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Old 04-17-2017, 03:44 PM   #1
fastfiat
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Default Panhead Vibration




My 53 pan has excessive vibration at anything above about 2500 rpm. Bad enough that there is no its going down the freeway with out beating its self to death. So i started with a basket motor. The left side case was in such poor condition i replaced it with a Cycle Works left side. Phil at Cycle Works assembled the bottom end honing,reaming,bushing etc everything needed to make sure all was correct with the lower end including end play and truing. I assembled the rest of the motor and after the first ride the vibration was excessive so i pulled the lower end apart to have the balance checked. Dont no what the balance was but it needed 25 grams taken out to get to 60 percent factor. Put it back together and still the vibration persist. Other things ive checked are motor mounts, frame cracks, compression 170 front,170 rear, clutch hub run-out within 5 thou, engine pulley 2 thou, intake pressure checked, Andrews J cam. Motor is 74 inch. Flywheels are T&O. Bike is ridged long bike. Vibration is rpm related not speed so wheel balance is not a factor. Any and all input is much appreciated. Thanks. Also all paint was cleaned from motor mount surfaces and shimmed as needed. .010 shim under both front mounts.
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Old 04-18-2017, 12:39 AM   #2
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Default Re: Panhead Vibration

If balance was done wrong first time around how do you know the crank was trued properly? Maybe a wobbly crank?

Have had motors that vibrated a lot until properly jetted and or timed correctly.
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Old 04-18-2017, 01:20 AM   #3
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Default Re: Panhead Vibration

Balance was not checked the first time but wheels were checked for true and were within .001. Motor was then assembled and vibrated from initial fire up. I then pulled the flywheels out and had the balance work done. It was about 25 grams heavy for the 60 percent balance factor i wanted. So balanced, trued and back together with no appreciable difference to the way the bike feels. I can put around town but no way its going on the freeway. Thanks
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Old 04-18-2017, 08:17 AM   #4
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Default Re: Panhead Vibration

I'm no Harley expert but I do know for any bike the frame is a factor with vibration. Longer thinner non trussed tubes can enhance vibration.....Have you ridden a stock frame Pan or Shovel? How does the vibration compare to your bike?
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Old 04-18-2017, 09:13 AM   #5
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Default Re: Panhead Vibration

All my other bikes are swingers. This is the first ridged i have built or road so maybe thats just the way it is. The vibration just feels excessive to me. I think my next move is to have some other guys ride it and get there feed back. Thanks
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Old 04-18-2017, 12:31 PM   #6
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Default Re: Panhead Vibration

I've had a similar thing going on with a triumph
Gradually getting to the bottom of it
but was a combination of components vibrating at a certain rpm
tank, engine mounts , chain...
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Old 04-18-2017, 04:37 PM   #7
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Default Re: Panhead Vibration

My rigid is smooth up to about 105mph. I have a six speed so it's not a great comparison but sounds like something is up with your bike.

It vibrated more when I first got it on the road but came to find out my timing was slightly retarded. Small change and it smoothed right out.

Have a triumph that if I go one jet size bigger is unridable due to vibration. Proper jet and it's super smooth.
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Old 04-18-2017, 05:31 PM   #8
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Default Re: Panhead Vibration

My pan does vibrate but not to that level!

It's definitely something causing that!
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Old 04-18-2017, 08:40 PM   #9
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Default Re: Panhead Vibration

So i had two guys ride it today and there is definitely something wrong with the bike. So i will swap the trans and belt drive for a known good unit and see what that does. If there is still a problem then ill put my shovel motor in and see what that does. One way or another ill get to the bottom of this. Thanks everyone for your input. I will post updates.
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Old 04-19-2017, 04:32 PM   #10
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Default Re: Panhead Vibration

I would like to see that top motor mount, and how long it is. A top motor mount, will make them vibrate like your old ladies best friend.
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Old 04-19-2017, 04:44 PM   #11
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Old 04-19-2017, 04:45 PM   #12
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Old 04-19-2017, 04:49 PM   #13
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Default Re: Panhead Vibration

Rode it a bit with a ratty shovel motor without the problems i have now.
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Old 04-19-2017, 04:52 PM   #14
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https://youtu.be/z_Tp6BJOq4A
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Old 04-19-2017, 08:13 PM   #15
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Default Re: Panhead Vibration

If you ran that frame, with another motor, and had no vibrations, then it is something in the pan motor doing the vibrating. Not like you did not say that to start with. Unless there were other changes, other than cosmetics. I have had Phil at Cycle works do work for me as well, and I found him to be abrupt, but expert at his work, so it would amaze me, to find that he built it wrong. But, as I have been doing this for many years too, we all make mistakes. Who did the balance, and was it someone with serious experience? Or a shop, that just threw someone in there to make a show?

Usually, if the vibration is bad enough to shake you to death at highway speeds, it will also shake at idle, and mid range too, to a point. But, I have never seen one, that shook that bad, but only at faster speeds. But, that makes no sense, unless something is loose, and that usually results in engine failure, not just vibration.

I chased one, a few years ago. Basically the same, but this one vibrated at most engine speeds. Recently rebuilt, so that clued me in to look internally. Used a bore camera, and noticed that there were two different pistons, and both were also different sizes. .020 on one, and .040 on the other. Now, it would not seem that a small amount of difference would shake that bad. But, the pistons were not equal in compression, or weight. He ended up just getting new cylinders and pistons, and it cured it, perfectly. This is not your problem, but it is how some people get rid of a problem, with the least amount of money spent. Other than the pistons, and the shake, the bike was pretty decent runner, after the new ones were in.
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69 XLH
68 XLCH *project*
66 FLH *Daily Rider*
66 Shovel/Pan/Pan
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60 XLCH Doc Dytch*project*
51 FL *project*
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Old 04-19-2017, 08:26 PM   #16
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Default Re: Panhead Vibration

I spoke with Phil today and im going to take the motor down there tomorrow to go over everything with a fine tooth comb. When pulling the motor today everything was as it should be. Mounts all tight, clutch drum, motor pulley etc were all good so i really hope Phil can find something in the motor. Thanks for your input. I will update when i no something.
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