Messing about with this carb for 2 years had 3 attempts at re-tuning it. It does start just, but pops,bangs, misses tick over is lumpy and air screw/throttle adjustment does work but below 1000rpm it just fades and stops. Plugs are sooty black and always have been.
- Needle 280,Main 106,Needle groove 2,Pilot 25,Cold Start 40,Slide 3.1/2.
Help
Popping and banging is often…
Popping and banging is often (but not always !) due to an intermittent ignition ,sometimes this is as simple as an oiled plug giving an occasional spark.
Amal Running Problems
Hi Malcolm
It's very frustrating.
Have you tried cleaning the Pilot Circuit?
Cold engine. Remove the pilot air screw, squirt in a small amount of carb cleaner. Wait a few minutes, wipe away any excess. Replace the pilot air screw.
Hope that helps
Air leaks?
Air leaks?
Stan's the man...if the…
Stan's the man...if the carburettor is clean and new and has the correct settings.. it isn't the carb. If it's a twin and one plug is bad, it will still run properly but badly on one cylinder.
Air leaks cause weird things.
The only other thing is stuff you can adjust. You say plugs are sooty. You are turning the pilot screws the right way?
Amal Mk 2 Carb
Where is your Pilot Jet located? The Mk 2 has 2 locations, in the top of the float bowl and in the base of the carb. For all down-draught situations the pilot jet should always be in the carb base, Also make sure you have a 4 stroke main jet holder, the 2 stroke version is flat at the bottom whereas the 4 stroke has a boss at the bottom and sits further down in the well of fuel at the drain plug.
Oh yes it can......
You may have bought a carb that before fitting would sit on a piece of glass or other confirmed flat surface at the manifold. Check it again for rocking.
It doesn't take a lot of over tightening to cause distortion, not much at all in fact.
Hi Neil Stay up float…
Hi Neil
Stay up float fitted and set to 2mm below bowl mating face.
Hi Robert 2 new NGK plugs…
Hi Robert
2 new NGK plugs fitted. I am messing about with 0.025 or 0.030 plug gap what do you reckon?
Hi Tim It's a new MK2 Amal…
Hi Tim
It's a new MK2 Amal but I am taking it off again and checking for machining burrs in carb body.
Hi David Yes I can get the…
Hi David
Yes I can get the correct response from the air/throttle adjustments but it nowhere near 1.1/2 turn out on the air screw.
Hi Terry Its in the carb…
Hi Terry
Its in the carb base and yes it's a 4 stroke jet.
Hi Robert It's got a Boyer…
Hi Robert
It's got a Boyer EI and is set to 28 Deg BTDC i'm going to try 30 what you think?
Hi Stan I'll check that…
Hi Stan
I'll check that,thanks.
Hi Neil I'll check that…
Hi Neil
I'll check that,Thanks.
You need to halve the…
You need to halve the possibilities. I would try another carb , if no better then concentrate on the ignition system . Beg or borrow a carb
Stay up Float 2mm below the lip
Is that the recommended height? I thought it was less than than that.
Small changes in plug gaps…
Small changes in plug gaps or timing are unlikely to have much effect on normal running ,however if your spark is tracking down a dirty plug insulator then a reduction in the gap may help reduce this. Once running and working hard the heat generated will sometime clear the plugs and help starting ,however many plugs in production today have insulators that absorb carbon and are hard to recover. Most now have a built in resistor which is ok as long as you dont double up with resistor leads or plug caps which can upset an already weak system. Plug grades that worked in the distant past may not be the best for light use in modern traffic conditions and with todays fuel brews.
Idling Jet
The idling jet needle must be close to 1-1/2 turns out, otherwise the air velocity across the jet is incorrect and decent idling will not be achieved.
Change the jet size.
Cold Start
Check the cold start plunger has black seal fitted.
I'll keep this short.
Try a stay up float. Not enough fuel for one carb. as standard,