Don't poke through your pilot jet

A reference for the PWK carbs...
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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.
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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!
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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:
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