Keihin CV34 Repair Kits

I got the calipers out and it seems to be M6 x 0.75. That sound about right?

calum wrote: I got the calipers out and it seems to be M6 x 0.75. That sound about right?

No. It's not .75. I'll check the garage and look for the tap I bought. I want to say it's .5.

Edit: I was wrong. It's 6mm x .75. Mikuni BS carbs are 6mm x .5 thread. I mixed them up.

Now I know what I'm doing this weekend...

I rebuilt a (thoroughly cleaned) second set of carbs with the kit. The main jet nozzles and the pilot screws were too big. It wasn't the threads on the pilot screws, the bottom section was too large for the hole in the carb body. Same deal with the nozzle, the nozzle section that is usually a press fit with the carb body was way too tight.

Here are the sections I'm talking about:



All the rest of the parts were fine and the float needles made it through the initial test (setting the float height). I got the carbs on the bike, vacuum synced them and set the idle.
Hoping for some fine weather tomorrow so I can get the bike out for a proper test.

calum wrote: I rebuilt a (thoroughly cleaned) second set of carbs with the kit. The main jet nozzles and the pilot screws were too big. It wasn't the threads on the pilot screws, the bottom section was too large for the hole in the carb body. Same deal with the nozzle, the nozzle section that is usually a press fit with the carb body was way too tight.

Here are the sections I'm talking about:

All the rest of the parts were fine and the float needles made it through the initial test (setting the float height). I got the carbs on the bike, vacuum synced them and set the idle.
Hoping for some fine weather tomorrow so I can get the bike out for a proper test.

I had the same issue with the pilot screws, but the main jet nozzles were alright for me. They were tighter, but could still be pushed in and removed without much trouble.

I measured the pilot screws (at the end as you indicated, where they bind), and the stock ones measured ~3.00-3.04mm, and the ones from this kit measured ~3.07-3.20mm. The lower sizes (closer to 3.10) were usable, but the 3.20mm pilot screw had no chance of fitting.

I think these parts are generally pretty good, but the tolerances just aren't as tight as they need to be.

Yeah, overall a pretty good kit - can't beat it for the price!
There was no way the nozzles were going in on my set - sanded one down a bit and tried some encouragement with a drift and a hammer, but it wasn't going in without damaging the end.

calum wrote: Yeah, overall a pretty good kit - can't beat it for the price!
There was no way the nozzles were going in on my set - sanded one down a bit and tried some encouragement with a drift and a hammer, but it wasn't going in without damaging the end.

You got me thinking - I went out and looked at the remainder of my kit. I didn't fit the nozzles, I'd just forgotten. I don't think they fit either, same as you. So I ended up using most of the parts in the kit except for the nozzles and some of the pilot screws (my pilot screws were in a bad way, one needed to be removed with a bolt extractor).

If those parts are so inaccurately machined, I wonder how accurate the jet orifices are.

I got out for a test today and the bike ran smoothly through the entire rev range for the first time since the rebuild. Seems like the other parts are accurate enough

I imagine the jet orifices are a lot more uniform than the outer surfaces - given that they are basically just drilled holes. I'm not sure how close to the given sizes they are but I'll be putting a third set of carbs together soon and will have this set back off the bike, I'll see if I can get hold of some gauges to check the jet size against the stock jets in my first set of carbs.

For now the bike is running fine so I'm going to call that a win