FrankinShin build

[Woodwackr]

When I bought a bunch of old Shindaiwa parts a year ago mixed in the pile was an odd cylinder. It looks just like the 5-6 series (45, 49mm) but is a 51mm like the 7 series (750, 757), and is a closed port, unlike the 5/6 series. 7series are closed but completely different cylinder design.
It does not fit the 757 case but does fit the 575/680/695 case. Soooo.
I put a case together today and played with the 49 vs 51mm topends. The 757 51mm piston is a bit taller (2.5mm) than the 695s 49mm but that was easy to fix by slightly beveling the bottom corners of the 51mm piston skirt. Piston crowns are exactly the same. Squish for the 51mm, no gasket, is around .030.
Squish for the stock 695 topend....060+ . I know these are domed pistons but, sheesh.
The 51mm piston I'm using is trashed...just needed one for testing...I have nos.
If it works out I'll have a 695/757 hybrid...well, sort of,

 

[Woodwackr]

I still no idea what this cylinder came off of. I've checked IPLs dealer parts lists back to '89 and zip.

 

[jacob j.]

I still no idea what this cylinder came off of. I've checked IPLs dealer parts lists back to '89 and zip.

It may be something they didn't intend to release to the public but sent to a few select dealers.

Stihl did that in the 70's with their two-piece head for the 075 platform.

 

[Woodwackr]

It may be something they didn't intend to release to the public but sent to a few select dealers.

Stihl did that in the 70's with their two-piece head for the 075 platform.

Quite possible. The old dealer I got everything from was part of the Shindaiwa 757 prototype program…I have 4 of the original 757 prototypes called the 750 and a bunch of parts. None are in usable shape but I get a kick out of the 2-digit serial numbers I need to order some of the production parts just to see how well they match the prototype stuff. Winter projects.
When that program was starting, Stihl found out about it and asked Jim if he would try their new model out as well…the 044. Shindaiwa and Stihl paid for everything, saws, parts, labor, etc. most of Jim’s clients were pro fallers in northern ID. 12 dealers in the US took part.

At first I figured this cyl was off their larger cut-off saw but it isn’t.
It almost looks sleeved.

 

[Woodwackr]

So, from the Shindaiwa spec sheet, squish is supposed to be .075-.100 with a max of .18 dang. Explains their compression #s of 140-156 with a 90 min.
OE gaskets are around .016
I wondered if I'd have plug clearance with a .030 squish...no problems.
I'm not sure how/if it will work, looking at the piston position in the exhaust as well as intake ports. I don't have a degree wheel but this is a good excuse to get one

Here are some pics of the 2 pistons...49mm 680/695 vs the 51mm 757. There is a different in the crown from tot of ring to edge. Will that be a problem? 51mm is about 3mm taller, overall and i beveled the bottom corners for. Learance. Any other skirt trimming suggested?

 

[Woodwackr]

TDC, intake

 

[Woodwackr]

BDC, exhaust. No base gasket, about .030 sq

 

[Woodwackr]

Manual, specs