2 stroke missing/no power (Scrambler) Part 2

[PowerTrike]

Bought Polaris Scrambler 250 recently and it ran well once it got started for the first couple times I had it out. Lots of power. However would sometimes die or not start and gas would back up into airbox. Sometimes it would start just fine. :( A few days later it just boggs way down or misses anywere from 1/8 to WOT. Hardly any power or throttle responce at all. Idled fine. Still doing it! Have new plug that shows strong spark when it is pulled. I don't know if it is consistant on the higher revs? Any way to check for an electrical problem or do i have to start replacing parts?

I just tore the carb apart and cleaned it out really good. Now will fire right up first pull and idles as smooth as any 2 stroke could. No gas in airbox. I've had it started like 15 times today and it was consitant. Also washed the airbox out along with cleaning the air filter best I could. The carb itself has a good clean flow of gas. Still the main missing problem is there!

Tested compression as best as I could with a crappy automotive push in tester and it checked out good (90+psi i believe) Head gasket looks like it might have been leaking slightly, tightened head down as tight as I could (seemed a tad loose), no impovement at all. Also took a flashlight and checked the reeds visually the best I could. They look fine to me. Removed the exhaust to check for blockage and found none. I think a little gas is leaking into the bottom end because a little came out when I drained it. Doesn't seem to affect the problem with gas in or out. I wanted to pull the head off but ran out of time. First the whole gas and oil tank has to be completly removed and out of the way before I have room to do that...

Could this have anything to do with the oil injection? Airleak or something?

Please Help! Any help given will be GREATLY appreciated!! Thanks.

[PowerTrike]

Any ideas? Let me know even if they sound stupid. I haven't really worked on 2 strokes much before except for tinkering with sleds...

Plug looks suprisingly normal.

[RideRed250R]

is the spark plug correctly gaped? also u might need to re seel the head with some hi temp gasket sealer, i would mess witht he air/fuel ratio see if it could be leaning out, also check and if it was the oil injecter trailprotrailpro engine would be DONE. theres supposed to be a small amount of fuel in the bottom end for lube
adam

[MTS]

dont use high temp gaslet sealer on a 2 stroke metal head gasket :rolleyes: use a thin film of copper coat or nickel coat, as for the compression, if im not mistaken 90psi is actually very low.....it might be worth the 5 min to pop the head off and see what the piston+jug look like, you never know the oil injector could gone, and in that case you would be toast :cry:

[bigredhead]

you have replaced the plug with a new one right ?

[PowerTrike]

you have replaced the plug with a new one right ?

Correct. Also gap changes didn't help. I guess I am going to have to pull the head off when I get a chance and have a gander. Going to take a lot longer than 5 min on this trike though. Lots of other stuff has to be taken off first. So it still could be a compression/jug problem when it idles fine huh? Almost seems like a timing problem but thats not possible.

Thanks for the ideas. Keep em coming!

[a-camp]

(90 lbs seems low) Compression on my bike is 195-8 205 with other head . I worked on sea doo's for years they ran at 178 lbs . Check you specs. I dont know for that bike

[PowerTrike]

Tested Compression again and read a little over 100psi with a push in tester that doesn't really fit under my frame so I'm not sure if the seal is 100%... I'm pretty sure that stock specs are 130psi.

Head gasket was leaking some. I thought it was blown and I was going to replace it so I tore off the head and cleaned everything really good where the head meets the cylinder. Gasket looked ok so I just reinstalled it and retorqed the head down 25ft lbs each nut and it doesn't seem to be leaking at all anymore. Cylinder looked smooth with no scratches at all. Piston looked fine too!

I'm back to thinking its the damn carb again. I had it running after I put the head back on and it was still missing and running the same. Messed with the carb adjustments a little and it died and now won't start at all again. (Adjustments returned back to how they were.) After pulling it over a long time the plug stays dry. Earlier this week i just pulled it over once with the pullstart at -12* (sitting outside) and it started the very first pull and idled (still was missing top end). When i cleaned the carb I didn't take out the main jet because it looked perfectly clean so I just sprayed some carb cleaner and blew it out with compressed air. I'm pretty sure I took out everything else completly and cleaned the carb very good.
-Could it still be the main jet? I removed/cleaned pilot jet out very good. Starting doesn't have anything to do with the main jet does it?? Sound like a carburation problem to you??

Thanks for any help given!
Nick

[ATCwithdrawals]

you might want to pop off the muffler and see if you can blow air through it, if had been running rich for a while it could of plugged up your spark arrestor inside your muffler.

[PowerTrike]

... Removed the exhaust to check for blockage and found none.

Thanks but I already checked that.

[Howdy]

If this helps at all: I took My wife's Scrambler out Yesterday for a spin. While in the shop it fired up good and run fine ( it was warm in the shop ). Once outside and pulling a sled it seemed to not have the power it had before. It wouldn't idle for crap. Removed the sled and ran it 2/3 throttle and it ran fine. I figure it hates the cold. I will know for sure later this week when it warms up ( mid 40's to low 50's ).
Howdy

[BLAZERONE22]

Our 2 stroke polaris quad did that one time. Turned out the float needle was bad, and it had filled the crankcase up with fuel.

[PowerTrike]

Thanks for all your help guys. I found out what was causing it to miss really bad! Reverse Override/rev limiter went screwy on me! After long hours of tearing stuff apart and cleaning/checking stuff all I had to do was track down a wire and pull it! Searched around a quad forum a little and found someone who had high idle on an old Trailboss and linked it to the override switch so I thought it would be worth a try. "Smokinwrench" said he saw that before also. So I put er back together and had some fun in the snow. Ran like a raped ape. Still think I have a carb problem where it will somtimes start and sometimes won't but I'm happy for now.

Thanks again.

[conig]

I wouldn;t think the override would affect the forward gears, it should only engage the rev limiter in reverse at a point as low as 2/3 throttle. I only ask this since you have a rare trike I would love to have but are you sure, you didn't somehow remove the rev limiter all together did you? it kind of sounds like you did so be careful.

I wanted to remove my reverse override on my 2002 scrambler, with a clutch kit my srammy won;t even move in reverse without pressing it, but was told I would be removing the rev limiter all together if I overrode it so I never bothered. I lack the self control to not blow the motor.

glad you go things worked out to your favor though, just my $0.02

[PowerTrike]

You make a good point. Actually I think that I might have completly disconnected the rev limiter. I tried to stay easy on the throttle while riding today. I plan to hopefully replace whatever went bad so I don't blow the old Fuji. Thanks for the input.