Plug reading

[plane_ben]

What you folks think? To lean, or just right? Maybe the next main jet, or just raise the needle one notch? I'll add that this is on my re-phased stock motor with home built Joe-Wise guy type single carb manifold, 38mm Mikuni VM carb, #180 main jet, #20 pilot jet, 159-P6 needle jet, and P8 needle.

 

[TwoManyXS1Bs]

I don't see anything alarming there. Plug readings are more meaningful when operated at a specific throttle setting for awhile, then do a shutdown, coast to the side of the road, pull plugs, read. If it runs fine now, you could just leave it, or do small incremental changes to get the performance or mileage you're after...

 

[plane_ben]

Went up a size on pilot and main jet. Almost the same look on the plugs as yesterday, but the bike runs ten times smoother and pulls great in 5th gear. Everything the same as above but pilot jet is #22.5, main jet is #190, and readjusted air screw to two turns out.

 

[TwoManyXS1Bs]

Plugs still look fine, longer term riding will tell more.
This is an interesting imbalance/nonsymetrical setup, rephase with unequal length 1-2 manifold. The carb sees 'suck, suck, wait, suck, suck, wait'. Which runner sucks first, short or long? What would happen if this were reversed. I can see where one configuration could help mixture balancing, the other hurt it...

 

[5twins]

You've just learned one of the first rules of jetting - when you think you're right, try the size above and below to make sure. You understand you're not done yet, right?

 

[plane_ben]

Fivetwins. You are right. I ended right back where I started except for the pilot is 22.5 instead of 25.

Tomany. One thing I noticed with this set-up is both plugs look the same. On my stock engine copper with two carbs, the left plug is always way darker. This may be due to the fact that the left cylinder runs cooler on a 180degree crank. Haven't checked the head temp of the re-phased engine yet.

 

[TwoManyXS1Bs]

Did you see bearcat's thread:

http://www.xs650.com/forum/showthread.php?t=27063

 

[plane_ben]

No, I hadn't seen that thread. I read up on Teecat's thread with a joewiseguy manifold.

I didn't have any of the one side rich problems bearcat had.