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It was a used set I got on eBay. Great shape, wasn't planning on using the pistons, that's when I found I lunched one of my good ones. I put them in used rings and all with a light hone. The bores have light scratches in them now. I honed them and they will work. I see a 1075 or 1105 in my future.
Steve

These are used pistons and rings going into a different block? Done that myself too. Just hope your rings bed in.

I cant find nos old design wiseco rings for my GPz615 so I'm going to have to risk it and use 'quick seat' lube from total seal and some running-in oil.

Maybe check your installed ring gap to match the pistons to the bores as best you can, there is often a measureable difference - 4 thou on my last used set.

swest wrote: It was a used set I got on eBay. Great shape, wasn't planning on using the pistons, that's when I found I lunched one of my good ones. I put it one used rings and all with a light hone. The bores have light scratches in them now. I honed them and they will work. I see a 1075 or 1105 in my future.
Steve

Go big!
My curiosity : what kind of oil do you use?

thank you

Those were the stock pistons for a KZ 1000. I just fitted the new rings to the bores. Didn't have to shave any of them. New piston clearance is .002 so I can hone more to get the marks out or at least most of them. Got some room to play with. These are Wiseco 10.25/1 pistons. Taking my time and they should be fine.
I'm using Rotilla oil.
I didn't want to use the old rings that came with the stock pistons but had no choice. The oil on the pistons is after two years of running. The bike ran like a scalded cat even tho it did have low compression. I figure with the 2.5mm drop, I was running at 7/7.5/1 compression. With these new pistons, I should be at around 9/9.5. Good enough for now.
Steve

Got the bores looking pretty good. My stones were loaded up so I sanded them and kept going. Still a tight .002. The block and pistons were brand new. It had two chips out of the fins so I got them for $100 delivered. I'll do a little more when I'm fresh in the morning. I'm not getting the 45* cross hatch I'm looking for. I knew I should've picked up some course stones. My old bottle brush is useless. I'm making up some better ring compressors this evening.
Steve

Similar story here, I bought an unseen 'gpz550' motor that turned out to be a kz550 on the inside, but the lower compression pistons (9 instead of 10 to one) ran really nice..

Good squish and combustion chamber design is worth a point in compression ratio all day imo. I think flatter top pistons have some advantages in an old- school design.

It was in 87 when I had the crank welded and put it in. Being I didn't have stock pistons, I didn't notice the deck height. When I was accused of lying about it really being a 750 crank and I'd have low compression, I started wondering if it was or not. I'm not in the habit of lying about things and if it was a 903 crank, it would be stronger off the line. No reason to lie. I'm confident now it is a 750 and whatever compression I've lost will be made up by revs. It does want to bury the red line.
We'll see what it looks like tomorrow.
Steve

Worked up some ring compressors. Used metal tape to keep them together. We'll see how well they work or not.
Steve

Have you ever had problems using that much RTV silicone?

I never use that much. Going one piece head gasket you have to fill the groove where the O ring sits. I will never use a two piece gasket with a O ring that WILL leak ever again.
Steve

I'm confident now it is a 750 and whatever compression I've lost will be made up by revs.

And when you get around to boring it out, the motor will become even more 'undersquare' .
What you lose in bottom end tourque I guess you could pick up more pm power.

Seems like with all that deck height you won't have any issues with valve/piston contact. Not sure if there are any other problems with the extra deck height. Valve to valve clearance seems very generous on mine. You could even get some slotted cam sprockets and tweak the valve timing for more overlap and some more retard for rpm power, or find hotter cams.





www.hottr6.com/triumph/CamBasics.html

Thanks Tyrell. I may get some more aggressive cams but only looking to the future. I wish I had invested in some used 1075 or 1105 kits when I had the money. Didn't think of eBay. The crank, if it is a 750 is wasted on a normal build. $100 or so will buy me a 903 crank and I could sell the 750 to someone restoring a Z2 or building a turbo whatever. Live and learn.
Steve