Where to get Jets?
 

I am looking for a source for both the primary and secondary jets. The bike is an 86 xt600 USA model. A source that is in USA would be great. Im looking for leaner as the bike runs like a dog above 2000m. When the secondary opens, it falls on its face and misses horribly. At 200m, it runs like it should. I plan on going to the interior of Mexico and we will be riding up to 3000m on parts of the trip. Thanks in advance for the replies.

Jets or needles
 

The jets only determine the mix at full throttle, which is probably not how you are riding all the time.
Better to lower the needles one notch, this leans out the mix and is pretty easy to do. Be careful to replace all rings and washers in exactly same locatio, and don't loose the litte clips or take some spares.
Finally, make sure to put the needles back in original position when descending again.

Auke

Needles
 

I would agree with Auke, lowering the needle is the best option.
At altitudes the engine will get less of oxygen, make the fuel mixture
more poor.
The main jet only influences mixture at full throttle, when the needle is completely out.

Matt

Lowering the needles sounds like a plan. At 1500m the bike starts missing badly at 4500rpm (which is half throttle or a bit more). It seems like it running OK on the primary but when the secondary comes on, the motor doesnt like it. Should I lower both needles or just the secondary. What effect would taking the spark arrestor out have. Im assuming that it will run leaner (stock pipe). Im trying to keep up with a bunch of Honda xr650rs and they have a big horsepower advantage over the XT. The nice thing about the XT is that my stock tank still has fuel in it when their 5 gal tank is empty.

Whatever you do when changing carb settings, is do only do to ONE THING AT A TIME.

That way you can always go back when and if things arnt working. Only change the needle one setting at a time too.

I guess I dont have to tell you that you shouldnt even go near your carbs until your certain that the valve clearances are correct, the air filter is clean, spark is good and reliable and your bike is in general good condition.

Taking the baffle out the exhaust will make it leaner yes.

The jet sizes effect the mixture at all throttle positions ranges. If your bike idles fine and will pull ok from closed throtle then leave the pilot jet alone. It its seriously bogging down on half open throttle then you could experiment with a smaller main jet or try dropping the needle.

Be very careful when leaning a bike out though. If you go too lean you will cook the plug and the top end.

on the subject of cooking the top end i put a new stainles steel exuast on my bike with a e marked baffel and after a 6 mile run i noticed that the down pipes were red hot were they come out of the head is this a norm or is she cooking

cheers
:eek3:

RED HOT ??? No, that aint normal. Not unless the pipes are very poor quality or very thin.