mystery problem

[matt79]

my friends 96 HX 718 rotax has had the motor rebuilt. We have taken it out 4 times and it has run well for about half an hour each time but then just starts running rough like its on one cylinder then just stops. when we try to restart it. it sometimes runs but very rough and at full throttle it only puts along. By the time we get home to flush it, it runs perfectly on the trailer.

the second time we found the two one-way valves off the fuel tank that are supposed to oppose each other, were facing the same way. we fixed that but it still breaks down.

sometimes when you open the fuel cap there is a pressure release or vaccum sound. we have replaced most of the grey fuel lines, the tank and filter have been cleaned out and it has new fuel. there is spark when we test it.

he is running out of patience. please help

 

[nswillin]

Hey Matt. Sorry about your troubles. Main thing in rebuilding these engines is proper break in, and finding the cause of the rebuild in the first place.

Break in is key after a rebuild, if the engine gets too hot too quick it will break again soon.

I'd say with it being a 96 and it had been run with the gray lines for that long, I carb rebuild is what you need. There are small filters inside the carbs that will clog up and not allow fuel into the cylinders and will cause it to die and sputter away like you said.

 

[matt79]

thanks for the reply. the cause of the original rebuild was a blown big end. pieces of the bearing jammed the rotary valve and caused the RV drive cog to strip. that part is all fixed.

Will run a carbi kit through it and hopefully that will do the job.

thanks again

 

[seadoo-owner]

Yes Clean your carbs out
had same problem on 95 XP ran great for while then rough as hell
little fuel filters inside the carbs were partly blocked restricting fuel flow

dead easy to to fix


See seadoosnipes carb sticky here on the forum for how to
http://seadooforum.com/showthread.php?t=5563

 

[Nate Surveyor]

:agree: with the others. And if you still have the gray fuel lines, they will continue to disintegrate into the fuel, and will re-clog the filters.

These motors really like their fuel, and anything that clogs the fuel system, will make an unhappy motor!

Nate