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-   -   Crankshaft balancing without counterbalancer, how to verify? (http://husaberg.org/mechanical/362-crankshaft-balancing-without-counterbalancer-how-verify.html)

PowerFiend June 15th, 2004 09:06 AM

Crankshaft balancing without counterbalancer, how to verify?
 
Hi all,
Apparently the previous owner removed the crank counterbalancer on my bike. There are two additional lightening holes near the crank pin, but how do I verify that it is balanced correctly? I have ridden it minimally prior to tearing into it, and it did seem to vibrate a lot. Is there any way to verify that it is balanced correctly for minimal cost? :?:

LINEAWEAVER June 15th, 2004 11:30 AM

Hi Powerfiend,
Regarding an assembled crankshaft:
One needs an accurate scale and a suitable pair of knife edge rollers.
Kind Regards,
Dale

Taffy June 15th, 2004 11:56 AM

for my old v-twin ducati they have a balance factor of 50%. i'm not sure what that means but at a guess i would say that they weigh (on the ducati) two sets of shells, rods and their bolts and two pistons complete right down to the circlips. then you must add the crank gear, the stator, tab washer, flywheel. what you have now is the total weight of everything - THE LOT.

weigh them all to the nearest gram and then put it on the crank as a weight, a form of 'blob'. in the ducati's case they only put 50% of the weight on.

next they balance the crank 'dynamically' rather like a car wheel by spinning it at speed. i believe you can still do it by letting the crank sit between a pair of rollers each side for zero friction. you then let the crank 'flop' as per wheels etc.

i would suggest that if you have drilled holes in your crank webs that it has been rebalanced. ducati cranks are notorious for being totally out from the factory gate.

if it's been balanced, an honest specialist will charge you very very little for checking it and finding it to have been done. it may cost you more in postage!

I HOPE THIS HELPS :shock: :shock:

Taffy

PowerFiend June 15th, 2004 01:21 PM

The holes that are drilled are smaller (maybe 1/4in.) and not quite all the way through. From Dale's pic of his balanced crank he removes a bunch more material.

I want to make sure it is correct. By the time I'm done I'll have over a grand in parts getting it back to A1 shape(Not counting any upgrades). The latest issue I found is a cracked magnet in the flywheel. I don't want the motor to rattle itself apart in short order after spending a bunch of $$$ on it.

LINEAWEAVER June 15th, 2004 01:38 PM

Hi PowerFiend,
Depending on application I also add slugs of heavy metal.
This requires boring a precision hole in the hardened crankshaft, pressing slugs of heavy metal into the bore and tig welding into place.

Regarding Husaberg:
A balance factor of 70% +/- 10% depending upon intended application is the norm.


Hope this helps.
Best Regards,
Dale

Splat June 15th, 2004 04:19 PM

Quote:

Originally Posted by PowerFiend
I want to make sure it is correct. By the time I'm done I'll have over a grand in parts getting it back to A1 shape(Not counting any upgrades). The latest issue I found is a cracked magnet in the flywheel. I don't want the motor to rattle itself apart in short order after spending a bunch of $$$ on it.

Find yourself a shop with a balancer machine and have them check or rebalance the assembly for you. Proper balancing will increase the engine power output as well as extend engine life. Money well spent, especially since you are investing $1000 in parts. Don't be penny wise on this issue.

Splat June 15th, 2004 04:21 PM

There is a shop in Phoenix that has a dynamic balancer, customers rave about the improvements.

PowerFiend June 16th, 2004 06:26 AM

Thanks all for the replies. :)


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