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the charging system seem alright. but bike still stumble like three minutes into ride,not sure of what the .... is going on getting frustrated.

That's a pretty cryptic description of the problem, but having owned a few old Brit bikes myself in the past I'll take a shot at helping you out.

Right off the bat I'm guessing you have a faulty ignition coil. If the motor runs fine until 3 minutes into a ride, that sounds to me like a heat related problem and the coil is usually the culprit. If the bike is cutting out on one cylinder only, try swapping the coils around. If the problem happens on the other cylinder, then it is definitely the coil.

Other than that, check the routing of the fuel line to make sure it isn't vapour locking as the motor gets hot. Do a load test on the battery to make sure it is in good shape - the charging system may work fine, but a toasted battery can cause all kinds of problems.

And remember - if it doesn't smoke and it doesn't leak oil, it ain't Bristish.

thanks for the help. Is it possible to use any kind of coil or do i need to use lucas coils, or should i just change all the wiring and charging system to somthing simpler.

You'll need to use Lucas coils, or at least something with the same specs as them. Boyer-Bransden makes an electronic ignition conversion kit for British bikes that takes a lot of the hassles away and there are kits available to change the charging system to an electronic regulator/rectifier. British Cycle Supply up in Nova Scotia are people you need to become very familiar with.

Actually you can use any coil as long as you wire it in correctly. Some coils will give you better spark than others. Back in the 70's Chrysler Marine made some coils that were the same size as the Lucas units but quite a bit hotter. I once used a pair of K-mart automotive coils on a BSA 650 twin.

Johnj wrote:Actually you can use any coil as long as you wire it in correctly.

Not entirely true - if you use coils with the wrong impedance, you will go through lots of points contacts and capacitors. It's better to get the proper ones and, yes, wire them in correctly.