Maintenance & Technical > KX500 Original

jetting info from the pipe

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js:
the other day I ran into a 2 stroke oil engineer. that was trying to tell me how to read my pipe to get my jetting correct. stating that the first 3" of my pipe would give me the correct info to jet my bike. saying the pipe won't lie like a plug will. anyone got any input.

hughes:
You would need a works pipe (non plated or painted) to read the color of the pipe. In some cases you can see where a plated pipe might get a light gold color to it but real hard to read anything on those pipes. The bike would need to ran in it's peak output area for some time to get those result just hopping along the trail may not give you the result your looking for when reading the color of the pipe. With good jetting the works pipe will get a good tan/brown color to it. A rich jetting will burn cooler and cause the exhaust gas or waves to be cooler. Once the exhaust gases reach a given temp the exhaust waves are more effective in helping hold in incoming fuel/air charge and help purge the burned exhaust out of the cylinder.

Platypus:
It has been a long time since I read about this stuff but I'm sure an exhaust temperature gauge would be a heck of alot more accurate than looking at the color of the pipe. 

hughes:
All my jetting is done by the seat of my pants. I feel that pipe color is more of a end result of good jetting.

Hillclimb#42:
 :? :? I've heard of this on Pulling tractors and derby cars. They paint their headers white and want them to stay white,I think. Green color close to the block indicates lean, I don't remember if it is also green when rich. I have to think that the plug only lies if you check it cold or after idling around. Great point about the computer sensor. It may tell you rich or lean, but wouldn't say much about how to fix it.
 It seems the 500 is harder to tell by ear than my 250. Its surge and agressive nature seems lean, but is real loaded up at start up. I am either used to the 250 or somethin because it is easy to set by ear. It pings when pinned and has a run-on surge when lean, and gets loaded up easy when rich, but the k5 is plug tuned.
 I started with jetting chart, put the right jets in and started with stock mixture screw setting and was very close. Too bad that engineer didn't have a bit more info, because the farther you venture from stock, the less you have to go by.
Pipes, Temperatures, Humidity, Fuels, Ring wear, mixture ratios and a few dozen more things affect the overall jetting. Thats why it is such a big topic. BDI pointed out that some after market upgrades don't work well together and may cause more problems than it helps.
 Shifter carts adjust thier mixture going down a straight away. Multi cylinder bikes and quads have multiple carbs, pipes and tuning issues, I am thankful I have only one carb at a time to tune. :-D

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