E: Engine Kicking RPM

[Cyborg]

Can anyone tell me what the average kicking RPM would be on a twin…

 

[ACD]

The fella I sent my magneto to for repairs made an off handed/passing remark; “an average individual should be kicking at around 25-30 MPH”. So I’m guessing if that’s 4th gear its somewhere around 1000-1500 RPM?? Bear in mind this wasn’t in relation to any specific context it was just him thinking allowed, so it could be consider in tech terms as an ass pluck. However if you think about it, around 1200RPM would be where the ATD should just start to come into play. Which means kicking any faster than that and your starting to advance your timing, so his ‘AP’ may be on the money??

 

[Gary Gittleson]

Sounds pretty doubtful to me. I'd guess a good kick lasts around one second or so. If that produces two revolutions, we're talking about 120 RPM. I'm sure that's off a bit, but I bet not by a factor of ten. 1200 RPM? Nah.

 

[LoneStar]

Not a direct answer, but the Lucas low-speed test for a KVF magneto is no more than 5% missing at 130 rpm, spanning a 5.5 mm gap.

 

[ACD]

Garry, thinking in literal terms, actual revolutions I'm assuming he's comment wasn't related to actual RPM as such, but equivalent travel speed of the component??

 

[Cyborg]

Not a direct answer, but the Lucas low-speed test for a KVF magneto is no more than 5% missing at 130 rpm, spanning a 5.5 mm gap.

I’ve tested the mag at 130 rpm and get a really good consistent spark on #1 with a 5.5 mm gap. #2 with the ignition retarded struggles at anything 200 rpm or less. I don’t know how many degrees retarded, because I haven’t measured it yet.
It has a manual slack wire advance which creates a bit of a challenge. If I knew what sort of rpm I could generate by kicking, I’d like to test the mag at that rpm with it retarded to about 4 degrees.

 

[greg brillus]

Kicking speed is probably similar to a slow idle at around 500 to 700 rpm.......achievable on a single, but on a twin is probably slower due to the extra cylinder......however, the effects of a higher compression and also how thick an oil you run will have a big impact on this figure as well. I know after changing my twins oil from a 20w 60 to 15 w 40 this made the engine spin over much better. Having big duration cams will make starting much harder.......this was the case with my bike..........Now its got electric start, I hardly use the kicker anymore........All good fun.

 

[Cyborg]

Thanks
The engine only has 8:1 pistons and Mk2 cams, so shouldn’t be too bad? If I can get close to 500, I should be good. Getting the thing remagnitised should help.
A photo of my Rube Goldberg test bench. The lathe is old school belt drive with a limited choice of speeds.. I rigged a variable speed treadmill motor to drive the chuck via a belt and installed a tach. The tach doesn’t like the mag much. It needs more shielding.

 

[Vincent Brake]

From my experience its lower, about 400.
Than again. Not that strong.....

 

[CarlHungness]

Kicking speed is probably similar to a slow idle at around 500 to 700 rpm.......achievable on a single, but on a twin is probably slower due to the extra cylinder......however, the effects of a higher compression and also how thick an oil you run will have a big impact on this figure as well. I know after changing my twins oil from a 20w 60 to 15 w 40 this made the engine spin over much better. Having big duration cams will make starting much harder.......this was the case with my bike..........Now its got electric start, I hardly use the kicker anymore........All good fun.

What kind of oil are you using. I've used Valvoline 20-50 for about 30 years and if I can get it to spin over more
easily, I'll sure make a change.