Topic: cb750 cam chains/tensioner for road racers

[gschuld]

I know there are threads discussing different cam chain/tensioner options for our Hipo cb750s.  I've read my share.

But not much specifically in relation to road racing applications.  Mid to full throttle high rpm, cycling back and forth hard for +/- 20 minutes is a pretty rough environment for a cam system.

I am interested in thoughts on what people are/were using and what is considered the latest version of "ideal" for this application.  This is in reference to a large displacement, fairly big cam, ported head engine, with about a 9500 to 10,000 rpm ceiling.

I'm considering the cost as being secondary to durability and quality on this.

All thoughts are welcome, hands on experience MOST welcome.

George

[bwaller]

Slipper style tensioners are most supportive on chains. Not many moderns using rollers. Mec went through this earlier, I'll send him a note asking for an update.

[gschuld]

I have found Brent's (Captain) thoughts on the subject very interesting and undeniably logical.  Making it work with our engines and our cam chain designs is the trick I suppose.

I'm guess the market exists if a Vance and Hyde level solution becomes available.  I'm in.  Messermoto seems to be making a bunch of effort in that general direction.

George

[gschuld]

One of the factors involved is the fact that the backsides of the hyvo cam chains are rather smooth and the pressure evenly distributed across the width of the chain.

Our old school HD cam chains are VERY different.  Two distinct outer running surfaces with a separate inner surface.  I would think our HD cam chains would have far more of a cutting/wear effect on any slider surface than the hyvo chains would, even if the chain is evenly supported on both sides as Captain and 30 years of more modern engines suggest is the way to go.  But then again, no sohc4 is making 180 RWHP either, so it's all relative

George

[bwaller]

The smaller 4's have the same chains with slipper style tensioners and rev higher to boot George. HD chains with a full link plate slide along merrily.

[gschuld]

Good to know...

George

[Big Jay]

Seems the chain will wear into the tensioner until the rollers make contact, then the rollers ride the tensioner and it can't wear in any further.

[turboguzzi]

sohc cam chains are not that old school. all air-oil gsxrs use the same not hy-vo chain and work like a charm. non hy-vo is a non issue....

[gschuld]

Seems the chain will wear into the tensioner until the rollers make contact, then the rollers ride the tensioner and it can't wear in any further.

Perhaps I am misunderstanding your comment Jay.  By wear into the tensioner are you talking about the fixed position guide on the opposite side (pics below)?

Brent (Captain) seems to suggest that the fixed guide is a major part of the problem, as it allows the chain to run pretty straight along a straight guide rather than the modestly curved guide he developed for his dohc race motors.

Curved guides seem to have been the way forward in cam chain guide design since the early/mid 80s(?).

I'm wondering if anyone has successfully tried a curved fixed guide on our motors before.  There is some development work going on regarding this now.

I'm not an expert on this by any means, but the subject interests me.

George

[gschuld]

Turboguzzi,

You have using modified gsxr tensioner parts in your cb500 engine right?

[turboguzzi]

Turboguzzi,

You have using modified gsxr tensioner parts in your cb500 engine right?

i used a gsxr chain with a CBR600 tensioner

[simon#42]

two bikes that dont break ....... good thinking yossef !

[turboguzzi]

might be not that great at riding them, but i know how to build them simon!

if it's of any help, here's a gsxr tensioner for side plate chains, has already the bump in the center to support the rollers.

[MessnerMoto]

Will see how this works. But for now everything fits in Should enable engine to rev higher

[gschuld]

Wow.

I have been looking forward to you finishing your prototype.  I know you put a lot of thought into this and I hope testing either validates your design or points you toward a way to refine it.

George