Eton 90r 2stroke
Everything installed:
Hetricks -Bkit with everything that is included
-52mm port & polished cyl.
-Tether kill
The Problem
Son was racing at Lorretta Lynn's GNCC and obviously went thru some mud/water and also he said, had it roll over 1-2 times in the woods. ran 2.5laps and then started sputtering and then slowed down and let out a big puff of white smoke and then died and wouldn't restart. after getting it home I cleaned up the carb/jets/ports full clean job, no dirt in reed cage area. started right up but wouldn't rev strong past about 3/4 to full throttle sitting in neutral or under load. it revs then cuts out quickly then back into rev. almost like a soft rev limiter.
Here is a list of all I have tried

checked comp- 90-95 with carbon fiber reeds, 115 with fiberglass reeds
honed cylinder to put cross hatch back in it
cleaned carb/ports/internal parts 3 times & Air filter
rejetted up and down
changed out with new stator & coil
removed Hetrick spark box used just Stock CDI
removed Stock CDI used just Hetrick box
checked with inline spark test that you hold on outside of plug wire- checked at all different rev areas
cleaned and regreased elec connections
checked kill switches
bypassed kill switches
bypassed all electrical from stock wiring harness that i knew of
ran extra grounds to coil and engine
Sprayed carb cleaner around seals,cyl., carb/intake, no rev up's.
checked float to see if running out of fuel
Installed new Crank, connecting rod was loose, and Bearings and seals

Is there a bank angle sensor in these that maybe was tripped and has not reset?
I am pulling my hair out!!! Please help.
Thank you!

 

Sound similar to what happen to me and it was the gas tank, the vent on the tank had plugged and also the delivery hose had a kink in it. Looks like you have covered everything else.

 

I have used a fuel bottle to eliminate the tank and pet ****

 

In its simplest sense any motor is just a big air pump. With all that you have checked and done - this is going to be some odd-ball thing.

How about something on the air intake side that at high RPM doesn't let air thru; collapsing rubber tube to air filter, collapsing air filter, etc.

OR, something on the exhaust side; inner lining collapsed on exhaust pipe (don't think that I am crazy - had it happen once on a car; outwardly the exhaust pipe looked great, but internally it had collapsed to only 40% !!??!! ). Something internally blocking the muffler.

Sorry, that's all I have. Good Luck - eventually you'll find it ( or in the 'Institution', you won't care)!!!

 

I have to say that I am stumped, I did copy and paste and email it to my engine builder to see if he has an idea. If you figure it out let us know

 

Hey, no, anything is a good thought at this point! Like the Teach said in school to all the class " No answer is a bad answer!"

I have blowen out the exhaust with compressed air. Although there is not much to worry about there because Hetrick's pipe is a true fatty pipe so you would see any dents and no internal walls that you can't see.
changed intakes with no avail either.
This sucks!
bout to take out to Penn. to Hetricks
look forward to hearing about any other thoughts!
Thanks!!!

 

first thing is that your compression is low expecially for a race quad. you need to check the squish which is the distance from the top of the piston to the head at tdc. even though you have a hetrick ported cylinder it could be too tall and need to be decked. i have built these race motors for years and have seen cylinders bought from the same manufacture have a difference of 2 to 3mm in total height. your compression needs to be in the 150 to 180 range for a high performance motor.

Mark

 

are you saying that that could change in the middle of a race? Everything was running fine at breakin and 2 laps into the race then it started acting like this.