Difficult to start when warm!

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Difficult to start when warm!


Post by biker_grunt » Mon Dec 15, 2008 3:20 am

GUys.. I know this one has been covered somewhere, but I couldn't find it on this forum.

My pan starts well when it's cold, but even after just 5 minutes of running it, it's nearly impossible to get started until it cools down most of the way.

Is there a fix for this and/or what causes it?!? Very frustrating as I can't even go gas up or to the store without having to sit there a half an hour before it will start again.

Any input appreciated!

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Re: Difficult to start when warm!


Post by Cotten » Mon Dec 15, 2008 4:07 am


There could be many causes, and perhaps more than one at a time, so the only valid suggestion is to sort them out, one at a time.

(Meaning: Don't change more than one variable at a time, or you may not know what fixed it!)

The odds are that there is a vacuum leak, especially since modern fuels eat common O-rings to shreds, and holes get bigger when they get hot.
A simple test is described at: http://virtualindian.org/11techleaktest.html
Please bubble-test the pan cover screws over each intake port as well, as occasionally they have been perforated into the port.

If your assembly passes the bubbletest with not even a blister of foam after a minute or two, we can go on to the other variables.


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Re: Difficult to start when warm!


Post by FlatHeadSix » Mon Dec 15, 2008 5:14 am


As Cotten pointed out; ZERO intake manifold leakage is the only acceptable condition.

But, before you try anything else, try opening the throttle a little bit more when kicking it after the engine has warmed up a bit. The cold starting procedure in the rider's manual indicates a nearly closed throttle position when starting and it usually works as you mentioned. My bike gave me the same problem, I could never get it to start reliably after it had run a few, or a bunch of miles, until it had cooled off completely. But I was hard-headed and consistently tried to use the nearly closed throttle "cold start" procedure. My bike will start now any time, every time, on one or two kicks when hot, if I open the throttle about 2/3rds open.

try it, let us know how it turns out.


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Re: Difficult to start when warm!


Post by steve_wood » Tue Dec 16, 2008 12:56 am


I'll pile on with what Mike said. Sometimes, with some machines, when you shut down the cylinders get loaded up with fuel/air mixture. Remember, you've killed the spark, but the engine is still turning and it's still sucking in fuel. Then when you go to start it, it's very sensitive to flooding. That's probably why Mike's technique works - opening the throttle adds more oxygen and less fuel!

If Mike's technique works, you could also try this: Open the throttle wide just after you kill the spark. This might reduce the fuel "loading".


PS: The stuff about intake leaks is very important. Even if you fix this problem, you should check for leaks unless you're already 100% certain there aren't any.

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Re: Difficult to start when warm!


Post by sprucecreek » Wed Dec 17, 2008 1:27 am

Throttle half open and my 56 FLH starts hot on the first kick every time :D

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