CAm chain bridge....

[planedick]

What does the cam chain bridge actually do? I've had many motorcycles in the past with a cam chain and none of them had a bridge. I've been troubled by noise and I thought it might be the bridge rattling so I removed it and went for about 6 mi ride. The noise is still there, but I wonder just what it's supposed to accomplish. Any ideas?

[prometheus578]

Like the cam chain dampers running up from the cylinders, the bridge give the chain something to "ride" next to to help stop it from slappin' around. Or sagging, in the case of the bridge. Helps keep tension. Would also tend, I would think, to keep the chain aligned as it crosses from cam to cam to prevent derailment.
Some Kawasaki's have a hard rubber bumper-like -thing mounted to the top of the inside of the valve cover to press down on the chain to accomplish the same thing.

[planedick]

Following thought.....

If the chain needs support there, why isn't there such devices from tranny to wheel on chain drive machines? Chains tend to run smooth at high speed. I've installed many chain drives in machinery I make and have seen and serviced literally thousands of such devices in industry, and I still wonder what was the real reason those Yammi Mammy engineers had in mind when they decided to put that bridge in there. I think maybe that was put there for those who never did any maintenance and never adjusted the chain. Being the inquisitive type I've always been one to ask the questions, stupid ones sometimes even. LOL

[prometheus578]

Dirt bikes and such have chain guards and long stretches of plastic runners for drive chains to ride on or against. I would reckon that the bridge is there to keep the chain tight and not sag during acceleration and deceleration of the engine, which would affect valve timing.

But then again, I don't design them, just ride them.