Why do you guys use stuffed cranks? Is it a stored momentum high revs thing? When I was working on motorcycles we'd drill holes in every last thing to lighten it all up. Is there a durability factor or is it mostly a race thing?
Anyone have complaints about a stuffed crank on a daily driver?
Okay, there you go, my daily attempt to make myself hugely popular...
stuffing the crank reduces parasitic drag in the crankcase and lowers the crancase volume which creates higher transfer pressure. on bikes with a low-volume crankcase it can have a big effect, bikes with a large volume dont make as big of a difference. wont hurt anything on a DD. its really just to boost you from 50 mph to, say, 52. one of the more extreme tuning measures, cost wise.
A stuffed crank ups the "pre-charge", and thus the effective final compression ratio. Higher compression = more low end power. And if you have a stuffed crank you will notice the difference. My aprilia has a stuffed crank and it is night and day.
please also remember that stuff you"do" to motorcycles (4 stroke) dose not normally relate to 2 strokes. By reducing rotating mass your engine builds rpm's faster so lightweight is great but the crank is not where you loose weight on a 2 stroke. Lighter magneto assemblies & lightened gears are the place to look.
Balsa wood makes a good crank stuffer. Seal the pores with gel superglue and glue it to the crank with regular super glue
some sort of caulk or expandable foam might be something fun to try too. just make sure that shit dont come loose. theres a million other things to work on first though.
strange that it really boosts u much at all, i run a stock usa av7 moby crank in my bike right now and it pulls just as hard if not harder and tops out in the same zone if not faster than both (bret and peter) the other super mobys with stuffed cranks. i have a doppler crank i'm going to install soon but it will be ahrd to tell if it really makes much difference without a speedo or a tach.
hmmmmmm.....now im looking at the holes in my crank wondering what to stuff in it.....
arent those holes there to balance the crank?
With a pipe in high RPM it doesn't make squat extra HP. Just helps before the pipe kicks in cause the pipe sucks the shit out of the crankcase at higher RPM anyway.
yeah, aren't we talking stuffing the crankCASE here?
Thanksgiving is soon.
Nope stuffed crank. The cheep home made "stuffed" cranks have there balancing holds stuffed with something lightweight.
This will cause the crank to no longer be balanced
The aftermarket stuffed cranks normally are constructed with stuffing in mind. A small amount of the con rod side of the inner webs of the crank is machined away and they use some lightweight filling material in it's place.
The only way to properly stuff a crank is to open the balancing holes of the crank to compensate for the weight of the filler you are using.
so does that just reduce the "windage" or the friction of the thing spinning around?
i was thinking along the lines of reducing and shaping crankcase volume to increase compression (less volume the piston is pushing down on) and direct flow.
also im assuming this is only for case inducted motors.
Any induction type engine 2 stroke. You know Matt that the Peugeot crank is very tight in the case already stock.
the lightening in the cranks of these for balance would be hard to fill space because it is open and not a hole that can be filled. I'm sure there is some way to do it though. When the pipe sucks all the charge out of your crankcase more charge can be sucked in through your reeds so you are getting an effective primary compression ratio than is greater than a stk pipe unit and that affects secondary CR also. It's no wonder we blow these things up
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