Keihin CR special carbs

I recently purchased a pair of Keihin Cr special carbs from Jim Schmidt. They're replacing the Mikuni single carb that was on the bike when I bought it.

The Mikuni works well, starting quickly from cold when using the choke (I use the E-start 99% of the time on cold starts) and idles perfectly. It's just lacking at the top end, which was starting to spoil my enjoyment.



The CR carbs come bolted together and sync'd





Jim machines a new cable pull wheel for the carbs



The kit comes with short manifolds and twist grip which is nicely finished





A pair of thick rubber boots are also included in the kit. They are drilled for a brass balance tube which is also included.







At WOT the slide is fully retracted, giving the smoothbores their name



Squeezing the carbs into the bike is a bit of a chore. I run an Old Britts support arm for my battery side cover. I had to loosen the bolts for this and the oil tank support to get the carbs mounted. I found that loose mounting the rubber boots on the manifolds and levering the carbs into place while pulling the cover mount and oil tank bolts pulled as far back as possible was the best method.



It's a tight fit for sure. and the center bolt holding the Old Britts support is hard up against the carb. There's no way to tighten that bolt. Hopefully it will be secure.



Mounting the K&N filter was another squeeze. The Jubilee clips need a bit of fiddling to get them in a position that grips them well onto the carb manifold.



I'll be finishing off the installation in the morning and hopefully get a test ride in tomorrow, then I'll let you know my thoughts on the performance.

I got a set of 33's from Jim to bolt on once my engine is back together, Fullauto head and a few more of Jim's goodies.
I was running a 34 mikuni and found it ran out of fuel when I opened it up. Cant wait till you give us your opinion on the carbs when you run them.
JUG

It's like looking at a fine piece of artwork or a precious jewel... (Does that say something about me?? :lol: )

Mark, thanks for the pictures! I am very interested in any change you see in fuel mileage from the single Mickey. Was yours the "standard" 34mm?

Nathan

Took the bike out for a quick run around town this evening.

It felt much stronger from down low through to mid range - I didn't really get to open up around town. Roll on mid range throttle is night and day better than the single mikuni. They bike pulls really strong rolling on the throttle in third at about 30mph.

Didn't plug chop, but pulled the plugs when I got home and they were a nice light tan color. Jim seems to have got the jetting right in the ball park. I'll put a few more miles on during the week and then really get to test it at the Hansen Dam rally this weekend.

Nate, I'll be able to tell any gas mileage difference, but no exact figures. I also put on a pair of new electronic Smiths clocks this weekend because my old odd/trip was acting erratically. The speedo worked fine, but I always had to guess how far I'd gone. I was somewhere in the 45mpg with the Mikuni.

Jim asked me to post some photos of the carbs mounted on the bike, so here they are.

steelcap said:

Jim asked me to post some photos of the carbs mounted on the bike, so here they are.

Click to expand...

Thanks steelcap. I have an Atlas and I appreciate seeing how well they fit into a Commando.

Photo below shows the petcocks of a 71 Roadster fiberglass tank. Were these the only tanks with petcocks located forward? How popular were these tanks and do people still use them with today's Alky laced fuel?



The photo below is of steel tank with the petcocks located towards the rear.