In all due respect and not to seem judgemental, your weight of 286 lbs (130 kilograms puts a whole lot more oomph on the kick-start lever than my 160 lbs. and I'd say you just may be generating a whole lot hotter spark than me.
ET: Engine (Twin) Starting Procedure Twin…Using Chokes or Not?
- Thread starter CarlHungness
- Start date
Nope!
The rear cylinder fires, 50 degrees later No2 hits TDC, then 310 degrees later No1 hits TDC on exhaust and 50 degrees later N0 2 hits TDC on the bang stroke, a total of 410 degrees, then 270 degrees later NO 1 hits TDC on the bang stroke. That means the front, No 2 cyl has the most rotation of the magneto armature to induce the fattest spark. Having said that Mag BTH CDI of HD or other electronics driven spark, I just give it a boot and drop the comp lever 1/2 way through, and if it hasn't lit by then I look to see what I have done (Fuel off? Ign switch off)
I've seen and studied the diagrams of what you outline, and you are of course correct. No 2 has the most rotation. You are basically saying you, 'give it a boot, drop the comp lever 1/2 way through..." I surely try to do the same but drop the comp lever AS I kick, and am not getting it to start consistently. Thus, what is your suggestion for me. Does the battery ignition provide more, hotter spark than a mag? I'm attempting to learn something here.
Given a magneto like the KVF is an AC device, the max amount it can produce a spark is no more than 180 degrees of rotation.......it can only produce a spark during and after the peak of the magnetic flux, not before it........if you advance a magneto to far the spark simply stops........just like turning the ignition key off on a coil ignition system.......but after this peak, or in any retarded point the spark will continue, but its strength will drop off........the number one firing position of a KVF is therefor the number one cylinder (the rear one).......if it was the front cylinder the spark simply could not occur on the rear cylinder as the internal timing of the magneto is less than 180 degrees........If your magneto has a weak spark there are various reasons why, but after a rebuild the common issues will be either the iron core of the armature has been turned down in the lathe to true it up, or loss of magnetism in the housing.......if the armature core is even 10 thou smaller than the factory size (bang on 2.00" from memory) the spark strength especially at low (kicking) speed will be less than it should be.
And if you read Magnetoman's exhaustive analysis of the instruments on the BRITBIKE forum, you'll understand that magnetos can be made to work very well indeed. All you need to do is find someone who'll fit the correct capacitor, rewind if necessary and properly re- magnetise the thing. I'm a bear of little brain, but that's my understanding. Greg had a sadly deceased friend who did all this properly, so he knows!
At the moment I have most options fitted/
Rapide with H D box and coil. Just started it last Thursday, first time since October last year. The second kick was required because it had sumped a little so also trying to spin the flywheel through some oil.
Rapide with new BT-H. I did have some carb issues I had been chasing but with that corrected usually just one or two.
TTR with and AEI magneto That will set some tounges wagging. Big compression maybe 10 or 11 to 1, and no decompressor. stand on the k/s until it rolls past compression, One boot, first time every time
Post war Comet with a mag, good starter
Prewar Rapide, started well with the Lucas mag but was worried about spares bits as it is a bit of an odd one, so swapped it out for the BTH, yet to be tested more than just a few times.
And recently put a Lucas mag on a shadow with 8:1, Mk2 cams and shadow carbs. was being a right pig until it was found that one of the mag mount screws was too long and just as you nipped up the ATD it jammed at full advance. Once that was sorted, first or second most every time.
That's pretty much all my experience, with mags anyway. Once sorted I wouldn't hesitate to use one. Dan's Rapide that went to South America and back, ran a mag there and back, and then to Alaska and back.
Rapide with H D box and coil. Just started it last Thursday, first time since October last year. The second kick was required because it had sumped a little so also trying to spin the flywheel through some oil.
Rapide with new BT-H. I did have some carb issues I had been chasing but with that corrected usually just one or two.
TTR with and AEI magneto That will set some tounges wagging. Big compression maybe 10 or 11 to 1, and no decompressor. stand on the k/s until it rolls past compression, One boot, first time every time
Post war Comet with a mag, good starter
Prewar Rapide, started well with the Lucas mag but was worried about spares bits as it is a bit of an odd one, so swapped it out for the BTH, yet to be tested more than just a few times.
And recently put a Lucas mag on a shadow with 8:1, Mk2 cams and shadow carbs. was being a right pig until it was found that one of the mag mount screws was too long and just as you nipped up the ATD it jammed at full advance. Once that was sorted, first or second most every time.
That's pretty much all my experience, with mags anyway. Once sorted I wouldn't hesitate to use one. Dan's Rapide that went to South America and back, ran a mag there and back, and then to Alaska and back.
I sympathise with Carl I am another old timer who never got the technique right, but when you are young it was easy, I would leap into the air bike just sitting on its tyres and come down with the kick start leg with all my weight behind it, technique or not, the B**stard usually started and if not i just balanced and launched myself again. When I got over 40 it became more difficult my method was to fit RE decompressors and adjust the cables so that the front decompressed on a half pull and both on a full pull. When I got to 70 odd I gave the twin to Ben, and when he races it I start it with the foxley starter much the easiest!
I have no experience with Lucas mags on a Vincent, my twin had a BTH when I got it and I fitted my Norvin with twin points and coils when I built it 30 something years ago. However I have Lucas magdynos on my 11-50 Brough Superior and SS100 replica.
They will not start cold fully retarded, the sparks are too weak, in fact as the 11-50 is a 60 degree V you lose the front spark entirely, once running it will retard ok but you can hear the front pretty much missing.
As a comparison when I got it the magdyno needed a rebuild so I converted another magdyno to take a HD adv/ret, ground one cam lobe off and fitted a twin points plate and two coils.
With this set up you virtually had to just lean on the kickstart and it started (it's a SV so not a lot of compression) and ticked over like a Swiss watch, the only problem was I didn't have a reliable dynamo at that time.
In effect I did the same with the SS100 until I could source the correct parts to build a 50 degree magdyno but I have to say they both start and run better with coil ignition, I just like the reliability of a good magneto.
They will not start cold fully retarded, the sparks are too weak, in fact as the 11-50 is a 60 degree V you lose the front spark entirely, once running it will retard ok but you can hear the front pretty much missing.
As a comparison when I got it the magdyno needed a rebuild so I converted another magdyno to take a HD adv/ret, ground one cam lobe off and fitted a twin points plate and two coils.
With this set up you virtually had to just lean on the kickstart and it started (it's a SV so not a lot of compression) and ticked over like a Swiss watch, the only problem was I didn't have a reliable dynamo at that time.
In effect I did the same with the SS100 until I could source the correct parts to build a 50 degree magdyno but I have to say they both start and run better with coil ignition, I just like the reliability of a good magneto.
The mileage has grown another 25,000 miles after that trip, still same mag. This bike was known to be a one-two kick starter. I am running Dan's bike now,, starting is not my forte yet (only just 500miles on it in the last month of owership), it is more consistently 3-4 kicks under my boot. Dan tells me he installed a new old stock original Lucas capacitor some time ago now and he gave me an Easy Cap to install if it starts to give issue.