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Discussion Starter #1
Hi,

I am trying to figure out what old parts I have and what they can be used for, and also some info that can help me fabricate new piston pin bush with the exact diameter they should have. So...

What are the different piston pin diameters for:
748
916
916SP

What about the bush? Do the outer diameter differ for different conrods like Pankl Titanium rods and standard steel rods? What are the outer and inner diameter for the bush for:
748
916
916SP

The thing is that I have a crank with two Pankl Titanium rods on, but the bush in the rods have been changed to fit a standard 748 piston by a professional cylinder/piston/heads mechanic (don't ask why, it was a mistake). I measure the inner diameter of the bush to be 19.5mm now, is that as it should be for a 748? And then I would like to know what the exact diameter I should make the new bush in if I want to change it to a 916 or 916SP piston (I think the pins are 20mm and 21mm).

Also, I do this because I want to sell the rods and crank, but I think they will sell better if they have the correct size bush in them. But for selling, do you think 916 or 916SP diameter would be best?

Thank you
Søren
 

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all are 20mm, except the 888sp5 and 916sp which are 21mm.

if they're ti rods you need to find out if they're small end or big end located. there were some corsa rods of the 916sp era that were small end located - narrower at the small end, but still the normal width at the big end - but all the production road bike ti rods are small end located and narrow at both big and small end. they require small end located pistons or else the rods will move side to side and that can cause excessive blowby.
 

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Discussion Starter #3
I measure the bushings outer diameter to be about 23mm, are they small end or big end? Does anybody know the exact outer diameter for those so I can fabricate new ones for a perfect fit? And are the inner diameter exactly 21mm for SP, or must there be som room for oil (like 0.1 mm or so)?

Thank you
Søren
 

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Not sure what crank it is, I think it says "A8" on it. The stroke length fits 916. I have attached some photos.
The rods are steel H beam Pankls, not the ti versions. They were found on the 916SP's and possible the very first 916's. Not sure about the 888 era bikes as I'm not familiar with their spec. They are 21mm small ends and small end located. On my 916SP, the distance between the boss on the piston was 22.4mm:



Crank also looks like an SP with the lightened machined crank webs and balanced heavy metal. Pretty sure the standard cranks didn't have this.

To answer your original question, if its was me, I'd just replace the bush the the 21mm that should be on these rods.
 

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looks like a 916sp crank, after that they started cutting the ears off to lighten them.

it's a pretty unique fitment. not sure making the rods 21mm pin will make it any more desirable. the later 996 style rods are 20mm across the small ends.

my 888 had rods that looked like that, but i don't think they were labelled as pankl. see the first two photos here:

BikeBoy.org - 888 Part 4 Making A Little Good Of The Bad
 

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looks like a 916sp crank, after that they started cutting the ears off to lighten them.

it's a pretty unique fitment. not sure making the rods 21mm pin will make it any more desirable. the later 996 style rods are 20mm across the small ends.

my 888 had rods that looked like that, but i don't think they were labelled as pankl. see the first two photos here:

BikeBoy.org - 888 Part 4 Making A Little Good Of The Bad
My logic is that this item is really only of interest to someone rebuilding a period bike and wanting to keep things 'correct'. If you are looking at performance gains or replacement rods, then there are way better options than these!
 
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