Don't poke through your pilot jet

A reference for the PWK carbs...
Post Reply
Gold Member
Gold Member
Posts: 726
Joined: 06:59 am Jan 27 2017
Country: US
Location: Florida

Don't poke through your pilot jet

Post by John_S »

This is a precautionary "don't do what I do" story. I was getting ready for a ride yesterday and my carb hasn't been off the bike for a couple of years. I decided to pull the carb, check the float height, do the jet block gasket test, and clean up the float valve seat. During that I held my pilot jet up to the light and it looked like it was partially clogged since it wasn't a perfect circle of light coming through. I have those wire jet cleaners and I used the smallest one which is a flimsy piece of wire that's much smaller than the hole at the top or bottom of the pilot jet. It wouldn't go through either way so I spun the jet in my fingers until it poked through and then ran it up and down a few times. Looking through the pilot jet now into the light it looked like I cleaned it out.

One thing about this bike is that it always starts on the first kick and after a couple revs idles just fine even if the jetting is off. It took 5 kicks to start it and I figured it was because I just blew air all through the carb. It started so I clicked the choke off and shut down the engine. I get to my riding spot and again it took about 5 kicks to start it but then seemed fine while warming up. While I was riding I could tell something wasn't right. It would stutter rich and lean bog all in the same minute and barely hold an idle. The air screw was at 1.5 so I turned it to 2 and was able to initiate a consistent lean bog when stabbing throttle. I then turned it to 1 turn out and the rich stutter was worse so I went to 1.75 and rode it with the occasional lean bogs and rich stutters, never running great. All day it would idle for a second or two and then die if I didn't gas it. I turned my slide stop screw all the way in just to be able to idle for 5 seconds or so. I had no idea what was happening. On the way home I was thinking the only thing different is me cleaning out that pilot jet. The bike only acted like that one time before and its when I used an aftermarket ProX pilot jet. It wouldn't idle and the air screw settings were all over the place so I realized I screwed up that Keihin jet.

I got home and swapped this 40 pilot for an old genuine 40 from my 33 PWK. It started first kick and had a really high idle because of how far I cranked the slide up. 2 turns back out and it was idling ok. I took it for ride and got it up to temp and it's all good now. I have 4 more genuine Keihin pilot jets so I decided to hold them up to the light and they're all the same. It's like looking through a mini kaleidoscope. It looks like there are 6-8 mini holes on all of them even if I plug the side holes with my fingers. Apparently it's not supposed to look like a perfect circle.

Long story short...if you need to clean your pilot jet, try soaking it in a little cap of brake or carb cleaner then blow it out with compressed air. I was scratching my head thinking the reeds are bad, its down on compression, its got an air leak. Nope, just a dumb move trying to fix something that wasn't broke.
User avatar
Posts: 5093
Joined: 05:11 am Aug 23 2009
Country: USA
Location: Tucson, AZ, USA

Re: Don't poke through your pilot jet

Post by SS109 »

Yep, I think we've all been there. I learned a long time ago to never put anything through your jets (main, pilot, or power/leak) other than liquid as you will almost always screw it up and make it useless. Glad you got it figured and it wasn't something more serious!
AZ State Parks OHV Ambassador - Trail Riders of Southern AZ
'11 GasGas EC250R
Current KDX: '98 KDX220
Old KDX: '90 KDX200 -White/Blue
My Youtube Channel: WildAzzRacing
User avatar
Posts: 13608
Joined: 06:45 am Nov 01 2004
Country: United States of America
Location: AL, USA

Re: Don't poke through your pilot jet

Post by KDXGarage »

Cool that you had spares handy! Thanks for sharing.
Thank you for participating on :bravo:
To post pictures from a device: viewtopic.php?f=88&t=24128
Post Reply