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Dangerous_Dana

jetting

7 posts in this topic

I have a 2001 xr650l. I put on the supertrapp quiet core and a k&n air filter. I rejetted from 152 to 155. Plug reads slightly on the lean side of chocolate. (more tan than white) Bike runs very good. I would have gone to 158 except that I was told these bikes were designed to run really lean. I'm only questioning my decision after reading other posts talking about 165 jets. Question: Given the plug reading (done WFO through the gears and then killed and checked) and the fact that it runs great, do you think my slightly lean reading is fine?

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What kind of riding do you do? For most trail riding, I'd say that you'd be ok. For desert work, jet rich to be safe. Gulf coast is Texas?

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Should've asked before, but what are you running for a pilot? If that is still stock, I'd go up size or two on that too. I don't think XR's run better lean, that's the way the EPA makes them come jetted to meet emissions. I think even stock you'd benefit from jetting up.

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Dana, How do you like the supertrapp? I am trying to decide on a muffler for my "L". How loud is it? I am in South Ga, so my jetting should be identicle to yours? Thanks-Robert

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If your bike runs great, and the plug is tan, your fine. I run a 52 pilot and 155 main with stock exhaust. I'm thinking of trying a 158 main...just for the heck of it. A lot of guys that run 160-165 main jets use dyno jets. They have different flow characteristics (at least according to dyno-jet). I think with genuine Keihin jets that would be overly rich.

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Some trail riding. Mostly back roads mostly paved, some dirt, very seldom over 75mph. Lots of wheelies, but that's probably less than 3/4 throttle. I really never run the crap out of it. My bike probably has twice the miles it shows on the odo. The hardest wear and tear on my bike is on the front wheel , when it touches down at 65mph. Gulf coast for me is the Mobile bay area in AL.

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When my bike was stock, it popped a lot during off throttle deceleration. It runs perfectly now. Once the bike is hot, not just warm, but hot, It doesn't pop or hesitate or anything. I got a little power increase from the pipe and even less increase from the filter, but the sound is great. I opted for the quiet core after reading several posts stating that the other supertrapp was WAY TOO LOUD. The quiet core is louder than stock, but I can still run it WFO through the gears with a city cop within ear shot. It really sounds good. I think I'll keep the current jetting. In my experience, a tiny increase goes a long way. White is bad, tan is good, and my reading is in between, but much closer to tan. I will check it again after the pipe is a little older. I'm sure it will blow/burn a little of the packing out which should further reduce back pressure. However, I think those tiny diameter stock headers are the real restrictors.

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