Eccentric Crank Pin

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12/18/2017 8:09 PM

I would like to find one of these to make a stroker YZ125
It appears that there is enough clearance to spin the bearing on.
Apparently no case mod required.
Would the pin have to be TIG welded after to prevent spinning?
With a 2mm stroke the cylinder head height would need to raised, would this be done with base gaskets?
Thoughts?
Photo

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12/19/2017 3:50 AM
Edited Date/Time: 12/19/2017 3:52 AM

How would you ever get the rod bearings on and still retain the proper clearance with that offset. That may work on a
two piece rod, but on a 2 stroke rod?
Also, a 2 mm lengthened stroke would more that just a base gasket change as that would alter port timming.

Paw Paw

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12/19/2017 4:35 AM

Paw Paw 271 wrote:

How would you ever get the rod bearings on and still retain the proper clearance with that offset. That may work on a
two piece rod, but on a 2 stroke rod?
Also, a 2 mm lengthened stroke would more that just a base gasket change as that would alter port timming.

Paw Paw

Could use a bearing with loose rollers. Slide on the cage, install the rollers and slide on rod.

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Take it to the limit, one more time!

12/19/2017 6:49 AM

These are designed for 2 stroke racing scooters. From the product listing;
Even though the crankshaft pin is set eccentrically, the use of the usual size bearing (20 x 26 x 15mm, Art. Nr.: GDT0304A) is still possible. During assembly lubricate the crankpin with plenty of oil first. Starting with the bearing held at a slight angle, screw it firmly but gently into position.

Maybe the clearances are higher between pin and rod on these scooters than YZ etc? Chris Applebee's in UK will build these cranks for YZ125, cost £180. Trying to get additional info.

">Chris Applebee's youtube
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12/19/2017 3:07 PM

I think that rpm were doing this before they sold to max power in Wisconsin, but that was a long time ago and it might have been someone else

Whether you stroke the crank or use the eccentric pin, it opens up all sorts of headaches like port and ignition timing, case clearancing, pipe design and a bunch of other stuff.

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