New kart with HF Blue, Re-jet questions

[rkcarguy]

I just picked up a Italkart shifter chassis this weekend that was converted to a clone kart with a harbor freight blue lifan engine.
It's bolted to the chassis with the 15* angled motor mount.
The engine still has all the stock parts and gas tank, but the seller included a mikuni pulse pump, fitting, and fuel line to plumb in the chassis mounted tank.
After I get a few hours on the engine, I'm going to be removing the governor, installing a header and RLV mini muffler, a high flow air filter and adapter, and plumbing in the chassis mounted tank.
At sea level, what's going to be a good starting point(main jet #) for re-jetting the engine for all these changes?

 

[devino246]

No cure-all size. It may not need it, you'll just have to see. If it does end up running lean, get a numbered drill bit set or a few different sized jets and try a few different sizes.

 

[rkcarguy]

Found some info on NR racings site.
Drill or purchase jets in the .037-.039" range, for sea level operation once you've done the external bolt ons.
The stock one is .029" so that is quite a difference, I'd be concerned with damaging my engine if I left it jetted stock with the upgrades done.
The clone is brand new, we filled it up with oil and gas, lifted the front of the kart for a few seconds to get some oil into the head, and it started on the 2nd pull

 

[devino246]

Found some info on NR racings site.
Drill or purchase jets in the .037-.039" range, for sea level operation once you've done the external bolt ons.
The stock one is .029" so that is quite a difference, I'd be concerned with damaging my engine if I left it jetted stock with the upgrades done.
The clone is brand new, we filled it up with oil and gas, lifted the front of the kart for a few seconds to get some oil into the head, and it started on the 2nd pull

No harm in it running lean for a short time.