Checking Valve Clearances Hot vs. Cold

On the 650, check them cold, get the clearance as close to 0.150 mm as possible. Ride and enjoy.

See, that was easy!

Without being a judge about the issue, how many of you have actually checked the valve clearances, by accident or deliberately, with both a cold and a hot engine and can tell for sure either way?

www.motorcycleproject.com/motorcycle/text/cows-clear.html

ibsen22000 wrote:

Without being a judge about the issue, how many of you have actually checked the valve clearances, by accident or deliberately, with both a cold and a hot engine and can tell for sure either way?

www.motorcycleproject.com/motorcycle/text/cows-clear.html

I don't know who Mike Nixon is, but I'd certainly take that article with a large grain of salt. I think I would rather rely on the info gathered from conversations with the guy that designs the cams for the top Nascar teams.

Regarding ramps "They're also, paradoxically, almost accidental, being more byproduct than intentional -- what is left over after the lobe's shape is built"

Maybe thirty or forty years ago this was true, but it certainly hasn't been true for a long time. Ramp design is critical to valve train and engine life, it's probably the most critical part of a cam design, and is affected by many things, especially the mass of the valve train.

Oh well, I guess everyone is entitled to have their own opinion

ibsen22000 wrote:

Without being a judge about the issue, how many of you have actually checked the valve clearances, by accident or deliberately, with both a cold and a hot engine and can tell for sure either way?

www.motorcycleproject.com/motorcycle/text/cows-clear.html

Well I have, just today.

I had to stick around the house today and had some time to kill so I did the comparison on the valve clearances on a cold and a hot engine.

Here is what I did.

The bike idled for 10 minutes, enough to say that the bike reached operating temperature. I then wheeled the bike in the garage and put on my gloves, pulled the tank, coils and valve cover. Pulled out the feeler guages and checked each valve while they were still very hot.

Then I let the bike cool off for about 4 hours and rechecked the clearances. I found that there was a difference of 0.06-0.10 on the feeler guages.

So based on my rudimentary, completely unscientific experiment from today, I would say that the shims and or associated valvetrain components expand on average 0.08 in thickness in a hot engine versus a cold engine.

Incidentally my Kawasaki Kz650 mechanic's manual says that clearances should come in between 0.08-0.18 mm. Which makes sense on the lower range of the manual recommendations for a hot, operating engine.

Cheers-Colin Firth-Ontario Canada

Post edited by: reborn650, at: 2007/06/09 22:43