Howling belt drive

[57pan]

I posted this over on the old board too so if you respond there you don't have to reply to this message. Just trying to cover all the bases.

A couple of days ago I noticed a kind of howling sound on the bike. Using the ol' rubber-hose-as-a-stethescope trick I tracked it down to the primary belt drive, more specifically, to the point where the belt teeth disengage from the pulley on the tranny. I have put over 1500 miles on this belt drive setup and it never made this sound until a couple of days ago.

Have any of you experienced this before? Why would it suddenly start making this noise? And what can I do about it?

Now, I should also mention that about two weeks ago I replaced the engine sprocket shaft seal. The one that I had put in when I installed the belt drive was not sealing well and I was getting some oil on the belt. I suppose that it is possible that the oil on the belt was preventing the howl and now, after two weeks of running dry, the belt finally dried out and started making the noise.

I should also point out that when I started it last nite (after not running for over 24 hr.) the noise was completely absent at first and did not start until after it had been running for maybe a minute.

Looking for some ideas...

[VintageTwin]

mainshaft noise from a worn bronze bushing in the transmission?

[57pan]

Thanks to everyone who responded to my post about the "howling" primary belt. I have diagnosed the problem and now I at least understand what is happening.

The belt is rubbing up against the backside of the clutch basket.

basket.jpg

As I mentioned, I had replaced the engine sprocket shaft seal a couple of weeks ago because it was leaking. Consequently, there was some oil on the belt which was preventing the howling sound and, now that the oil source has been eliminated, the belt is dry and as it rubs against the back side of the clutch basket it produces the howling sound. I guess it just took a couple of weeks for the belt to dry out.

I put a light coat of oil on the surface of the clutch basket and the howling is gone but I need to double check the pulley alignment.

[SkyHogg]

My suggestion is to determine if you can make some adjustments and eliminate the howling that way. By putting oil on it you are curing a symptom, not the problem. If it is rubbing like that it may be putting lateral stress on the shaft ... I ain't no engineer, but it can't be a good thing. Might create problems a year or two down the road.
Just mutterin' out loud ... you know us southern boys ....

[Faustmill]

I have the same problem with the belt rubbing against the side of the clutch basket. I am not sure if it is because (1) the basket is cocked sideways a little and not parallel to the inner primary case or (2) because the basket is sitting too far in so it is too close to the inner primary case relative to the engine sprocket. How did you align the clutch basket with the engine sprocket? Thanks.

[VT]

We're working on the belt chapter now. I'll present the belt rubbing problem to Stett and see what he says.
But, don't wait for us for a suggested fix. Tell us what you know about it now and I'll report any info pertinent to the specific problem when I find out.

[Faustmill]

This is a 65 FLH with a 1 1/2 inch Primo belt drive. The outer edge of the belt is rubbing on the edge of the clutch basket, causing a whining noise --in the same spot as on the picture above on this post. I have not yet removed the clutch hub (in the process of getting a puller) but the rest of the clutch is off, including the basket. I took a straight edge, held it tight across the hub liner (the fiber ring that is held onto the hub with the rivets) and measured the distance from the straight edge to the face of the inner primary case to see if I could tell if the hub was square to the face of the case. All measurements were equal, so as best I can tell the hub is straight and not sitting cockeyed on the mainshaft. I assume this is also true for the clutch basket (what some call the clutch shell), when it is riding on the hub. Since this is OK, I guess this means that the shell needs to come away from the face of the inner primary case in order to be lined up with the engine sprocket. I assume this is done with shims, but I have not seen any clutch hub shims in the catalogues. I see posts on this forum where guys are happy with their "quiet" belt drives. Mine is definitely not quiet. Any advice is most appreciated. Thanks.

[john HD]

faustmill

i would have to think renewing the fiber plate on the face of the hub would be the easiest way to gain additional clearance.

better yet, switch back to a chain. i did this years ago and couldn't be happier. adjust twice, set the oiler properly and forget about it!

i believe that belts have run to tight for the clutch hub to work properly, i noticed my bike shifted much better after i went back to a chain. that and the compensating sprocket helps cushion the driveline.

keep in mind this is just my personal experience and i am sure there are thousands of folks who have had plenty of good experience with belts. i just like the added piece of mind knowing that the chance of breaking a chain are next to nil.

john

[Ohio-Rider]

Dave- I replaced a 3" open Primo with the 1.5" BDL last winter. After about 500 miles I was having the same problem your decribing. What I did was to re-adjusted the tension on the belt so as to have 3/4" slack up and down. (Thats 1.5" total.) I know it sounds like abunch but I've put 2K mile on it since then and have had no more problems with it.

Yes with that amount of slack in the belt I can almost slip the belt in and out laterally on the sprockets. With it adusted this way cold I've found that after a long hot ride the tention reduces to about 1/2 what it was while cold. Anyway its something you could try. -Steve

[Ohio-Rider]

Oops.. Forgot to give the credit for this procedure I used to Arizona-Craig who suggested it to me. -Steve

[Faustmill]

Those are two good suggestions -- (1) to renew the hub liner to move the clutch basket out and (2) to loosen the belt. This is a new five finger hub so the liner is new, but I am going to look at it and maybe it is possible to put two liners on top of each other. As to loosening the belt, I have tried this and set it to where I thought was pretty loose (but not as loose as Steve is saying). It still whines, even when it first starts and the motor is cold and the belt is still loose. Plus, the outside edge of the belt is shiney where it is rubbing on the basket, so I still need to get the basket lined up better with the engine sprocket. I know the belt tightens up alot when the motor goes from cold to hot. When I get this all back together, I definitely am going to set the belt as Steve suggests. Thanks.

[VintageTwin]

'65 is beyond me, but since most of the pieces are the same as '41-59, here's what I know: According to Primo® the free play on a 1.5" belt is 1" (with a cold drive train). Grasp the belt top-center and push up and down using about 10 lbs. of force.
Since a '65-up transmission doesn't move forward and back on a mounting plate, for primary chain (or belt) adjustment, I'd wonder if the clutch shell wasn't moving back and forth or cocking side-to-side, while the motor is running, due to slop between the clutch hub rollers and retainer?
The "Big Fix" kit contains 52 long rollers that take the place of the short off-set rollers. The rollers are inserted between the hub and shell, resulting in a smoother, more positive, wobble-free clutch operation.
The "York" clutch assembly (18-0517) runs true as well. It's a dry clutch assembly that consists of hub, bearing, discs, diaphragm, spring, retainer plate, and bolts.

[Faustmill]

On page 655 of the J&P catalogue it says "One of the largest contributing factors to premature belt failure is the misalignment of the front and rear pulleys". They sell different thickness shims that go behind the motor pulley to achieve proper front to rear belt alignment. I need a couple days to sort this out. I will let you know how it goes. Thanks for the help. (I just bought a new $75 clutch hub with the 20 rollers (the one that is causing the rubbing) -- I wish I had spent $85 on the Big Fix hub with the 53 long rollers, instead).

[Ohio-Rider]

Won't putting shim behind the motor pulley make your problem worse? Seems like that would be going the wrong way to stop the belt from rubbing the hub.-Steve

[Faustmill]

Yes, you are exactly right. I am hoping that when I get home from work tonight and (hopefully) rig up a puller to get the engine pulley off, that there will be a big fat shim behind the pulley that I can toss in the trash and maybe substitute a thinner one. If there is no shim behind the engine pulley I do not know what I will do. I still am not sure what the procedure is to check the alignment between the two pulleys. It is impossible to eyeball since you can't shove your face inside the inner primary case. Maybe I will just have to start the motor without the primary cover and see how it runs.