Balance shaft go/no go?

Blue bandit

New member
Hi all

Ordered new crank from nr racing for my gx270 and see it has gear for balanceshaft and counterweight also looks a bit different compared to the other one.

So will I be fine running without?, are 270´s & 390´s balance gears the same, since nr-racing only have for the 270

engine will turn 6-7000rpm loaded

The old balance shaft question. If you remove it, it will vibrate. At what rpm, is hard to say. If you remove it I would strongly suggest balancing the rotating assembly. I would say 58% to 62% balance factor.(56% would probably be OK for that rpm range). This will typically result in adding weight to the crank. This adds expense and its not real easy to find a shop capable of doing this properly in all areas. Or willing to do it. Leaving it in is easiest option. If aftermarket rod is used, will probably have to clearance it a little. it will rob some power but may save a lot of headache if not properly balanced. I dont know if 270s and 390s are the same. I have seen 3 different ones in the 390s and 420s Ive messed with. Good luck.
I can tell you that Vegas Carts 440s are 4 ounces light on the crankshaft counter weight @ 7200 rpm. They can be balanced with 1 3/4 by 3/4 shot of heavy metal. You do need to remove the balance shaft gear.