Has anyone done their valves in a 4 stroke?

[sho305]

Wanted to ask; when I swapped a 16hp clone into a G9 I checked out the stock engine. Its a '91 and the oil ring let go, it still ran ok. The valves had big grooves worn into the seats, really nasty. I wonder if anyone here has done them and did it help it run better. In kart racing and such getting the highest compression is a big deal they do valves all the time. I should do mine but going to swap it to a 16hp anyway, and weather is going away here not sure I have time to play with carts anymore this year.

[chompy]

I have swapped out valves in many different engines over the years. It didn't really make any difference on compression if you lap the valves. I just replaced them because they were so worn out. The engine noise was reduced slightly.

[Freezeman]

A compression test shows how much static compression a motor has. Leaking rings and valves reduces the amount of static compression a motor can make. Then a leak down test can direct you to the leaks. Most small engine shops should have the correct equipment to grind valves and seats. If they are worn like you say, the valve guides probably need some attention too. They don't run better with bad valves,seats, guides and rings.

[sho305]

I'm not sure what he will do with the engine, he likes the 16hp clone I put in there. I was just thinking mine has a little less hours on it it must look nearly the same, so a lot of them must be that way. Mine will get funny when it is hot out and lose power, run strange at low rpm at times, pop in the carb on starting. But I thought it could be the ignitor going bad too, it is fine when cooler or not worked hard. One time it did it and I ran it wot for half a mile down the road then it was fine for hours of riding after that, didn't make much sense.

But yes, his engine did make a little noise but did not show symptoms of a valves issue like misfiring/backfiring. I didn't check the compression. Checked mine years ago and forgot what it was iirc G9 are around 180.