carbs

[breakdirt916]

okay, time to tune the 2003 XR100R carbs

problem: popping under decel, feels "lean" in the midrange, and won't idle for > 5-10 seconds

history: bought the bike used, came with an FMF pipe, wouldn't idle. I pulled the carb, blew out the pilot jet, and buttoned it back together. It idles, but stalls after 5-10 seconds.

cranking the idle speed (which raises the slide) causes the engine to race too much; so I lowered it enough where it uses the pilot circuit, but once you get there, it still stalls after 5-10 seconds

stock jetting: 35pilot, 98 main

called Honda, they told me to call FMF. Called FMF, and they said it should be stock.

I pulled out the 35 pilot again, and honestly, it looks fine. I found a local shop with a 38 pilot, I screwed that in, and I'm going to try it out tonight!

I also dropped the clip on the needle by 1 notch...needle sits a smidge higher now.

[gregp]

The 38 pilot should help a lot. But you may have to raise the needle clip back to where it was, and dial in the low speed mixture with the fuel screw (not the idle speed screw!), if it has one. JMO.

[breakdirt916]

why not the needle too? shouldn't that help with the 1/4 throttle response if it's lean?

and honestly, it's a PITA to move that needle clip...when you re-secure it, you need to put this v-shaped pin in at an awkward angle; inside the slide

bike does have a fuel screw to fine tune the a/f ratio through the pilot circuit, but honda recommends leaving it as is...but I can adjust if need be

[WordTooYoMamma]

Pilot 0+
needle is 1/4+
MJ 1/2ish+up

Needle has nothing to do with idle. My guess is you screwed something up with your fuel screws or didn't clean something properly. Or you may have not synced your carbs properly after messing with them.

When you are riding around at cruising speed, not accelerating. Your bike shouldn't be jerky or boggy. Pilot screw handles this.
When you go from cruising to warp speed your bike should accelerate sharply. If it doesn't pull the choke and try it again. If that works you are running too lean and need to screw with the Mj/Needles. If it doesn't you are rich and need to screw with the same shit.

Its all trial and error.

[Kurlon]

One circuit at a time. Pilot, then main, then needle. Do not try and muck with multiple circuits at once.

Edit: And honda says to leave the idle mix alone because the EPA says you're not supposed to have access to it. Remove brass plug if present and muck with that screw, it's your bike.

Also, this is a bone stock XR100? It will NEVER be 'sharp' on the throttle, it's too choked up to be sharp, so just go for 'less bland than usual'.

[breakdirt916]

argh...I know you're right, I just don't want to muck with that damn clip anymore because I'm afraid it won't go back in after it comes out

I'm going to test the new pilot tonight...I'll re-adjust that needle before I fire her up

but ya, it is relatively mild for a bike, but it's enough for me!

[TheIglu]

Check the valve clearances.

[breakdirt916]

38 pilot did the trick! bam!

bike starts pretty much first kick, idles forever, and rolls on nice and smooth...I didn't change the needle clip position back, but it runs just fine

in true 4t style, this bike peaks its power (or lack thereof) in the low and midrange...the bike is best short shifted and chugged along

so you can just roll on (slowly too!) in 3rd gear and the front end will climb up for nice sitting wheelies

I'll have to see how it runs on the MX track next Thursday!

[breakdirt916]

more mx madness today...starts first kick, and idles great!

1/4 throttle roll on is (mostly) smooth...it misses sometimes

WOT is a little worse...next time I'm going to try a bigger main!

I rode milestone MX park...exactly 1 hour drive from home



5 tracks!



the beginner track is real mellow:



supercross included!



gopro shots are pretty clear!