the drill motor to turn the oil pump counter clockwise. Start the drill motor and see if oil comes from both lines.
I believe they will.
If you like, go to my thread, "a look inside a 787 engine". The size is different, but the design is the same. There, you'll see what the oil pump looks like removed, along with the shaft. Here's a shortcut to the picture of the oil pump.....http://www.seadooforum.com/attachment.php?attachmentid=44&d=1192672667
You just named your culprit.....the wrong oils. Although the Rotax engine is a 2-cycle engine, it's operation is very different and highly depends on that low ash, NON NMMA, NON TCW-3 type oil. This is the obvious cause of your damage, I already feel that in my bones. Oil requirments are very stringent in the proper operation of this engine. It must have a low ash oil to work properly. Both carbs have two different size jets in them to off set some of the issues in the posts made by Robin. The oil injection lines are directly behind the carbs, mounted under the bottom of the rotary plate.
You can do this to check them, but when you put them back on, you'll need to make sure they have been purged of all air.
On the front of the pto cover, you'll see the oil pump. It has a cable hooked to it that goes to the carbs. There are two allen head screws that hold it on. Take them out. With the two screws removed, you'll be able to remove the pump. Look at how the injection lines are connected to the pump. With the age of the lines, you may want to replace them anyway, unless your gonna go to premix. When taking out the pump, work the small lines either off the pump where they connect to it, or from the injection at the rotary valve and slide them out from under the carbs. Then, try and work the pump over to the side by the tank. When you pull the pump, the teflon gear shaft may remain in the magneto shaft, pull it out. That's what drives the pump. It's white in color.
With this all exposed, get a cup or can and put those two small lines into it for letting the oil drain into. Then, take a drill motor, hook it up to the shaft of the oil pump and set the drill motor to turn the oil pump counter clockwise. Start the drill motor and see if oil comes from both lines.
I believe they will.
If you like, go to my thread, "a look inside a 787 engine". The size is different, but the design is the same. There, you'll see what the oil pump looks like removed, along with the shaft. Here's a shortcut to the picture of the oil pump.....http://www.seadooforum.com/attachment.php?attachmentid=44&d=1192672667
PM.....
Keona Jane, I just sent you a PM. Please go to the top right of this page and you'll see a "welcomce" block with a link to your private messages (email).
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