26mm keihin needle jet

[marzini]

Hi—

My '62 CB77's carbs are a little tired.

I obtained a less-worn set of needle jets from a '65 CL77 and the pulling performance improved a lot.

Does anyone have the ID specification for this part?

I want to fill and drill my old needle jets (PN 16133 275 004).

I remember Fast Fred used to have this part for sale.

[Tim Allman]

This may not be exactly what you are looking for but it may help especially at the end.

https://drive.google.com/file/d/1nEnTN9 ... sp=sharing

[marzini]

Hi Tim, thanks so much for the excellent link.

I've been jetting for decades, and some day this kind of knowledge will definitely be a lost art. I've narrowed it down to the jet (for now), since I already know that the D9 needle is the closest alternative to the CB77's OEM 16151 259 004 needle (#11 on the parts manual). That's what I have to work with, so I will arrive at a needle jet spec optimized for the needles I have before moving on.

The performance difference between the older round-bowl and much cleaner, less worn square-bowl JIS thread carb sets I have is impressive. I'm confident that finessing the known issues with the Keihin needle jet is an objective worthy of my effort.

I've only found two instances stressing the critical relationship between the slide needle and the needle jet being mentioned in print— both specifically referencing the 60's Keihin carburetor and its fast-wearing soft-brass needle jets!

I'm on a mission, so I'll just measure the difference between the less worn needle jets and the older spares I have for a base-line, then flow a minimal thickness of silver solder and start sourcing reamers.

Eventually, I'll have serviceable specs for my application based on real-world metering.

I've been dealing with this CB77 since the mid 70s~ it's a karmic burden for sure, and even though it has kicked my butt— I've learned a lot about it, myself, and a few other people along the way.

[Tim Allman]

I've often thought a model maker's lathe and drill press would be useful in keeping these bikes on the road. It's getting hard to find someone who can or will work on this old hardware.

It too have a "karmic burden" in a 1966 Superhawk that I have owned since I was 16 in 1969. I have done a big rehabilitation on it over the last few years. It is now almost ready to ride but the goal gets pushed away as I approach it. Today I will be splitting the cases to retrieve the cam chain connecting link clip which, in spite of my thinking that I should block the downward hole to hell, I dropped it. :-(