Belt adjustment (again)

[ChrisH]

Having had two drive belts snap in 20,000 miles (second time round I had new pulleys fitted too) I'm now a bit paranoid about belt adjustment.

I wad doing a bit of a service at the weekend when a mate of mine was round. I'm a bit anal about adjusting the belt tension exactly as in the service manual, using the over-priced HD 'special' tool. My mate was adamant that I should err on the side of keeping it a bit slacker than the specified tolerances to prolong belt life.

My mate is far more experienced and skilled mechanically than I am. BUT he rides a (chain drive) Ironhead. So maybe he's wrong.

Scoured the net (and the archive here) but there are lots of contradictory opinions - so any ideas on this one; is it better to be on the tight side, the loose side or spot-on ??

ChrisH

[robbiemac]

Hi, from memory there have been 2 or 3 other folks who put posts on the sporty section saying about the belts snapping. It seems the common factor to me was putting it into gear initially when about to ride off. Why this should happen i do not know but can only surmise that it's the initial shock of it going into gear. A bit like Kawasaki's used to do in the 70's and 80's.

As far as belt tension is concerned, i would go with what the MoCo say and if anything i would personally err on the loose side as it would give your bearings an easier time of things.

hope this is of use.

[girlyglide]

Adjust it as per the MoCo manual using the tension tool.

I have never suffered a snapped belt or had a customer serviced bike suffer one either.

Ignore all contrary advice, I think after 20 odd years of using them the MoCo know what they are talking about when it comes to belt drive tension.

[girlyglide]

As a matter of interest does your bike still have the two stock belt guards fitted?

[Hawkeye]

Look on the US ebay site, i picked up my belt tensioner for 10 quid plus postage which was not a lot.

To my mind a belt being to slack is just as bad as being to tight, the raised part of the belt may get torn off. I could be wrong there though.


I deal with a lot of V belts in my job and they do have to be tensioned correctly, if not they cause excessive wear if loose or clap out bearings if tight. A flat belt with drive with teeth would need to be tensioned quite acurately in my way of thinking.

[HOG maniac]

I also deal a lot with V and synchronous belts at work. Synchronous belts have no slip so are under a lot more strain. Its also important that they are aligned correctly. I don't expect you to laser align it but make sure the rear wheel is adjusted correctly and square.

Also the chain guards can rub so take a look there as well as Phil said.

[Wareshome]

Had my belt snap luckily it was outside the garage but when I bought the new one I was surprised at just how supple it was compared to the old one. The old one had only done 12k but was 9 years old.

[ChrisH]

Thanks guys - sounds like I should just follow my instinct and stick exactly to the service manual.


I suspect that whilst slightly too slack might be better than slightly too tight with chains it's actually the other way round with belts ...

By the way - the second time the belt went I saw the pulleys were shagged. I was advised that they should probably have been replaced previously when the first belt went. The moral of the story being; putting a new belt on doodgy pulleys is a false economy.

ChrisH

[SJC69]

One point that is often overlooked is the belt adjustment is with a cold engine, ie not been run, probably best left overnight.
At any other time expansion will have taken place and the belt likley be set too slack.

The lower belt guard is the most important one for keeping crap out the belt, don't be tempted to remove it.

[HOG maniac]

Good point but I think you mean tight.