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| willem |
 Posted: Tue Sep 13, 2005 10:47 am |
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Junior member
Joined: 06 Sep 2005
Posts: 15
Location: Netherlands
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I just received my 72 mm bore gsxr750 pistons,
with a very nice 15mm wrist pin diameter.
They'r lighter then the old Japauto 70mm pistons: 176 against 194 grammes , nice for the stress on the rods.
To be sure I'm going to fit cb900f rods.
Deck height is 2.3mm lower, with cb900 rods 0.8mm
The crown is rather flat, also good.
The only problem is that the small-ends of the cb are wider (4mm) then those of the gsxr, don't know yet if I'm going to alter the pistons, the rods or both a little.
After I've found a good value for the piston clearance, I can have the block bored out..
Any thoughts about piston clearance and the rod problem? |
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| Satanic Mechanic |
| Posted: Tue Sep 13, 2005 8:26 pm |
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Moderator
Joined: 04 Sep 2005
Posts: 309
Location: Munich, Germany
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Good choice!
Piston clearance depends on the piston type (cast - smaller or forged - larger), piston material, engine type (air - larger or liquid cooled - smaller) and the engine application (street - smaller / racing - larger). I guess the GSXR pistons are cast, and you will race it, but I do not know about the piston material. I would take pistons and block to an experienced shop to bore and hone the block. My rough guess would be a clearance in the 0.07mm - 0.14mm range but that is just a ballpark figure.
As for the rod / piston fitting problem, I would machine both. |
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| willem |
| Posted: Thu Sep 15, 2005 11:58 am |
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Junior member
Joined: 06 Sep 2005
Posts: 15
Location: Netherlands
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I've consulted the mc_engine group also, and Ian Drysdale (from the v8) commented:
> Not so much materials, but piston design has changed radically.
> if you set them to 0.20mm you'll hear it rattling 10 km away.
> Even 0.10 mm is too wide for modern pistons, I'm not an expert
> with Suzuki psitons but I'd guess 0.05 mm is the maxium you'd
> want.
So I guess I'm going for 0.05 mm. Because they're so short, it is probably not wise to give much more clearance. |
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