95 Sportster - Runs Great, Then Not, Then Great

[stoian1]

Ok, here is the background. Have a 95 Sportster with a single Rotax. The Mpem has been replaced with a "gray box" type meaning it does not provide for over rev limit and shifter lockout issues. Given it was $160 vs $1200, worth the risk. I do not think my problems are related to MPEM at all but just want to make sure all facts are mentioned. Currently running a premix solution rather than injection. Not sure if injection system has issues or not as this how I purchased boat.

My boat starts like a dream and seems to run very well on dry land, with a very smooth idle. When I took it out the first time, hit the throttle and off we went...weeee. Then, started having intermittent problems which got to be so bad I could only get it slightly above a fast idle. Playing with throttle and choke would sometimes allow me get full throttle back but very unpredictable.
When I got back home, hooked it up to hose to make sure cooling system worked well, which it appears to do (a lot of water coming out of exhaust, and a little out of one of the three little holes near the ski rope mount). This is normal correct?

So, took it out again, ran a little better this time (maintained full throttle for a good 10 minutes) but as I backed off throttle, same issues developed. So, my guess is I have a fuel delivery or carb issue, rather than mechanical problem but, trying to determine where to start first. Here are as many details and symptoms I can think of to describe issues which I hope can help point me in the right direction. BTW, I have a full shop manual:

1) Checked plugs - very clean, no fouling
2) When running full throttle, right turns seem to bog the engine down less then left turns. Is this normal operation? Can't think why this would make any difference. Also, when I experienced problems the first time, engine seemed to pick up when I turned right or leaned boat right. Have checked steering cable for issues with throttle, do not seem to be any.
3) When in neutral, boat seems to have slight back drift. My guess this is just an adjustment but should not affect running of motor.
4) Playing with choke and throttle allowed me to get back to full throttle but this was hit or miss.
5) I took spark arrester off and peered in card throats to see if i could see fuel being pumped into throttle body thinking it might be related to accelerator pump (assuming these have one). Did not see any but may have to do this one more time to be absolutely sure.
6) This was very interesting. I felt the top of the engine(spark plug side) while it had been running for a while. I was very surprised to feel the engine was not even warm. Is this normal??? The river is very cold still so perhaps this explains it or the fact that it has a double jacket. But wanted to point this out.
7) I lifted shifter and throttle assembly out of the mount to tighten rear seat screws. Is it possible I messed up some time of adjustment in the process that manifests itself sporadically?

If a carb(s) is in need of a rebuild, do they behave erratically? Wouldn't it be the same always? If I need to start with a rebuild, does anyone know of a reputable carb rebuilding service? I am not afraid to tackle this as I am very mechanical, but given what a pain it is to get in the engine compartment, would like to have this done right the first time.

Ok, that is about all I can remember so any help anyone can provide is as always, tremendously appreciated.

Regards

Steve

 

[kustomkarl]

Steve, it sounds like it has carburetor problems. I would first clean them and if needed, if the diaphragms tear, rebuild them. What was done to the jet boat to winterize it. The cooling effect is normal, Cool Heads). the water coming out of the "Tell Tail" hose is normal. remember to start the boat first than open the water and do not run for more than 5 minutes on the hose, as the impeller jet pump bearings and seals aren't being cooled on the trailer. It depends on being in the water to cool it. Turn off the water first than the engine. This will keep the water from backing up into the engine.

Keep us posted on you progress or if you have any more questions give us a shout.

Karl

 

[stoian1]

95 Sportster - Runs Great, Then Not, Then Great

Thank you Karl. Yes, have been very careful to follow instructions for running on ran and flushing.

RE: Cleaning, is it possible to add additives to the fuel such as you might do for a car?? or will this negate oil lube protection? Also, what about spraying cleaning solution down carb throat? If this is possible, any limit on brand or type? An lastly, if not possible, the I assume cleaning carb means taking it off the engine, correct?

Many thx.

Steve

 

[kustomkarl]

Steve, the carbs need to be taken off the seadoo to clean them. There isn't a float and bowl as such like cars have. These carbs are diaphragm type and need internals cleaned. You can use carb cleaner to spray the internal journals and passages but just spraying it in the carb throat isn't going to do anything. If you want you could join as a "premium member". As a premium member you can down load a authentic seadoo manual from the seadoo manual library. In the library is a variety of manuals for almost all years and models. You can view as many as you like on line as a PDF file, or download it and print it for your personal and privet use. There are operator manuals and repair manuals for you to do your own repairs on your seadoo. The repair manuals have everything from troubleshooting, repair procedures to winterizing. It contains wire diagrams torque specs and pictures for disassemble and assemble instructions. In the spec sheets it tells everything needed to maintain oil changes, spark plug gaps, carburetor rebuilds and impeller wear ring tolerances. Click on the "Seadoo Manuals" link at the top of the page for more details. If you need any help or get in a jam, we are always here to answer your questions too.

Karl

 

[robin savell lloyd]

Just as karl said engine temp is normal and carbs do seem like they need to be taken apart and cleaned and new carb kits installed. you also need to replace grey fuel lines if you still have them as they are defective and clog carbs. good luck. Robin :agree: :cheers:

 

[stoian1]

Will Try Rebuild

Thank you to all. Will try and rebuild this weekend and see what happens. Will of course update as well. Take care.

 

[timmyboy76]

Heay stoian1....Hav'n the same prob. After docking, get past bouys...weeeee, bring to idle, then try WOT, wont go past 5-8mph, most time, sometimes it'll grab. Tell you what i've done,
*repalced all +/- wires
*Replaced coil and plug wires
*motor was already gone thru, with new everything
*replaced charging/ignition coils
*new plugs and temp sensor
*replaced whole carbon/ boot assy, think'n it was cavitation
*2 cans of carb cleaner
*looked at nuetral switch, checks ok
So as of now, I have 2 options left, B-4 I torched the DAMN thing
1) disconnect the rectifier
2) goin thru carbs now, play'n with needle/seat and springs
Let'n you know what i've done so far, so you don't have the pleasure of throw'n tools, and a grip of receipts from your nearest lake of gate entrys
....Keep you posted

 

[stoian1]

Rebuild Mikuni Carb Directions & I think I May Have Solved it

NOTE: Someone has done us a big favor by recording all the steps needed to rebuild a Seadoo Mikuni carb. Go to http://www.mediafire.com/?1nh4v0rnjzb to download a PDF (about 18 megs so takes a while) but well worth it. Made it really simple. Be sure to follow directions and do not take shortcuts as it is not worth it. be sure to do the pop-off test as well as this seems to be a critical test.

Ok, rebuilt carbs today and found that water seems to have gotten in one of the carbs and there was some rust. Not to mention, filters were clogged and diaphragms were shot as well.. There is no way to get any of this internal stuff clean without doing a rebuild. Well worth the time and I think that this has to be the first step whenever anyone is having these kinds of problems. Also replaced oil lines at the same time which just about dissolved in my hands...

Turned out at least one of the jets was clogged from the crud which I think contributed to the problem. Got it all cleaned and rebuilt. Started it up and seems to run fine but since it was late, had to shut down almost immediately. Will tune to tomorrow and hopefully get into water to see whether this takes care of the problem.

Stay tuned and good luck with your problem..

 

[timmyboy76]

RITE ON......This is gonna help alot, thanks

 

[kustomkarl]

That's great news....keep us updated on your progress... Remember to go have some fun this weekend.

Karl

 

[stoian1]

Rebuilding Carbs - That Did The Trick

Yeeha...rebuilt carbs did the trick and now she runs great. Slight misfire at about 1/3 throttle but I think that might be normal.

The only problem now seems to be that it seems as though at times it "slips", like the impeller is trying to grab but can't seem to get traction. Thought perhaps I picked up some leaves but did not seem to clear it up. Happens when I gun the engine, revs up high, gets up to plain, and then engine settles down as boat hits speed.

From reading the various posts, I guess it will either come down to a worn wear ring or a bad impeller. Any guesses??

Thx to all for your help with previous problem. VERY much appreciated.

 

[timmyboy76]

Rite on stoin1...glad to hear it ran good. Curious to know, when you rebuilt ur carbs, did you change the float arm spring, if you did, what size did u use, and if you also, what motor is yours and if you recall, what needle/seat was in yours.
Reason is, i'm get'n my parts tomorrow, and need a starting point. Thanks ahead of time..

 

[robin savell lloyd]

I have read to reuse your springs if you do not see any thing wrong with them.Good luck Robin :cheers:

 

[timmyboy76]

Hi Robyn...
I asked, because i just bought the boat, some parts in the carbs, tells me its been rebuilt, and might have experience the same problem which i'm hav'n now, in turn, they gave up on it. The way the seats looked, the boat sat for few years, they had, installed and rebuilt the pump, so ruled out cavitation, new impellor, inwhich gap, was 1mm or less. I'm think'n they installed the bigger of the springs, inwhich, i recall, they were the 115gm.
I'm gonna install the 65gm, considering the N/S are 1.2...I ordered the 2.0n/s, and 80/95gm, soooo, take to the lake, and see whats gonna work.

 

[stoian1]

Carb Update

Not sure if my email reached you so I'll provide reply just in case.

I reused my springs as I found the new ones to be too stiff and they were causing pop-off pressure to be way to high. The critical issue regardless of the springs is to check the pop-off pressure readings! Even if you put brand new springs, they can be off significantly. So, if you check pressure, you will be assured of the correct settings no matter the spring you end up using.

There are a variety of ways of "adjusting" the spring which you can find via web. I doubt float seat is an issue as boats usually do not get that much use to wear them out. When you check your pop-off pressure, you will be able to determine if your seats are bad. Just remember to use the WD40 (spray a little in the needle valve before checking) as this will assure a good seal to get the distinctive "pop". Also, very important to take plate cover off of regulator in carb. My screws were really hard to get off so I almost passed this step up. Glad I did not because this is where the jets are located and it was the high speed jet that was clogged (explains the loss of power). Be sure to take them out and eyeball them to make sure they are open.

You asked about motor but not sure as I am traveling and do not have access to my manual.

Hope this helps and good luck.

 

[timmyboy76]

Thanks stoin1...helps tremendouisly. I also when cleaned the carbs, bypassed the plate where the jets are under, because the screws were on good, didn't want t ostrip them, but when my rebuild kit comes in, definetly, take whole thing apart, again,.. thanks

 

[stoian1]

Screws

I use a powered screw driver with brand new tightly fitting bits. Really helped as I could not get the required torque otherwise. This may help to make it easier.