Forum

[MichaelV]

I have a problem with my AMAL 930 fitted to my 535cc Bullet.

Let me give the background:

The bike, a 2001 model, has a 535cc aluminium barrel and piston big bore kit (200074C) supplied by our hosts. It is superb. It was fitted with a VM28 jetted nicely. The bike is running superbly; it starts from cold 1st kick, warms up and runs perfectly, never misses a beat and idles smoothly. So, why, you may wonder, did I decide to replace the VM28 with the AMAL 930? I’m beginning to ask myself the same question…

Anyway, on to the problem. As stated above, after swapping the VM28 out and the AMAL 930 in, it still runs fantastically, starts easily and goes like the proverbial solids off a polished 304 (or maybe 316) shovel BUT, and it is a big but, every single time I pull up at a junction it cuts out. So, flip out the kick start, one kick it starts immediately and it idles beautifully. Off we go, riding wonderfully until the very next junction. It cuts out. Flip out kick starter, one kick it starts immediately and it idles beautifully. Off we go… repeat ad nauseum.

I have read, manifold times, John Healey’s excellent guide to tuning the AMAL, various other tuning bibles, all the threads I can find on this and other boards but, sadly, albeit some describe similar problems none offer a solution to this exact problem so, I am asking before what precious little hair I have left falls out in desperation, has anyone got any idea what on earth could be wrong?

Like I’ve said, otherwise the engine is perfect, ignition spot on, valves exactly set, and it’s a complete dream otherwise, easy to start, goes like the clappers etc. etc. but at every junction it cuts out. Starts immediately the next kick and idles beautifully.

All help most gratefully received (by my hair, too).

Thanks in advance,

Michael.

[vince]

Hi, I had this on a bsa. Turned out to be the brakelight switch shorting out as you braked and killing the motor. Vince

[MichaelV]

Hi Vince,

Thanks for the thought. It seems ok electrically in so far as I can test the brakelight before pulling away and it keeps going but I will make more checks on this. The only reason I'm a little sceptical is that an hour earlier with the original VM28 it never cut out and idle perfectly even when pulling up at the lights or a junction but I will check for that.

Thanks again for the idea.

[Wheaters]

My 350 had a similar but less extreme problem. I recently fitted an iridium spark plug, which so far seems to have cured it. The old plug was the standard type without many miles on it.

Also, try fine tuning the idle mixture again.

[windmill john]

I’m with Wheaters second point.

What if you richen the mixture by literally a tad.
What happens if you pull up to junction very slowly.
What happens if you pull up but get into neutral before actually stopping.
What happens if you have throttle the taddiest of taddies open when coming to the stop.
Try coming to a stop with the bike lenses over (hard to do) but wonder if float is ‘slamming’ shut.


John

[MichaelV]

Thanks for the input, John and Wheaters.

I have tried all manner of idle mixtures (well, as much as you can with a fixed, pressed in 0.016" jet). Rich, lean, correct (according to the AMAL published setting procedure anyway) doesn't seem to change anything, it starts first kick, idles great etc. etc. but just continually cuts out when I pull up. But, having said all that, I'm not averse to giving it another try so I will try the mixture setting again.

John, I've tried most of the things you suggest but will re-try: I've also tried all different idle speeds from a really slow 'one thump every second' right up to something akin to a Formula One car type idle at 2500.....same result, sadly.

If, as I am coming to a stop I rev it a little to try to keep it alive, if I do that, i.e. dip the clutch and rev, rev, (not excessively like a sports bike rider is apt to do) but just to keep it running, I can and it will then not cut out but if I ride what I call normally, i.e. clutch in as I pull up to a stop and brake normally to a standstill but don't rev it cuts out every time. I did think it was , possibly, a too-low idle, but that, too, didn't make any difference. That's why I'm stumped and looking for help as, in every other sense, it's a dream to ride, starts easily first kick on the choke, warms up and rides great even starts first kick again and idles normally when it does cut out at a junction or lights but it just has this incredibly irritating and, in my opinion dangerous, habit. You know the feeling, you're pulling up to a junction on the right (or left I guess in the places that ride on the right), there is nothing behind you but you have to wait for an oncoming vehicle to pass, you de-clutch and it cuts out.... then it's a mad panic to flip out the kick-start, and kick it back to life before someone comes racing up behind you and cleans you up because they weren't paying attention.. How many times, as riders, have we heard "Sorry, mate, I didn't see you!" to which I always reply "No, you didn't look!"?

I suppose what is really perplexing me is that with it's original VM28 it never cut out, I only went for the AMAL 930 as I'd fitted the Hitchcocks big bore kit (535cc) so, stupidly, thought a little extra mixture might be a good thing.

[MichaelV]

Sorry, Wheaters, I meant to say that I will order an iridium plug and give that a try - not lost anything in trying so good shout, let's see what happens when I do that, too. Thanks.

[Bullet Whisperer]

Try a 107 needle jet, it might help.

[Blown265]

Float height set too high (fuel level in the bowl) can cause the exact symptoms described- usually though it's an aggressive stop which brings on the fuel slosh/carb flood.

If the bike starts/idles/accelerates at part throttle/ WOT/cruises/(ie performs ALL of the above well), then it's not usually spark related. A bad spark will give grief in at least one of the operating conditions listed.

Assuming nothing else was changed at the time of swapping carbs, and the bike does everything perfectly except the stall, then I'd put good money on the float height being too high.
Regards
Paul

[PeteF]

I'm thinking float height too.