I have the GX31 engine and I have not manage to find material other than the IPL. You have to pay for a shop manual.

That said, you look for some sort of mark on the cam and the gear that drive the valve? I am just guessing the following because I never done that before.

Remove the timing chain, get the piston in TDC. Then rotate the gear that drive the valves so it is right in between one valve closed and right before the second valve open. That would be approximate the point of the transition of exhaust to intake cycle. If it is in between the compression and combussion cycle, there is a lond dead spot where both are closed, that's not what you want. YOu got to look for the exhaust to intake transition.

Take a look at the cam lobe, if it point in between the two push rod, you are in sync of the transistion between exhaust and intake cycle. If the lobe is pointing downwards, the crankshaft is in transistion between the compression and combussion cycle, you have to turn the crankshaft one turn to get the lobe pointing in between the two push rod.

With all that, you know you are at approximate correct position. Then look at the cam gear and the valve gear above and look for any arrow, there got to be some marks to tell where you should set the two gear. I believe even with the manual, they have to have some marks no matter how small and in-obvious they are. Then allign accordingly.

I am just using common sense guessing. The way I described is to bring the gears to approximate the correct position so you can look for the marks. If you can't find the marks, then........I don't know you!!!!!

Never had one apart. One would hope it makes sense when it is apart.

Here is a link that might be useful: Hopefully your Honda manual is here

Sorry, forget everything I wrote on the former post, I don't know what I am thinking!!! I was totally confused, mixing OHC with OHV. Just ignor the whole post!!!

Sorry