Cleaning and Rebuilding the Carb

The Honda parts diagram is slightly different from the parts diagram in the Clymer manual. My carb actually looks more like the Type III in the Clymer which is listed for the CT70 1969-1977. I've ordered the gasket set, needle set, screw set and valve set, all Honda OEM. That replaces all the gaskets, o-rings, brass parts, petcock packing and integral fuel filter.

This is the Honda parts breakdown. Part 3 is different in the Honda diagram than the Clymer manual.


This is the Clymer illustration. Part 3 is a washer instead of a brass fitting. I think this is what my bike came with. See the question below.



Since all the parts that meter fuel are brass, I bead blasted the carb body because I wasn't having any luck removing the gunk with carb cleaner. It came out pretty well. I didn't get too close to the part and turned down the air pressure a little so it's not pristine, but way better than it was.













A question, What is the purpose of this small hole under the carb to manifold o-ring? It doesn't seem to go anywhere because when I blow air into it, the air just comes right back out the hole.



Does anyone know where this small wavy washer might go? It didn't come out with a brass screw/jet and just appeared on the workbench so I'm not exactly sure where it might go. From the parts breakdown, it may be the seat for the main jet holder (3 in the Clymer manual). I'm pretty sure its not from the main or idle jet adjustment screws, the float bowl drain screw or the petcock switch and integrated fuel filter.

Clymer is a good publication but, covering some many different models & years, along with their sometimes oddball nomenclature, can be very confusing.

Bead blasting doesn't play nicely with these zinc castings. Looks like you controlled it very well, though. As long as you didn't blast the venturi or slide bore, this should be fine...though it might annoy a few hardcore purists.

The rest of the small parts can be cleaned by soaking them in PineSol. The brass parts, especially, clean up beautifully. Run a thin wire through all of the orifices in the emulsion tube/main jet holder; this is THE crucial element of a carb rebuild. Immersing the float in hot water is a good way to check for leaks. As the float heats up, the air inside expands leaving a visible trail of bubbles if a leak is present. I'd estimate about 10% of the floats I've tested over the years have had small cranks...nearly all were easily repaired, using plumbing solder.

This carb kit is as good as it gets, includes all of the small parts. I recommend holding onto the original main jet, it may be a different size. That could (and often does) compensate for 21st century pump gas. If it's too far off, you can always reinstall the original. Brass is a stable material, main jets don't "go bad".

The washer could possibly be #14, just my guess.

Thanks,any thoughts on the stray washer?

I dont think the wave washer belongs in the carb anywhere. It is metal and not hard rubber? The hole isnt supposed to go anywhere on this model carb, maybe it was used somewhere else or its a hole used to drill into body of carb to connect passages then plugged later

There is a tiny hole visible if you look into the carb where the slide goes in. Its on the pilot circuit and needs to have air or carb cleaner come out it when sprayed in the pilot screw or pilot jet hole

OLD CT said:

The washer could possibly be #14, just my guess.

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No, those are much bigger and both are present.

hrc200x said:

I dont think the wave washer belongs in the carb anywhere. It is metal and not hard rubber? The hole isnt supposed to go anywhere on this model carb, maybe it was used somewhere else or its a hole used to drill into body of carb to connect passages then plugged later

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Not hard rubber, something springy so I'm thinking steel.

hrc200x said:

There is a tiny hole visible if you look into the carb where the slide goes in. Its on the pilot circuit and needs to have air or carb cleaner come out it when sprayed in the pilot screw or pilot jet hole

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I checked and it has carb cleaner coming out when I spray it in the hole where the pilot screw goes.

I've looked, but I don't know where that washer came from or where it goes. It's really small. The only thing I've messed with that has hardware that small is the carb.

I don't think I've ever seen a washer like that on a Mini Trail.
I'd stick it to the wall with some spit. If you don't find a use for it before it falls...fuggetaboutit

I thought I was going to get my carb parts yesterday since the tracking said they were in Houston. They didn't come in the afternoon mail so I checked the tracking again and they went from Houston, TX to Seattle, WA to Kent, WA and on the delivery route! I see this morning they are on their way back to Houston. Thanks USPS.

FYI, next time you have a really nasty carb body that needs cleaning, put it in a small pot full of lemon juice, and bring it to a boil. Do this OUTSIDE, because it will smell terrible. Let it sit at a low boil for a few minutes, turning a few times to get it into all the crooks and crannies. Then take it out and rinse it VERY well with hot water to get rid of ALL of the lemon juice. It should look brand new.

Dennis McDonaugh said:

I thought I was going to get my carb parts yesterday since the tracking said they were in Houston. They didn't come in the afternoon mail so I checked the tracking again and they went from Houston, TX to Seattle, WA to Kent, WA and on the delivery route! I see this morning they are on their way back to Houston. Thanks USPS.

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FedEx and UPS does ridiculous shite, too...UPS, especially. Saw an overnight UPS shipment that went from Farmington, MI, to suburban Toldeo, OH - ~80 miles SSW, on it's way to Windsor, ON ~35 miles due east of its shipping point of origin. "The tightest ship in the shipping industry"