Pistons 73.4mm diameter for GSX11

[bomberone]

I got hold of a set of madly cheap pistons on fleabay recently.. Meant to be for an efe, but i've had a search & looks like they could be GSXR1000?

They measure 73.4mm dia. they are named 'ART' with various other labelling i.e '6M1''  can anyone confirm/suggest what they're off please?.  They won't fit my 1074 but they might fit something in future!

[inazumarob]

I do not know all you need, but think art are American company if that helps. 73mm is 1mm oversize for @1100cc.

[jameskat]

ART is a Japanese company and supply a lot of motorcycle manufactures. By the the look of the pistons they are forged like the ones for the hayabusa (81mm), so would measure the gudgeon pin etc and seeing if they match any production motorcycles.

Edited March 14, 2019 by jameskat
more info

[arnout]

Looks a lot like regular EFE pistons to me. These should be at least 73.880mm in diameter though according to the manual.. So I wonder if you've measured them correctly (at the skirt).

[bomberone]

Thanks for your replies.. I will re-measure the piston size, i had measured near the top.   I'll also measure the gudgeon pin diameter as mentioned..  

Is 73.88 std size for the 1135 block?

Cheers

[arnout]

23 hours ago, bomberone said:

Is 73.88 std size for the 1135 block?

No.. that's the service limit for the piston diameter specified in the manual. Cylinder bore size is 74.000-74.015, service limit at 74.080mm.

[bomberone]

OK I measured the pistons at the skirt as suggested, using an old fashioned vernier caliper ( they never used to be that difficult to read)!.  I got between 73.74 & 73.94 so i guess that makes them a little too worn maybe?. Shame cos they look reasonable.

Gudgeon pins measure 19.76/19.82mm across all 4.

[arnout]

Your gudgeon pin measurement makes me think your calipers might be out about 0.2mm's. Because according to the EFE service manual the service limit of the pins is 19.980mm.

This would also explain the low numbers on the piston diameters! It is however also a possibility that both parts are worn beyond the limits (but ~0.20mm wear is an awful lot on pins) , and your measurements are right. So first I'd suggest checking the precision of your instrument.