Rebuilding a 3bbl carburetor

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rebelrider
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Rebuilding a 3bbl carburetor

Post by rebelrider » Wed Dec 27, 2017 2:39 pm

Before I get started, does anyone know of a good carburetor forum? I've done some Googling but no success so far.

So, that wasn't a typo folks. Honda's old cvcc engines have 3bbl carburetors. The extra barrel feeds a pre-fire chamber with the spark plug. I'll spare you the technical explanation (unless you're interested) and just show a cross section:
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So far I'm 0 for 3 in successful rebuilds. They're not failures though. I'm just experiencing delayed success. :lol: So I figured this time around I'd share the process with those of you who might be interested. I'm also trying very hard to improve my video skills. Both in visual quality and value. As you can see, I'm not there yet, but I'm working on it.


This is a 45 minute video, so if you don't wanna watch the whole thing, I totally understand and take no offence. I interspersed several parts reference pictures in the video. Here's them and a couple extra:

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I chose to do all these identification pics with the parts used and dirty, because I figured that's how they're gonna look as a carb is being taken apart. Here though, is a picture I took just for fun of all the cleaned up parts together.
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Might be better to keep the parts organized by assembly though, just to avoid confusion. Especially if it's not going to be reassembled in the near future.
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One piece of trivia I found interesting is that these carbs are made by Keihin. Same company that makes the carbs for the old Honda Rebels, and many of the carbureted Urals, I think. I was all set to learn Ural carburetors, and then I bought a 2014, :lol: So I learned the OBDII thing instead.
Mike
Image2014 Ural M70 "Trogdor"
1987 Honda CMX250C "Rebel"
1979 Puch Moped "Wasp"
1971 Honda SL100

rivers
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Re: Rebuilding a 3bbl carburetor

Post by rivers » Wed Dec 27, 2017 3:34 pm

Yikes what a freak carb. Looks like a cross between a mc and car carb. Electric anti-diesel solenoids on a a mc carb??? I've dealt with wierd V8 car carbs but sprung for either factory or after market shop manuals before diving in. Parts manuals are good for identifying parts and assembly schematics but they don't include set-up specs. If'n were me I'd look at that thing as a project but with nothing to test it on and would start with "calling" not emailing SUDCO's tech dept. They are the US importer for Keihin. They should be able to either supply a shop manual/sheet for setting one up. Or guide you to one of their retailers that might. An old time Honda dealer could maybe steer you in the right direction. Where did you source the new bagged parts from? Cool project, you got a good correct motor to test it on?
Best of luck.
Joe
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Re: Rebuilding a 3bbl carburetor

Post by hotflash44 » Wed Dec 27, 2017 3:36 pm

CVCC, Honda is that the same engine that my 1971 Honda car had? it was a air cooled twin great car/engine wish i still had it. :? :cheers:
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Re: Rebuilding a 3bbl carburetor

Post by rebelrider » Wed Dec 27, 2017 4:37 pm

Hotflash44:
Your old '71 would have predated the cvcc. I think they were introduced in 79-ish. I don't know much about the air cooled engines, but lots of folks in California have done excellent work restoring those cars. They're quite fun to look at. :)

Rivers:
I think I forgot to mention that this carb is for Honda's cvcc car engines from roughly 1980-1983. My car is specifically a 1980 Civic wagon.
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Once the rebuild and adjustment is done, it will be going on my car which currently has a defunkt carb, but a freshly rebuilt engine.
Mike
Image2014 Ural M70 "Trogdor"
1987 Honda CMX250C "Rebel"
1979 Puch Moped "Wasp"
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Re: Rebuilding a 3bbl carburetor

Post by rebelrider » Fri Jan 05, 2018 3:33 pm

Made some progress on the carb. Lots of steel parts have been de-rusted and painted, the main body is back together, and I've adjusted the floats.


Still looking for a good carburetor forum to join if anyone knows of any. :)
Mike
Image2014 Ural M70 "Trogdor"
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Re: Rebuilding a 3bbl carburetor

Post by rebelrider » Fri Jan 12, 2018 7:04 am

Found a couple rebuild kits with parts that will fit my carb!

Also made some more progress:
Mike
Image2014 Ural M70 "Trogdor"
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Re: Rebuilding a 3bbl carburetor

Post by lee 303 » Thu Jan 18, 2018 4:43 pm

Good Lord it's been a long time since I rebuilt one those. I ran an independent Honda repair shop from 1991-2006 towards the end I was last guy around who could rebuild them. I don't remember the name of the aftermarket outfit (sorry) that sold rebuild kits but they were in California and by then OEM parts were impossible from the local dealer. The kits were very complete and included the power valve diaphragm which if it leaks raises all kinds of hell when the engine is cold.If you soak the bodies in Hydra seal or any of those highly toxic/corrosive cleaners be sure to check the wedges that stake the cast boost venturi to the carburetor body for tightness. They can get loose and the engine will lose power or stall when making hard turns to the right or left but I can't remember which way. I discovered after one of my competitors called me. He spent three days checking and rechecking his work. After a road test in which I could duplicate the complaint I asked what had been done. He had sent the carburetor out for "hot tanking" after that I discovered the venturi was moving around and would unport the vacuum and kaput. Installed a new o ring drove down the wedges with a punch= fixed.
The most common problem on Accords and Civics was vacuum lines right at the back of the carb would get cooked and crack then leak air. They would deteriorate from the inside and it would be almost invisible until you pulled them off and had look.It was also very common for cars driven by older clients or people who were very light on the thottle to have frozen secondary butterflies. Those could be easily freed by shoving a stick between the seat and gas pedal, soaking the thottle plate carb cleaner and manipulating the linkage till it moved without binding.They thought I installed a supercharger.
Good luck
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1984 r80rt with sputnik
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Re: Rebuilding a 3bbl carburetor

Post by lee 303 » Thu Jan 18, 2018 4:57 pm

I forgot to congratulate you on keeping that old car running. The hull looks great if it was in New England it would be powder by now! I hate ---king road salt!
My last new car was an 87 CRX HF that little gem got 62 mpg with a carburetor. Unfortunately only 2 seats and as soon as fatherhood arrived that car got replaced by a Volvo 240 wagon a total pig on gas but the safest in it's day.
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1984 r80rt with sputnik
1967 r60/2 solo

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Re: Rebuilding a 3bbl carburetor

Post by rebelrider » Fri Jan 19, 2018 3:38 am

Thanks Lee!
I'm always happy to get tips and advice from folks who have actually worked on these carburetors. (Or any carburetors.) Especially when I get to the on-car adjustment! A while back, I read up on checking for vacuum leaks. I'll have to refresh myself on that topic. Seems to be a very common malady on old cars.

I haven't settled on a chemical I like yet for cleaning carbs. Most carb-specific cleaners don't play well with plastics, and mine has bits of plastic in the linkage that I really don't want to mess with. So I've been experimenting with unconventional cleaners. There's a degreaser made by POR-15, formerly called Marine Clean. It's not good for the aluminum though. I've also tried Pine Sol. Recommended by lots of folks, but again, it seems to produce an oxidized film on the aluminum. This time I just soaked everything in regular gasoline. That did a great job of getting rid of all the excess grease and dirt on the outside parts.

I used a spray can of carb cleaner to clean out all the internal channels and crevices, and went back with canned air to verify that the channels were clear. For stubborn crusty stuff, I used a tiny wire brush on a rotary tool. Though I'm always worried an errant wire strand will come loose and get stuck somewhere.

But yep, our old carbureted cars get better fuel efficiency than most hybrids today. I think it's a combination of a lighter overall construction, as well as not needing as much power. My Honda was getting around 38 mpg when it had its good days. I just got the engine rebuilt last year, and hopefully with the newly rebuilt carburetor, It will have some really good days in the near future. :)
Mike
Image2014 Ural M70 "Trogdor"
1987 Honda CMX250C "Rebel"
1979 Puch Moped "Wasp"
1971 Honda SL100

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: Rebuilding a 3bbl carburetor

Post by lee 303 » Fri Jan 19, 2018 10:40 am

I just cleaned them with an aerosol can of Gumout brand and compressed air.If the jets or float seats look awful try soaking them in Hoppes #9 gun cleaning solvent that cleans the brass without harm.The trouble with any of those decarbonizing cleaners like Hydra Seal and Turco Transpo are the huge disposal cost as they are hazardous materials. No need reinstall the epa mandated anti tamper cover over mixture screw. One of the simplest ways to set idle mixture was with a propane torch.Remove the mixing head of torch and slip a piece of rubber hose over the torches pipe. stick the rubber into the air cleaner or near the primary air intake then slowly open the torch valve and you want to get about a 50-100 rpm rise at idle. That indicates you set the mixture to the lean side of 14.7/1.
Very often cars would come in with a lean misfire and if you checked the mixture with propane you would see a more than 100 rpm rise with propane flowing this would be indicative of a obstructed idle circuit. The solution was to remove the air cleaner rev up the engine and then put your hand over the primary to completely block the air flow. This creates a high enough suction to pull whatever blockage there is through and you wouldn't have to take the carb apart and the mixture would usually be restored to the correct ratio.
That wagon doesn't even have rust at the wheel arches Wow!
I'd tried googling my old supplier for rebuild kits but I'm afraid to say I can't remember and it's been 20 odd years since I dealt with them.
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Re: Rebuilding a 3bbl carburetor

Post by rebelrider » Wed Jan 24, 2018 9:26 am

Finally, the peripherals are done! (Well except for the choke.)
All the old parts I was going to reuse have been replaced with the new parts from the kits I found. I also got outside today and checked the electrics in the car that might affect fuel delivery. They're all working, so the issue must be in the carburetor. I'm very close now to swapping them out!

Mike
Image2014 Ural M70 "Trogdor"
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1979 Puch Moped "Wasp"
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Re: Rebuilding a 3bbl carburetor

Post by rebelrider » Sun Jan 28, 2018 3:39 pm

I've finally got the car moved into the bay where I'll be able to work on it sheltered from the weather. This has been weighing on my mind for a while, as I wasn't sure just how I would be able to do it. I finally decided to just get up and do it with whatever I could find lying around. Here's a (relatively) short video of me moving the car. I hope you all find it entertaining.


Next up will be finalization of the carburetor, I think. I also need to add some lighting and wind protection to the work bay. It's just a flat spot under my deck as you can see in the video, so its not as protected as a proper garage would be.
Mike
Image2014 Ural M70 "Trogdor"
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1979 Puch Moped "Wasp"
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Re: Rebuilding a 3bbl carburetor

Post by rebelrider » Fri Apr 27, 2018 5:37 pm

My car is back from the dead! It seems my rebuild and swap was successful.
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I even took a test drive around the block a couple times and it worked great, apart from a tendency to stall while coasting. I've got some video I'll share later after editing. But just having the car running again is pretty freaking cool! :boogie:
Mike
Image2014 Ural M70 "Trogdor"
1987 Honda CMX250C "Rebel"
1979 Puch Moped "Wasp"
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Re: Rebuilding a 3bbl carburetor

Post by lendrinkard » Sat Apr 28, 2018 7:35 am

Wow That is great. You are one determined guy. Nice work on a complicated project.
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Re: Rebuilding a 3bbl carburetor

Post by rebelrider » Sun May 06, 2018 7:07 pm



Last off-car video! Up nest will be the carb swap. :)
Mike
Image2014 Ural M70 "Trogdor"
1987 Honda CMX250C "Rebel"
1979 Puch Moped "Wasp"
1971 Honda SL100

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