Thicker studs when upgrading a 50cc to a 70cc?

John Lusignan /
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I'm rebuilding a Yamaha Chappy LB50 motor for a friend.

We went with the Polini 70cc cylinder kit, Puch 70cc high compression head, vforce 8 petal reed block, and Mikuni 20mm VM round slide carb. No pipe upgrade as of yet.

My question is this:

I've seen some people talk about retapping the cases to accept thicker cylinder studs. Is this a necessity? I'd rather not if possible but yet I don't want to do all this work only to have a stud break at some point in the future. I realize we're increasing the amount of power significantly from stock. The original studs are M6 btw. IF you need any more info please let me know. Thanks in advance!

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