Jump to content
Sign in to follow this  

Quick question can a new cam chain give bike extra power.

Recommended Posts

I been wondering here, I put new piston and rings and cam chain in my bike as my bike was getting slow at bottom end had to ride it more like a 2 stroke, anyway since I put new piston, rings and cam chain the bike goes like new again :smirk:, the reason I'm asking the question about the cam chain is the owner who had it before me said new piston was fitted which I believe as I could see the bolts that holds the head on had been taken off and the bike was still like new so not many hours on the bike at all, I put about 30 hours on the piston before I did the rebuild, but I don't think a 30 to 40 hour piston would make a bike slow? No blow by past the rings everything still looked fine with the piston but still wanted to change it, also my valves was in spec before I put new cam chain in , but when new chain was fitted I had the reshim some of the valves is this normal? I'm sure it is because if the chain had stretched abit it would make th valves a different tolerance to the new chain?

Many thanks Carl

Share this post


Link to post
Share on other sites

In theory, yes. A worn chain that wants to kink on you will cause more drag and therefore slightly reduce horsepower.

In reality, not really. I'm not really sure what's going on here. I would say maybe the rings weren't broken in well before, but I would think that would cause some blow by. When you torqued down the cams, if you did it different than the last guy that could explain why you would need to re-shim. The chain shouldn't have any effect on the valve clearance.

Maybe the timing was off by a tooth before? Was it like this since you got the bike, or did it gradually start acting like this?

Share this post


Link to post
Share on other sites

No the bike just got abit slower after 30 odd hours on the piston n rings, correct me if I'm wrong but if the chain had stretched abit would that not make the cams a bit out of line to then make the cam lombs closer to the buckets?

Thanks Carl

Share this post


Link to post
Share on other sites

What made to me ask about the chain is if the chain had stretched as it was abit, that would make the valves not perfectly open and close in time which then would make the bike be down on power? Does that make sence

Share this post


Link to post
Share on other sites

The new cam chain should not have changed a thing for your valve clearances. I would go recheck your homework and verify your valve clearances.

The chain would have to be pretty stretched out to cause a power problem but I don't think that happened. I would vote for Karl's explanation that your rings just didn't seal properly. A glazed cylinder which wasn't cleaned up before the new rings could certainly cause the rings to not seat properly.

Share this post


Link to post
Share on other sites

I used to put a new piston and rings in my sons bike every 40 hours when he raced. He could tell the difference when the bike had close to 40 hours on it that is wasnt pulling as good. He would also notice the differance once a new piston was installed. Just FYI. I agree with everyone else I highly doubt the timing chain was the cause. The valves not being adjusted (being to tight) could have been part of the issue as well.

Share this post


Link to post
Share on other sites

I'm with the others on the worn piston and rings. However, a worn cam chain causes the cam timing to be off a degree or 2. You've seen it when the dots on the cams don't perfectly line up when the crank is at tdc. But install a new cam chain and everything lines up again perfectly. altered cam timing will most certainly affect performance.

Share this post


Link to post
Share on other sites

I'm with the others on the worn piston and rings. However, a worn cam chain causes the cam timing to be off a degree or 2. You've seen it when the dots on the cams don't perfectly line up when the crank is at tdc. But install a new cam chain and everything lines up again perfectly. altered cam timing will most certainly affect performance.

Thank you that's What I thought myself but wanted to see what other people thought, wouldn't that make sence with needing to re shim some of the valves? Cam chain stretched makes the cams out of line abit which will also make the cam lombs out of line abit on the valve buckets?

Share this post


Link to post
Share on other sites

Except when you are checking the valve clearance, you are doing it with the lobes pointed away from the buckets. Through most of the cam's rotation, the diameter is the same so it doesn't matter if it is slightly off when you are checking valve clearance, just as long as it hasn't started to "ramp up" yet.

I think the cam chain would have to be pretty dang stretched in order for it to alter the timing enough to cause what you describe, but who knows?

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Reply with:

Sign in to follow this  

×
×
  • Create New...