Why smaller main jets

[Sheesbest]

Replaced stock crank with a hotrod stroker, wiseco,s and head spacer gasket. Shee not happy, not revving up. Plugs verry wet. Before 300 mains down to 240. Problem solved. Why smaller jets with this mod.

[BenBB]

Blowby with the old/worn setup maybe? Less exhaust loss (or whatever the hell the term is for the intake charge that goes out the pipe and gets drawn back in) with the stroker perhaps? Just guesses tho...

[No Limit Powersports]

When you increase stroke length you increase your pulse length which will pull on the main harder causing the bike to need to be down jetted to keep the air/fuel correct.

[dajogejr]

Bigger pistons and/or a bigger stroke normally require less jets/less fuel to a certain extend...

Two of my buddies 4 mil cubs like a LOT more fuel than my 10 mil cub, for example...

 

I would also double check to make sure you don't have an air leak as well...just to be safe.

[J-Madd]

Bigger pistons and/or a bigger stroke normally require less jets/less fuel to a certain extend...

Two of my buddies 4 mil cubs like a LOT more fuel than my 10 mil cub, for example...

 

I would also double check to make sure you don't have an air leak as well...just to be safe.

 

 

Just to help clarify..the 4 mils need larger jets, not necessarily more fuel, than the 10 mils due to the pulse signal drawing through the intake, and ultimately, the main jets. Larger stroke = stronger signal, can pull more fuel through smaller jet. Basically what bansheestang said.

 

I know you know this, just restating it a little different for others. :thumbsup:

[dajogejr]

J...very, very true...and thanks for posting that.

After re-reading what I wrote, hell...I'm even confused and I wrote it...LOL...

 

Thanks for the backup!!!

[Sheesbest]

Thanks, This down jetting had me goin for a while.