How do I tune the engine for high altitude and cold tempuratures

[snowbanana]

I ordered a Grubee Skyhawk and i am waiting on its arrival. I live in salt lake city utah where the elevation is about 4,500 feet and its about 25 degrees right now, but it gets near zero sometimes. im wondering if i will need to change the fuel mixture or tune the carb to make the engine run good.

 

[ibdennyak]

High altitude has thinner air, so it will tend to richen the mixture. You may have to move the clip on your needle. In extreme cases you may have to go with a small jet even. Cold has just the opposite effect...the air is denser, so it would require more fuel. It all requires experimentation, so the above is just pointing you in the direction. How much you will have to determine.

 

[snowbanana]

thanks. cant wait to get it and start my experimenting.

 

[happycheapskate]

Its highly likely that you can make your bike work with the available needle/clip settings on the stock carburetor.

You might employ some type of intake air heater, such as an intake pipe which goes into a good filter box, that draws fresh air, but is heated by the muffler or fins to a degree. This won't help you cold start it but will help it keep from knocking or sputtering.

I live in sunny North TX, but have been driving my mb on some 20-35*F days. Once warmed up, it runs great, but starting is harder, esp with the new high flow performance air filter.

I heat the motor up with a hair dryer in the morning to help it start easier.

 

[snowbanana]

thats a good idea with the hair dryer because I have a little honda and it takes over 20 minutes of giving it throttle and keeping the choke on before it will run without stalling.

 

[happycheapskate]

Do it outdoors or garage, and be careful not to ignite any fuel vapors. (like not right after fueling)
I use a $10 vidal sassoon 1875 from walmart. (the air sucks in the back and blows straight out)

Just heat the fins and maybe the carb bowl if its really FFFFFFF cold outside. Don't blow into the air filter/carb or you will likely flood the engine.

 

[snowbanana]

thanks