Which way to move stop on needle valve to lean out mixture?

[Earthman]

I’m using an engine kit from Bike Berry in which the motor and exhaust are painted with black powder-coat paint. The paint on the exhaust is flaking off in large chunks, exposing the steel beneath. I’ve only run the engine for about an hour. Is anyone else having this problem?

I wonder if my mixture is too rich and the unburned fuel is being consumed by the catalytic converter, which is making the muffler hot and burning off the paint. I think this may be a possibility because I checked the temperature of the motor, exhaust pipe, and muffler using an infrared thermometer. The temperatures were <200 deg F, <200 deg F, and >400 deg F respectively. I can’t measure anything greater than 400 deg F.

I guess the paint could be peeling because of poor workmanship too. In any case, if I wanted to lean out the mixture, which way do I move the stop on the needle valve in the carb - toward the top or bottom?

Thanks.

[Creative Engineering]

Move the clip on the jet needle up to lean out the mixture.

Jim

[Ghost0]

Have a look at your spark plug to know how your fuel mixture is. Yes temp can be used but the plug is a sure fire way to tell.

[tyrslider]

That is not powdercoat, it is paint. Exhaust systems do not welcome paint. Because of heat and because exhaust is corrosive. It's corrosivity seems to undermine the paint.

It takes good surface treatments for exhaust systems to keep their finish; they don't waist time or $ w/ that on these motors.

Ghost0 is right, read your plug. Also, what is your oil ratio? More oil means less gas and vice versa!

Some of the kits say 16:1 for break in 20:1 after. That's too lean (gas) and too much oil. Go something like 20:1 B/I and 32:1 after a couple tanks. Good luck!

This may seem irrellivant, it's not, too much oil affects your motors ability to burn gas which causes heat to build up and messes w/ your plug readings i.e. can make it look darker/richer. Cleanly burning (and not exploding) fuel helps keep your top end cool!

[Earthman]

All of it great advice - thanks!

[midatlanticcycle]

started to run 4 ounces of quality 2-stroke oil (NOT the family dollar store weedwacker crap) after second tank of fuel. this is about 32:1 and seems perfect. these motors are pretty understressed. clip down for rich, up towards top for lean on the main jet needle. try NGK B5HS in place of the chinese stock plug. looking for dark brown to tannish color on center porcelain electrode area. white bad/lean and black bad/rich. hope this helps

[Cabinfever1977]

the paint on my cat muffler is perfect still and its from my gasbike.net engine kit.