Gs850 new pistons

[Jinks]

What is the ring gap for new pistons & rings.

[Brendan W]

Are we talking ring end gaps or groove to ring clearances?
Free end gaps, before fitting, of 35 and 37 thousandths inch for rings 1 & 2. Limit 28 & 30 thou.
Fitted in bore 4 to 12 thou for both 1&2 with a service limit of 30 thou.
Manual here

https://gsarchive.bwringer.com/mtsac/~cliff/storage/gs/GS850_Manual_HiRes.pdf

What are you doing? Fitting oversize? Aftermarket parts?

[Jinks]

Yes, cruzin image, 70's. Couldn't find it in the haynes. Thank you.

[Brendan W]

You're welcome.
Good luck with it and we love pictures

[Nessism]

Yes, cruzin image, 70's. Couldn't find it in the haynes. Thank you.

Haynes is bad.

Cruzin Image rings may be different from OEM. You might want to ask their spec. That said, do you trust them?

[Jinks]

The engineer doing the rebore was happy with the pistons. 1&2 ring end gap in the bore is between 8& 14 thou. Have never done new pistons & rings before, is the gap OK? What is the proceedure for running in? Cannot do pics on this device.

[Jinks]

Don't know what happened, did not put amp in text!

[Brendan W]

Text throws up funny characters sometimes depending on the devices etc etc.
I think I get your numbers anyway.
On the face of it your 8 - 14 thou in the bore compares well with the stock 4 - 12 thou. The service limit is 30.
What are the free end gaps? The difference between free and fitted gaps is a measure of the rings reserve to compensate for wear.
As Nessism suggested, I would ask the supplier what the numbers are supposed to be for those rings.

[Jinks]

Free end gap on the rings is 8 to 10mm.

[Brendan W]

That's a lot more than the factory spec.
How to interpret that I don't know but it would seem they are a larger ring diameter that needs a bigger squeeze to fit but may be easier to get into the piston grooves.
Without knowing what they are made of or how much they will set after a few heat cycles, it's just speculation about drag on the bore.

[Jinks]

Well the 850 is up & running, the compression is very good. I've riden it 500 klm & slowly incressing the revs, 6K at the moment. When I put it together I used an idea by Brook Henry, he runs VeeTwo a bevel ducati business, (check it out) I used WD40 ( sparingly) on the rings & a little bit down the bores when I had the head on & cranked it over to get the new oil flowing, with spark plugs grounded on the head, it used about 20mils of oil in the first 100klm's & none since. Looking forward to travelling around Western Australia.

[Grimly]

Well the 850 is up & running, the compression is very good. I've riden it 500 klm & slowly incressing the revs, 6K at the moment. When I put it together I used an idea by Brook Henry, he runs VeeTwo a bevel ducati business, (check it out) I used WD40 ( sparingly) on the rings & a little bit down the bores when I had the head on & cranked it over to get the new oil flowing, with spark plugs grounded on the head, it used about 20mils of oil in the first 100klm's & none since. Looking forward to travelling around Western Australia.

I did similar when I rebuilt mine. A dry build, with just enough oil to lube the rings as they slid up the barrels.
Then, when the head was on, I turned the engine over twice by hand before lubing the bores down the plug holes.
Hardly any oil consumption to speak of in the last several thousand miles.

I described this technique to another builder who reported his rings had jammed up afterwards.
Turned out he'd half listened and had went straight to electric starting the dry engine.
Plonker.