Only running on one cylinder. Help.

[CoastsideXS650]

Bike is a 1980 special with a 1977 motor.

Motor is a 277 rephase running BS34 carbs and using the stock wiring harness from the 1980 bike. Pamco ignition and a PMA from Hugh as well.

The bike is not running on the left cylinder. It ran fine a few days ago then I took off the exhaust to seal the mufflers. It is popping and running like shit now. So I started with the basics.

Checked for spark. There is spark at the plug.

Checked the carbs by swapping with another working set I have. Still same problem. I doubt very much that both sets of carbs are not working properly (The test carbs run flawlessly).

I checked the valves and clearances are not way off. (I didn't check with a feeler gauge as motor was hot but it felt about where it should be so Im not worried)

I am stumped as to what is not working here. I don't think its a compression issue but right now Im not sure. I do not have a compression tester but I also don't think its a lack of compression. The motor probably has less than 100 miles on it after a top end rebuild and everything seemed to be working just fine.

Anyone have any ideas?

 

[pamcopete]

Coastside...,

Spark plugs?

 

[CoastsideXS650]

Coastside...,

Spark plugs?

Its funny you mention that. I checked for spark at that plug and it was firing just fine. So I thought I was clear of that problem.

After you so bluntly repeated "Spark plugs"? I realized that I never put new plugs in just to see what happens.

So I put new plugs in and it fired right up no problem. Its funny how it is almost the simplest things. Thanks for the kick in the ass Pete.

 

[tonyc]

Always do the easiest most inexpensive item first.