Bike bogs stalls and looses power when hot

[CatatonicBug]

so what way would i turn the air fuel screw to lean it ?? clockwise ??

Screw it in (clockwise) to go lean, out (CCW) to go rich. However, the tips have a tendency (especially in the earlier model carbs) to get snapped off down in the carb body, and if that has happened, no amount of turning the screws is going to adjust anything.

[psycoreefer]

yes, clockwise, that will change mostly your idle and have a small effect on "cruise" mixture.

take a look at the tech tips for adjusting idle mix, I come from a snowmobile background a bit as well, and I find its much faster to adjust the idle mix by ear first, and then fine tune from there based on plug color. Another thing to keep in mind is that these carbs are way different then most snowmobile carbs, I've not worked on anything newer then late 90's but all the snowmobile carbs I've seen the throttle lifts the slide...these don't work that way. On XS carbs lowering the needle will lean out the mixture, but not over the entire range, the consensus is that the needles effect mostly from 3500 to about 5 or 6k, however I think throttle position also plays a big part in that equation.

Best way to go is to tune from the top down, go out and find someplace you can do a wide open run (up hill seems to work well) in 2nd or 3rd gear. Kill it before you throttle back, coast off and check your plugs, if they look good, your mains are the right size, if not adjust the mains. Once you get those right, work with the needles for the middle, then the idle jets for low.

I'm surprised no ones asked yet, what year and model bike do you have? Any modifications, like K&N filters or 4-1 exhaust?

[dezmitchell]

Its a 1980 xs just straight piped

[CatatonicBug]

Its a 1980 xs just straight piped

And you have adjustable needles?? Those are only in the older model carbs. Do you have a dynojet ket? The straight pipes are likely causing a lot of the trouble. You need some back-pressure from the exhaust for the engine to operate properly.

[cywelchjr]

And you have adjustable needles?? Those are only in the older model carbs. Do you have a dynojet ket? The straight pipes are likely causing a lot of the trouble. You need some back-pressure from the exhaust for the engine to operate properly.

+1 on the straight pipes causing trouble. These carbs on these engines really tend to NEED at least some backpressure to work properly, and they will not work right without it. You will fight and fight and never be able to get the entire range at all temps right without some backpressure. Ivan tried putting cherry bomb glass packs on his and finally ended up giving up and going to a regular exhaust system because he couldn't get it to run right through the entire range.