My results so far, messing around with carbs on my KLR650. Unless
otherwise noted, I have been using the stock exhaust and the stock
airbox.
1- Stock carb with t-mod. Lean surges a little, decent power.
2- Stock carb, mixture screw turned out to 1.25 turns (stock was .75).
Less lean surging. Dynoed at 36hp, normal.
3- Mikuni 38mm roundslide carb. came jetted really rich, 35mpg. Instant
response, lots more power rolling on, but too rich for steady cruising.
Typical of a racing carb.
4- Mikuni 38mm- leaned way out, mileage up to 45mpg. Instant response,
overall power feels like stock. Dynoed at 33hp, but felt like more power
because there was no lag when you opened the throttle. really clean,
reliable 9I used this setup for the Sandy Lane enduro, 40 mi of 1st gear
puttering in the woods, no fouling, no overheating). This is definitely
the ideal offroad setup, except for the heavy throttle feel. I cut two
coils out of the throttle valve return spring, but need to trim more.
5- Stock carb, mix screw 1 turn out, went up 1 on pilot (stock #40,
installed #42). Drilled out slide vacuum port to .125", removed rubber
snorkel from airbox. Better response than before, but felt crappy
because I was used to the roundslide. 35mpg!
Apparently the pilot jet is the culprit. Bike ran rich on woods trails,
stumbled a bit after a while. Now I know why Dynojet doesn't change the
pilot, and instead opens the mixture screw 3 turns- what is really
needed is a custom pilot jet in between 40 and 42.
6- (tonight) Stock carb, stock pilot jet, mix screw out 1.5 turns. A
little bit of lean surging, better response than before I drilled the
slide, same power. mileage seems like it's back over 50mpg. Curious to
see what 2 turns out does.
7- Next idea- either fit a KLX needle, or get a spare stock needle
(anybody have a donor?) and reshape it to reduce the shoulder, so it has
a more normal taper.
Devon