NO SPEED OR RPM AT HALF carbs are not the problem

[robert30172robert]

I have a 1993 gtx 3 seater it has a 587 white motor daul carb motor. It starts up and runs great. It will sit and idle all day long If you let it. It has plenty of power on take off. and it will plane out. And about half throutle it just wont go any more. and what i mean by that is. at half way it all most seams like the jet ski has reached its full rpm. and wene i give it more gas it does nothing. it does not spit or spuder, bouge down or any thing else. it just does nothing. It acks like at half way theres no more throutle. This is what i have done to it. I cleaned the carbs,new fuel filter rebuilt the reserve valve.new fuel lines. I have check the ignition timeing and it is right on the money, I have checked the rotory valve and it is right on the money the clearance is fine to. I have checked the rectifier it is also good.checked compession it is 145. So what else could it be or am i just missing somthing. I have heard some of these machines have rev limiters could this one be fauly and it not allowing the motor to reach its full rpm. Im not sure what the rpms are because i do not have a tach. To read the rpms. but if i was to guess i would say it is around 3000 that it tops out at. these motors should run around 6000 or so. So what could be the problem PLEASE HELP Chould it be a bad stator or coil. I have done ever thing i can think of and i am all out of ideas need some help. I know the carbs are good because I took them off and put them on another machine and they did great.

 

[Dave_eng]

Thought on no rpm

On my Seadoo (1997 GTS 717 engine) I have chased problems which appear fuel related but later found a weak spark to be the culprit. When the load on the engine is low, the cylinder pressures are low and a weak spark will be OK but when the throttle is wide open and cylinder pressures high, the energy is too weak to jump the spark plug gap.

Years ago when cleaning spark plugs with an abrasive blast was the norm, I had a machine sold by Champion Spark plugs. First you would blast the plug and then, using compressed air, and with a high voltage lead on the plug, raise the chamber air pressure until the spark could not jump the plug gap. There was a mirror and a window in the chamber so I could see the plug. What this taught me was the effect of air pressure in an engine on a plug's ability to fire. A static test with the plug laying on top of the engine and producing spark does not ensure all is OK.

Suspect the ignition side of things when a lot of effort has been put into the carbs with no result. If a brand new plug appears to make things better for a few minutes and then your problem returns it is further proof of weak spark.

I don't profess to know all 2 stroke Seadoo engines but in most or all of the ignition systems there will be a coil behind the flywheel which is independent of the three coils used to charge the battery. This single coil sends a timed high voltage pulse to the CDI ignition module which is the unit where the spark plug wires come from.

The coil is not expensive ($50) but you need a special flywheel puller to get at it. The CDI unit is easy to get to but expensive.

What the choke does unrelated to its role in starting the engine with a richer fuel mix is to lower the pressure in the cylinders by restricting how much air gets into the cylinders. It can make a weak spark problem appear to be a fuel problem.

Get a tach at Northern Tool. About $30. It just has a wire wrapped around the spark plug wire to determine the rpm. Knowing what your rpm's are will be a big help in finding your problem.

Search for "Seadoo Manuals online: in Google and you will find a place to download a shop manual and more for free. A big help in just knowing what parts are called. The stator for example is not part of the ignition system.

Dave p

 

[robert30172robert]

That real did not help me any. I need to know if it could be the stator or the cdi box. or even the rectafier but it is charging the battery so i dont think it is that.

 

[riding high]

I am just assuming that you have checked to make sure that the butterfly valves are opening all the way. I don't mean to question your ability but I have seen this issue before because of mal adjusted cables.:willy_nilly:

 

[robert30172robert]

yes they are opening all the way up. and they are ajusted to the manual (low speed jet)1 1/4 turns out. (High speed jet) 1/4 to 1/2 turn out any mor then that it runs like crap. my personal opinion it has a bad stator plate. and like i said before it runs great from stop to about half throtle. then it does nothing it does not spit or spuder it just wont it just wont gain any more speed. Does any body know how fast these models go?

 

[El Toro 33809]

Does any body know how fast these models go?

The chart I've seen shows 40mph.

 

[riding high]

I agree with you that you should be turning more rpm's. The rev limiter at spec is 6500 +-100. I would hope that Doc or Lou jumps in on this. If they don't, send them a PM. Sometime on the weekend's or if they are real busy they miss some of these post. There are others on here that have a world of knowledge also but those two in particular seem to have a pretty good knowledge of what is going on. Wish I could be more help be it seem like you have covered most of the bases.:banghead:

 

[ocod]

yes they are opening all the way up. and they are ajusted to the manual (low speed jet)1 1/4 turns out. (High speed jet) 1/4 to 1/2 turn out any mor then that it runs like crap. my personal opinion it has a bad stator plate. and like i said before it runs great from stop to about half throtle. then it does nothing it does not spit or spuder it just wont it just wont gain any more speed. Does any body know how fast these models go?

close the HS to zero turns out.

http://www.seadoosource.com/carbreference.html

What do your plugs show?

 

[Dr Honda]

Hummmmmm....................


This thread looks the same as one you just posted the other day. WHY did you copy and paste, to start a new thread??????? It makes it very hard to continue a train of thought, and it clusters up the board. Not to mention... the same questions get asked. SO... don't do it again.

Since the first post on this thread is a copy/paste of the the thread started 3 days ago... I'm locking the other one.


Now that's out of the way....

Did you ever check your RV clearance as I asked? You shouldn't have to ask "What should it be" since you should have the manual if you are working on your engine.


As far as your question above.... about the electrical parts. The answer is... yes it could be any of those parts. BUT... it's highly unlikely that it's the MAG coils, or the CDI. If they are firing to plugs... and you don't have a very bad ignition miss or studder... then they are doing their jobs.


If it's the rectifier... it's an easy thing to test. Just disconnect the red wire, and go for a ride. If it is 100% better... then that's the issue.


If the engine is running smooth, and just wont go past mid RPM's (around 4000 ???) then I would point my finger at the fuel system. And... before you say... "I've check the carbs"... read this.

http://www.seadooforum.com/showthread.php?33643-Even-the-Pro-s-screw-up-once-in-a-while

 

[robert30172robert]

the plugs look great they are burning fine great color. the rv clearance is 0.011 the manual says between 0.010-0.014 so it is within range. and i have pulled the carbs of at least 4 times in the last week and rechecked them. and HSJ is at 1/2 turn out why does it have to be at 0 turns out? what should i consintrate on wene i take the carbs off Again. could it be a week fuel pump maybe it is not getting enough presure for the pop off to work right?

 

[Jimnut]

Can you post a picture of the plugs?

 

[robert30172robert]

here are some pics of the plugs.they look fine but i cant be sure. I dont know if this matters but wene i had the carbs apart i check the jets and the main jet(big one) has 125 stamped into the top of it. I checked the manual and it is supose to be 107.5 jet will that make a differance. something else i did not mention is that it is going trough gas like crazy.