More like its been set up rich to compensate and it didn't fix the issue....some bikes go years with this fault undiagnosed. I fixed a Sporty a coupla months back, it had been carb farting and back firing for 4 years (during which time it had 3 different owners and many changes of jets) until I changed the manifold rubbers

 

What happens to many (carbed bikes) is that as the air leak progresses you compensate with the choke. The cylinder that still has a good seal then blackens the plug (with choking compensation) and the bad cylinder fires better due to the richer fuel supply from using the choke. It's the only way to compensate for the leak and of course it gets worse.

There is an upgrade (aftermarket) of a different designed intake that is all solid and can improve air flow.

That's IF it fails the leak test.

You could have a carb someone has already tampered with (changed adjustments or jets). I hope not for your sake. With several metering jets, 2 or 3 ways an idle can be adjusted wrong, and in some cases parts may have been swapped out to improve performance, it can be tough to get it set right without knowing precisely what your doing.

 

I have never really found Keihin carbys, either butterfly or CV that hard to adjust.....its no biggie, just chuck in the standard jets as per the manual and go up from there until its right.

 

I realize that you are a master at working on bikes but speaking for those of us who comaritavley know absolutley nothing about motorcycles the fuel/air mixture screw on a kehin is a PITA to get to which is why I switched to an S&S. If there was a trick to getting to the fuel/air mixture screw on a kehin I ain't smart enough to figgure it out.

No scarcasm here just an observation.

 

The trick is to make a tool to fit....I ground down a screw driver and sawed the handle in half :-)

 

Figgures it would be something as simple as that.
Thanks for the trick.

 

Johnny, The solid manifolds aren't that good, as the cylinders expand, they can't move and adjust so they tend to leak. The reason the manifold on the V-twins are designed the way they are is to allow the rubber seals to move slightly when the cylinders grow. That's what causes leaks in a seal that worked for years. They wear out!!! Hope this helps.

 

All this info is good stuff. I suspect I 'll be going thru this soon, 90 fxrs-sp. Love reading this stuff, hope I can find it when I need it. Great board!!!

 

You can subscribe to threads so you don't lose them.

 

Just want to thank all of you for your replys and knowledge.

Thanks again
MICK!