Kawi2strokes.com Forum

BUT, balancing the pistons and rods is only half the job, what about the crank it's self? 2 strokes are a pain in the butt to balance because the crank must be assembled without the rods and with weights (bobweights) simulating the weight of the rods and pistons then spun in a balancing machine. I know this because I do own the equipment to balance engines.

I have been meaning to get Porschedave to set up a test crank to see just what it would take in time and materials to balance a triple but my spare time has been well used these days as I am not in the shop every day now, maybe 2 or 3 days a week.

Don

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Don

The problem is, though decent metal, triple cranks usually get loose after a couple of disassemblings.

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Twist the throttle, tilt the horizon, and have a great time. What triples are all about...........

I was going to have Dave assemble using used pins that I will polish the press area so as to not wear the pin bores. Shouldn't need the full interference fit for balancing. Also thought about making a set of pins that would bolt the crank together and not stress the pin bores.

Don

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Don

So true. Not only the pins but the center where the crank and web press together. Once these "smear", it is not good

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"Let's keep your crankshaft great!"

Do you ever weld the cranks Charlie?

It seems welding cranks is common practice among the Yam. TZ 250 gang. On subsequent rebuilds the welds are ground out for disassembly and re welded on build up.

J

I just weighed my pisons and wrist pins and on piston is 1.30 grams over than the other 2 pistons that weigh the same weight.The right piston alone is almost 1.5 grams heavyer than the other ones. the rods will be done when I get them also (new rods) Question is where should I remove material to make more have piston assy. the same as others? and on rods also.

Long ago, I made sets of crank pins that have expansion ends, fit into their bores, expand them as you true to hold them in place, balance, take apart, then build the crank as needed. Added benefit, make the pin so inserts can change the gram weights so you can match the pins you will be using.

This also makes it a heck of a lot easier to fit the correct bob weght for balancing. Lots of work, but, if you want to do it the right way, then.....................

i balance each set as individuals, then check over all.

Seems to me last time I had that situation with the pistons not matching, it was a set of Wisecos, and I removed material from under the crown, uniformly, until the weights matched. I've never had my rods off to weigh them, but I suppose I'd start by removing the rough junk left from forging.

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If it surges, that's normal, upshift.

If you remove the flash left from the forging process, you'd better get the rods shot-peened afterwards.

Agreed, but I suppose no matter where you remove material from the rods to balance them, you should peen them after.

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If it surges, that's normal, upshift.