2V belt tension question (!!)

[scott_araujo]

They run much better with proper valve clearances, rather than the cost based new tolerances...

than they ever would with harmonically adjusted belts.

Just sayin'.

+1.  Go to the old spec.  I set my valves to the old spec and my belts with and allen key.

Also, I've seen brand new belts loosen considerably after 1000 miles or so.  Check often.

Scott

[Langanobob]

The FIM banned Aprilla from using gear driven cams because the bikes were much faster than the stock chain driven cams.  I couldn't believe how much better my bike ran when I replaced my belts last summer.  I used a program that gives a digital readout for the frequency.  It was pretty easy to use.

Don't have all the facts (of course) but I don't think the Aprilia gear driven cams were banned solely because the engines were faster.  I think they were banned because they were faster and the cam gear drives were not homologated on stock street bikes.  If Aprilia had sold the gear drives  as original equipment on enough stock street bikes (150?) they would've been within any reasonable interpretation of the rules and would be allowed.

But regardless if my view above is correct or not,  it's interesting that the gear cam driven engines were significantly faster.

Bob

[bigiain]

Also, I've seen brand new belts loosen considerably after 1000 miles or so.  Check often.

I don't know that they need checking "often", but checking them at least once ~1000miles after setting them is certainly a good idea.

(Has anybody ever needed to retention them more than once between fitting them and replacing them on schedule?)

big

[scott_araujo]

I usually check around 1000 and tighten up a bit.  No other checks have needed tightening so far.  I check often because my first set of belts got so loose they looked like they were going to skip a tooth.  Only takes 10 minutes to check.

Also, it begs the question of how critical tension is.  Most people get them put on and never check again until it's time to change them.  They're going to loosen up at least a little which means no matter how perfect the tension was it's off after 1000 miles or so until you replace them again.  4V seems more critical but setting 2V belts doesn't need to be rocket science.

Scott

[ducpainter]

I usually check around 1000 and tighten up a bit.  No other checks have needed tightening so far.  I check often because my first set of belts got so loose they looked like they were going to skip a tooth.  Only takes 10 minutes to check.

Also, it begs the question of how critical tension is.  Most people get them put on and never check again until it's time to change them.  They're going to loosen up at least a little which means no matter how perfect the tension was it's off after 1000 miles or so until you replace them again.  4V seems more critical but setting 2V belts doesn't need to be rocket science.

Scott

Everyone checks tension cold, because that is where the spec is given.

Have you ever re-checked a belt that is loose cold, when hot?

I still maintain that as long as the belts aren't so loose that they can skip when cold or so tight they make the tensioners scream when hot, it's all good.

Valve clearance is much more important to proper running.

[vaclav]

Did anybody who did the frequency thing with a DS1000 engine ever go back and slip some allen wrenches through to see what it worked out to?

[KRJ]

   Awsome, the $20.000 question...an ambiant temp. static, manual adjustment, replicating the proper harmonic method....

[Langanobob]

...Valve clearance is much more important to proper running.

Valve clearance affects the valve opening and closing time.  Also the total valve opening amount or height, but I'm thinking that a thousandth of an inch or two are not going to be noticeable on a street bike, but maybe they are.   Loose belts also affect the valve opening and closing time.   It seems to me that it's equally important to have both properly adjusted.   It "seems" that loose belts would have even more effect on valve timing than a slightly maladjusted valve clearance, but I don't know that for sure.

[ducpainter]

Valve clearance affects the valve opening and closing time.  Also the total valve opening amount or height, but I'm thinking that a thousandth of an inch or two are not going to be noticeable on a street bike, but maybe they are.   Loose belts also affect the valve opening and closing time.   It seems to me that it's equally important to have both properly adjusted.   It "seems" that loose belts would have even more effect on valve timing than a slightly maladjusted valve clearance, but I don't know that for sure.

Put it back into context.

Have you ever checked your belts when hot after you determined that they were loose cold?