Interesting deal...Shindaiwa 750 protype

[singinwoodwackr]

Some time ago I wound up with a bunch of misc Shindaiwa saws and parts from the late 80s-90s. Included were several of the model 750 protypes for the production model 757.
In playing with a couple of them to help answer some questions for another member the other day I discovered two different cylinder configurations. Saw #10 and 19 had completely different transfers than later prototype cylinders...that also went into the production 757s
Stumpshot Steve liked the production cyl better than the early prototype.
My goal is to rebuild 1 of each and compare.
First Pic is the later 750 prototype/production 757.
Both cylinders have the same intake and exhaust configuration. Both are 73.5cc, 51mm, windowed piston type.
Project was in the late 80s to '91 utilizing 12 US dealers who catered mainly to pro loggers.

I wonder what made Shindaiwa switch.

2nd Pic is the early one.

 

[EFSM]

I really dig that angled tunnel one. Never seen the likes.

 

[jacob j.]

Great thread Mr. C -

Stihl did some similar testing when they were developing the 045. They designed and produced several different cylinders and sent them out to the field for testing. The last dealership I worked at have two of the prototype cylinders and they had different transfer configurations and combustion chambers.

 

[singinwoodwackr]

I really dig that angled tunnel one. Never seen the likes.

The slanted tunnel is interesting. I just wonder why they tightened up the ports like that. Smaller ports to reduce volume?
Steve asked what type of intake system they had. The first ones used the exact same parts from the older 695 saw with 49mm topend. The filter is a 2-piece cartridge, similar to the 038 Stihl, etc. the later ones, and production models got a big, round HD style, K&N filter and cover that is about 4” taller.

 

[singinwoodwackr]

Great thread Mr. C -

Stihl did some similar testing when they were developing the 045. They designed and produced several different cylinders and sent them out to the field for testing. The last dealership I worked at have two of the prototype cylinders and they had different transfer configurations and combustion chambers.

According to the retired dealer I got all this from, he was contacted by Stihl just after the program started, wondering if he would be interested in doing the same with their new model coming out…the 044. He did and the fallers ran the two saws side by side. Stihl, like Shindaiwa, provided all the saws, parts and paid all labor costs. We know which one won out

 

[singinwoodwackr]

Air filter setups, early and late/production

 

[singinwoodwackr]

Here is possibly a transition cyl.
The larger transfer ports were epoxied to close to the production specs.

 

[singinwoodwackr]

Hand made intake
Seems to have been carved out of a chunk of plastic then epoxy was added.