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Commando timing RPM

Submitted by martyn_hambling on Sunday, 28 August, 2016 - 01:00
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Commando

Hi folks

I am trying to set the timing of my 74 Roadster.

it is fitted with a Boyer Bransden mk3 unit.

i have set it static at 31deg BTDC but not sure what RPM to run it at for the strobe.

The workshop manual says run at 3,000 and and a Boyer Bransden installation guide that I found on Old Brits.com says run at "up to 5,000 RPM" which seems really high?

I have looked through historic threads on our forum but can't see a reference to it!

What's tne best RPM to run at for a strobe setting and I assume that 31deg is also correct.

The bike starts ok now but does not run cleanly and I want to make sure the timing is bob on to rule it out before I look at other areas.

Thanks Martyn

Submitted by john_holmes on Sunday, 28 August, 2016 - 01:01

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For the Boyer 5000 revs is correct, the bike will want to wander but a rubber mat under the centre stand fixes that and I can just about strobe with one hand and operate the throttle with the other, the 31 is also correct as the Norton has a good combustion chamber and can take a bit more advance. Because of variations in the electric components strobing at 3000 rpm 28 degrees will notbe accurate enough at 5000 to guarentee the 31, so strobing at 5000 is safer. Use a helper is 5000 next to your ear is daunting.

Submitted by david_evans on Saturday, 3 September, 2016 - 01:00

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Yes well worth getting some ear protection and if you get a friend to help, get them to sit astride the bike off the stand. It won't jump around all over the place nor will the strobe marks and you will get a better view of the strobe marks. (don't melt the strobe wires on the exhaust)

Submitted by adrian_bates on Sunday, 14 May, 2017 - 01:00

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Hi Martyn

i have the same question as you.

Just to check did 31 degrees at 5000 rpm work out ok ?

regards

Ade

 



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