Forum

[sab]

I have a 1955 Bullet 500cc with a 1990 engine. It starts OK when cold, but as soon as it has warmed up, if I switch off and then try to re-start, even after 15 minutes, it is a right pain to get going again. I notice sometimes that I get exhaust fumes blowing back through the air filter when trying to re-start but the engine doesn't fire up. Is this a timing issue perhaps? The timing seems OK for starting when cold. Or maybe it's a fuel / carburettor problem. Not sure. Any ideas?

[simon]

Sounds like it is too rich. Check the spark plug colour and if it's black you need to lean up the mixture. The idle mixture screw would be the place to start but it will probably only need a quater to a half turn but I don't know whether the mikicarb has an air or a fuel adjustment so you'll need advice from someone else or the manual for that info.

[Les H]

Hi Sab. nice to hear you got your ammeter to function. The starting problem is not that uncommon, but it is very often just down to technique. Once you have the engine running and the engine fully warmed up, spend some time adjusting the carb air screw and throttle stop until you get a very reliable tickover. Once you have that, all warm starts should be done with no throttle applied at all. Still carry out the over TDC on the compression stroke routine and when the engine fires you might just need to catch it on the throttle, but often it will start and go straight into a reliable tickover. Give it a try a few times…keeping your right hand off the throttle to avoid subconscious tweaking. If this doesn’t work for you it could be the ignition side of things including a faulty spark plug.

[trevorch]

Hi san, My 2007 Bullet was also reluctant to hot start, especially annoying as it also had the traffic light syndrome, both with the original Micarb and later with a new Amal Monoblock. First off, follow Les H's advice to set up mixture and slow running with engine hot. 2nd, my dealers advice, when I had the Micarb, no choke, ignition off, decompressor open then with throttle wide open, give it three or 4 vigorous kicks. Then close throttle and start like normal, no choke of course and with throttle fully closed or just a tad open. Too much throttle it will probably back fire. Theory was that kicking over with wide open throttle a few times cooled the combustion chamber down enough for a near normal start. Much to my dealers surprise, same technic worked also for the Amal. Cheers TrevorCH

[PeteF]

You could check your float height. There's a tech note on here showing you how.

[simon]

If you do find you've flooded the motor when hot I find the Flight of the Phoenix solution of opening the throttle fully and kicking it over a few times with the decomp open will generally return you to a combustible mixture.

[PeteF]

Just thought of another possibility - could be the condenser. If they're on the way out they sometimes don't work so well when hot.

[sab]

Thanks for all the advice everyone. I've adjusted the mixture using the tech notes for the carb on this site. And also taken heed of the advice not to touch the throttle until it 'catches'. And hey presto - it works fine. Been out and about today and has restarted first or second kick every time, so I'm very happy! Bike still struggling a bit on hills with two up - struggling more than it should I think. And was occasionally missing this evening too. Think I'll change the spark plug tomorrow to see if it makes a difference.