Single cylinder Bonneville

[henry_norton]

My bonneville (1966 engine with boyer ignition) only wants to run on one cylinder at the moment - the weird thing is it'll run on two if I pull the plug cap half off the spark plug of the dead pot. The answer might seem obvious (dodgy cap) but I've tested both leads and swapped them over yet it still does it.  

Any ideas anyone?

[L.A.B.]

Have you tried swapping the ignition coils over (what happens then) as well as leads/plugs/ plug caps?
Are you certain the coils are wired correctly with regard to polarity (+ve Earth?)  and also wired in series with a Boyer, are the coils the correct type for the system (2x 6 Volt?)?
Have you tried different spark plugs?

[TBS]

As the Boyer runs wasted spark system, swap leads over eg the left lead goes to the r/h cylinder and vice versa,  if the same cylinder is mis-firing, I would suspect a plug. try another set.

[henry_norton]

Thanks for the replies. Turns out my battery is mullered too which isn't going to help, (2 cracked, empty cells). I'll give it a go and let you know.

Fingers crossed....

[TBS]

That's definately the cause then, as the Boyer system only runs with at least 10v

[henry_norton]

Sorted! thanks for the advice.

Interestingly(?), the dead pot was running the wrong spark plug (NGK B9 instead of B8 ). I don't know what the actual difference is - hotter, colder, softer, harder, but it finally cured the intermittent running. Replacing the battery also helped as it now starts on the 2nd or 3rd kick now instead of 20th or 30th.

Happy days again (ie. just oil leaks and a piss poor SLS front brake to contend with)

[TBS]

The '66 has a full width hub so it is a quite reasonable brake when set up. Does it pulse when you gently pull the lever on? This would show an out of round hub which can easily be sorted by skimming, Hagon can do this for you with the tyre still fitted. The drum might be glazed so a good rub around with some emery paper will help to remove the glaze. To set up the shoes undo the brake abutment, use a spanner to pull on the brake really hard, then tighten the abutment, this will make sure that both shoes are expanding on the drum equally, 3 hands are a good idea or 2 with a foot on the spanner
I run Denso platinum plugs W24ES-ZU. NGK rating go from 2 being the hottest to 12 which are the coldest. NGK equivalent B8ES or Champion N3C.

[henry_norton]

Thanks again TBS,

as it happens my bonnie is a 1965 with a 66 engine so I've got the pre-66 SLS. I'm thinking along the lines of replacing it with a 68-70 TLS; I hear they're pretty good although my experience with them has been pretty limited, ie. a ride around a car park....

[TBS]

To do the TLS conversion you will need a new hub as the later machine's hub has a raised flange to accommodate the spokes on the brake plate side. Go for the later 69/70 brakeplate with the brake cable running down the back of the fork leg, this is much better than the '68 as the cable doesn't stretch.