need help with 50 bogging issue.....ready to break something

[jplltz50]

Got an issue that is really making me angry. Our 08 drr 50 . During a ride it will leave good once. The bike is a rocket wide open but if you let off the throttle and get back on it it will bog for about 10 feet then take off again. Also it will not launch again without rolling 10 feet first. I'm out of ideas. This is what I've done:
New top end 140 psi
New crank seals
Passed leak test cold
Changed coil/cdi.
New variator/ rollers 3.0 & 3.25 mixed
Tried 3 different t springs;
Koso 1500
Hebo red
Ztr 1500
cleaned all grounds have dedicated ground from engine to frame
Fuel filter is new

[jerkyboy]

Need more info. Is this a limitted or a production 50?
Could be a jetting issue but not likely. Sound like its not down shifting fast enough. Make sure rear pully is working smoothly.
Try all 3.0 rollers/ raise the stall / shim variator. I use to run 2.3 and 2.5 rollers in our 50 stall around 7600.

[Christiansdad]

Put it on a stand or block..fire it up and hold throttle for five min wide open..show no mercey it cost usually 500-700 for new crank and topend...you can ask my brother about that. You said it has to move 10 feet foward then stop then goes pretty good or has roll out 10 feet then launches.

[EthansDad]

what Jerky said is the important Q. the 08 limited with that 16m carb and 1 piece pipe is hard to mess up. I'm guessing you've mod'd it up to a production 50.

depending on what pipe and carb you have, my best guess without more info is you've got the pilot circuit or needle jet circuit off. I've seen this a bunch of times, and yes, it does act like a CVT issue - dead on bottom, then hits the main jet and rips.

Other bigger bikes are more forgiving if your jetting is off down low, but the little 50s just sit down in a hole if they can't make power on the pilot.

If you give more info like cylinder, pipe, carb, ignition, I'm sure the folks can help point you in the right setup direction.

-EA

[jplltz50]

Thanks everyone I actually found the problem in the rear pulley like Dale Raven said , the rear pulley was binding when the belt was all the way in and coming back out........but it doesn't matter right now because Saturdays first moto we blew the top end. I pulled it apart and have no idea what caused it. Missing half the rings top and bottom facing exhaust port but no real sign of rings catching the port.

2 fridays ago build top end.....motor ran awesome all last week pulled really hard midrange and on top, Saturday practice went well , first moto nice holeshot leading half lap and boom........insert profanity here......spend overtime check on parts and do it all over.....f'ing mini quads....I must have done something horrible in a past life

[selbygirl]

a few years back we had a bike with low compresion in between motos.... so i did a parking lot topend rebuild job it only lasted one moto and blew the piston ring,... my guess i didnt lubercate it well enough when i put it back together.. now when i put a motor together i use a ton of two stroke oil on all the internall parts .... check your pipe and see if you have eny junk in there.. that may get sucked up in your motor ...and does your piston have the little pin in it where the ring meets each other

[Christiansdad]

Same thing happen to me....Brand new cylinder kit and didnt run right after the first moto..the second moto it was spitting taking of the line then finally we loaded it up..thought i maybe had it jetted wrong or somthing..i played around for two weeks jetting it(first timer) got it in the right range..the next race came up..drove almost 2 hours..practiced once..checked the plug for the right color..good..leaving for the first moto..shut off..snapped a 1/4 or so from where the ring seats in the groove.bought another ring been runnin hard for 6 or 7 months now...if i had to do it again...i'll just buy the drr 50 ethansad has.

[EthansDad]

if i had to do it again...i'll just buy the drr 50 ethansad has.

sold it day 1 at LL, the guy rolled it back to his trailer after moto 2. nice family and great kid. we might see the ole red and white back in action again next year....

[coffing918]

JJs 50 did the same thing at the last 3 nationals! no more 50s and no more CVTs for JJ