Gx390 balance shaft removal?

dubs27

I am waiting on a billit rod for my gx390 and have been doing a little research on the timing marks of the balance shaft I didn't see any marks when I removed it. I have read on some of the gokart forums that some aftermarket rods can hit the balance shaft and that they recommend removing the counter balancer? Some complain of more vibrations from doing so.

BGW

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flyingw

I don't have experience with it but I have also red the same things u have. I would recommend leaving it in. Unless your building an all out screamer that's turning 8k, I would go for longevity. Just my 2cents.

sho305

I can't find a solid answer on this, some have taken them out of stock G9 also since the case wears and they knock. Some say no difference some say it shakes.....hear same from clone crowd. Lot of kart racers do take them out for more power/less weight. It seems to matter less at higher rpm use I gather.

dubs27

Okay I plan on leaving it in. I just read some aluminum rods have clearance issues and that's what I was worried about. Plus I couldn't find the timing mark on it until tonight. Mine will only turn about 5200 rpms usually.

fstg21

Leave it in. If it close, use a file to remove a bit off the heel of the rod or the balance shaft. I've never had problems, intalled about 30 now. Timing marks are dimples on the outer gear of the crankshaft, camshaft and the balance shaft. wipe off the oil, you'll see them. A paint pen helps on reassembly. Line them up and you're good.

dubs27

thanks!

sho305

Put the HD valve springs in and let it rev some. I gained 5mph or something, valve float is a bad thing anyway and the springs are cheap. I dont know if it will hit 6K rpm or not, my cheap tach gets strange after 5500. I rarely go that fast anyway. Mine also did 5200-5400 with ported/cut head and advance key, better airbox/header/jetted. It pulls past 5500 much better now with vegas HD springs in it though I also put 1.3 ratio rockers in.

dubs27

I put the h.d springs in at the same time I removed the governor. The motor is a bone stock 13hp with exception of the vegas carts carb. And timing key.

sho305

Good plan, you put on the rev kit more or less. It could be all the other stuff I have done makes it rev more. The 390 usually gets more rpm than a 420 all else equal, as they use the same cam.
In gokarts they tend to run 500rpm higher with stock engines, but not much load on them that way. 420 may have a little more bottom end. But my 420 has a ported head cut .080, 4 degree timing key, 1.3 rockers, HD springs, jetted carb, airbox from a car, 1" header from Robertson into a car muffler.....all that stuff helps, though I think it would help more with a cam. But until I can afford a rod and cam and better valvetrain parts all together I will not put a cam in. It runs pretty nice I hope I will have more power with the new clutch on it, getting the power to the ground is also important. Also trying to fab a new intake to put a motorcycle carb on as the stock one sucks IMO but all one can expect for its intended purpose. Thought about the vegas carb but wanting to try a CV carb I want much better drivability.