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mirkothun

Website User
VOC Member
Hi Comet specialists,
my Comet motor in the Metisse has started missfiring after a 30 km ride and cuts out. I pushed home. In kicking again it started but doesn’t take any good throttle and gets off again with no chance to start again. I checked the carb, seems to be ok, but I‘m no mechanic... Fuel is running, plugs are changed. It‘s said to be a 600 cc conversion, Mk 2 cams with twin plug head and boyer bransden ignition.
Any advice?
Thanks,
MirkoDC3F2208-8A05-4A92-B5E1-CAE0C92F3C5C.jpeg
 

BigEd

Well Known and Active Website User
VOC Member
VOC Forum Moderator
It sounds like you might have an ignition problem. These are classic bad capacitor symptoms if you are using a magneto. You are using Boyer-Bransden so it might be a black box problem or maybe your battery is on the way out. The early Boyer-Bransden boxes were very voltage sensitive. Try new or clean plugs first. Might be worth checking that the magnets on the rotor and the backplate with the trigger coils are secure and in the correct place.
 
Last edited:

Robert Watson

Well Known and Active Website User
VOC Member
Certainly seems to me like a battery. I used to race an R3 with Boyer and total loss. As the battery voltage dropped it would start to miss at high rpm, and then get worse quite quickly.
 

Black Flash

Well Known and Active Website User
VOC Member
I had the same problem with boyer ignition on various bikes, if the voltage drops to around 10.5 volts the ignition goes crazy, I had one foot long flames out of my S type command's exhausts.
Load the battery over night and see if the bike starts again. If so you are likely to have a problem on your charging side.
Bernd
 

bodlan

Well Known and Active Website User
VOC Member
I had the same experience. Thought it was the battery/charging issue but it turned out to be the BB rotor had lost its magnetism. There is a test in the BB fault finding notes on their website. If the rotor will not stick to a spanner it's shot. I think a new one was about £25. Been perfect ever since. I only found this out in a casual conversation with a Triumph owner in a cafe. Thank you stranger.
 

b'knighted

Well Known and Active Website User
VOC Member
I had a similar problem with the Knight. Always started well but would fade away. If I stopped and swapped front and rear plugs it would fire up and go again. When it nearly killed me by fading away while I was overtaking on an A road, I decided to strip it all out to get to the root of the problem. In the course of stripping it I started to remove the tank but it was full so I decided to drain it first. With the pipe in a funnel I turned the tap on and got the merest dribble of fuel so I turned on the other tap as well and got no appreciable improvement.
With the taps removed I could thread a throttle cable through them but could not see light through them. They were Triumph style lever taps, probably new at the beginning of this century and I assume that they had rubber seals which were damaged by ethanol. Fitting non-motorcycle taps with stainless balls in nylon seals cured the problem.
 

mirkothun

Website User
VOC Member
I had the same problem with boyer ignition on various bikes, if the voltage drops to around 10.5 volts the ignition goes crazy, I had one foot long flames out of my S type command's exhausts.
Load the battery over night and see if the bike starts again. If so you are likely to have a problem on your charging side.
Bernd
Seems to be the old battery and perhaps some dirt I fished out of the carb. Alton has been checked some weeks ago and regulator been changed. So I will get a new battery and hope everything will be fine.Thank you!
 

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