Hi , stupid question maybe but does the pilot jet have a hole running straight through it ? I broke the top off of one on cleaning the carbs !! I got it out and bought this replacement

SLOW / PILOT JET for PWK KEIHIN OKO CVK # 38 | eBay

And I noticed a hole all the way through. Now this is odd as last year I cleaned them all and all the small holes in the sides cleaned up fine but there didn't seem to be a hole running through to the screwdriver slot end, but unless this jet I bought is incorrect , I still have 4 blocked pilot jets,

Would be grateful if somebody could help
Thanks

 

Actually, there is a hole that runs through both the pilot and main jets. That's how the fuel flow is metered. The holes are small and if any fuel is in them, it makes it hard to see light when looking through them.

When I get one that is blocked, sometimes I run a bristle from a wire brush in it to clean it out.

If you have the carbs off, I would highly recommend going with stage #1 jets and/or stick coil mod. You will not regret it.

 

The jet you linked to looks like the right style. And, yes, if you look through the slotted end with a light sourse towards the top end, lenghtwise, you should see light coming through. Sounds like you might have clogged jets. This is the most likely place to be clogged because it's probably the smallest passage in your carb.
I put a Webber carb on a '72 S.Bettle and had the same problem occasionally. The nice thing about the Webber was that the pilot jets could be services by just unscrewing the jet holders on the outside of the carb body

 

Thanks all for your thoughts . I also found this site Buy Keihin Jets @ PJMotorsports .com

Which has half way down the page " Keihin N424-21 Pilot/Slow Jet
28mm in length with a 5mm Round Head "

It shows that the PWK jet I bought should be compatible with the Keihin.


Well, at the moment I've got the damaged jet soaking in vinegar to try loosen any blockage if there. I have a second pilot jet out and apart from the maybe center blockage ( again ), looks clean. I'll check the other two tomorrow .

I just cant see how the jet gets its fuel ( Thinking out loud ) As it stands , the jet would need to get fuel through a port in the carb body via the side holes and release it at the top , but the side holes look like they are designed to disperse in my opinion. And surely the fuel comes up from the bowl just like the main set.

Only one way to find out I think. Cut the wrecked jet in half !!

The CBR has always not ideled very well so may be I'm getting to the route of the problem. And in the past I discovered the fuel tank breather pipe blocked , had to change the tank. So maybe this is the previous owners way of trying to fix the sure to be vacuum problem .

Timbuctwo , can you elaborate on the stage #1 Where would I get them ? Also thought I saw stick coil info so I'll go read.

Cheers All

 

Sorry - seems I gave you wrong info
Funny that - maybe MY idle jets are blocked too................EEEK !
I'll check the jets on my spare set of carbs but I swear the ones in my bike don't have holes right through them........perhaps my jets are different or they ARE blocked. It's always had a slightly lumpy idle which I put down to the Dyno jet kit......
I learn new stuff every day
Again, sorry for the error.

 

All pilot jets should have a hole on the crown Pete - but it is the first one to always
get clogged up with fine grain crud - what I have found anyhow from working the
three different version of carb's the last few months

 

Well just had time to check the other 3 jets and they are ( maybe ) blocked as well to but the rest of it is clean and clear . So I'm to cut open the broken one tomorrow .

 

There is stock (factory condition). Stage #1 is slightly modified from stock (better flow air filter and pipe). Stage #2 is moderately modified (same as stage #1 but hotter cams and maybe bigger carbs). Stage #3 is all out modified.

These bikes ran lean from factory due to emissions requirements. The addition of ethanol also requires bigger jets. I have K&N air filter and TB pipe and have ethanol in the fuel. I run #135 mains/#45 pilots. The #38 you posted above will be to small even for a factory setup bike with modern fuel. #125 for the mains and #42 pilots would be the smallest.

I used this LINK that Sprock posted and ordered the jets from them. Best price and helpful calculator.

This is the stick coil LINK and the how to LINK.

 

On the money TBT

 

Thanks TimbucTwo \ Sprock thats great info . Still haven't cut that jet in half yet. But great links.
looking to see if I can get a jet kit shipped to the uk as soon as funds allow .