Spits and Sputters as Powerband Comes on...

[Stinger]

While my Banshee is not rideable, I've been riding my RM125 dirtbike. It developed a small sputter at powerband onset that has now turned into a refusal to accelerate over about 4 grand. It spits, sputters, backfires through the intake, etc. unless you let off the throttle some.

 

Engine only has about 15 hours on a complete rebuild top and lower end. I've pulled the carb and cleaned it out twice as I thought it seemed like there was a chunk of crap plugging the main jet at times. No change. Checked the reeds and they are fine. Compression in 157psi cold.

 

It also has a strange smell once it warms up...I can't even figure out how to describe it.

 

Any ideas?

[pimp559]

While my Banshee is not rideable, I've been riding my RM125 dirtbike.  It developed a small sputter at powerband onset that has now turned into a refusal to accelerate over about 4 grand.  It spits, sputters, backfires through the intake, etc. unless you let off the throttle some.

 

Engine only has about 15 hours on a complete rebuild top and lower end.  I've pulled the carb and cleaned it out twice as I thought it seemed like there was a chunk of crap plugging the main jet at times.  No change.  Checked the reeds and they are fine.    Compression in 157psi cold. 

 

It also has a strange smell once it warms up...I can't even figure out how to describe it.

 

Any ideas?

371803[/snapback]

Maybe a half way plugged up pipe or silencer or maybe your powervalve needs cleaned.

[race-a-holic]

Do you think it may be running a little lean?Sounds like it might be to me.

[Stinger]

My buddies powervalve got stuck shut and it just didn't pull hard up top...still ran fine.

 

It does "act" like it's running lean (because of the backfiring and such) but the plug doesn't show it, nor does the carb show any reason why it would be lean.

[bigboybanshee]

I always thought that spitting and sputtering meant that it was rich What does your plug look like? You said it didn't look lean, does it look like it could be rich? If it's not your jetting, I would start looking at the electrics of the bike. Check all the wires, make sure they have solid connections and nothing grounding out. Also, check your air filter....if it's pretty dirty, it would cause it to do this too. If you run an outerwear, make sure it's clean as well and not clogged with oil or anything from the filter

[Guest turbodohc20]

I had same problem on my shee, was CDI unit.

[rriggs]

when was the last time you washed it?....check the stator cover gasket...rm 250 was doing the same thing....pulled off the stator cover and water came pouring out