[ericdudee101]

Ok, first I have a 97 TRX300EX which has a 11:1 high compression piston and a FMF power core exhaust, and a K&N air filter with the lid off the air box.


One thing I notice is that with It neutral at half throttle or so it dies off fast over and over as if it were hitting the rev eliminator and I don’t notice it as dramatically in gear but it still doesn’t feel right riding. I think it is probably a carb problem, maybe too righ because it has a loud higher pitched backfire when you let off. More of a popping sound.


The other thing I notice is when holding it at a steady RPM, it seems to miss to the point that in 1’st and second gear you can really feel it jumping. I’m not sure if this is also a carb problem or an ignition problem.


The carb either has a main jet or 120 or 122 because I am at a high altitude (5,000ft.) in northern Arizona. Can anybody give me some advice?

 

[tomgodd]

It sounds like a carb issue. Check your plug and see if its running lean or rich.

 

[JerseyTrueBlue]

Not tryin to thread jack but how can you tell rich/lean by checking the plug? Not being smart I seriously would like to know lol.

 

[tomgodd]

The color of the electrod. Black=rich White=lean cardboard Brown is the color you want.

 

[JerseyTrueBlue]

Great info to know thanks buddy.

 

[mud99]

Not tryin to thread jack but how can you tell rich/lean by checking the plug? Not being smart I seriously would like to know lol.

A tan colored plug means that the engine is running normal and the air/fuel mixture is correct. This is the correct color a spark plug should be and it tells you everything is fine with the engine. You would install a new properly gapped plug. When installing a new plug, replace the old one with the same heat range. This plug shows normal wear in the center electrode. A new plug would have square edges that helps the plug fire better.

A black dry fluffy colored plug is caused by deposits from a carburetor that is running too rich (too much gas), or excessive idling on some engines. Black smoke coming from the exhaust is a sign of a rich air/fuel mixture. The rich air/fuel mixture must be repaired before installing a new spark plug. Common causes for a rich air/fuel mixture are: dirty air filter.
air mixture screw or carburetor needs adjusting.
choke is sticking.
carburetor float height is out of adjustment or float is sticking open.

A white colored plug is caused by engine overheating. Failure to repair this engine will result in severe engine damage. Common causes for this are: Incorrect spark plug (too hot heat range).
Low octane fuel.
Timing is not set properly.
Cooling problems, (dirty cylinder fins, no or low water if water cooled, low or no engine oil).
Carburetor air/fuel mixture is too lean (too much air).
Leaking crankshaft seals, no oil, base or head gasket leaks, or crankcase leaks on two stroke engines.

 

[mud99]

Ok, first I have a 97 TRX300EX which has a 11:1 high compression piston and a FMF power core exhaust, and a K&N air filter with the lid off the air box.


One thing I notice is that with It neutral at half throttle or so it dies off fast over and over as if it were hitting the rev eliminator and I don’t notice it as dramatically in gear but it still doesn’t feel right riding. I think it is probably a carb problem, maybe too righ because it has a loud higher pitched backfire when you let off. More of a popping sound.


The other thing I notice is when holding it at a steady RPM, it seems to miss to the point that in 1’st and second gear you can really feel it jumping. I’m not sure if this is also a carb problem or an ignition problem.


The carb either has a main jet or 120 or 122 because I am at a high altitude (5,000ft.) in northern Arizona. Can anybody give me some advice?

42 slow 3 turns out on air/fuel screw 134 main. Thats with a full after market exhaust and air filter. Not sure about altitude or adjusting for it.