94 Fatboy belt rubbing
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Joined: Oct 2021
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From: Sacramento
94 Fatboy belt rubbing
Hey fellas just got my bike up it's a 94 Fatboy with a 140 rear tire I noticed my belt is rubbing on my tire only when I'm backing my bike up is this normal with a 140 tire? I know that's about the widest u can go without modifying anything I measured center to center from my swingarm bolt to axel nut and it looks good maybe off by less than an eighth of an inch if any so is my 140 tire to blame? And is this something I need to worry about? Thank u in advance
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Joined: Feb 2016
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From: British Columbia
Try Again
You need to align your rear axle closer than about 1/8 of an inch. Finding center in the rear axle is kind of difficult. I lay a center punch inside the axle as a center point and measure to the swing arm bearing center when I align after a tire or wheel bearing change. Best of luck.
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From: Sacramento
Thank u for the reply and advice I'm still learning to wrench on my bike just trying to figure it all out but everybody on this forum has been a big help u all have walked me through some difficult stuff and I appreciate u guys
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Joined: Feb 2016
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From: British Columbia
For more help and understanding as you go,try and get hold of an owners manual for your year and model of bike. It will be a big help along the way. It's a good investment that you use and keep or valuable to a further customer if you sell your bike. Best of luck in all that you take on.
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From: Sacramento
Fatboy belt rubbing
So quick update I re measured my rear axle and it's spot on so I'm still trying to figure out why my belts rubbing I got plenty of room when going forward but soon as I back it up and the belt shifts it runs so Im thinking I might have to put a spacer behind the drive pulley?
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So quick update I re measured my rear axle and it's spot on so I'm still trying to figure out why my belts rubbing I got plenty of room when going forward but soon as I back it up and the belt shifts it runs so Im thinking I might have to put a spacer behind the drive pulley?
I have read that on some years/models the belt moves inboard slightly when backing and then back outboard when moving forward....
I forget the specifics of why some say this is "normal"... But IIRC, one "explanation" was due to the way the belt cord structure is wound on the belt. Another "explanation" was due to something about a taper to the trans gear....
I'm very skeptical of these "explanations". If someone is aware of them or why belt movement would be normal.... hopefully they will see this thread and add their expertise..
Personally, I believe if the belt moves side to side on the pulleys, it's due to a misalignment. It doesn't take much of a misalignment to cause the drive belt to move when wheel rotation changes...
I'm very **** about setting my belt tension and rear wheel alignment any time I remove the rear wheel.. I have been fortunate enough that I have not experienced this phenomenon..
However, if you are running a non-standard width rear tire (I believe your bike came with a 130 rear) and the belt contacts the tire, while it is still riding within edges of the rear pulley... I'd say your custom sized tire is the problem...
I wouldn't be messing with the wheel spacers on OEM wheels or adding spacers to the pulley on an otherwise OEM setup, without consulting an expert. My advice is to find someone who is experienced with modifying the rear wheels/tires on a Harley softail, if you want to keep your 140 rear tire... then follow their advice.
If it were me, with OEM wheels, I'd be going with OEM tire sizes....
Good luck with your mod...
Tourer
Joined: Feb 2016
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From: British Columbia
Keep trying to think it through. Something isn't right. Do not measure from a flat on the axle nut. You had mentioned that in the original post. Measure from the axle center to the swing arm bearing center. Is the belt moving inboard toward the trans or out toward the clutch ? Think what adjustment would correct that. Make slight change and see what it does. Is the belt tensioned enough after the adjustment. Kinda like 1/4 inch movement on the bottom with upward 10 lb forced movement ? Get a belt adjustment gauge. Has the bike been tweaked in to a curb ? Like maybe a twisted swingarm. Has it done this all along. Did it do it after a bearing change or tire change ? Are your swingarm bearings without up and down or side to side or fore and aft movement. Are you making your measurements and adjustments with the rear wheel off the ground ?
Years ago when I was learning these same things, I had a belt movement issue of traveling inboard after a tire change. It wasn't an issue going forward. So next opportunity I spent a good deal of time looking, adjusting and learning. Figured it out and haven't ever had the issue again.
The only other thing I might be suspicious of would be your pilot bearing on the transmission input shaft. They do wear and usually make a strumming howl noise. That's a somewhat involved job and you need specialty tools to pull and reinstall the bearing and to hold your belt hub in place to knock off the large nut holding it on. That's an opposite pitch threaded nut.
Years ago when I was learning these same things, I had a belt movement issue of traveling inboard after a tire change. It wasn't an issue going forward. So next opportunity I spent a good deal of time looking, adjusting and learning. Figured it out and haven't ever had the issue again.
The only other thing I might be suspicious of would be your pilot bearing on the transmission input shaft. They do wear and usually make a strumming howl noise. That's a somewhat involved job and you need specialty tools to pull and reinstall the bearing and to hold your belt hub in place to knock off the large nut holding it on. That's an opposite pitch threaded nut.
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From: Sacramento
Fatboy belt rubbing
Ok so to answer all questions bike has never been curbed,dumped,or anything like that I don't even ride it hard I baby my bike so I know it's not from that but when I measured to see if my axel was aligned properly it was off the ground on a bike jack is that ok or do i need to check while it's on the ground? It's got a 140 rear tire I put on new bout a year ago but the old one was also a 140 and I ordered the same exact tires that was on it only thing that's different is it had the rev tech 3 spoke mags that I'm getting the done so I put some original solids on it for now when I had the rev techs on it I don't remember having the problem but I also think my belt is a little to loose so could that alone be causing my belt to walk? I'm starting there today and just start eliminating stuff gotta say I'd be lost without this forum brother so thank u all for the reply a and advice
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From: Poolville
It is very typical for the belt to shift inward when backing the bike. Put the bike up on the jack and trans in neutral, while spinning the rear tire forward where exactly is the belt riding in the front pulley.? If your axle is aligned properly it should pretty much ride the center of the pulley. Also some 140 mm tires are actually wider than others and it could also be that the hub on your REV Tech 3 mags are a little wider. If it bothers you, you can always install a pulley spacer. Vulcan Engineering in NH makes about the best ones I've ever used..
https://secure.vulcanworks.net/store...t-Spacers.html
1/8" should do just fine.. Just make sure you use red loctite 272 on the pulley bolts.. Pretty sure I was torqueing them to 60 ft lbs.
https://secure.vulcanworks.net/store...t-Spacers.html
1/8" should do just fine.. Just make sure you use red loctite 272 on the pulley bolts.. Pretty sure I was torqueing them to 60 ft lbs.
Last edited by 98hotrodfatboy; Jul 21, 2022 at 12:01 PM.
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From: Sacramento
94 Fatboy belt rubbing
U know now that u mention it I've had the impression that my rev tech hubs are a little bit wider to be honest it don't bug me that much I just worry about weakness in my belt from the rubbing not sure if it will hurt the belt just trying to do it right like I was saying I still got a lot to learn about the mechanical part but I'll get there