Banshee runs great when engine temp is cold.....but

[speed-racer]

My banshee runs very well when the engine temperature is cold, but after 10-15 minutes of hard riding it starts to run bad. By running bad I mean that it has trouble getting into the powerband. Once it gets there, it runs ok but not like it did when it was cold. Always starts great.......have to choke it when the engine and weather are cold and crack the throttle a tiny bit to start it after riding for a while. The engine is new and has never been dialed in just right, so I was looking for some direction for my next jetting change. Its a ported 4 mill with 34mm PJ carbs and Toomey T5s. Everyone with a similar setup has far different jetting from person to person, so I am not looking for a jet size but more a direction to lean torwards (rich, lean, main, pilot and so forth). If I could make it run just like it does with cold engine temps it would be perfect. Thanks in advance.

[350BANSHEE350]

hmm check compression and re-torque you head bolts in case

when everything gets good and warm it might expand you head gasket nd cuase it to run bad

 

if not then my gess is electrical

[jbooker82]

You need to go leaner. Cold motor pulls in cold air wich is more dense. When the motor warms it heats the air up so it is pulling in less air because warm air is less dense.

 

Start with the Main, then the needle clip position, followed by the pilot and air screw.

 

What jetting do you currently have with your PJ's?

[speed-racer]

hmm check compression and re-torque you head bolts in case

when everything gets good and warm it might expand you head gasket nd cuase it to run bad

 

if not then my gess is electrical

 

 

I have retorqued everything recently. I have never got the engine jetted right in the first place. It is real close, I just need some direction for jetting based on engine operating temperature.

[speed-racer]

You need to go leaner. Cold motor pulls in cold air wich is more dense. When the motor warms it heats the air up so it is pulling in less air because warm air is less dense.

 

Start with the Main, then the needle clip position, followed by the pilot and air screw.

 

What jetting do you currently have with your PJ's?

 

Why do you have to choke a cold engine? I completely understand the air density, but the air coming into the engine should be relatively close to the same temperature when the engine is hot as when it is cold....especially when moving 30mph. Not trying to disagree, just looking for more clarity. WOW! I just reread my post.....it's really hard not to sound like an ass when typing. Sorry

[jbooker82]

Why do you have to choke a cold engine? I completely understand the air density, but the air coming into the engine should be relatively close to the same temperature when the engine is hot as when it is cold....especially when moving 30mph. Not trying to disagree, just looking for more clarity. WOW! I just reread my post.....it's really hard not to sound like an ass when typing. Sorry

 

 

It is ok. You need a rich condition to start because the engine is cold. With cold air comming in to the motor. Pluse if the motor has not ran for a while the gas in the crank case has evparated so you have no fuel in the engine.

 

As for when it is running.

 

When the motor is warm it warms the air up. Especially on a 2 stroke since the air goes in to the cylinder then down in to the crank case.

 

So at the carb you are pulling in cold air and mixing it with a given amount of fuel. On its way to the combustion chamber it warms up as it travels from the carb in to the inake box then down into the crank case, then back up in to the combustion chamber. Still has the same amount of fuel but less air becase it has expaned from the heat.

 

That is why when the motor warms up it richens up. Try pulling the choak out when it is running back and see if it gets better or worse.

 

josh

[speed-racer]

Makes a lot more sense......I guess the condition would not be as apparent on a four stroke since air does not have to travel through the crankcase. Thanks a lot for the help.