Running on one cylinder

[Barry]

We had quite a nice sunny afternoon here today so I thought I'd have a decent ride on the bike to get the oil properly warm. It started on the button as usual but then began intermittently running on one cylinder which is most unusual especially as I've used the bike for work every day this week and it's been fine. I pressed on for a few miles as you do and the duff cylinder eventually chimed in OK.  Then a few miles more off it went again so I thought it would be wise to turn for home as an R45 is a bit slow on one cylinder and I was getting in the way of other traffic. A few miles from home it started running perfectly again which was kind of annoying as the ride was curtailed and now I'm not easily going know for sure what the cause was. The plug looks dry and perfect colour so it must have been lack of fuel rather than lack of spark.  It'll have to wait a day or so before dropping the bowl off the carb and pulling the jets as I expect it'll be frowned upon if I venture into the garage tomorrow.

Merry Christmas to everyone even if you don't get to tinker with the bike.

[Luca]

I'm willing to bet that a few good minutes of running would bring a wet plug back to looking normal.

If the jets look good I'd consider having a look at the plug caps.  Those resistor type bits can fail and cause headaches, and they're not too expensive to replace.

[clonmore1]

Hope you get that fixed Barry, probably good timing with the Xmas period giving you time to fix it.

I shall be in the garage attacking the handlebar switchgear and getting the bodywork ready for paint over the holidays, looking forward to spending some time not working and doing all the little jobs ready for the final push to completion...

[montmil]

A bit of junk in the fuel line to the offending Bing? Intermittent interruption of fuel flow?

[mrclubike]

 The worse thing is trying to fix something that isn't broke.
Been there way to many times  

[montmil]

Swap the spark plug leads. Could be a failing plug cap, HT lead or, if you have twin coils, a coil breaking down. Gotta be something simple.

[Barry]

Swap the spark plug leads. Could be a failing plug cap, HT lead or, if you have twin coils, a coil breaking down. Gotta be something simple.

Should have tried swapping the leads while I was out on the ride Monte because I knew which cylinder wasn't firing from it's cool temperature. I have a couple of spare plugs with really wide gaps which I can put in the caps and crank it as a test to see how the sparks look.  

[Barry]

Sparks were nice and blue on the spare plugs with 80 thou gaps.

Got around to dropping the carb bowls this morning and it was water. Some in both carbs but half a teaspoon fell out when I removed the main jet holder on the side that had been playing up.  This is condensate from the breather as there was no evidence of water in the bowls. I think the state of the air inlet elbows confirm it was condensate.  I'm not sure I've seen them this bad although I usually have to clean the carbs once every winter. It's the inevitable result of short runs that don't get the oil hot enough.  

Another nice sunny day so I'm just back from a 25 mile ride to heat the oil after which I removed the dipstick to let it breath. It ran like a dream of course so problem solved.

[montmil]

...I removed the dipstick to let it breath.

You draining carbs or a wine bottle?
Glad you got it sorted. Airhead simple, as usual. Yea us!

[Barry]

You draining carbs or a wine bottle?

Been doing some of that too