Strange problem

Your tank vent may be obstructed, In a well ventilated open area with something less than a full tank, crack the fuel cap when it begins to exhibit the symptoms; you may, alternatively, have a restricted fuel tap; try running with both taps on. An air leak will yield the similar symptoms; the rubber adapters get a degree of stress and don't live forever. I don't remember if you purchased a kit or just the carb. In any event if you spray carb cleaner on and around the air joints on the intake system a major change in idle behavior will tell that tale. As Jim from NH points out the Boyer may be ailing, they too don't live forever.

The fact that the symptoms are common to the new and old carb leads me to believe that the carb is not the issue; however, If you get to the point where you have lost faith in the carb I am happy to look it over at my expense and either repair or replace the carb or give you a full refund.

Yes just run it with both taps on and the gas cap clicked slightly open-ajar , to see if that makes a difference.

Thanx Bill.I dont think it is the carb at this point .I tried the cracked gas cap when it first started. No difference. So everyone here knows the carb was set up perfectly out of the box. Gas flow restriction? Maybe. Another thing to check. Oh almost forgot. It is new manifold adapter from you. And Ive done the air leak check. Again thanx for everyones input.

Did you get an adapter that does not create an air dam ? Is it sized to the head type intake ?

I had the very same issue a few years back on a 73 850. Turned out to be the one of the coils had bought the farm.

A coil? Really? Not that I dont believe you, but wouldnt there be a starting issue if bad coil? Also if they both ohm out ok statically how do you find out which one is breaking down with heat? Im really intrigued here because I dont think its a carby issue any longer

Both 6v coils show 2.4 ohms

Roxie said:

Yes that is the correct way to set idle and i have always done so. I am traveling and dont have many tools or parts with me. At present we are in NH. I will try to scrounge up a spring and timing light.So no one thinks this could be a cracked cyl head?

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I live near Newfound lake (Plymouth) area and have some Amal springs (and tools etc.) for you if interested. Give me a PM or just answer here if you want. -Pete

Pete. Thanx for the offer but i think ive got it worked out. Will explain later. Have to get cleaned up to go out for dinner now

Roxie said:

A coil? Really? Not that I dont believe you, but wouldnt there be a starting issue if bad coil? Also if they both ohm out ok statically how do you find out which one is breaking down with heat? Im really intrigued here because I dont think its a carby issue any longer

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Coils can test fine when cold on the bench but start to break down with heat. Not at all unusual. I had it happen 4 years ago on my 66 bug.

I know how frustrating it can be to go thru all this and never hear the end result. So here it is. I used an old mikuni spring and fit the 2 together. A bit difficult to compress them both enough to fit the cable to the slide, but manageable. Then I replaced all the fuel lines and put new less restrictave in line filters on. I have some rust in the tank so filters are necessary. Took a long ride and all seems ok. Which one cured the problem? Probably a combination of the 2. Thanx for all the help. Don

Roxie said:

I know how frustrating it can be to go thru all this and never hear the end result. So here it is. I used an old mikuni spring and fit the 2 together. A bit difficult to compress them both enough to fit the cable to the slide, but manageable. Then I replaced all the fuel lines and put new less restrictave in line filters on. I have some rust in the tank so filters are necessary. Took a long ride and all seems ok. Which one cured the problem? Probably a combination of the 2. Thanx for all the help. Don

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My money would be on the slide,the amal spring fits in easily

Yes. Prbly the slide. I did not have a amal spring on hand so i used the 2 mikunis. Right wrist will be getting much stonger now