[acecarlos]

Just did an XC race yesterday. Bike made it the 80 minutes. Barely. Ran out of gas minutes after crossing the finish line. And I was not running near as hard as I did on my old 450. Do these really suck that much gas?

Specs
'87 stock bore, just redid top end, had 135psi prior to hone and new piston/ring job, single gasket head gasket, 50/50 mix av gas and 93, Lucas 36:1 oil, .022 plug gap, 158 main, 42 pilot, air screw 2 1/2 turns out, choke/throttle screwed all the way in, fmf gold pipe, foam filter with per filter lid cover. DGH needle, clip on top groove. New throttle cable.
It was almost 80 yesterday, low humidity here in texas.

Second question, I'd let it warm up for a few minutes and then have to really hog on it to clear it out or it just bogs and sputters real bad. Smokes a lot. But after a few quick third gear runs, it clears out. Racing it though after that I have no issues with it loading up. Wouldn't clear out by just revving it, I have to have a load on the motor. Really but absolutely no bottom end. Once power and kicks in its definitely a handful. Plug chop shows a good chocolate color but the plug ring is wet. Electrode and ground strap are not.

So with the needle at the top already and pilot at 42 and choke/idle screw all the way in and it still running rich down low, what else could it be?

The jetting sounds low to me already. For SoCal it would be way lean at 0-1000', 80F, 35-50% Humidity. I also don't like your needle position, this tells me something else is not right. If your IGN is weak, or the engine is getting a poor spark, fuel wastage is high. FYI...and as a reference in the old Desert Races on Ported OEM cylinders running Race Fuel we would get around 2 hours on a full tank of gas going a lot further than you did.

Carlo

 

[acecarlos]

The more restricted the airbox or filter are, the smaller your jetts will need to be. As an example, just removing your lid or outerware will lean out your engine.

Carlos

 

[acecarlos]

Let us know how it goes for you....

Carlos

 

[acecarlos]

After some screwing around, I pulled the prefilter off, set the pilot at 40i AS at 1 1/2 out, main at 155, DGH needle on middle clip. Seems to run very well. Plug looks a bit hot but I haven't been able to really open it up either. High 3rd, low 4th is about all I was able to do this weekend. Had a 38 in it but when it started cold it revved very high like the choke was stuck on. Figured that was probably too far off. I may try the 42 again now without the prefilter but it just scares me to run without one in a 90 minute long race in this Texas dust. I'm hacking dust up for days after the race as is, I can only imagine what the motor could suck up.

Try a Uni filter, well oiled. The two stage filters are very restrictive, likey why your jetting Is as low as it is. Bottom line, if it works for you, then you are on the right track.

Carlos