Scooters - 125 to 300 > Bet & Win 250

B&W 250 will not rev to high rpm

(1/1)

Gbrown:
Hello all! New to the forum.
I'm working on a b&w 250 that will not rev over a couple of thousand rpms.
I've cleaned the carb, and checked the slide diaphragm a few times for holes and tears (none), the carb was actually really clean.
I've adjusted the valves, they had 0 lash.
I tested the tps using an ohm meter, meter moves up and down the range ok, no dead spots.
I pulled the air box intake hose off, and when I put a finger into the throat close to the slide, I can get it to rev to redline!
It seems to point to carb problems but I cannot find anything wrong with the carb.
I connected an external fuel supply to eliminate bad gas and fuel pump.
Bypassed the 2 vacuum lines on the intake manifold.
I sprayed liquid around the intake and carb to check for vacuum leaks, no change in idle or reving.
It seems no matter the circumstance the bike won't rev.
It's as if the timing is not advancing.  I'm going to put a strobe light on it today and see what happens.
Any suggestions in the meantime?
Thanks
G.

doublej:
Pull the airbox apart and look for a mouse house or mouse storage area in there

mrbios:

--- Quote from: Gbrown on March 27, 2015, 03:27:25 PM ---Hello all! New to the forum.
......
It's as if the timing is not advancing.  I'm going to put a strobe light on it today and see what happens.
Any suggestions in the meantime?
Thanks
G.

--- End quote ---

It's not the advance nor the TPS which does almost nothing (TPS does a lot in EFI but has no way to "control" a non-electric carb.  Even zero advance would be minor and not cause what you are experiencing.  My first guess is that the it is a carb problem.  Verify that the main jet is installed and did not unscrew and fall off.  Review my carb videos and perform the "diaphragm test".  Post results.  Also, Year, miles, length of ownership.

Carburetor Cleaning Part I   
Carburetor Cleaning Part II   
Carburetor Cleaning Part III   
 

Gbrown:
I guess the third time cleaning the carb was the charm!  Runs like a champ now.
thanks
Gbrown

mrbios:

--- Quote from: Gbrown on March 31, 2015, 09:38:41 PM ---I guess the third time cleaning the carb was the charm!  Runs like a champ now.
thanks
Gbrown

--- End quote ---

Awesome, thanks for the update.

Navigation

[0] Message Index