717 engine not running right

[brewersmotorsports]

ok so for starters, i have a 96 seadoo GTI 717. I just put a reman motor in it from SBT and when i first cranked it it was running fin, but then it started to loose power at half throttle and back firing so i did some timing adjusting and it was worst. not i put it back the way it was and was having problems starting it so i changed the brain out and it still dident start, so i switched it back to my old one. Finally got it to start and it idled for about 10 sec then revved wide oven so i pulled the kill switch and it still was running wide open so i jerked the spark plug wires off and i did not shut off. I had to put a rag in the carb to kill it. anyone know what is goin on. It is double carb. I need HELP. i have too much money into this thing now to just give up

 

[Bills86e]

runaway

air leaking in. The rag is a good kill. get it to idle and spray carb cleaner around in a
small squirt at a time. if engine rpm rises, you found the spot. it could be crank seals, RV seal intake, ect ect ect.
Take off flame arrestor screen and Look down venturi to see if fuel is gushing
or dripping. You got the fuel lines connected.....correctly? Supply goes on the bottom and out top. Pulse from engine case goes the mag carb fuel pump.

 

[brewersmotorsports]

would that make it still run wide open even when i pull the spark plugs???

 

[Bills86e]

detonation of carbon or a Glow plugger.

 

[brewersmotorsports]

ok well i will tear it all back down and see what i can find. But i think its just that SBT sent me a ghost motor

 

[Bills86e]

Lines wrong or U need carb re-build, maybe you lost a seal?

If the engine continued to run without the electrical system (i.e. the lanyard was removed), the fuel has to be getting ignited from somewhere. Likely you have some carbon deposits in the combustion chamber that are getting hot enough to ignite the fuel. Carbon deposits are very common in two stroke engines. In addition to rebuilding the carbs, I'd suggest decarboning the engine using your favorite method. You'll likely need to replace the plugs afterward, but you should do that annually anyway. Seafoam is a good product for that, if you can shine a lite down plug hole
and bring piston up, if top is black...Thats carbon. It can burn like a charcoal grill.

Ever hear the term "Glowplugging" the tip of the sparkplug gets red hot and ignites the fuel without electrical imput to the sparkplug.
This happens when the motor runs too lean of an air/fuel mixture. Too much air, not enough fuel. Fuel keeps the combustion temps within a certain safe range. Take away the fuel just a little bit and you have a glowplugging motor that revs to the moon !

 

[seadooya]

think your rotory valve isnt degreed correctly...147*/65*

 

[brewersmotorsports]

now that makes a little more since so ill do a carb rebuild and clean up the cylenders and give that a whirl. Thanks for the info

 

[Bills86e]

front or rear seal missing?

ok well i will tear it all back down and see what i can find. But i think its just that SBT sent me a ghost motor

You won't know to blame them until you can pinpoint the problem.
Did you leak test the shortblock before you put your parts on?
Did you thoroughly test your carbs ect, and torque to Specs?
Investigate on!!!!

 

[seadooya]

its a brand new motor, there aint carbon in it. Need to pull the carbs, verify that the rotory valve is degreed correctly, then re-seal carbs. Double-check the fuel lines, make sure there mounted correctly and to the correct fittings.

 

[brewersmotorsports]

ok thanks will do

 

[Bills86e]

its a brand new motor, there aint carbon in it. Need to pull the carbs, verify that the rotory valve is degreed correctly, then re-seal carbs. Double-check the fuel lines, make sure there mounted correctly and to the correct fittings.

:agree: Thanks

 

[brewersmotorsports]

oh yea just thought of somethin, everyone is saying that its the carbs or somethin sucking aig, its a brand new motor, like at the max 10 min on it, WHY WOULD IT STILL RUN WITH NO SPARK PLUG WIRES ON IT????? there should not be that much carbon in it to run like that

 

[onebadcav00]

air leak will make it run with no spark, happend to me last year. clean the carbs and reseal. it will work.

 

[brewersmotorsports]

ok thanks man