Balancing an 80mm 650 crank

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jar944, are you going to turn it down?

What cases are you putting it in?

Cheers spanner
 
78mm stroke x 105 piston = 675cc
78mm stroke x 108 piston = 714cc
76mm stroke x 108 piston = 696cc
Just thinking :cool::cool::cool:
 
so first impressions of the 0.62 balance factor on the 80mm crank at 100mm bore are very good

the main thing i noticed when i first did 0.75 and no CB was vibration through the footpegs below 3000rpm

then tried 0.58 was better, then 0.55 which was worse

its a different build with lighter parts but this one at 0.62 has very little vibration through the pegs

engine feels very strong and revs up quick with the small loads im giving it, will see what its like after the weekend when i start revving the tits off it.
 
upper rpms are also quite good

engine responds more like a jap 450 MX bike than the stock 650

possibly more "buzzy" vibration through the bars at high rpm than my 700 but its a different chassis/bars etc
 
Good to hear about the positive results, Bushie!
I have just measured my 80mm crank, 145mm Carillio and 104mm JE piston, which are all quite heavier than OEM!
Left hand side web "imbalance": 442,6g
Right hand side web "imbalance": 455,4g
Piston, rings, pin and clips: 440,8g
Conrod: 393g
Crank pin and bearing: 392,4g
If I add the two webs "imbalances" and withdraw the crank pin and bearing weight, that would sum up to the total "imbalance" of the crank, right? (442,6+455,4-392,4=505,6). The reciprocating mass would be rod and piston together (440,8+393=833,8 ). Then the BF would be "crank imbalance"/"reciprocating mass" (505,6/833,8=0,606). Does this make any sense, or do I really need to cut down on my Pilzsaft consumtion?
 
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it looks good but im not sure mats :D

i'll have another look after Ive had a few bottles :)

my sober gut feeling is that if you add weight to the piston and rod then the balance factor moves toward zero rather than 100%

so more like 0.4 ... something rather than 0.6
 
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I see Ducati make an aluminium flywheel.
Might be some weight saving there.
Now how do you get those magnets out?:)
 
soak in Gunwash (MEK) for a week should kill the glue

crank balancing ... the worlds first v twin triumph was homemade


figure1.jpg


http://www.xs650.org.au/Technical Info/vtwin.html

http://www.xs650.org.au/Technical Info/smoothness.htm
 
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How does your balanced crank vibrate with different RPMs? I have a CB removed 2005 628 with stock piston, rod and crank. It shakes to the handlebar worst, but I'm going to buy rubber handlebar mounts to help with it. My bike has pretty much mild-medium vibrations under 4000rpm, 5500rpm absolutely smooth, 6500-7500rpm bad vibration (peak power range...) and 7500+ rpm medium vibration. Stock aluminum engine mounts were cracked so I replaced them with steel mounts.

It's a street bike so it doesn't see over 6000rpm that often, but it would be nice to try to get rid of some of the worst shakes with the next engine overhaul.
 
Smoother than the stock engine with counterbalancer at high rpm

Vibration is worst at idle decreases up to about 3000rpm and is mostly felt through foot pegs
 
Hello!
Has anyone tried a bigger balance factor than the 0.75? I've now cut the crankshaft so that the balance factor is 0.79 and wondered is this be bad? :unsure:

EDIT: i grinded more, and now my balance factor is 0.73. I wonder if 0.65 it would be good?
 
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