What's the ONE best internal engine mod?

/nads.com wrote:What's up with people saying Tsubaki "heavy duty" cam chain?
Isn't that new soobaaky just the same chain that's already in there? And if they do stretch then what's ta keep the new one from stretching? I'ts just that everyone says replace chain replace chain, I'm wondering if they really know why or if it's another mooo thing. One cow turns right ohter cows come too. And I'm that funky looking cow that noone will play with. :woohoo:

The Tsubaki cam chain is much heftier. The pins and side plates are all heavier duty. Installing heavy-duty springs, and high lift cams cause more stress to be put on the cam chains.

It is rare for a cam chain to break, but they wear and stretch. When they stretch the cam timing changes causing the bike to become lethargic. If you look at what Kawasaki says is the chain stretch limits and run the numbers on cam degrees, you'll see the exhaust cam can be 3-4 degrees retarded and the intake 6-7 degrees - that's a staggering amount.

The Tsubaki chain doesn't stretch as quickly.

If you run slotted cam sprockets you can compensate for the stretch.

Given the price difference between the Tsubaki cam chains and the OEM chains (or OEM equivilent), this is a no brainer - always go with the Tsubaki chain.

Hey Jeff is there any need for the HD chain or will the regular Tsubaki be fine for many years of street use? Seems like the HD one would be more moving mass, thus a tad less HP. Probably can't feel it tho...

To answer that question reasonably would require defined criteria.

Eg. I have my motor completely apart. My riding realistic riding style is.....whatever they claim....

I intend to go through the bottom end completely and assemble with new cam chain, idlers, etc. What would the most logical / cost effective performance upgrade be from there?

Now, given the clearer picture of the intention of the build, it's possible to suggest what could be done and why it should be done.

For any given engine rebuild, there is a purpose for which the engine will be used. Without that, the only answer that covers all general purposes is to increase the bore size. Everyone can use more cubic inches. After that, the real tuning takes place in the head, cams and carburetors.

Those items must work in conjunction to support the design goal & the choices must be made wisely.

Cams cost the same from mild to stupid grinds.
Carburetors cost nearly the same.
Port work will vary to some extent with costs.

A touring motor will benefit from the same type of mods a race motor will benefit from. It's just knowing how much of which to apply for each specific design application...

Now that didn't answer the guys original question any better than anyone else's answer did but it at least lays out a correct format for logic..... I HOPE ANYWAY :laugh: