Lean rear cylinder

[Randy Grein]

There is a jetting differential front to back, can't remember for sure  
which way - but sounds like you need to go up a size on the rear.
Randy Grein, WMRRA #141

On Oct 1, 2009, at 10:04 AM, Ernest Montague wrote:

> My rear cylinder is running super lean for some reason.  The header  
> interior is clean and light grey/white with no carbon. I am running  
> pump gas, which always leaves my headers a bit black.  But the rear  
> is very light colored, the front the normal blackish.  It's not a  
> head gasket leaking water ( at least last time water got in the  
> combustion chamber via head gasket it steam cleaned everything. The  
> chamber just looks lean, valves very clean and grey/tan.  I looked  
> for missing vacumn plug, bad slide rubber, plugged main jet, etc.   
> The mains front and rear are 170s a range that has worked well in  
> the past with the M4 system and BMC big mouth race filter (factory  
> pro design).    Even if it was the main I can't believe it would be  
> so different from front to back.
>
> Also backfires and pops at cruising  2500-4000 rpm.
>
> Bike is mostly ridden at full throttle on the track.
>
> Suggestions?
>
> Ernie
>