Hi all,

Decided to check my valve clearance on my HH250SS today. Followed the Honda CN250 manual & lined up the little punch mark & pointer under the rocker cover. (btw, it took me a little while to find the marks). After aligning the marks, I decided to check the position of my piston using a long dowel in the spark plug hole. The piston was down near BTC!! WTF! It is supposed to be at TDC according to the manual. Anyway, I went ahead & adjusted the valves as per the book & the buggy ran & idled fantastic.
Out of curiosity, I decided to try again, except this time I set the piston to TDC on the compression stroke by using my piece of dowel & re-adjusted the valves.....Buggy ran but was slapping itself silly! What gives? Aren't the valves supposed to be adjusted with the piston at TDC? Needless to say, I re-adjusted following the book and we're all running happily again.

Has anyone had this happen to them? The manual even says that aligning the marks will set the piston to TDC on the compression stroke, but it sure wasn't when I checked. Does anyone think that setting the valves with the piston in this position will do any harm. It certainly seemed to work well. The buggy was singing along afterwards.

Any thoughts?

Cheers,
Beetle from Australia.

You must manually place the piston at TDC before adjusting the valves, it is not automatic.

i think what happened is when you adjusted the second time for curiosity and just used the dowel and run the piston up with out looking at the marks you was on the exhaust stroke.
the piston will be up at TDC but that is exhaust.that would be my guess i hope that made sence
pud

Beetle the manual states to adjust the valves with the marks aligned and with the piston on the compression stroke because the piston goes through 2 cycles for each revolution of the cam. The second attempt you made--with the piston at TDC and (hopefully) the marks aligned was correct. I can only guess that you must have flubbed something on that attempt.

Be careful using a dowel to find TDC. If the sparkplug hole is angled you can snap the end off the dowel pretty easy as the piston hits it. Gee, how would I know that...

When I found TDC using the dowel, the piston was definitely on the compression stroke. I put my finger over the spark plug hole as i was rotating the engine (using the variator pulley), & air was trying to escape past my finger. When this occurred, I put in the dowel & continued to rotate until I reached the highest point of piston travel. Then I did my adjustments.
I understand how a 4 stroke engine works, that is why I find it a little strange that I wasn't at TDC when the marks were aligned. I checked this more than once, thinking that I must have done something wrong. I rotated the engine again & re-aligned the marks, then checked piston position again....still nowhere near TDC.
I don't get it.
Not that I really care. The manual procedure works well (as it should) so I'll be sticking to that in future.

You guys make this more difficult than it really needs to be.
I always adjust my valves with the motor running and warmed up. Just hold onto the adjuster and listen to the valvetrain.
Tighten up where it sounds best, but not totally quiet.
This has worked with solid lifters for many, many years.

-J.R.-

Finding the cam punch mark on the CN250 is too much of a hassle on many of these karts. On some you have to remove the gas tank or rear rack to get to the inspection hole. We don't even bother.

Here's how I do it: Pull the spark plug and remove CVT cover. While using a small screwdriver, I rotate the CVT fan counterclock-wise until the piston is at TDC. Then loosen both adjusters. I then move both adjusters back and forth. If they are hard to move (or don't want to move at all) then the piston is at TDC on the exhaust stroke, so I rotate the piston down and back up again to get to TDC compression stroke. The adjusters should move back and forth easily with a definite STOPPING POINT. Then move both adjusters in then back out till they stop, then back in one mark and tighten.

Ricduncan,

That's exactly what I did the second time around. It made my buggy idle worse. Yes it is a pain to get the inspection hole off, but I found the buggy ran better if I did it that way.