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Clearancing +5mm crank to 94mm JE piston?

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Does anyone happen to know how much should be shaved off the piston skirt (JE, 94mm) when using with the hotrods +5mm crank?

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I don't think it's the skirt, is it?

I think it's the boss under the pin at the center of teh piston. Isn't that the closest point to the crank cheeks?

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It should be fine. I have the same setup and didnt have to clearance anything. Fits just fine.

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Had a brief look at mine, after receiving it from Eddie.

He had grinned of a couple of millimeters on the ridge.

Guess he wouldn't have done it if it wasn't needed to get clearance ...

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Yeah, ok- it does need to be trimmed somewhere because as it is currently the piston contacts the crank near BDC. I have a lukes racing single compression ring piston here for reference and that is an obviously custom piston with a shorter skirt but allows the crank to rotate freely without issue.

I thought it was the skirt that was making contact but perhaps its somewhere else. Looks like the balancer may also be coming into contact though its difficult to see with the piston filling the crankcase at BDC.

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just checked mine.. Looks really close.. but doesnt contact.. i guess i'll trim it a bit when i put it together.. I would post a pic but i have no camera..

How much has to be trimmed?

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Ah ok, the wrist pin boss - well I can experiment but it would be good to know how much to mill off.

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Does anyone happen to know how much should be shaved off the piston skirt (JE, 94mm) when using with the hotrods +5mm crank?

Ok, so I did a bit of measuring. This is me reporting back.

The Lukes racing piston measures 4.05mm from the bottom of the wrist pin hole to the base of the wrist pin boss. The JE 94mm piston measured 5.05mm - due to a small raised web of aluminium 1mm high. I shaved of this web, (1mm=0.0394") so I removed another 0.001" over the minimum of 0.03" recommended. Now the JE piston measures 4.05mm from the bottom of the wrist pin hole to the wrist pin boss - just like the Lukes racing custom piston which does not need clearancing.

Voila, the crank now rotates fine.

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