Carburettor informations and setup

Hi everybody, I discovered that the carburettor of my honda ct70 1970 had leaks and so I decided to change it to that of a honda ct70 1972 but I noticed that the covers of the pilots jets were not identical so I wondering if these two carburetors did not have a different throttle cable length? Also I would like to know what are your techniques to make a complete adjustment in a carburettor because the techniques that are explained in the manual do not work. Indeed when I'm in 2nd gear and I want to accelerate, I get a lot of hesitation from the engine so I think I have to readjust the jet pilot and also the air screw. Your opinions will be greatly appreciated.

Rebuild kits, including all of the seals/gaskets are readily available, on both sides of the US/Canada border...cheap, too. I'd seriously consider rebuilding the original carb, or at least replacing the seals, gaskets and inlet needle & seat. While the bowl is removed, check the floats for small cracks/leaks...the problem could be as simple as a leaky float. If the motor was running well with the original carb, you could just swap-in the K1 float...if that was the issue.

MonkeyBikerCanada said:

the covers of the pilots jets were not identical

Click to expand...

Could you post a photo, or two? I've no idea what you're referring to.

As for adjustments, the pilot airbleed screw only affects idle to ~1/8 throttle. What you want to adjust is the jet needle height, via its C-clip. Setting it into a lower groove richens the mixture, higher grooves make the mixture leaner. Before doing that, however, I'd pull the float bowl, remove the jet holder (which is also the emulsion tube) and run a thin wire through every single one of the minuscule orifices, located between the threads & tip of the tube. That's a common cause of poor fuel atomization, restricted fuel delivery via the main circuit and...drum roll please...lean stumbles above 1/8 throttle opening.

I think the original carburetor is not reusable because I think it is cracked some place but against the carburettor honda ct70 1972 worked perfectly on my ct70 1972 before I install it on my 1970 ct70.

1972 cover

1971 pilot jet cover

So finally my question is how to completely set a ct70 1972 carburetor? It include the adjustement of the pilot jet, the air screw and the idle screw. How many turn do you put on all these particular screw

Okay...

Pretty much the same as the `69-`71 K0/HK0 initial adjustments. (Final tweaking can only be done while the engine is up-to-temp & running.) Pilot airbleed 1-1/2 turns out from seated. Curb idle screw, initial setting by eye; look into the venturi, noting when the throttle slide just starts to move, then give it another turn. This is anything but precise but at least you won't get a runaway idle on the initial startup. As for the jet needle, based on you results so far, I'd start one groove below center. If throttle response is still weak, try dropping it to the lowest groove...then post your results here. I don't want to over-complicate things from the start.

FYI the cover in your first photo is the cap, which goes over the throttle slide. The second photo is tiny, with no specific part highlighted, or identified.

Ok thanks a lot racerx