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February 6th, 2014, 03:06 AM   #11
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Re: Balancing an 80mm 650 crank

Thats interesting Carl

ive seen the 02 OEM BF specs at 40% (simon) and 51% I think that was weeds calculations

in any case Ned and weed both said the vibes sucked when the CB was just removed without a re balance

weed reckoned it vibrated horribly at idle and just got worse as the revs increased

I think the whole crank design and the weight distribution of the rod are some variables that make it a bit difficult to compare the 82 and 80mm cranks so i don't know how yours would go.

did some grinding this afternoon... pics coming
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February 6th, 2014, 03:21 AM   #12
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550 Crank



550 OEM piston (298gm)

BF approx 0.55
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February 6th, 2014, 03:30 AM   #13
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Re: Balancing an 80mm 650 crank

Im showing how to do 1/4 of this the backyard bushmechanic way

use heaps of electrical tape to seal off the gap between the sides of the rod and the crank (keep the grinding debris out) and wrap it up in some woolen socks

marked out the bit to get rid of



this is about the minimum you need to remove to get the stock setup closer to 0.6



used the 5 iron with a semi so i could hold the camera with my free appendage

if you angle it like this the sparks don't try to melt the stuff protecting the big end



finished 1/4 of the pin end of the crank i don't reckon you'd want to take any more off than this

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February 6th, 2014, 03:37 AM   #14
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Re: Balancing an 80mm 650 crank

new bob weight with just one corner missing 188gm

so i got rid of about 40gm (effective wt not actual wt)

4 corners means the final bob weight will be around 310gm

then I'll need to take some metal off the fat end of the crank to bring it back, reducing the overall weight of the crank by a bit.

for the rest of this job Im taking it apart and making a smaller diam dummy big end pin to be able to reassemble and check the BF without wearing out the crank pin bore

and I'll see if I have any milling cutters hard enough to make some sparks .

just wanted to show that you could do the whole thing with a grinder and without taking anything apart.

Im going to lighten the con-rod a fair bit as well
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February 6th, 2014, 06:56 PM   #15
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Re: Balancing an 80mm 650 crank

Hi Bushie,

That is what I had in mind for compensating for the Carrillo rod. (grinding those corners off)

How much weight could one remove from a crank before it is to light? ie detrimental to performance.

Do you use the lighter flywheel/stator that came out on the FC model?

Cheers spanner
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February 6th, 2014, 08:31 PM   #16
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Re: Balancing an 80mm 650 crank

Hi Spanner

Im not sure, its always a bummer if the bike is easy to stall

the RFS enthusiasts who play with this stuff run 78 -79mm stroke and can get down to 3.8 kgs (rod plus crank)

I like the idea of the lighter crank and reciprocating parts because it reduces the loads on everything

the FC flywheel I don't think would reduce any of the main loads by any useful amount .. so if it does stall too easy I guess the flywheel is a good place to add weight.

cheers
Bushie
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February 6th, 2014, 08:33 PM   #17
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Re: Balancing an 80mm 650 crank

Originally Posted by plumbbob
Had a bit of a weigh up today,

[attachment=0:1r10ii37]crank 650 resized 2.jpg[/attachment:1r10ii37]

little end of rod 119g

piston, pin etc... 354g

bob weight 178g

(473x119) x BF = 178+119

Balance Factor = .628

SO that should be good if i remove the balancer right?

At the moment with the balancer it has real harsh vibes between 4 and 5000rpm.

Carl

what Piston is that Carl ? seems nice and light.. or is it a light little end pin ? what weight are the rings ?
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February 6th, 2014, 11:20 PM   #18
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Re: Balancing an 80mm 650 crank

You could have posted this a month ago while my engine was apart. Thanks for the tip on the kibblewhite springs though, the 650 loves em!
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February 7th, 2014, 10:47 AM   #19
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Re: Balancing an 80mm 650 crank

Hey Bushie

The piston and rings are 283g and the pin is 70, forgot to weigh the rings separately.

I'll try and get some pictures up later.

Carl
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February 7th, 2014, 04:36 PM   #20
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Re: Balancing an 80mm 650 crank

so a about 260gm for the piston ... jebus thats gotta be the lightest berg piston ever

thats why your "OEM" balance factor is higher than weeds

could be worth a try

he went for 70% last time, ill find out how that went

FE 650 good to hear the Kibble whites work i reckon compared to the other junk they are sensational and you can go to a 16mm lift cam if you need to ... the others are more limited

i did a thread on balancing years ago where i copied weed and welded some stainless weights onto the fat end of the crank
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