The BSA A7-A10 Forum
Technical (Descriptive Topic Titles - Stay on Topic) => A7 & A10 Engine => Topic started by: tiggy on 19.08. 2015 12:38
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Hi, does anyone out there know, or would like to hazard a guess at the R.P.M. a kickstart generates. An unusual question but there is a reason for asking.
Thanks
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Depends on whether you have had your Weetabix.
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or any compression *smile*
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My penny's worth of an estimate - never specifically measured it, but I'd say 'in the 200s' minimum, maybe 300 even? Depends on the size of crankshaft sprocket, kickstart gearing, compression ratio, force of prod etc. And your Weetabix intake natch. Some bikes have rather low-geared kickstarts, but an A feels 'about right' to me and so I'll guess at 250+ with a decent swing from a practised person of ample proportions lauching the assault after one cylinder is just over compression.
Has to be something like that to start the thing, as a mag won't provide a decent regular spark below roughly 100-120 armature rpm (more if it's manual advance and set part-retarded), which = 200rpm+ on the crank. Many need a fair bit more than that. (Hence that sturdy breed seen pushing things out of pub car parks . . .)
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Thanks for the replies. I have found the A10 starts first kick with weetabix/shreddie intake but only needs a gentle hand push after a mouthful of spinach, I don't recommend olive oil.
The question was prompted because new cdi ignition systems for my latest project need 150 to 300 rpm to create a spark. Seems the old reliable kickstart will do that given the right conditions. It seems like a bit of muscle will match or better a starter motor.
Thanks all.
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interesting question... there are obviously variations due to engine gearing and the fact that the kicker is accelerating the engine from 0 rpm to the point it fires, so an average won't be useful, rather the speed it achieves at the end of the kick.
I'm no mathematician but assuming a kick takes 1/2 a second to turn the engine one full cycle you'd come up with 120rpm average, so would that equate to 240rpm best speed or thereabouts?
My cooking single happily idles at a gentle thump .. thump, which I'd guess would be no more that a couple of hundred rpm at most.
No facts just guesstimates *dunno*
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I thought around the same RR. A good tune gives a one kick start. The motor goes through two cycles and usually fires on the first cycle giving the 120rpm figure cred.
Cheers
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Hi All, I talked my controls engineer mate who thought it would be fun to convert his Triumph Tiger 100 to fuel injection. Really ??? However he managed to put a late electronic ignition system on his '66 Triumph Tiger 100. Yours might not be this sophisticated but I thought it may be related to your question and therefore worth a mention just in case.
His system actually was a very compact engine management system. He got it all running but didn't often start on the kick. What he found was that the software didn't fire the ignition coil LT very time it got a single pulse from the crank trigger. Apparently this is to stop false sparking.
Instead the software looked for three or more regular pulses from the trigger before it triggered the first spark. Clearly meant for an electric start engine which could merrily spin the motor until ECU saw three regular pulses then it started sparking the ignition. So this was why the Triumph didn't kick but would always bump. Apparently regular bike upgrade electronic ignitions sold for kick start bikes don't have this need to count to three and spark for every single pule whenever received and doesn't wait to see a regular pattern of three plus. DM
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G'day Daftmate. That sounds like a Dyna 2000 for HD's. Can be set either way, 0 for kickers or 3 for lecky start. The idea being for the starter to build up speed before the big bang. So the leg must be stronger than a 2 horse starter.
Cheers