1970 Honda CL70 stumble under load

punkrock randy /

This is a 4 stroke Honda with a stock Keihin carb. I just acquired this, so I don’t know a lot about it. The compression feels great, it starts and idles great and doesn’t smoke at all. I have the air screw 1 1/2 turns out and the idle screw needs to be out about 3 1/2 turns to drop idle to where it sounds good, warmed up of course. I’ve cleaned the jets and assured clean and clear orifices. New fuel and fuel filter. Spark plug is clean and properly gapped. Fuel seems to flow freely thru petcock, but I noticed a small air pocket will form between filter and petcock, not sure if this typically happens. Haven’t exactly noticed that on other small engine stuff I own. Any input much appreciated:-)

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Re: 1970 Honda CL70 stumble under load

punkrock randy /

Nothin eh? Is it because it’s a shifty or cause it’s a dumb question? I’m cool with either, LOL. Just a stupid carb issue, I’m sure I’ll figure it out eventually. I hope everyone’s taking advantage of this warm winter:-)

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Re: 1970 Honda CL70 stumble under load

yup, nuthin here for 4 strokers or no pedals.

Re: 1970 Honda CL70 stumble under load

punkrock randy /

Yea, 2 stroke carburetors are sooo different! I’ll glue on some peds and rephrase my question;-) Cheers anyways

Re: 1970 Honda CL70 stumble under load

Sometimes the air will work itself out while riding , but , if it doesn't , make sure the petcock is clean , including the sediment screen .

Get good flow through the petcock with the fuel line barely on the nipple , so any air in the line has an easy escape . Once the air is out , secure the line to the nipple and get some riding done . ;)

Re: 1970 Honda CL70 stumble under load

Check the oring between the carb and intake, I've seen those leak all the time. Also check intake for flatness. There's a bunch of stuff that can cause your issue though, lack of fuel, timing is off, points not gapped correctly.... list goes on.

Re: 1970 Honda CL70 stumble under load

punkrock randy /

I’ve sprayed ether around both ends of intake whilst running and the idle doesn’t jump up at all. So I’m confident of no intake leaks. I put a new NGK plug on it gapped properly to .024” No change whatsoever. But the plug is definitely getting doused in fuel, waaayyy too much fuel definitely seems to be it’s issue. Also, the guy I bought it from says he replaced the points. Like I mentioned, it starts good cold or hot, and idles great, just doesn’t wanna rev up. I’m going to tear of the carb off when I get off work and really go to town on it. I appreciate the help on this, can’t wait to ride it.(edited)

Re: 1970 Honda CL70 stumble under load

When revved does it stay revved for a while and then back down?

Re: 1970 Honda CL70 stumble under load

punkrock randy /

No, when it revs up it drops about as you’d expect. And it revs most normally when it’s sat there idling for awhile. But as soon as you rev it up a couple times it starts stumbling hard, and doesn’t wanna rev up much above maybe 1200rpms or so.

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