Piston Weights
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Road Captain
Joined: Sep 2012
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From: Mo
Piston Weights
I did a 107 BB on my 2013 Electra Glide over the winter and once I started riding it, I noticed a vibration. So far I have replaced about every rubber part on it. Made sure the exhaust/mufflers were not hitting anything, replaced the rubber muffler mounts and made sure that the mufflers were aligned perfectly so they didn't bind in the rubber mounts. I even replaced the front motor mount rubbers. I also tried a couple of different tunes that had slightly different timing curves. Both tunes were Auto Tuned as I have the PV with Target Tune. I installed a new Screaming Eagle compensator, which made no change. I rode the bike yesterday for a couple of hundred miles and it was miserable... The floorboards vibrate badly and the hiway pegs on the crash bar vibrate way more than they ever did. I can pull in the clutch at speed and the vibration goes away. I can rev up the engine in neutral and get the same vibration. It's definitely in the engine. The bike was fine last year and I have owned the bike since new. Right now other than a short ride, it is basically un-rideable. When I built the engine this winter, I checked the runout on the crank the pinion side was .0015. So my question what is the weight of a stock 103 piston, rings, pin, circlips compared to a Wiseco 10.5:1 piston? Just trying to figure out my next step....
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Joined: Jun 2006
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From: san antonio
HD pistons are typically heavier than aftermarket. I learned the hard way experiencing a similar situation. All bore 107; crank trued and balance by Darkhorse; JE forged 4.125" pistons. Cylinders would not hold a straight bore and damaged pistons could not be reused. Cylinders and pistons were replaced; pistons were CP. JE piston assembly weighed 656g compared to CP at 540g. Bike vibrated badly up and down the rpm range from about 2200rpms to near 3000rpms and was unrideable. Took me a while to figure out the differnce in piston weight was throwing the crank balance off. I was able to re-fit a set of JE pistons and the problem was solved; motor was returned to balance and very smooth.
Don't know what a TC 103 stock piston is but a stock TC88 piston, rings, pin and clips weighs 593.5g, so I suspect a stock 103 piston is a bit heavier. A 3.938", CP forged piston with a 6cc dome weighs 544g but don't know how that compared to the weight of a Wiseco 10.5:1 piston weighs. Lighter pistons will throw the crank balance off and some say it takes a 100g variance to be a problem. However, after talking to John Dahmer at Darkhorse, we came to the conlusion that a 10% weight difference (lighter) would throw crank balance off; the lighter the piston, the worse the problem.
Perhaps another forum member has a set of stock 103 pistons on the shelf; someone that recently went to 107? They could weigh the piston, rings, pin and clips for you and you can call Wiseco for the weight of their 10.5:1 piston and you will know the weight variance and can move forward with next step.
Don't know what a TC 103 stock piston is but a stock TC88 piston, rings, pin and clips weighs 593.5g, so I suspect a stock 103 piston is a bit heavier. A 3.938", CP forged piston with a 6cc dome weighs 544g but don't know how that compared to the weight of a Wiseco 10.5:1 piston weighs. Lighter pistons will throw the crank balance off and some say it takes a 100g variance to be a problem. However, after talking to John Dahmer at Darkhorse, we came to the conlusion that a 10% weight difference (lighter) would throw crank balance off; the lighter the piston, the worse the problem.
Perhaps another forum member has a set of stock 103 pistons on the shelf; someone that recently went to 107? They could weigh the piston, rings, pin and clips for you and you can call Wiseco for the weight of their 10.5:1 piston and you will know the weight variance and can move forward with next step.
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Road Captain
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From: Mo
Don, Thanks for the input. Sure appears that I will be taking it apart again. At first I thought I could live with it until next winter but I cant stand to ride it. It would be nice to figure out ahead of time what I need to do piston wise to fix it. Unfortunately I threw out the old pistons so that's why I was asking. If these Wiseco's are lighter then it might be difficult to get the weight right short of changing wristpin weight....
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Joined: Oct 2019
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From: OH
I replaced stock 88" with CP 98" 3cc dome without issue
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From: san antonio
Stock TC88 piston assy = 593g
CP 98" 6cc dome piston assy = 554g
Crank balance might have been OK but I replaced the CP piston pin with a thicker wall pin to bring the CP weight up to 599.5g; not taking any chances after the previous experience with lighter pistons.
CP 98" 6cc dome piston assy = 554g
Crank balance might have been OK but I replaced the CP piston pin with a thicker wall pin to bring the CP weight up to 599.5g; not taking any chances after the previous experience with lighter pistons.
HDF Community Team
Joined: Jun 2006
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From: san antonio
Don, Thanks for the input. Sure appears that I will be taking it apart again. At first I thought I could live with it until next winter but I cant stand to ride it. It would be nice to figure out ahead of time what I need to do piston wise to fix it. Unfortunately I threw out the old pistons so that's why I was asking. If these Wiseco's are lighter then it might be difficult to get the weight right short of changing wristpin weight....
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Road Captain
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From: Mo
It would be helpful if you knew the difference in piston weight. There is a forum member, 60Gunner that just upraded from 103 to 107 and he probably has the OEM pistons. I have texted him and requested that he weigh a piston assembly and post the weight in this thread. If he has the pistons, he will do it but it may take a day or so while he finds a suitable scale. Meanwhile, you should call Wiseco for the weight of their 10.5:1 piston. I looked in their catalog and they list every stastic but weight. I would also ask if they have .240g pins; standard is usually .160g. At least if you have the righ information, you will know what you need to restore crank balance, if in fact, that is the source of the issue.
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Road Warrior
Joined: Sep 2021
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From: So fla
I just did a 107 also. And have my old 103 pistons.
so i could give weights also incase he tossed his
so i could give weights also incase he tossed his
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From: Dubuque, IA
With the rings only they are 401g each. With rings, wrist pin, and circlips they are 530g each.
I haven't rode mine yet but dyno'd it Thursday and smooth as could be. New S&S crank balanced for the new pistons and balance assembly tho.
I haven't rode mine yet but dyno'd it Thursday and smooth as could be. New S&S crank balanced for the new pistons and balance assembly tho.
Last edited by 60Gunner; Apr 11, 2022 at 06:35 PM.
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From: san antonio
