Hi ........... I'm having trouble with my 1957 B31 overheating badly, when I start it (first kick) within a minute the downpipe is glowing red. I must admit I don't know anything about the manual advance/retard system, but I've adjusted the carb needle valve and lifted it one slot, which appears to have made a very small amount of difference. Can anybody recommend somebody in the Portsmouth area that would be able to take a look at he bike for me, unfortunately because it's overheating so badly I unable to ride it. My number is 07766766259. PLEASE HELP!
Have you just had the bike?
Is it something that has just started to happen?
Without a bit of history it is difficult to diagnose the possible problems.
I hope someone locally to you can help but it would be very useful to know all the facts first.
Obvious thought is timing....
Hi ............ Thanks for your replies, I've had the bike around a year and it's been running perfectly, I hadn't used it for around a month and then when I started it, it was red hot straight away. Because it's running so hot I can't run it to take it to any repairer, it would need to be collected :(
Hi Chucky,
It sounds as if you might rather have someone look at your bike than try to diagnose and fix it yourself - however, it sounds like the most likely causes could be weak mixture, retarded timing or a combination of the two which you might want to investigate a bit?
Looking at the end of the mag/dyno from the nearside, if the advance/retard cable enters at the top right (rear) then it's pull to advance and release to retard. If it enters at the top left (front) it's t'other way round which is kind of important to know for correct operation!
So, when you start the bike you would normally have it a tad off fully retarded. Advancing will then cause the engine RPM to increase and, if timing alone was the cause of the problem, should also help with the overheating.
As the bike starts OK it doesn't sound like the timing is way off so I'm wondering what position of the advance/retard lever you normally find best for starting and riding? That info might help with diagnosis.
If it's gunge in the carb causing a weak mixture or incorrect float level then a stripdown, clean and check of the carb setup is called for.
Cheers,
Bernie
Check the timing. I expect it's retarded and that fuel is still burning when exhaust valve opening hence red exhaust pipe.
I had the same problem on an AJS. Pipe went cherry red almost straight away. Timing was way off, about 15 degrees too late but it still started easily.
Have you got a manual for the bike?
Thanks all for the advice, i'll have a look at the adv/ret cable and see if that's operating correctly, likewise will strip the carb and check it's clean etc. cheers
:) :)Hi
Only just read this--I would suspect that either your exhaust valve not closing properly or its burnt at the edges. PLease let us know the answer when you get it sorted.
Mike 8) 8) 8)
Quote from: Mike Farmer on 24 Nov, 2019, 09:28
:) :)Hi
Only just read this--I would suspect that either your exhaust valve not closing properly or its burnt at the edges. PLease let us know the answer when you get it sorted.
Mike 8) 8) 8)
agree with mike sticking exhaust valve can cause similar.
Yup .... or poorly adjusted valve lifter maybe?
Cheers,
Bernie