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Commando Boyer ignition timing

Submitted by andrew_jago on Thu, 10/03/2022
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Commando

I am puzzled about the ignition timing on my 850 mk3 with a Boyer ignition I put on back in the 70s.

I really don't want to time the ignition according to the Boyer instructions ie at 5000rpm, so have found one of a few threads that give timing values through the rev range - this suggests you can strobe check at various rpm, for example 23 degrees at 3000rpm.  The timing value stated in the workshop manual for the original contact breakers is 28 degrees ( max advance? ) at 3000rpm.  This suggests the motor is meant to run 28 degrees at 3000, so why does the boyer specify 23?  There is a small voice inside my head telling me to put contact breakers back on! - it not like I am doing thousands of miles a year anymore.  

Submitted by martin_edridge on Sun, 20/03/2022

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I have often felt that a part of the reputation that Boyer equipped Commandos were more reliable was down to the softer curve of the ignition. I fitted one back in the 70's and it was undoubtedly easier to live with and more reliable but never had the same urgency under acceleration that the points system had. Unfortunately I don't know how to make the curve faster without resorting to the original points and ATD unit which I am not prepared to punish myself or the bike with.

Those days are over, for better or for worse. :-(

Submitted by webmaster on Mon, 21/03/2022

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Hi Andrew,

 

I’ve timed my Commandos over the years with a Boyer with no issues. I think its fine to rev the engine to ensure you get to full advance. Think about it – its not under load, just sitting on its centre stand and it only takes a few seconds each time to check and adjust the Boyer plate to get the correct timing position. Have a go.

 

Regards – Paul.

Submitted by william_downie on Mon, 21/03/2022

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I have just decoked my 850 MK2 to restore compression due to valve seat degradation and leaking. Bike now has very good compression and starts first kick cold or hot. Only prob I have is slight surging when cruising at 60/65 mph. Acceleration is good and bike runs well as did 250 miles last time out but surging is annoying and it feels like carburation rather than ignition. Anybody any ideas what causes it and how to cure it ?

 

Bill Downie

 

Sorry Tony thought I had put in new subject. Clearly my FORTRAN 4 training 30 years ago doesn't work on these new wonderful it thingamybobs. That's why I have old British bikes. Apologies Bill

Submitted by julian_wells on Mon, 21/03/2022

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Bill's engine surging problem may be down to worn needles and/or needle jets; at the same time, good to check that the slides aren't rattling.

Many thanks Julian I did have bother fitting one of the carb slides and needle assemblies back into the carb body after the decoke. I may have distorted the needle or it has moved on the clip slot I'll have a look.

Again thanks 

Bill

 

 

 

 



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