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Maybe rotational mass? I dont think you would want somthing that heavy spining around.
 

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I suspect the rotational inertia of the crank is based on mathematical calculations. Once they near their target weight the remaining volume and weight need to be taken up by lighter material, hence the tins or plastic.
 

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Carlos I am a little confused the tins are sensitive and u don't want tins marked to have gouges or marks in it. But I am confused because like the pics I sent u my tins are marked and have some spots that are like gouged not tore but the tins have deep marks and u said they looked ok please clarify for me thanks
 

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Discussion Starter #25
Ideally you don't want the Tins molested, beat up, or groved....that would indicate someone or something has stressed the Tins. The pics of your crank Tins looked like normal marks, not beat up, or molested.

On some cranks you can even see the Factory crimp marks, that happens when the crimp die squeezes the Tins closed or rolles the Tin lip over, that is also normal and acceptable.

Carlos
 

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Discussion Starter #26
Hrere are a few more pictures of current crankshaft rebuilds at BDT Motorsports:

20130728_131555.jpg 20130728_131534.jpg 20130728_131833.jpg 20130728_131856.jpg 20130728_131921.jpg

The two pictures on the Left are the begining of a destroked 250R crankshaft, the bore is done to offset the crank pin to a destroked 56 MM stroke for the BDTM Selvy WURKS 200R. The 200R crankshaft will get bushings welded in the new pin location, then bore to 56 MM, and assemled. Once assembled weights will be added, and static balance.

The last 3 pictures on the Right show a Saber crankshaft we built a few years ago needing rebuilt....note the welded Tins, the Yamaha Rod, and the added weights to help bring the heavier Rod and piston into the proper balance.

We do all our own crankshaft work, welding Tins & crank pin, all machining, adding weights and Static balance internally here at BDTM.

Carlos
 

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Discussion Starter #27 (Edited)
Here are a few more pictures of a TRX250R crankshaft we rebuilt, added weights, welded the weights and crank pin in place, note the arrows. We Static Blalanced the crank, this crankshaft is for a Sphynx build.

ATT_1375123712289_photo.JPG ATT_1375123719449_photo.JPG ATT_1375123727423_photo.JPG

On the BB builds, specially at or above 78 MM, balancing the crank, rod, CB and piston as one unit is important in keeping vibrations down or close to OEM stock.

Carlos
 

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Discussion Starter #29
are the tins to be welded on that crank also ?
Not on this crankshaft....this one is for a small bore Sphynx, and does not need the Tins welded. We have seen no issues with the HotRod crankshafts up to 370CC without welded Tins.

Carlos
 

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if money wasn't an option would it be better to rebuild the factory Honda crank as I have a few laying around or buy a hotrods crank. Guess what im getting at is which one is overall better/stronger?
 

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Discussion Starter #31
I would not bother rebuilding a HotRod, however, if the OEM was in good shape as far as Tins, and Shaft jornals (main bearing diameters) are concerned, rebuild the OEM Honda crank. Hard to beat Honda OEM....IMO

Carlos
 

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Discussion Starter #33
We try to provide as much information as we can. We also perform 100% of our own crankshaft work including welding, heavy metal addition, stroking, balancing and final assembly to OEM specifications. If anyone has additional information needed, please call the shop at your convinience.

Carlos
 
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