jetting info from the pipe

[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.

[BigGreenMachine]

I think the EGT sensor is the way to go. That or a dyno.

[FuriouSly]

I did notice a guy with a kx450 that had a sensor welded into his pipe with a wire going to a computer on his handlebars. he said it was for jetting. what kind of info could you get from that type of sensor. temp? and at what rpm the temp was at. from there can you tune the needle,pilot,main....js

I use an O2 sensor setup for all my 4 strokes (quads and bikes) to get them jetted correctly.  Basically an O2 sensor that you weld the mount into the head pipe about 12"-18" from exhaust port and thread it in with some anti-seize.  This sensor is powered by 12vdc to heat the element to operating temp for more consistent readings rather than having engine exhaust gases doing it (my 4S all have electric start with batteries).  The output is displayed on an air/fuel gauge, usually in l.e.d. bars or dial.

I can't find a picture of my set-up but it is a common sensor (summit racing/national performance/jegs) and an autometer l.e.d. guage.  I have a handlebar mount that easily allows moving the set up from bike to bike.

This is basically how all new fuel injected vehicles monitor and adjust air/fuel mixtures for optimum performance or cold/hot operation.

Reason I do this?  4 strokes are hard to jet.  Most of the time they are way too rich and run hot, resulting in power loss.  You can set the idle, needle, and main with this set-up.

Example...  my daughters YFZ450 quad stock was around a 148 main if I remember correctly.  After full Big Gun Race exhaust (header and muffler), Cams, Airbox mod, lightened flywheel, and a RevBox the books said a 175-178 main.  After all was said and done, 165-168 is the proper jets depending on season/elevation.  Even a 162 is run at 6000 feet.

2 stroke???  no, I don't jet with an O2 sensor on two strokes because they are actaully easier to feel/look/listen for jetting.  Mostly though because the sensor does not like having the premix on the element and you will have inconsistent readings as well as burn the sensor out, which is a $80 part.  When a modern fuel injected car starts burning oil and wearing out, the residue in the exhaust gases start effecting the O2 sensors in the headers/crossovers, eventually burning them out and messing up the ECM's ability to operate the engine.

Anyways.... interesting topic so I had to throw out my experience with this tool.  I will try and get a picture of my set-up on this thread soon.

Sly

[don46]

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.

Don't know how you would do it from the outside, are you sure he wasn't talking about the inside of the pipe? I know when the race bikes are jetted right the exhaust at the silencer is a DRY gray.

[KXcam22]

Good thread!  I have heard about the pipe "appearance" method.  As I understand it you can get an indication from how far down the pipe discolours.  Now this is 4-stroke only and would never work on a 2-stroke.  I find the whole idea a bit too unscientific for my liking although perhaps it works for guys with much more experience than I have.  The o2 sensor or EGT is the absolute best way to jet a 4-stroke (good writeup Sly).  On a 2-stroke the plug reading is quite reliable, and when combined with some "seat of the pants" impressions, you can get excellent jetting results.  4-strokes are a lot harder since the plug color doesn't seem to vary as much from too lean to too rich.  On my sons XR100 I did most of the jetting by trying a jet in a range I expected to work then flipping the choke on and off to see if the bike ran better or worse.  An O2 sensor would have been appreciated.  Cam.

[jigggawatt]

Anyone every try a Infrared Thermometer.