Hello,
I plan on checking and most likely adjusting the valve clearance or lash on a couple of atvs (03 Prairie 360, 01 Warrior 350 and 94 Timberwolf 250). I understand the concept, why it needs to be done, and have the tools. All of the bikes are single cylinder. I know I have to set the piston to TDC, but from what I understand the bike is in TDC twice for each cycle (4 strokes). I'm just wondering when should it be in TDC to set the valve clearance? I'm thinking it's at the end of the compression stroke when both valves are closed and the spark plug fires? I know people say I won't be able to move the valves because the rockers are tight, and that's an indication to rotate the crankshaft 180 degrees. Or do I set it to TDC after the exhaust stroke? I'm a little confused, and if someone can explain it to me, I'd greatly appreciate. I know the bikes have 'T' or punch marks, but I'd prefer to understand how it works, than rely on these. I would like to know so I can watch either the intake valve go down and up (end of compression stroke, TDC), or watch the exhaust valve go down than up (end of exhaust stroke, TDC) to adjust the valve clearance.
Thanks!

 

You want the whole story so I will give it to you.

You want to be on TDC. In other words:

Lets start on the intake stroke. The piston is at the top of the bore. The intake valve is starting to open and the piston is going down drawing in air and fuel with it. As the piston gets to the bottom the intake starts to close. At BDC the intake is close or almost closed.

Now the piston is starting to go up on the compression stroke. Both valves are closed. Now the piston is at TDC and both valves are still closed. This is where you want to adjust the valves. (Both of them)

BOOM, the mixture is lit. The piston travels down on the power stroke. As the piston gets close to the bottom the exhaust valve starts to open. As the piston travels up the exhaust valve is open to let out the exhaust. At the top the exhaust is starting to close and the intake is starting to open (overlap). The piston is at the top and the intake is starting to open and the piston is starting to go down for the intake stroke..............and so it goes...............

I just get the rocker up on the heel of the cam and adjust the valves.

You will know if you are 180 off because one rocker will be tight and one will be ok to adjust.

Hope this helps.

Weewwwwww, now that was some typing!!!!

 

Thank you so much!!!!!! I appreciate it, and now see what stroke I need to be to adjust the valves!

I know this pertains to the subject, but I'm having a hard time finding feeler gauges that are in metric increments, and are angled. Any suggestions? I already searched eBay, amazon and visited both my local Autozone and Advance Auto Parts.

Thanks again!!!

 

Glad I can help you.
As far as the feeler guage goes:
Use Online Conversion - Convert just about anything to anything else this link and cross it over. There is a spread on the spec's so don't freak out if it's not exact.

Good luck!!