Topic: Help with Keihin CR26 carbs on a CB500

[roach374]

In my perpetual quest to upgrade anything and everything on my '72 CB500, I took the plunge and splurged on a set of CR "Special" 26mm roundslide carbs from DCC.

Unfortunately, the manual is next to useless (other than providing an exploded view and list of part numbers, which might come in handy): No idea where the bowl drains are, where the integrated vacuum ports are, or how to actually hook up my stock fuel line (5.5mm ID) to the carb (looks like 1/4" ID fitting). I really want to get up and running since I've heard good things about these carbs.

Has anyone installed these before? Or can recommend a decent guide on how to get them setup / tuned on a '70s Honda?

Failing that, can someone point me at either a replacement petcock with 1/4" fittings, or else a 5.5mm to 1/4" fuel line adapter?

[Kemp]

I'm with you on that!! I have a set of 26MM CR carbs on my CB400F project "The Raptor" and I'd like info also on the same issues ie carb sync!!

[roach374]

Soo, I finally heard back from Sudco, and got a couple of answers:

1) There are no "integrated vacuum ports". DCC just made that up. The ports on the sides of each carb are air intakes for the choke. They're meant to be left as-is.
2) There are no bowl drains. These are meant as racing carbs, and so they don't want to be spilling fuel all over the track (but I guess spilling fuel out of the air filter is fine though? Doesn't make a lot of sense to me...)

I picked up a 6mm-to-8mm fuel line adapter (which is sort of close enough), and a 1/4" fuel hose, but the fittings on the CR carbs are plastic instead of metal for some reason, so need to be a bit gentle trying to get the fuel line in there.

Also seems like there are a lot of interesting threads on these Keihins in the "High Performance and Racing Forum" area.

[MRieck]

 If you use the 500 manifolds you will have to drill and install nipples for synch tubes. Motion Pro make nipples that you can drill and tap for. Better is to get a set of CB550 manifolds that drilled and tapped for synch tubes.
 There are drains on the bowls.....they are the 17mm nuts. Under them are your main jets. This set up makes it very easy to change main jets.

[Old Scrambler]

You may want to enlarge the fuel spigot to allow adequate fuel-flow while on long straights..........those larger spigots on the carbs are there for a reason

[roach374]

If you use the 500 manifolds you will have to drill and install nipples for synch tubes. Motion Pro make nipples that you can drill and tap for. Better is to get a set of CB550 manifolds that drilled and tapped for synch tubes.
 There are drains on the bowls.....they are the 17mm nuts. Under them are your main jets. This set up makes it very easy to change main jets.

The 500 manifolds also have these holes built-in. No big loss.

You may want to enlarge the fuel spigot to allow adequate fuel-flow while on long straights..........those larger spigots on the carbs are there for a reason

Interesting! Well at least I know the first place to look if I start bogging down at high speed lol. I'm hoping that the 2-into-1 fuel line will help me out here, but we'll see.