honda gx620 performance modifications - anybody have info here?

[gran_pann]

I have a honda gx620 (well, three of them) that I am working on. Two are up and running, and I will be putting them on a tomberlin crossfire and a manco 706b.

Im looking into removing the governor mechanism, and am wondering what performance modifications I could do to these engines. Im no stranger to modifying engines, and have modified a few smaller industrial engines honda gx200, predator 212, honda gx390, and even made a stroker gx390.

So, looking into modifications it seems that there are few (if any) parts to be found. Sadly.

What about the rods on these things? Do they hold up better than the smaller engine rods as they have forced oiling?

Cams? springs?

My hope is that I can get away with keeping the stock rods, doing a mild port job on the heads, custom free flowing exhaust, maybe bump up the compression ratio a tiny bit with the autolite sparkplug, advance timing 4-6 degrees, heavier valve springs (these heads look an awful lot like the gx390 heads), hone cylinder, replace rings, possibly shave the head a few thousandths... if theres a better cam, maybe even replace that.

These engines are torquey already, and I dont think ill need more of it, just more RPMS without blowing a rod.


Any advice would be helpful.