One cold cylinder!!!

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Gijoerambo

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Mar 21, 2018
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Hey all,
Newbie here, I just picked up my 1989 v max with v boots with o my 19000kms and in excellent overall condition.

The guy who I bought it off had it since new and rode it very lightly so I know it has had an easy life.
The carbs haven’t been touched for a long time.
The bike starts and runs well and pulls hard. (I’ve had v maxes previously)
The left hand side rear cylinder is running cold..... even after a few minutes at idle you can still touch the bare pipe right at the head.
I thought it might be the pilot circuit being blocked however even with a few high revs and a couple of mins running it still feels cool, I would say 25% the temp of the rest of the cylinders..

I’m hoping this just needs a carb rebuild/balance?
What’s your thoughts guys?
 
Three things you need to check:

1) You have a spark. Something like this would be a good investment.
kcxkxckkcx

2)Check you have good compression or better still do a leak down test.

3)Balance the carbs and add some fuel system cleaner. If you still have issues do The Shotgun and if there are still issues, ultrasonically clean the carb(s)

What you are doing is eliminating possible issues in a logical manner.
IMHO knowing what ISN'T causing the problem is better than GUESSING what it might be.
Hope is a great quality but it often disappoints.
 
Thanks!!
I’ll get the compression readings back.
There was spark there, and I changed out the spark plug so I’ve eliminated that. (Might check for spark strength....?)

I’m keen to try this shotgun method...
I’ll report back.

Thanks again.
 
Quick update,
Compressions on all cylinders seem to be “grouped” welll however they seeem low at 130! However it’s a cheap eBay Chinese gauge and I’m not sure the battery is 100% so I’m not concern about that really as it doesn’t smoke and it pulled like a train. (Probably carboned up due to the previous riding style)

I did cover the air intake boot on the offending cold cylinder briefly and the Revs jams up! Then settled, and the cylinder did seem to get an injection of heat!
I’m guessing that force sucked some fuel through the partially blocked jets and started to run “better”?

I’m going to run a tank of fuel cleaner through it, however is this cylinder going to cause damage in it current “lean” state??
 
Have you tried a technique called a "shotgun". At idle , the pilot jets (also called the A/F jets) are what deliever fuel. If they are blocked, then no fuel will get to the cylinder at idle (and just off idle up to about 4K rpm at part throttle.)
 

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