Misc: Ignition Mysterious Meteor misfire - what am I missing?

[vibrac]

I dont think we should rush to condemn the BTH that road leads us to the magneto-coil-magneto loop that has bedeviled Vincents for 60 years. BTH modernand good as they ate comprise a moving item in an exposed position rust does get inside
here is our racing comet internals (it was still working OK)
It was designed by a guy who had suffered the setting up pangs of the Lucas and similar devices that rod holding the 'armature' is worth a lot of hassel I will stick to BTH when I need to replace an aging magneto

 

[Bill Thomas]

The "D" Distributor is the best setup, I think.

 

[Simon Dinsdale]

I dont think we should rush to condemn the BTH that road leads us to the magneto-coil-magneto loop that has bedeviled Vincents for 60 years. BTH modernand good as they ate comprise a moving item in an exposed position rust does get inside
here is our racing comet internals (it was still working OK)
It was designed by a guy who had suffered the setting up pangs of the Lucas and similar devices that rod holding the 'armature' is worth a lot of hassel I will stick to BTH when I need to replace an aging magneto

Tim
I like the idea if the slotted mounting holes to allow small timing adjustment and also the idea of the locking rod to hold in time when fitting. I also liked the BTH when it was working as it gave the most stable tickover I have ever had on a Vincent so it had a lot of postitives. The problem is the unit stopped working and I then hit a brick wall trying to get it repaired. I must point out that was 10 years ago and I believe BTH is now owned and run by somebody else.

 

[vibrac]

Tim
I like the idea if the slotted mounting holes to allow small timing adjustment and also the idea of the locking rod to hold in time when fitting. I also liked the BTH when it was working as it gave the most stable tickover I have ever had on a Vincent so it had a lot of postitives. The problem is the unit stopped working and I then hit a brick wall trying to get it repaired. I must point out that was 10 years ago and I believe BTH is now owned and run by somebody else.

Yes he is in Milton Keynes I am about to get the single BTH re checked when funds allow

 

[Chris Launders]

I have a modern BTH on my twin, I had a CDI unit go down after about 20,000 miles and sent it for repair, back in a week, mine is an early one and on test it was found one cylinder was 5 degrees out so a new correct mounting plate was fitted to fix that as well. I don't think you have an ignition problem. Is there no-one who could lend you a mag and carb to try, substitution is the best initial tool.

 

[Martyn Goodwin]

Is the carb getting hot - could cause fuel vapourisation and mis-firing

 

[CoreyL]

classic condenser / short failure in the vid'.
in CoreyL's situation given the symptoms i'd look for something simple; is the misfire affected if the choke is applied judiciously at high revs, are the points in good condition ie spring, pads square nothing shorting at high revs.

When I try closing the choke (richening the mixture) during the misfire, it doesn't help.

 

[CoreyL]

Is the carb getting hot - could cause fuel vapourisation and mis-firing

No, the inlet track gets hot but the thick gasket between the inlet and the carb body is doing its job and keeping the carb cool.

 

[CoreyL]

Yes he is in Milton Keynes I am about to get the single BTH re checked when funds allow

My BTH is now boxed up and being shipped back to Milton Keynes for post-mortem examination. The date on my mag is Jul 2015. I've owned the bike since Dec 2017 and it's run fine since then. I'm hoping something is found amiss, otherwise I'm back to square one (and may be tempted to revert to an old school, non-electronic advance, ignition system)

 

[oexing]

One has to admit the most reliable ignition system is the old contact breaker/capacitor/coil set. When you got a good magneto that is allright - but I would not count the rotating coil type among them. Provided there is a decent dynamo on the bike you could go for coil ignition. Not my actual needs but why not do a bit of lathe fun and adapt a Saab distributor onto the Vincent engine: You got one breaker, ATD inside, and go for a twin spark coil or two 6 V coils in series. The breaker cam will have to be modified for the 50 degree twin, no problem, machine one cam of the four from the Saab type (sense of rotation for ATD) and one breaker is all you need - the Saab was allright with one too.
Certainly you will have an adaptor with a ball bearing to bolt onto the engine case - fun on the lathe.

Vic