Belt drive on 1951

I've run into a problem with my belt drive, the belt is too short.

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Panacea
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Belt drive on 1951

#1

Post by Panacea »

Hi guys, I've run into a problem with my belt drive, the belt is too short. the tranny is all the way forward and I still can't get the belt over the pulley. I have a Gates HTD 30853x 1 1/2". I was told this is the longest belt available. I'm hopin' they're wrong. Other than that the re-build is going well, the steering dampener worked out perfect, as did the fork lock restoration. The frame is all re-built and repainted and I've got the motor and tranny back in. So now to figure out this belt problem. Any help is always appreciated! Mike
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Re: Belt drive on 1951

#2

Post by mbskeam »

does your belt have what looks like a bullseye symbol near the gates part# like this......
gates8mmbelt.jpg
this belt is a bit longer than a standard belt
if it does then you have to make the tranny plate slots longer, to let the tranny slide farther forward. I had to do this to mine, I think I added 1/4" to slot.

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Re: Belt drive on 1951

#3

Post by 108 »

I have a 11/2" belt on a '48 and I had to lengthen my slots also, and from what I hear, just about everybody does.
Panacea
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Re: Belt drive on 1951

#4

Post by Panacea »

thanks guys, I've lengthened the slots to the point where the boss on the bottom of the tranny hits the end of the slot in the plate, still to tight(1/4" deflection). I'll look for the bullseye!
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Re: Belt drive on 1951

#5

Post by Panacea »

I just checked, I do have the bullseye. So I'll just have to do some more slot lenthening and remove a bit off the front of the tranny boss, she also hit the oil tank mount on the ratchet lid,I'll get 'er. Thanks for the info, Mike
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Re: Belt drive on 1951

#6

Post by wallofdeath »

I've installed a 1-1/2" 8mm BDL 62-39SK-2 belt drive kit on a stock 58FLH and run into the same problem of the belt being too tight.
Transmission is right up against the seat post and can't be moved any further forward.

The kit comes with a 132T Bullseye belt which doesn't help.
Furthermore, I can't see how a Bullseye belt can be any longer than a standard belt to make any difference or it wouldn't track on the pulleys.
I could be wrong but the "bullseye" is either marketing or possibly a belt that doesn't pass spec so it's a reject passed off as a hair follicle longer. Someone can enlighten me on what I'm missing here as I keep hearing about the bullseye belt being longer and the solution to the problem.

Apart from the belt being too tight, moving the tranny up against the seat post also pushes the kickstarter return spring onto the rear header exhaust creating another issue.

Not happy with what I'm seeing so I tried a 138T belt.
The tranny is now pulled all the way to the extreme rear to get the correct belt deflection and no kicker return spring/exhaust issue but it's still not where it should be.
Clutch basket is possibly too far to the rear and may interfere with the outer primary cover.

I'm guessing the unobtainable 135T belt would be ideal and position the tranny about where a chain would.
Has anyone contacted BDL or Gates about such a belt?
Any ideas/thoughts (apart from going to a chain)?
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Re: Belt drive on 1951

#7

Post by RooDog »

I too had trouble with a BDL system. I contacted their sales rep and was told they may have a smaller motor sprocket. Count you motor pulley's teeth and then ask BDL for a one tooth smaller one.
Let us know how that works out for you.....
....RooDog....
PS: I wound up with a Super Max drive, but Phill Ross died, and no one took up the biz, and that sux....

Got this info from Scott at BDL on 9/26/2020......

scott@beltdrives.com writes:

This would be our 8mm. kit the 61 or a 62 tooth basket a 39, 40 or 41 tooth front pulley with our BDL-30853 ST or BDL-30853 BE belt all interchangeable. This is what I would have to offer to correct any fitment issues. Thank you, Scott
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Re: Belt drive on 1951

#8

Post by wallofdeath »

@RooDog

The BDL kit comes with a 39T motor pulley, so a smaller pulley is not viable.

As soon as I look at a bike, I can tell they're running a belt because the trans is jammed up against the seat post. I occasionally even see the trans lid scalloped out to get even closer/forward to the leaning seat post. There's even people notching slots in the trans base plate.

I personally feel BDL have got it wrong and the belt needs to be 2-3 teeth longer. At the very least, they should offer a suitable longer belt.
Frankly, after decades to correct it, I don't know how this is still an issue. Their belt kit clearly doesn't have the trans positioned correctly like the chain does.

And, the Bullseye belt is bullshit. I reckon they're having at laugh at your expense if you believe the belt is longer than standard.

Unless I can find a solution, I'll buy all the bits to convert it back to a chain.
Or if Gates can make a 135T belt at a "reasonable cost", that would be ideal.
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Re: Belt drive on 1951

#9

Post by 59Panman »

Did you loosen up the rear wheel axle and get some slack in the drive chain so the transmission may slide forward a bit in order for you to slide the belt over the front pulley? :wink:

My BDL belt drive fits just fine on my '59.
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Re: Belt drive on 1951

#10

Post by wallofdeath »

@59Panman
Right now, there is no rear chain installed so it's not the issue, but I do understand your point.
The transmission is as far forward as you can get and the belt is installed on both pulleys.
The problem is the belt is too short and you can't get the correct slack/deflection in the belt because the trans can't go any further forward as it's up against the seat post.

Every bike I see with this kit installed has the same problem of the belt being too tight and there's plenty of posts about it to verify the issue. People just run the belt tight as there's no other option. I'd rather not as it creates more issues.
The simple solution is a slightly longer belt but they don't appear to have one on the market.

Despite what I read, the bullseye belt is not the solution as it has the same number of teeth as standard and therefore the same length. Logic tells you the same number of teeth can't produce a longer belt or it wouldn't mesh with the pulleys. Regardless, the kit comes with the bullseye belt and doesn't solve anything. BDL obviously know the problem but do nothing about it. Rivera kits have the same issue in both 8mm & 11mm kits as I have them both.

Either I've gone full retard or BDL/Rivera have. Having fitted these kits to 4 stock bikes, tells me the latter has.
With not being able to know what a woman is these days, there's not much chance of solving the complexity of belt lengths.
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Re: Belt drive on 1951

#11

Post by 59Panman »

Here is my BDL setup.
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Re: Belt drive on 1951

#12

Post by flat38 »

I have also dealt with this issue many times. About 20 years ago I called BDL and after explaining the problem, I had to listen to a lot of reasons for the issue that boiled down to me not knowing what I was doing. Eventually, he told me that then did make a clutch drum with 61 teeth instead of the standard 62. I bought one and that took care of the problem. Still running it today. I don't know if they still sell them but it is worth asking.
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Re: Belt drive on 1951

#13

Post by wallofdeath »

@59Panman
So I downloaded your setup document and it is the kit that BDL ship and the one that I'm talking about which has the belt tension too tight.
39T front pulley
62T rear pulley
132T BullsEye belt

@flat38
A 61T rear pulley could make a positive difference but I'm hesitant to throw more money at BDL just yet.
Would you mind giving more details about how much difference it made?
How much belt deflection did you have with the 62T pulley and how much do you have now with the 61T?
What measurement gap do you have between the seat post and transmission?
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Re: Belt drive on 1951

#14

Post by flat38 »

I have a little over 3/4" belt slack and the case is about 1/2" from the seat post. The trans is a Sputhe 5 in 4 and the frame is an 86 Santee. Results with stock parts may differ. With the 62 tooth drum, the belt was very tight. In the past I have had to make the trans plate slots longer and in one case, mill the trans case a bit to clear the seat post. The result was a belt that was tighter than I liked, but good enough to ride.
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Re: Belt drive on 1951

#15

Post by wallofdeath »

@flat38
Thanks for the details.
Given that you're running a custom trans & frame and I'm running stock, I'm going to buy all the bits and revert back to a chain setup. I'm not convinced that buying a 61T rear pulley is going to give me the belt slack I need, so I'll give that a miss. Maybe one day a longer belt will become available and I'll give the belt drive another shot.
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