Box Stock

flywheel weights and idle

Yes flywheel weight does effect idle speed if you are using an ultra light, but you shouldnt have to idel it up that high. Is this a stocker or modified engine?
 
A flywheel on the single cylinder is a big difference.. idle is a lot harder to control with a light one for sure.. I can even tell a difference in idle with the car engines from a flywheel and a flexplate on my break in stand.
 
There must be some reason why manufactures put that big heavy flywheel on those small engines! Just a guess; probably to get them to run smooth at low rpm's. You think? A lighter flywheel would be cheaper, I'm sure the manufacturers would like that.
 
Ya it's not stock but it's not wild... once I get down to a descent idle it just pops and throws the fuel out of the carb and dies. Ive run the light weight flywheel before but on a lot different build and I expected that to idle a bit high
 
It's an old one I got used its not an arc it's another one I can't think of who made it off hand... but I believe it set at factory timing and I'm not using a cut key... I just wanted to see if it was normal to want to idle that high with these light weight wheels
 
I just changed from a stock flywheel to a raceseng s2 on a gx390, thats going from around 12lbs to 2.2 I think. I can get it to idle pretty nicely @ about 1250 rpm, could probably sneak it down lower if I wanted to. The only issue with the light flywheel is pull starting it is impossible, the inertia just isn't there to get over the kickback, before I could pull start it sitting in the kart. Smaller motors may not have this issue though.
 
Oman said:
I just changed from a stock flywheel to a raceseng s2 on a gx390, thats going from around 12lbs to 2.2 I think. I can get it to idle pretty nicely @ about 1250 rpm, could probably sneak it down lower if I wanted to. The only issue with the light flywheel is pull starting it is impossible, the inertia just isn't there to get over the kickback, before I could pull start it sitting in the kart. Smaller motors may not have this issue though.
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They do, they crank like crap with a light flywheel ..LOL
 
The ultralight flywheel is not allowed in any stock class that i know of, and have not seen any difference in idle with the other ARC flywheels that everyone uses on them or the stock flywheel they come with. That was my opinion. I assumed you were asking about stock classes, you dont have an ultralight anyways so that doesnt matter Tim
 
subbietjw said:
It's an old one I got used its not an arc it's another one I can't think of who made it off hand... but I believe it set at factory timing and I'm not using a cut key... I just wanted to see if it was normal to want to idle that high with these light weight wheels
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If its not an ARC then make sure the flywheel did not slip time, especially if it pops, spits fuel and shuts off....that sounds like the timing could have slipped enough to affect things a little, although not enough to keep it from starting up.
 
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