Running on front cylinder only

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kell
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Running on front cylinder only

#1

Post by kell »

If a panhead has spark and 95 psi compression in both cylinders, what could cause it to run only on the front cylinder?
Cotten
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Re: Running on front cylinder only

#2

Post by Cotten »

You mean besides an Evil Manifold Leak?
DuoDave
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Re: Running on front cylinder only

#3

Post by DuoDave »

I have had this problem. Turned out that one of the pushrod lock nuts had loosened off and the pusrod adjuster had screwed itself in so the valve would not open. Haggis encountered the same thing recently. I've heard that a spark plug can test okay in the open, but when screwed back into the motor will fail under compression. I have not come across this, but worth trying a new plug if you have not already done so.
kell
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Re: Running on front cylinder only

#4

Post by kell »

I had to leave the bike in a small-town bike shop a day's ride away. That was a week ago, I called today and they said it's ready. Will post what I learn.
Jonderson
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Re: Running on front cylinder only

#5

Post by Jonderson »

I have also had the pushrod locknut problem. Didn't think much of it, and thought it was a flukey thing. Perhaps I ought to rethink that now.
Cotton, have you seen a lot of this?
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Re: Running on front cylinder only

#6

Post by Cotten »

Uh,...no.

Normally, the adjustors are a very dependable and stable design, unless abused.
I've seen bent rods, broken rods, lotsa knarfed lock nuts and threads from over-tightening, etc.,...but otherwise, the only times I have seen rods drastically go out of adjustment was when fresh motors would beat a valve into a poorly cut seat, thus tightening the rod to where a valve would hang open; the opposite of what has been described.
Unless a valve is sticking or something gets under the valve, it is hard to think of a way it would loosen.
Beware of '48, maybe '49 rockerarms that had cups that would loosen.
panheadron
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Re: Running on front cylinder only

#7

Post by panheadron »

Check for spark . Swap the spark plug wires at the coil. You may now find the rear not firing. Swap the plugs?
58flh
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Re: Running on front cylinder only

#8

Post by 58flh »

GUYS doesent anybody use glypt on yer screws?-Never should a pushrod scrw itself up the tube!If yer running solids there are things to handle that POUNDING over & over--HYD are SWEET!,But im a solid tappet runner,always have been,just like to have things my way & I know about it.---spend time & pop the tubes watch the movement up & down put tubes on CORKS OLNY!--Have fun yer lucky thats all that happened!-(10 min of pleasure looking at pushrods go).& No mishaps in the back of your mind!---respectfuly----RICHIE
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