Left side not firing all of a sudden, but has good spark.

[Rip_ride]

Hey there. So after letting my XS sit for a week in the garage, I started her up to find that the left side wasn't firing. Checked the spark and it was good. Thought it might be the carbs so I pulled them out, gave em a good clean and re-installed. Same problem, have spark but no fire. Strapped on the sync gauges and I'm getting a reading so somethings getting through. Left pipe isn't completely cold but almost. What's the deal here, both sides were firing fine a week ago, then all of a sudden I loose the left? Can anyone gimme a clue?

Thanks,

 

[littlebill31]

Does this happen with the choke on? Off? Is fuel getting in the bowls?

 

[jayel]

put in a new plug, a plug can fail to fire under compression and throw good spark out in the open...
a old timers ( ir1) trick is to pull the non firing sides spark plug cap about a 1/4" off the plug while running, it may start firing cleaning the fouled plug as it gets warmed up

 

[scharny61]

Hey there. So after letting my XS sit for a week in the garage, I started her up to find that the left side wasn't firing. Checked the spark and it was good. Thought it might be the carbs so I pulled them out, gave em a good clean and re-installed. Same problem, have spark but no fire. Strapped on the sync gauges and I'm getting a reading so somethings getting through. Left pipe isn't completely cold but almost. What's the deal here, both sides were firing fine a week ago, then all of a sudden I loose the left? Can anyone gimme a clue?

Thanks,

I've had a similar problem in the past with my Honda CB450 twin. Turned out to be my float needed adjusting. No fuel to that cylinder. Could be a bit of gunk in the float jet. Remove the float bowl and check there's fuel in it.

 

[Visegrippe]

i second changing the plug, have had brand new plugs refuse to fire under compression, but seemed fine in the open air. always the last thing you check, too

 

[pamcopete]

Rip...,

What is the year / model of your bike and what ignition system are you running?

 

[Daniel Wojahn]

That is strange that we are all experiencing the same problem! When I noticed mine, I pulled the plug and it was soaked! I figured it fouled for whatever reason and burned it off with the torch, then cleaned and re-checked the gap. Checked and had good blue spark when grounded so I knew the coil and the plug were good. re-installed it and again only the right side fired and idled on one cylinder. repeated the entire procedure and finally got it to fire with a lot of smoke coming from the left side until it burned it out. So Im stumped.

 

[gggGary]

If you have the stock vacuum petcock check for a torn petcock diaphragm. It will let a bunch of raw fuel into the LH cylinder through the vacuum line. That and float valves are common issues has the gas tank/petcock(s) ever been cleaned? New fuel lines?

What carbs do you have?