02 SJ wont rev past 1/4 throttle...

[Bunkhouse Buck]

I just bought a 02 SJ. It was taking spells where it would run great, then go to where it wont pull nothing past 1/4 in or out of the water. Now thats all it will do. I have put in new plugs, drained the fuel and filter. Replaced with fresh fuel. Cleaned carbs, and trimmed the plug wires.

The plugs stays wet and dark with fuel. It kinda sound like it is on a rev limiter or something. i just dont understand how it runs great, then bad. Can somebody please help. I would like to ride it sometime.

It does seem to rev alot better when its first started up, but as soon as I put it in the water, its 1/4 or less. Didnt know if this would help. TIA

 

[felix5oh]

What's your idea of "cleaned carbs"? The needle could be varnished, the pilot jet could be parcialy clogged, the four holes near the closing if the throttle plate on the main venturi could be clogged, even the tiny fuel filter behind the needle and seat could be clogged. That's probably it.It's fuel delivery.

 

[Bunkhouse Buck]

I didnt tear them down that far. I can see your point, but why is the plugs so wet if its fuel?

 

[Mike W]

If your hitting the primer to keep the ski going the plugs will look like that.

 

[Bunkhouse Buck]

Doesnt have a primer. Cant nobody else give me anything? Im stumped

 

[djkorn1]

Exhaust leak. Run it with the hood off and look for smoke. You could be choking it out. :biggthumpup:

 

[Bunkhouse Buck]

Thanks, but tried it with the hood off, no luck,

 

[Shonuff]

Is it going into limp mode?

 

[Vumad]

My ATV had that problem because of valves. It's a 4-stroker. It sounded like a rev limiter but it was a compression loss. It had no power arround 1/2 throttle.

I don't know much about 2-strokers to know if a messed up piston could be the problem. I know very little about 2-strokes. The piston and etc will change size with the heat (could explain why it works sometimes and not others) and leak more at higher compressions, (could explain why it works fine at an idle, but craps out at a higher RPM) so it could be the problem. A compression test could be done to check.

That's basically the worst case. My ATV, I did like you, I checked the plugs, cleaned the heck out of the carbs, checked the fuel for water or dirt, checked the plug wires for any arcs. Don't know how much different the 2-strokers are from the 4-strokers.

My quad was blown because of an air filter problem. Yours wont have dirt in it, but if you have a bad water pump it could have over heated. Or, if you still have the oil tank on it, it could have fouled up and not pumped the oil and that blows up a lot of 2-strokers. Most 2-strokers I have seen have been converted to pre-mix.

 

[restosud]

isn't there a temp sensor on those?

 

[Jumper]

isn't there a temp sensor on those?

I think that is what Shonuf was alluding to also. If the overheat sensor kicks in it will basically chug along at near idle speed. I had mine kick in a number of years ago when I had an obstruction in my cooling line. When you get it in the water, give it a little throttle, and see if you are getting water out of the bypass. After 10 seconds or so you should start to see water come out. If no water, or only a dribble, then you probably have an obstruction in the line between the pump and the exhaust manifold.

 

[Ross_C]

It was already mentioned, but you need to check the internal filter in the carbs. This is on the pump side of the carb and is not hard to get to with the carbs off. Just pull the 4 screws and you will be able to take the two parts of the pump off and will come to the internal fliter, which is notorious for gettng clogged with "cat hair". If that is clear...check compression. If all that checks out, pull the manifold and check the reeds.

How modified is the ski? Do you still have the temp sensor in the head?

 

[Bunkhouse Buck]

The ski has 150# so thats good. The ski has a Coffmans pipe and MSD ignition for the most part. Is does have the temp sensor, but the pink wire isnt connected because MSD install so it wasnt needed. The filter side is the side near the hull, right? I havent never tried that before, but Ill give it one. Thanks for all the help, keep the ideals coming and Ill keep the thread updated.

 

[cdubb]

Filter side is on the motorside. Not sure where the cat hairs come from,,but they where in my filters. I wonder if they are strands out of the main filter?

 

[Bunkhouse Buck]

cdubb, did the cat hairs give you any problems?

 

[cdubb]

That and all the other junk in there. It was alot dirtier then I figured it could be with that prefilter. That and the water in my carbs and fuel:banghead:

 

[Bunkhouse Buck]

So exactly where is the filters? Are they behind the plate that has the 2 phillip screws? What else did you clean? Felix mentioned this also. Where is a good thread on cleaning them?

 

[cdubb]

Yes behind that plate. I dont know where a thread is,,but the mikuni site has a parts diagram to help show ya, Ill see if I can link ya

http://www.mikuni.com/pdf/sbn_manual.pdf


pg 6 shows the part locations.

 

[Bunkhouse Buck]

Thanks cdubb. What you your problems so I can compare them to mine?

 

[cdubb]

After wide open runs it would bogg down and die,would restart but wouldnt take throttle. After feathering it for a while it would come back,but it took a while