TOPIC:

Kawboy, do you have info about what's the slack of new chains on hand?

StanG wrote: Kawboy, do you have info about what's the slack of new chains on hand?

Sorry Stan. I don't. I have new chains fabricated by Ramsey Chains in South Carolina. I sent them 2 old chains for identification and they made me up 2 new ones. All Ramsey does is Hi-Vo chains.
On all models of the KZ, Z, and ZN series engines, slack and stretch in the primary and secondary chains will have retarding effect on the valve train timing plus of course slack stretching in the camshaft drive chain.
Because there isn't a tensioner in either primary or secondary drives chains, as the rpm's accelerate and decelerate, the valve timing could change as much as possibly 20 degrees. 20 degrees is the equivalent of one tooth on the camshaft sprocket.
My main concern is that by design (or maybe better said design flaw) as the chain stretches /wears between the drive face of the chain and sprocket teeth, as the chain is put under load, the chain rises up off of the teeth and starts driving the sprockets on the tip of the teeth rather than on the major face of the teeth. I know I've seen a video of this effect but for the life of me, I can't find the source of that video.I wished they had put a slack adjusting system on boththe primary and secondary drive chains to control the slack. I don't like the fact that the valve timing can change as much as 20 degrees between load and no load. We all should know what happens when the camshaft jump a tooth because of a loose cam chain. Bent Valves.
Retarding the intake valves will delay the opening of the valves which starts the intake flow late but worse is that the delay in closing the intake valve will have an adverse effect on compression stroke. The valve closing on these camshafts is 70 degrees after bottom dead center. That only allows 110 degrees of compression. under perfect conditions ie. new chains. Delay that closing by 20 degrees means you now have a compression stroke of 90 degrees.
Delaying the exhaust timing by 20 degrees allows the power stroke an extra 20 degrees of combustion pressure on the piston, but it also allows the flame front more area on the cylinder walls to dissipate heat. It also delays the flow of exhaust gases out of the cylinder which effects cylinder scavenging. The worst is that closing the exhaust valves late means that the exhaust valve will be lower in the combustion chamber and interference with a piston is more than likely.
The camshafts on the KZ and Z have a 280 exhaust duration and 270 intake duration. That's a lot of cam but needs to be on an under square engine (smaller bore than stroke). The ZN Voyagers changed that spec to 260 degrees duration for both the intake and exhaust. That should tell you something.
One phenomena I have found with measuring the camshafts is that for some reason, all 6 sets of camshafts I have in my possession measure out at 290 - 310 degrees of duration. I think a lot of why I'm measuring this is due to the small base circle of the cams. Had they designed the engine to use a bigger base circle, there would be a lot more room on the cam to better control all aspects of the cams. These cams are lazy to get going and lazy to close. Compound this phenomena with late timing and you're asking for trouble.

Hmmm, 20 degrees out, that is not good. I didn't knew that a slack primary chain could affect valve timing, but of course the camshaft is not driven directly from the crankshaft as in most other engines, but from the secondary shaft, which will not follow the crankshaft exactly if the chain is slack. I wonder if anybody know the estimated life of a new primary chain or how many KM or miles one can expect before it reach the service limit of 22 mm slack.?

Vilhelm wrote: I believe Hy-vo chains are noisey by nature, .

Morris chains are actually quiet as far as chains go -quieter than roller chains.

Kawboy’s excellent analysis of the short comings of the 1300’s unusual valve train has dented the impression of good solid engineering that I had regarding this power plant. That such a variation in valve timing can occur due to the HyVo chain slack seems to be a major compromise in the design. What effect on power output will this have? Why was this design chosen? Does the CBX use the same system?

I really don't want to highjack VIlhelm's thread here but short and sweet, the CBX drive the camshafts off of the crankshaft so the only retarding of the cams would be in the primary and secondary camshaft drive chains themselves.



If we wish to discuss the camshafts and camshaft timing further, let's open up another topic. for Vilhelm, I would like to see a topic specifically on his build out rather than carry on with a topic of "New Member" please