idle and top end speed rpm

[Curtbutler]

hi guys,

ok so i thought i had a compression problem but then i found out my tester was lieing, im at 149 on each cylider. so my problem is it ildes, but then slowly looses rpm till you give it a little gas to jump it back u. and at half throttle its alll good but from half to WOT there is only a 5mph increase and goes from like 6300 to 6600 rpm. i changed plugs and ran it for a half hour and they were pretty black after that short time. WHATS GOING ON? is it a simple carb adjustment?

 

[Dr Honda]

2-stroke engines will make the plugs black. So... without seeing them... it's hard to say. BUT... the running issues, are... issues.

Here's the list:

1) Do you still have tempo fuel hoses?
2) Are we sure the second gauge is reading compression right?
3) The carbs need a cleaning.



OK... the idle sounds like it's loading up, and the top end is low. The typical, top RPM on the 720 engine should be closer to 6800 RPM. Your low RPM could be from:

1) a choke that isn't open all the way.
2) Plugged flame arestor.
3) Miss-adjusted throttle cable, and they just aren't opening all the way.
4) Wrong jetting, or needle settings.


The stumbling idle can be:

1) High clearance in the rotary valve. (but that also causes hard starts)
2) Low Pop-off
3) Low needle miss-adjusted.
4) low idle. (should be 1500 in the water)

 

[Curtbutler]

ok so yes i just replaced the fuel lines thats when i started haveing problems, so fuel lines are good, i tryed cleaning the carbs but the two screws that you have to take out to get at 2 of the 3 jets i cant get out, i tried and almost stripped them. the second compresion test was done at a local seadoo service dealer. so it is correct.

 

[RebuiltSeadooBaffles]

ok so yes i just replaced the fuel lines thats when i started haveing problems, so fuel lines are good, i tryed cleaning the carbs but the two screws that you have to take out to get at 2 of the 3 jets i cant get out, i tried and almost stripped them. the second compresion test was done at a local seadoo service dealer. so it is correct.

The carbs need to be taken completly apart and completly cleaned, try to get those screws out. Either way I would not ride it till the carbs have been gone through, pop off set and screws adjusted properly. A lean condition will blow a motor.

 

[Curtbutler]

the plugs look like they are rich, very black after a half hour of rideing