What 102 mm Pistons can one get?

[Typ 4]

Hello everyone,

I have sourced a set of 4 Deutz cylinders in 102 mm from our local Deutz agent. They came of an engine that blew a piston and for whatever reason and they kept these 4 good cylinders. I got them for a box of beers so that's not too bad.
The cylinders were manufactured in 2018 and have QR codes on them, hence I'd like to keep them this bore size.

At this stage I'm not too sure where to get pistons from, I have seen the J&E and Wiseco however the price of these is prohibitive with the exchange rate and shipping to NZ.
What is everyone else using?

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[Typ 4]

I have come across Yamaha Grizzly/Raptor pistons in 102mm with 22mm gudgeon pins, they are flat top and have a pretty low compression height. It will be a 102x80 with 5.500 rods so these should work in theory.

Yamaha Grizzly Raptor.png

[Wally]

Good find!
I used JE for my current 102 Deutz build, but this seems pretty interesting and a quick and less costly solution. They might not be all alu as well, so you can maybe run less wtw clearence compared to my 2618 (iirc) JE material.

[Typ 4]

Thanks Walter!
The cost of the JE is a little high, however they do work, that's guaranteed!
There is just one little detail that stopped me ordering these Yamaha ones, they are more for an upright engine and when you look at the skirt you can see there is a "chamber" where the gudgeon pin inserts. I'm concerned if this will fill up with engine oil in a boxer, it could "pump" engine oil into the combustion chamber.
Still looking, plenty of time until building time, currently working on my IRS chassis and then tranny.

[Wally]

With the speed and acceleration pistons travel, that would not be a concern for me tbh.

[Typ 4]

Have ordered a set of 4, NZ $ 273 or 170 euros for the lot including shipping. Lets see what they look like when they get here

[Wally]

Good price!
Aren’t you worried about that almost rudimentory skirt?

[Typ 4]

Yes, absolutely. The skirt worried me to begin with but then, some Grizzly's rev to 8500 rpm and the 356 and 912 also had a strange piston design that seems to work fine. When I looked at the other 102mm pistons like Wossner for the CRF, they have a very short piston skirt that seems to wear very fast. Hence they get replaced regularly. The Grizzlies and Rhinos are more of a workhorse where many have high miles on them.
I'll measure and weigh them when they get here, you never know until you try.

[Wally]

Maybe use a long rod for some help in that regard?

[Typ 4]

There are no longer rods available other than 5.325" at the moment, have contacted all leading suppliers for some 5.500" or even 5.700", none anywhere.

[wreck]

Do you have the crank already ?

[Typ 4]

Yes, got a 80mm AA crank and currently collecting one part after another. 2 head options, square port's with 47x39 semi done or type one port heads 50x40 that were never finished and would need a ton of work.

[Wally]

Start the work on the billet heads already: it will prevent any sealing issues forever, especially on 102mm and bigger.
No brainer

[Typ 4]

There are a few issues that and I'm not sure if it is worth doing. These are the only ones remaining from an enthusiastic private project that proved to be too costly in the end. Although they are squared up with all flanges and bolt on areas, the ports moved during the casting process and they are off centre. This could be resolved by welding and machining again but well, what knock on effect does that have for reliability later. The majority of surface area for valve seats to rest on is there, I guess it should be ok.
It would be cool to get these working but maybe it's better to just use the square ports.

[Wally]

Those look interesting, but indeed a ton of work still needed. Ask me how I know