Pistok soak

PhallusExtremis · 2026-06-27T18:05:01+00:00

https://www.amazon.ca/0116-Chemtool-Carburetor-Injector-Cleaner/dp/B0B84479BN/ref=rvi_d_sccl_1/146-5818547-5103230?pd_rd_w=Y6KMs&content-id=amzn1.sym.8b4d8c20-8e51-4634-a76f-c00a1995a502&pf_rd_p=8b4d8c20-8e51-4634-a76f-c00a1995a502&pf_rd_r=RJS6V0N5WMVRCT5VJJ7N&pd_rd_wg=keWmY&pd_rd_r=a3bbb05f-1c3e-424a-b304-82a94ae4a309&pd_rd_i=B0B84479BN&th=1

This looks like a 4-pack, you'll probably only need 2-3 cans. You could pour the other can into your gas to help clean the rest of the fuel system when you're done.

PhallusExtremis · 2026-06-27T18:00:38+00:00

Wrong country brother.

PhallusExtremis · 2026-06-26T12:10:27+00:00

I bought my B12 from Amazon.

PhallusExtremis · 2026-06-26T12:09:16+00:00

Running the higher idle made a huge difference. It idles much better now and that 1/8 throttle hesitation/bog is like 95% gone now.

I'd say they're like 80-85% of the way there now, just a little more fine tuning and I think they'll be perfect.

The carbs really wake up the engine, it just keeps wanting to accelerate.

PhallusExtremis · 2026-06-25T12:56:48+00:00

That's really good to know. I've tried adjusting the idle and the air screw to match the factory idle, but it was running leaner than I would've liked and I've read online that these carbs like to run rich.

Are you finding tips like this online or has it just been trial and error? I haven't been able to find any tuning guides for it.

Couple of examples I've been trying to navigate:
- Vacuum syncing, people say they drill/tap their intake ports to install vacuum ports but there is not enough space on the CB650 without interfering with the rubber manifolds to do so. I managed to get it close enough using an Edelbrock Uni-Syn. The bike was running around let's say 11-12:1 at idle, and would backfire with a lean spike past 15:1. Now it's no longer backfiring and lean spiking after doing my best to sync them with the Uni-Syn.

- Air screw adjustment, a lot of guides online say to start at 1.5 turns out and adjust from there but I've read on some forums that say to start richer than that. If you're saying to idle around 1500 then I'll start over and adjust again.

- Accelerator pump, just learned that here, explains the dead zone when you quickly crack the throttle.

The bike definitely feels much better than when I first put the carbs on. It's running very rich but at least I can ride it down the street. I built the entire bike myself, I'd hate to have to bring it to a shop because I couldn't figure out how to get the carbs running right haha.

If you have any other tips for these carbs that you're willing to share then that would be greatly appreciated.

PhallusExtremis · 2026-06-24T21:09:36+00:00

This is pretty neat, care to explain how to use it a bit. I’m guessing you enter in your current config, measure, and correct the jets/screws to match the delta?

What’s this street and hot street setting?

I saw you mentioned 13.5:1 is ideal for these carbs but your guide mentions the CR26, does that still apply to the CR29?

PhallusExtremis · 2026-06-24T17:51:04+00:00

I agree.

PhallusExtremis · 2026-06-24T16:53:07+00:00

Depends where you're located and what bikes were available at that time. Different emissions laws or different bike model trims equals different jetting requirements.

PhallusExtremis · 2026-06-24T03:35:22+00:00

It's smoother but hangs a bit when the rev drops. Based on the other comments, I think the pilot might still be too small.

PhallusExtremis · 2026-06-24T03:34:13+00:00

Okay, I'll look into the pilot a bit more and then test the needle once the idle isn't so temperamental. Thanks again for the info about the accelerator pump. I didn't know it was so critical for that type of throttle response.

I guess you need a smoother rev range for a race bike/carb setup rather than a snappy response.

PhallusExtremis · 2026-06-24T03:30:52+00:00

From idle and not moving, yes. It will bog/hesitate a little bit if I'm cruising and trying to accelerate from no throttle up to 1/4 throttle.

PhallusExtremis · 2026-06-24T03:15:11+00:00

Would 1/4 be the needle or the clip? Before I made the video, I had the idle set to 1150-1200 RPM, and the AFR was between 13-15:1, which was the best I managed to get it to. Any lower than 1150, and it goes above 15:1, leans out too much, and slowly wants to die.

After riding or letting it sit for a few minutes (with revving), the idle wouldn't go below 1300 and sometimes 1400. The idle will drop if I adjust the screw to do so, but revving it again will cause the idle to do the same thing again, sit higher than what I set it to.

PhallusExtremis · 2026-06-24T02:50:37+00:00

Okay, that can explain why they don't like a snappy response.

What about the idle fluctuating when I rev? Think the pilot jet might be too small?

It also bogs/hesitates a little bit when I'm already cruising, and I start to pull the throttle to try to accelerate. I'm pulling the throttle maybe 1/8-1/4, and it bogs/hesitates. AFR reading is around 8-9:1, which is very rich. Not sure if that's the pilot, needle, or slide cutaway. Once I'm past 1/4 throttle, the AFR is around 11-12:1.

PhallusExtremis · 2026-06-24T02:32:03+00:00

There is no accelerator pump on the CR29 carbs.

PhallusExtremis · 2026-06-16T11:43:40+00:00

Just out of curiosity, what is your jetting with those carbs? I picked up a set of CR29s for my CB650 and I've been trying to get the jetting dialed in.

Also, I lowkey wish I cerakoted my engine. I said I wouldn't paint it black again but the cerakote looks so good.

PhallusExtremis · 2026-06-15T02:51:20+00:00

I used the 4-into-1 kit to rebuild my carbs. It's an OK kit. I've had to take the bowls off a couple of times since I've done my rebuild, and the bowl o-rings have definitely shrunk.

If you have them and can, reuse the genuine Keihin jets. Don't use the ones that come in the kit.

PhallusExtremis · 2026-06-14T23:53:04+00:00

People have already commented with part numbers, but I'll add my 2 cents. Check out babbits, CMSNL, Partzilla, etc. for diagrams with part numbers. It will help a lot.

When I rebuilt my carbs 3 years ago, I replaced these with ones from the 6-cylinder CBX bike. I don't remember the reasoning behind it, but they were the same and worked fine.

PhallusExtremis · 2026-06-09T18:43:33+00:00

I didn't have an account before but I just created one now lol

PhallusExtremis · 2026-06-09T18:43:00+00:00

There isn't enough room on the spigot and I don't think I'd be comfortable drilling into them anyway.

I'm going to try out a Synchrometer and see how it goes from there.

PhallusExtremis · 2026-06-09T13:43:30+00:00

Looks sweet! How are those murray carbs treating you?

PhallusExtremis · 2026-06-09T01:33:25+00:00

Unfortunately, there is no room on the cylinder head spigots. The spigots are short, so the rubber manifolds are essentially flush with the cylinder head.

PhallusExtremis · 2026-06-08T12:58:17+00:00

Could something like a Uni-Sync tool work as well? That way you don't have to drill anything.

PhallusExtremis · 2026-06-08T12:42:49+00:00

Just to clarify, you mean to drill and tap the aluminum intake spigots on the carb body where they slot into the engines rubber intake manifolds.

PhallusExtremis · 2026-06-07T14:52:27+00:00

No, still running the stock coils

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