426 Jetting, and a good story

Ok, here's the story. My bike has a 165 main, and 48 pilot, fuel screw 2 turns out. I'm in New Mexico at about 3500 to 4000 feet, fairly hot and dry. The bike starts great and runs great but...I went riding yesterday climbing some hills and on one hill I was 3rd gear and keeping throttle about 1/2 open all the way up to a mound of sand, then jump the mound and come down. When I would land, the bike would sometimes stall. This has never happened in any other situation. This gets better. I climbed another monster hill and didn't make it, fell to the side, basically in a ditch and stalled the bike. I couldn't get the bike out and just happened to be by myself, perfect time to get in a bad predicament. Luckily someone riding a quad drives by and he helps me get the bike out, not easy for both of us, but we finally got it down. Ok I'm thankful, I got the bike down and everything is good, besides some new scratches on the plastic, ok not bad. So I go to start the bike, it will not start. I try everything, hold the compression release and kick through 15 times, hot start out, cold start out, nothing out...will not start. I figured the plug is fouled, it's not going to start. I try to push the bike down a slope and bump start, almost starts but dies. After kicking it over about 40 times I'm pretty tired. I did have a phone with me so I resort to calling the wife to come pick me up. She can't believe it but says she's on her way. I get ready to start pushing the bike a little closer to the road and figure I'd give one last try to start it. Boom, 3 or 4 kicks and it starts. I call back the wife and say nevermind.

Back to business, after falls this has never happened before, I usually pull the hot start and it fires right up, of course I've never had to drag the bike out of a hole on the side of a hill either. So in light of the evidence and facts, is my jetting not as perfect as I thought? And when going higher altitude do you increase the main and pilot jets to go richer or decrease to go leaner, in general? Riding everywhere else the bike has always run great, but yesterday was not the funnest time I've had on the bike, and now it has me wondering about jetting again.

I have noticed that if the bike stalls/leans at an acute angle (especially with a "nose" down attitude) that carb seems to flood the engine more readily, probaly wetting the plug. If this happens I normally switch the fuel off, give a couple of kicks (decomp), wait a while, again a couple of kicks (decomp) and then try start.

I also ride in the 3000-5000ft range and I am still running the standard jetting, without any problems (stock jetting is possibly a bit lean for sea level ?).

Higher Altitude should be leaner (air is rarified/thinner).

Cold ~ more dense ~ richer

Hot ~ less dense ~ leaner

Humid ~less dense (water vapour) ~ leaner

Dry ~ more dense (air only, no water vapour) ~ richer

Paul Card

00' 426

[This message has been edited by PSC (edited 05-03-2000).]


I'm going to check the plug tonight and see how it looks. The bike was leaning with the nose down quite a bit. I'll try that method next time I flood the bike. Thanks for the info.

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