cb650 keihin crs29 carbs

If you have a cb650 (or any jap 4cyl) and you’re looking to splurge close to an extra $1000… This post is for you.

79-80 cb650 actually have pretty good stock-oem carbs IMO: 29mm bore, mechanical slide and accelerator pump. However, if yours are getting shitty and want a nice upgrade, brand new keihin crs29 smoothbore race carbs are the way to go. 

If you have the shitty 81-82 constant velocity carbs, bummer for you. Def upgrade to the keihin crs.

Benefits of keihin crs smoothbore carbs

  • Brand new. Still made today. Every and any part is available still
  • Every single circuit is tunable to a fine degree 
  • They’re not too difficult to tune
  • You’ll prob get a few horsepower assuming you tune them properly
  • Choke is on the carb body so no more shitty cb650 pull choke near handlebars
  • Nothing beats brand spanking new carbs… Best upgrade for any bike IMO

Keihin crs29 jetting for cb650

  • 115 main jet
  • 220 main air jet
  • 68 slow jet
  • yy6 needle – middle
  • Air screw 1 turn out 

If you have a 4-1 exhaust, and you’re basically at sea level, above is the jetting I recommend to get you in the ballpark… to then fine tune.

Things to note

  1. Intake spigots need to match up: if you have 79-80 you’ll want Keihin intake spigot number 020-024 (below pic) for a Suzuki gs850. Needs to be long enough to clear the petcock as seen in below photo. Also need to shave off 1mm from the end that sits into the intake boot so it seals properly.
  2. Pod filters won’t really fit. They hit the frame on cylinders 1 and 4. So I’m running the velocity stacks that come with the carbs.
  3. You’ll need a different “pull” throttle cable. Use the “push” from the CB650, and then buy a “pull” from a 78 Kawasaki kz1000. KZ cable is slightly longer looking but the cable/housing ratio is what you want.
  4. Where the cables thread into the carb holder…You’ll need to bend the tabs up and to the left a hair, so the cables clear the frame of the motorcycle. Seen in below pic.
  5. Get a pair of new rubber intake boots. Might as well, right.

Conclusion

Yea, if you have a 4cyl jap bike… These are the best carbs you can pick up, hands down. I also have a set on a 74 Kawasaki z1 and I love them. Don’t put carbs on your bike that are too big bore. Some people upgrade to the Mikuni RS34, which are too big. For a 4cyl, I love the Keihin CRS, and for a twin or single cylinder, I like the Mikuni VM.

These carbs will work great on any 70s Honda CB 500, 550, 650, 750 4cyl.

However, on 500, 550, you should run the keihin crs26. Slightly smaller bore will work better.

650

13 responses to “cb650 keihin crs29 carbs”

  1. Adam says:

    Wonder why the spigots are so long. Seems like the carbs could be closer to the intake boot which would make for more room for the filters.

    I agree, all our old bike should be running these. Only problem is $$$$$.

  2. Ed says:

    I can’t use shorter spigots because the carb body will then hit the petcock

  3. MIke says:

    will this 1,000 bucks make it fast enough to beat the average girls bike.. say a sportster?

  4. wayne says:

    hi ed, did you get these to fit straight off the shelf or did you have to get them spaced to suit the inlet tubes on the 650 head, if you got them off the shelf whats the keihin part number please ?, cheers

  5. Ed says:

    @wayne
    Re-read the post again. I think you missed a few things I noted.
    You want to buy keihin crs29 carbs with the spigots I mention in the post. Yes you have to space them out but it’s easy and you can do it yourself. It’s pretty easy to set it all up and get them working. Go with the jetting I recommend and it’ll get you in the ballpark then you can fine tune.

  6. Alex G says:

    Would you happen to know what kind of spigots you would need for a 81′ Cb650 or should I just assume it’ll face the same problem interfering with the petcock.

  7. Nicklas Johansson says:

    Can you recommend a good website where I can buy jets and needles? Can’t find any good site that has them al 🙁

  8. Joe says:

    Yeah, curious what size spigot for 81′ Cb650? Also I have the C model 650 with the teardrop tank. Wondering if that’s helps or hurts the petcock clearance issue…

  9. Kurt says:

    Has anyone tried putting the Cr 29 on the 1982 CB 650 Sc SOHC ” Nighthawk ” what parts are needed.

  10. David says:

    I have an 81 cb650c with these carbs on it, I ordered everything through dime city and had a little issue in carb spacing but they drop shipped a new set out directly from the supplier in Cali.

  11. Kevin says:

    So with the 81 cb650c having different carb spacing, how’d you get the intake boots on?

  12. Damian says:

    So. Are we saying that these carbs are good to go and will work fine with POD filters or velocity stacks? I have a 1980 CB650 Cafe racer that has the standard mechanical slide carbs. It runs Pod filters and is ok, but I have tried a complete rebuild, rejetting etc but it’s still not right. They were is a bad way as they had been stood for over 10 years, and really need replacing. Anyway, Thanks for any feedback you can give. Cheers.

  13. Ed says:

    @damien
    Yes these CR29 carbs will work just fine with pods or velocity stacks. My initial jetting was a little rich.
    I’d suggest with pods to go with 110 / 62 / yy7 needles / 240 air jet. Start there then fine tune to fit your needs. Every bike jetting is a hair different.

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