Carb issues A7 SS spec

[BSA500]

I am finding my carb will spit back and stutter/hunt at 3000-4000 rpm depending on which gear I am in. It is a 15/16 376 but should be a 1 inch. I have the 1 inch but you could fit a bus past the slide its so worn. The current carb has resleeved slide so that should be ok, but runs a little rich(pilot screw thread has gone so is held by ptfe tape ). Is this likely to be the carb for one and what could be causing the spit back at such a high rpm??

[Viking]

Worn Needle jets can cause spitting at that RPM.

Try manufacture new jets, and fresh needle.
It the float ok ?

or make a X mas wish for a brand new 1"  :-)

It give smouth running and cure idle issues....

[Triton Thrasher]

How far open is the throttle when this happens?

Is it ok at higher revs?

What sort of exhaust and silencer? 

Do you have an air filter? is it clean?

[BSA500]

How far open is the throttle when this happens?

Is it ok at higher revs?

What sort of exhaust and silencer? 

Do you have an air filter? is it clean?

Throttle at about 1/3 open
Difficult to assess higher revs usually run out of road on the way to work(bloody cars get in the way). I shall have stab
2 into 1 stainless into a reverse cone
No air filter

[Triton Thrasher]

I'd probably dump a carb with stripped adjuster threads.

Get a new needle jet, as said above.

Raise the needle a notch. If that makes it worse, drop the needle a notch.

[BSA500]

Prob look at having the 1 inch resleeved and start with fresh jets etc

[beezermacc]

Another forum member and I have been exchanging notes about carbs spitting back. we have both managed to resolve this issue. Fundamentally this is caused by weak mixture and, with perseverance, it can be tuned out. Basically you can try any or all of the following assuming your slide is a good fit:- smaller slide cutaway, lift the needle, bigger needle jet, bigger main jet, bigger pilot jet. At mid range the greatest effect will probably be achieved by lifting the needle but you may also benefit from some or all of the other tuning options.

[BSA500]

Another forum member and I have been exchanging notes about carbs spitting back. we have both managed to resolve this issue. Fundamentally this is caused by weak mixture and, with perseverance, it can be tuned out. Basically you can try any or all of the following assuming your slide is a good fit:- smaller slide cutaway, lift the needle, bigger needle jet, bigger main jet, bigger pilot jet. At mid range the greatest effect will probably be achieved by lifting the needle but you may also benefit from some or all of the other tuning options.

I think the best option for me is to have the correct 1 inch refurbed (resleeved and jets) as the current carb has had a resleeve so changing the slide is a no no. I will raise the needle on the current carb for the fun of it until I am allowed to spend some money on the carb. Checking the amal site I do at least have the correct jets etc at the moment.

[BSA500]

Well raised the needle and some improvement but still some stutter and when giving it a handful a spit back. Is there any chance the mag could give these issues. I hope not as she starts first/second kick in all weathers, ticks over and seems to pull well(until the spit/stutter). I notice that when 'cold' its not such a problem but starts when the engine is warm-it was horrible on the two hot days of summer 

[Viking]

My iron head A10 GF had a spitting problem this summer.

The issue was adressed with fitting af manufacture new 106 needle jet.

Don´t mess about with old jets...

[Angus]

When the A7 was first rebuilt it had a horrible spit and splutter at about half throttle (she too is to SS spec). Roger (the builder) spent ages lifting and lowering the needle adjusting mixture, I think he even changed the slide. It was the carb that was on the bike when I purchased it in 1976 and I don’t recall a problem back then (I think it was a 15/16 376. Anyway He swapped it for a new 1 inch carb and it has run as sweet as anything since.

[BSA500]

When the A7 was first rebuilt it had a horrible spit and splutter at about half throttle (she too is to SS spec). Roger (the builder) spent ages lifting and lowering the needle adjusting mixture, I think he even changed the slide. It was the carb that was on the bike when I purchased it in 1976 and I don’t recall a problem back then (I think it was a 15/16 376. Anyway He swapped it for a new 1 inch carb and it has run as sweet as anything since.

Yep I'm  thinking along those lines replace the 15/16 with the one inch after its been refurbed

[BSA500]

Well I have had the carb rebored and a new brass sleeve fitted, and the stutter is still there  . Don't get me wrong the carb is good steady tick over improved running but a stutter remains on acceleration. I have changed plugs,leads, new needle jet(106) new needle. The bike has had a rebore new mains,big/small ends so whats going on. Not to lead you on but I have not done head work as all seems fine. There is also the odd spit back 

[BSA500]

Sorry more detail 270 main,30 pilot 3 1/2 slide(sometimes a quick rev out of gear gives a puff of black smoke-richish)

[rocker21]

try a JRC 26mm carb, i know it is not original but i put one on my 1960 A7ss and it runs a treat strait out of the box, and a lot cheaper than a new Amal.