Rotax 717 Cylinder Pitted

[WhiteZombie]

So I'm rebuilding the carbs on a 1998 Sportster with twin 717 engines. The needle valves on both would not hold the 10psi. One leaked down instantly, so I ordered new 1.5 gram needle kits per Seadoo manual specs. Got them and noticed that they were smaller than what is in the carbs. Mikinu documentation says that the 1.5 is plenty big for the carbs capabilities, and Seadoo info says pretty much same, but in overthinking that point I conclude that Seadoo is assuming the engines are bored to their specs which is 82.50 max bore. But still Mikinu says they are feeding the carb all the fuel it needs with that port size. Anyway upon seeing the change I decided to pop the tops off the engines to see what I have gotten myself into, as I was most likely going to anyway. I have checked the compression with a brand new gauge and found all cylinders to be hitting 150 psi by the third turn over, with each reading around 145psi on first turn.
So what I found and think I understand after reading numerous posts is that my piston has a 1.00 stamped on it and that is the biggest piston available to my understanding. I was a machinist by trade, so I measured the bore with a Mitutuyo caliper and a Starret bore micrometer, which is a bit challenging to get a good read on due to limited contact area. Basically 3 cylinders are bored at 83.08(3.271) and the third is coming in at 83.10(3.73ish). So around .001-.002 over the other bores. Seadoo says 82.50 (3.248") is max bore. Upon inspecting the larger bore, I noticed some pitting. Not very deep, can only feel with fingernail.
I'm attaching some photos. I would like to know what may have caused this pitting on this one cylinder if we can get an idea. I am also at a crossroad on it cause i've got a lot of time this spring spent on working on the boat to get it in the water. I don't know if I should just get it running to get in the water to see what it does and what else it may need with intentions of doing the work in the winter, or do I take these cans off and hone them and be done with it. I can't say it is getting any worse and have no idea how long they've been like this, but I'm guessing quite a while. I wonder if the piston had rusted in the cylinder and they freed it up and put it in. I do know this engine does have shims installed on the motor mounts so I assume it is a changeout of some type. Funny thing is this engine is the one that was running. I got both running before taking the carbs off.
Fortunately I do have a "mill drill" that I use for projects like this. I also have a small boring head so I can bore a couple thousandths out and then hone it if I have to, but idealy I would just get a good hone and do it all. I can make a jig to hold the can. And then the carb jets are a question too. I can't read the numbers on them, but the high jet is measuring around .071" with a dowel pin. I have no idea if these need rejeting or not due to the 50 over bore, but I do know the high jet adjustment was 1/4 turn on one and totally closed on the other, which after reading several posts is acceptable. The manual says 1/4 turn. The low jets were set at factory spec too pretty much, so basically I have a 50 over bore with not much carb adjustment unless they did rejet and wound up with same adjustments. Anyway, I'm too the point where i am getting past my knowledge on engine tuning, so I need some help. I can do the work, I just need to know what to do. I do have the service manual with addendum. I did not open the needle kits just in case I do need a 2 gram. I have been putting everything back to factory spec to this point. I hope I don't get into a jetting nightmare with these 50 over bored engines. One other thing is this engine does smoke, but I was thinking it to be a carb issue as the needle had a piece of the clumpy chalky fuel build up debris between it and the port, so it was flooding I would assume. Thanks for reading. I know this is a lot, but I'm just at that point of frustrating confusion. Thanks in advance!

 

[mikidymac]

You have a bunch of surface rust on those cylinders and that is what the pitting is from.

Either not blowing the water out after a run or not fogging the cylinders or both are the cause of the rust and pitting. It is not great and can cause blow by.

As far as the carbs you need to run the stock jetting, needle and seats and springs, you do not change them because your engine is bored to 1.0mm. Don't start changing needle and seat size, springs or jets because you think it needs more.

 

[WhiteZombie]

You have a bunch of surface rust on those cylinders and that is what the pitting is from.

Either not blowing the water out after a run or not fogging the cylinders or both are the cause of the rust and pitting. It is not great and can cause blow by.

As far as the carbs you need to run the stock jetting, needle and seats and springs, you do not change them because your engine is bored to 1.0mm. Don't start changing needle and seat size, springs or jets because you think it needs more.

Thanks for the reply. i put the heads on today and am planning to run it to see if it can get me thru the summer and then hone it this winter. if it burns oil bad I'll prob pop them off and hone if needed. How do you blow the water out? I see a lot of oil and I assume water under it in the exhaust manifold. I'm going to put it on a hose later this week so hopefully that will get it out. It's like a half inch from pouring in

 

[mikidymac]

People get water in them by running on the hose and having the water on and the engine off. There is no reason to run on the hose unless you are flushing the cooling system.

To blow the water out you should start and rev up the engines after you pull the boat out of the water to blow the water out the exhaust.

You will not help it by honing as it will not remove enough material to get the pitting out, you will have to bore to the next oversize and install larger pistons and rings.

Finally, the pitting on these will not cause you to burn oil like on a 4-stroke.
It can cause you to seize the engine though. The pitting can cause hot combustion gasses to get past the rings and this will burn the oil film off the piston skirt and cause them to seize.

 

[L. Dean Ficarro]

How is the boat? Did you ever get rid of the old tempo fuel lines and clean your carbs out?

 

[WhiteZombie]

I bought the boat as a project boat not sure of all the issues. The lines are changed out with all being black except a small one on the carb I think. I rebuilt both carbs and have installed them (oem kit). I have now removed the shaft on the starboard side due to some play. I have another post going on that issue and am about to post some pics of the seal, etc that I was told had been replaced but had enough play in it that i thought it necessary to remove it to check. The port side seal looks good and has clearance for assembly type movement only so I am hoping to leave it be. I have also found an oil leak I have been trying to figure out mostly looking at the valve area. I found it this morning. I think it is coming from the crank bearing area behind the flywheel on the port side engine. I have the oil line pinched off to see if I maybe can get by with just installing a shutoff on the oil line. Seems that is the fix for some of these oil leaks so thinking that, but really I am over my head on the specifics of these motors and have found myself refering to youtube and the manuals to show me how to turn the wrenches. I'm hoping for some help on the questions I have, so any advice is appreciated. Oh, when I rebuilt the carbs I did find some water looking crusty mess on the diaphram and one of the filters was about full of the clumpy powedery material it seems can be found in these. I'm thinking about finding a generic mesh filter screen type water seperator. I found one that I think won't be any more restictive than the strainer type filters that the factory installed. Thanks

 

[WhiteZombie]

The post I referred to above is Sportster 1800 Seals. Nobody has responded to it so I don't know if it is in the right area or not. If a moderator can check I would much appreciate it. I have a bunch of pics attached on it and could use some advice on how to proceed. I gotta get this boat on the water or I will be riding with my in-laws on a every Sunday basis. Heeeeeellllllllpppppp!
I want it done right, and while I have this out no doubt it will be fixed correctly as soon as I find out what I need to replace. But I do know I will be doing some work on this in the winter

 

[L. Dean Ficarro]

REGARDING carbs/ bore/ fuel:
You should have no issue tuning with the high, low, idle adjusters; that shouldnt cause any lean burn if done correctly. (Literature, manuals, forums and youtube will get you through) Look into the next size piston and bore/ deck the jugs, soak in rust-away and thoroughly clean everything. Last, coat it in 2stroke oil to keep it from drying out and rusting again.

MAC addressed your other concerns later in your initial posting so there is no need to repeat it, lol, he is “johnny on the spot with those replies.

SMOKE: 2strokes gonna smoke but if it is a lot, id look into checking oil pump adjustment. Its one cable, two lines and minimal monkeying with a couple adjustment nuts to align the marks.

With the drive shaft being out of true, pull the seals and needles then replace them along with a couple new or used parts that are true. Or true/ turn them on your own if you can.

Cheers!

 

[WhiteZombie]

REGARDING carbs/ bore/ fuel:
You should have no issue tuning with the high, low, idle adjusters; that shouldnt cause any lean burn if done correctly. (Literature, manuals, forums and youtube will get you through) Look into the next size piston and bore/ deck the jugs, soak in rust-away and thoroughly clean everything. Last, coat it in 2stroke oil to keep it from drying out and rusting again.

MAC addressed your other concerns later in your initial posting so there is no need to repeat it, lol, he is “johnny on the spot with those replies.

SMOKE: 2strokes gonna smoke but if it is a lot, id look into checking oil pump adjustment. Its one cable, two lines and minimal monkeying with a couple adjustment nuts to align the marks.

With the drive shaft being out of true, pull the seals and needles then replace them along with a couple new or used parts that are true. Or true/ turn them on your own if you can.

Cheers!

Thanks for the info. I adjusted the oil setting when I reconnected the carbs- happened to see a youtube on it trying to learn about how leaks in that area occur. I am currently trying to understand why the bearing behind the pto hub is leaking. I have the oil line pinched and plan to install a shutoff if it proves to help.

What I'm dreading on the carb adjustments is ones I make after I put it in the water because the air intakes are all in the way. After rebuilding the carbs I at least know better what screws do what. I plan to put it on a hose soon and adjust the carbs. I'll prob test on the engine that I have the shaft out of so I don't have to worry about cooking the seals. If it does ok with the factory settings I'll feel ok about the other engine. But with the seals out I should be able to rev it up a bit I would think. I also have to reconnect the steering assist part of the throttle cable because it was disconnected. I assume it rattled loose and they never noticed or didn't know the difference when they did. I haven't heard anyone mention disconnecting this feature so I assume it isn't something people mind, so not leaning toward they maybe disconnected it on purpose. The nut was close to the bottom of the bolt when I found it and I would think if they disconnected it they would have at least tighted the holder to the cabinet. But it will likely take me some run time to get that adjusted as i doubt many have started from scratch, and unfortunately the throttle adjustment screws came loose too so I don't have the original adjustments to start with. I hope I don't discover they disconnected them for a reason.

On the bore size and needing more adjustment, the carbs were set close to factory specs, like one was dead on the low with the other 1/8 turn richer. High on one was 1/4 turn and one was all the way closed. I put back as the manual said all the way closed and set the low needle to spec. I put new gaskets on when I installed them.

So it sounds like you are thinking the drive of the jet is out of true? I was thinking the wear ring was put in half way and got screwed up but upon looking at it today it is neat on the edges and pretty level with rim. I think the kicker for me is that no matter how I look at it I am looking at .050" shim clearance which .040 is max. I have .040 at the low spot now. So I was thinking cheap aftermarket wear ring is what I am looking at. The other jet, I doubt I can get a piece of aluminum foil under it, but I'll try tommorow to get a measurement on it, but it is no more than .010" and I am not joiking. It is a white plastic. I will look at the manual tommorow. It has a section talking about the drive shaft. I think I recall .002 being the max runnout. I have the mic dial indicator setup they use so I'll check it. I have it on the bench anyway checking the oil level, etc. I assume this is would tell me if it is out of line. But if it is inline, I think I need a new wear ring being it is out of spec

 

[mikidymac]

Ok, lots of info so lets try to unpack it all.

1. IF you are actually leaking oil at the engine side of the PTO Flywheel then you have a bad crank seal. This is not supplied by the oil tank so closing that hose will do nothing as the oil tank does not supply that bearing/seal. The only fix is to take the engine apart the change that seal or you will run lean and blow up the engine.

2. The carbs will run perfectly with stock settings, unless you are at high altitude there is nothing to "tune" if it doesn't run correctly then something is wrong.

There is nothing to shim on the pumps. The only thing you move to correct alignment is the engine and it can only be done correctly with the special alignment tool. Wear ring can't be installed 1/2 way and can't be shimmed.

 

[WhiteZombie]

Ok, lots of info so lets try to unpack it all.

1. IF you are actually leaking oil at the engine side of the PTO Flywheel then you have a bad crank seal. This is not supplied by the oil tank so closing that hose will do nothing as the oil tank does not supply that bearing/seal. The only fix is to take the engine apart the change that seal or you will run lean and blow up the engine.

2. The carbs will run perfectly with stock settings, unless you are at high altitude there is nothing to "tune" if it doesn't run correctly then something is wrong.

There is nothing to shim on the pumps. The only thing you move to correct alignment is the engine and it can only be done correctly with the special alignment tool. Wear ring can't be installed 1/2 way and can't be shimmed.

You say it will run lean, is that by pulling in air at the leak site? I have a feeling it is full of water and oil from what I am reading. Every morning I find a little puddle on the hull floor about an inch out from the motor mount. I can't see it for the flywheel, but the oil is directly under it on the engine casing so gotta be the bearing. But where is the oil coming from cause it just keeps flowing and I'm not running the engine at all.
What is the probablility of seizing soon? Could I get it thru the summer? I plan to pull the cans off late fall anyway. I doubt it just started cause the floor of the engine compartment was pretty much black before I cleaned it for hours.