1952 plunger Flash (Amal 276 adjustments)

[anjimehra]

Have started the flash after a complete rebuild & am using an Amal 276 on her.The problem is that although she starts very easily,she runs for a bit & then suddenly spits back through the carb.If idle speed is low she'll cut out but restart immediately.If idle speed is high, engine will continue to run after spitting ( ill mannered brute !!!)

No spitting once the revs rise, so I presume its a problem with the idle circuit

All galleries in the carb are clear, no petrol starvation & the spark is strong & regular.Valve & ignition timing are spot on, tappet clearances are at .008. Float level appears OK. Cant locate any air leaks at the flange
Could this be because I dont have an air filter? Or that there is no choke slide in the carb? ( never was )

Anji

[wilko]

Try putting a finger partially over the slide cutaway while running. See what it does, and report back.

[MikeN]

Wind pilot air screw in.Then out 1 1/2 turns as a starting point.
Does it spit back when you blip the throttle? If so, try a size larger cutaway on the slide.
Then raising the needle one notch (or 2).
 if you have a spare slide it is easy to file the cutaway bigger (not so easy to put it back).
Mike

[MikeN]

Sorry, I should have said a size SMALLER cutaway (to richen the mixture) in my reply above. Which is what wilko is suggesting.
MN

[muskrat]

G'day Anji,
              sounds to me that the pilot is too rich. Try leaning it off with the screw another 1/2 turn. At a fast idle it will be starting on the slide which seems Ok.
Also mentioned elsewhere the 276 tends to flood when on the side stand, so make all adjustments with it on the main stand.
Cheers

[anjimehra]

Hi Wilko
Tried what you suggested but no difference.

Hi Mike & Muskrat, Ive tried all postions on the air screw fromm 1/2 turn open to 3 turns out, she still spits back & cuts out on slow idling
The carb is almost new with no play in the slide.The only thing missing is the choke slide.
Dont have any extra slides, but I would have thought that the slide cutaway would come into play on transfering from Idling to 1/4 throttle??

I have an old monoblock somewhere & will see if this makes a difference.
Thanks & take care
Anji

[chaterlea25]

Hi Anji,
On the newly rebuilt engine it maybe that one of the inlet valves is sticking a little intermittantly
Have you blocked the return to the oil tank with your finger to force oil to the head?
I make a habit of doing this every time I have the oil cap off to check level / flow etc

I had the same happen to me a long time ago with a newly built engine

HTH
John O R

[Brian]

Just a couple of small things, you say it has no choke slide, has the hole in the top of the carby that the choke cable should go in been blocked off and does it have a belmouth on.

Spitting back is due to a lean mixture, too much air or not enough fuel. You say the carby is almost new but is it the correct one for the bike. There are a lot of carbies with the correct throat size but they are not always the correct carby. It is amazing how many variations there are in the 276 carbies.

[anjimehra]

Hi Brian
Yes, the cable entry for the choke is blocked off wth a bolt. Cant locate any markings on the slide & needle but the main jet is 170

Anji