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12th overbore piston pins- can stock honda be used

2796 Views 10 Replies 4 Participants Last post by  beedub
the overbore pins that come with the large pistons are really thick and much heavier than the stock Honda. Can the stock Honda pins be used ok? the piston bosses are large and thick, and it seems silly to increse the mass of the piston assembly by such a large factor. the fit is exactly the same, no slop there (see below!), and Hondas are a little shorter but not much, 1/8" ?

soemone also told me the pin holes are supposed to have a clearance of .oo4" but I don't think sooo...0004" I asked? no, .oo4". ok i said. good to know. :)

so anyone know about this? seems to me increasing the reciprocating mass a lot would be more likely to cause bottom end or top end failure in the rod assy.

thanks, bw
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tbpmusic said:
From my Annotated 450 Manual.....
I'd probably go ahead and use the new parts, myself.

Well the stock pin weighs in at 107 grams, and the aftermarket at 147 grams. more strain ta high revs I think on parts used to less reciprocating mass. we'll find out one way or another!
Bird76Mojo said:
Have you weighed the pistons too?

I'd just use the new parts. It won't make that huge of a difference unless you're building a race engine where maximum revs are desired.

GB :mrgreen:
oversize piston with cutaway skirt: 200 gm
stock piston: 215gm...
Bird76Mojo said:
A 25 gram difference in total reciprocating mass is nothing to worry about IMHO..

GB :mrgreen:
actually , unless i wrote it wrong, the pin adds 40 grams and the piston 15 for a total of 55grams. the os piston is lighter because it has a cutaway. either way probably doesn't matter, I havn't heard of anything about this exceot for people blowing them up some other way i forget - think it is not gapping the rings enough and same for bore on pistons.
Bird76Mojo said:
You must have wrote it wrong then. Check your previous post.

What I was getting at was this:

Stock piston: 215

Total: 322

New pin: 147
New piston: 200

Total: 347

So you're saving 15 on the piston. Adding 40 with the new pin. All together, adding only 25g.

Adding a mere 25g is nothing unless, like I said, you're building a race oriented engine.

GB :mrgreen:
right, i get it,
but if i use the stock pin, then
Stock pin: 107
New piston: 200
total 307 versus 347= 40gms. so will that matter i wonder. at what point is the weight wnough to get a little extra snap? andwhy not use the stock pin anyway? dia is exactly the same.


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66Sprint said:
The stock pin will be shorter....the difference may allow it to shuttle side-to-side and eventually "hammer-dislodge" a circlip....Teflon "buttons" may be the cure.....maybe not....
will let you know, have found a machinist who will put in circlip grooves closely if I want at reasonable cost. then again, got the buttons.... I can't help it, I like the idea of the chainsaw rev acceleration but all else in the camshaft system must be right.. :)
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