2002 YZ250 bogs at full throttle

[bluesuitah]

I need some help.  Rebuilt top end, just rebuilt entire carb.  Rides great at low (1/4 -1/2) throttle.  Once you pin it it stumbles and bogs right down.  Not an issue for me because I never ride wide out, but would like to get it figured out.  Stock rebuild kit, bike has aftermarket fatty pipe. Inputs please.

[Bulldog5150]

Sounds like it is too rich on top. Drop down a size on the main or 2.

[FORMA MOTO]

Does it die like you pressed the kill button (too lean) or does it die like it's drowning, with a gurgle or a pulsing (too rich)......

[bluesuitah]

Bogs down like its drowning I guess. I tried to attach a video here to no avail. Stock rebuild with 178 main jet, 50 pilot, clip set at 2 per fact specs. I just found a rec online by fmf saying the stock jets are fine, also advised clip at third. I cant imagine it would run that poorly from just that though.

[BrandonCR125]

What ever happened, did you figure out the problem? Having the same issue on my 02 also.

[mlatour]

Old inactive thread since 2013, you might not get a reply from the poster

as his profile shows he hasn't been online as well since August 2013.

Edited September 20, 2018 by mlatour

[BrandonCR125]

That sucks, oh well gonna keep messing with it, we've gone through the carb and everything, seems like a spark issue to me

[mlatour]

Does it bog or, cut out intermittently (like a rev limiter)

[BrandonCR125]

Powerful low to mid but up top it feels as if it's hitting a limiter, doesn't die out just sputters and can't pull anymore

[mlatour]

Perhaps it's running rich or, maybe an ignition issue.

 

How old are the reeds?

Despite no damage or gaps, they do wear out from usage.

Low petal tension allows them to 'flutter' at higher rpms, bad for top end power.

[BrandonCR125]

Feels like up top it starts running rich due to a suspected ignition problem, besides high rpm bog/sputter it runs good, plenty of low end torque and fires right up every time, we just got the bike last week and ended up having to rebuild transmission, also put a new top end too (piston is installed correctly). We suspect the ignition coil might be the problem since the previous owner had the spark plug wire repaired it looks terrible. We didn't inspect the reeds hard, we'll check those after ignition coil. I'll update you on what happens.

Edited September 20, 2018 by BrandonCR125

[ss-racing66]

I had this type of problem on my 99 several years ago, spent countless hours troubleshooting. Turned out the core in the silencer was broken and was restricting the exhaust gasses.something to check.

[BrandonCR125]

THANKS ALOT for the suggestion, I'll check the muffler out!

[Roflawlsauce Yo]

Ever figure it out? Lol, having the same problem Brandon, newly rebuilt motor. Bike won’t idle and dies at full throttle, I’ve checked everything mentioned in this thread