sputter issue

[rustyk]

Test drove my new project yesterday, runs awesome, only problem is when im at full throttle it seems to sputter a little. Souds like a rev limiter on a four wheeler. Maybe jetting issue? Oh yeah, its a 80cc skyhawk, port and polished, high compression head, cheap racing carb, and an expansion chamber, thanks for the help.

 

[Chaz]

Hard to tell since everyone's definition of "sputter" can be different. But if she's running good all the way up to wot then I agree that it's probably a jetting issue. How does the plug look, colour wise.

 

[2door]

If this is a brand new engine I wouldn't worry about it. You'll need a couple hundred miles on the engine before you start playing with tuning and jetting the carburetor.

Give it some time. It will run better as you accrue miles. They all run rich at first. That's how they are se up from the factory. And the piston rings haven't seated yet so compression isn't what it will be later.

Go ride your bike d burn up a couple of gallons of fuel. If you're using the kit recommended fuel/oil ratio of 16:1 you'll want to reduce the oil content down to no more tan 24:1. 32:1 is even better.

Tom

 

[rustyk]

Makes sense. It is a new engine, not broken in yet. Not suppose to go wide open anyway I suppose, couldn't help it though.

 

[Chaz]

Absolutely right, Tom. Don't know how I missed that. I shouldn't post before my morning coffee.

Rusty, it's fine to go wot a little bit here and there just not sustained until she's broken in. The manufacturers suggest a fuel/oil mix that is over rich to protect the warranty. Go with Tom's advice.

I get the sense you are already addicted to this hobby, have fun.