Glowgeek

The combustion chambers appear to be of the same design between Dave's and mine. We can take measurements of the cylinder if nothing else is conclusive. If Wy8e is correct we won't have to.

Smart fellas, those Saito engineers. I can see where casting the crankcase cylinder mounting deck taller than needed would allow for easy changes in compression ratios during the initial prototyping/preproduction testing phases.

In the background of my earlier posted pic showing the overall piston height measurement you can see the top of the crankcase showing a visible line where the top of the cylinder spigot chamfer resided. Plenty of room there to drop the deck height if one desired to do so during preproduction testing. This is what leads me to believe that Wy8e is correct. We'll see.

Jesse Open

If the sharp Saito designers were sharing cases with the 120, they may have chosen to make the adjustments at the cylinder base

1200SportsterRider

Both of mine.

1200SportsterRider

Now can I get back to the Sky Raider wing?

Jesse Open

Thanks Dave

Glowgeek

Well, I'll be a uncle's monkey! Same piston, rod and case dimensions? On to measuring the cylinder. Will post pics later.

Thanks, Dave.

Glowgeek

Can't post pics for some reason......so here you go, Dave

Cylinder bore depth from bottom of spigot to squish band: 46.0 mm
This measurement was taken on the squish band and centered between the two valves at the front of the cylinder. Special care must be taken to stay off of the fillet radius when measuring.

Spigot protrusion from cylinder base: 6.0 mm

Cylinder base thickness: 7.26 - 7.30 mm

1200SportsterRider

I just switched back to Chrome and can post images at will. The 150 base thickness. Interestingly a 120 cylinder fits perfectly, but when you install a 120 piston and rod, at tdc the piston pushes the cylinder up about .050". The 120 cylinder base is 6.84 mm thick.

Glowgeek

Makes sense, Dave. The 150 crank has 2.7mm longer stroke than the 120.

Looking forward to the other two measurements.

easystar123

Another one of my Saito 62s flying the all abs plastic Thunder Tiger Beaver.

Glowgeek

Thanks for another fine vid, Aidan. I love the sound of the perfectly tuned 62 idling away in the background at the end of the vid.

easystar123

Thanks Glowgeek for your kind comments. The Saito 62 and Saito 72 are my two favourite engines. Kind regards, Aidan.

1200SportsterRider

My 150 cylinder depth, I took four measurements and four pictures.

1200SportsterRider

That's a great video Aidan, you're a smooth flier and have a smooth cameraman. You fly just like I do. That's what us white haired guys do. I'm going to be 82 in three weeks.

Glowgeek

Thanks, Dave. Just one more measurement to take.

How far does the spigot protrude down from the bottom of the cylinder base?

1200SportsterRider

I don't see how it can matter, but here it is.

Both cylinders are this.

Glowgeek

​​​​​​For comparison purposes that measurement is critical.

Your 46.02 mm measurement minus the 6.25 mm measurement gives the distance from the bottom of the cylinder plate to the combustion chamber squish band. When compared to my measurements your cylinder is lower than mine. Comparing all the measurements taken by us both, your piston top is getting 0.17 mm (0.007") closer to the squish band than mine, effectively reducing your combustion chamber size. If our measurement techniques were accurate that difference could explain some of the difference in compression ratios between early and later 150's.

I think we can both agree that we were looking for a more significant difference between early and later 150's. On my Saito 82 I had to lower the cylinder 0.023" to raise the compression ratio to 11.72:1.

Due to the difficulty in accurately taking some of these measurements without specialized equipment I'm deeming this exercise inconclusive.

Now, if you loan me your original 150S I can CC the combustion chambers of that one and mine and determine conclusively if they're different.

the Wasp

My Feedback: (1)

a few Saitos in this video.

Glowgeek

Very enjoyable, Jim. Thanks!

the Wasp

My Feedback: (1)

thumbs up!

easystar123

Thank you SportsterRider for your kind comments. I would like to wish you a very happy 82nd birthday when it arrives in three weeks time and many more of them. Kind regards Aidan.

1200SportsterRider

Where I fly, Thornburg, Va.The right field is 750 feet long, the left is 500 feet.

What I'll fly Thursday

The reason for my User Name.

easystar123

[QUOTE=1200SportsterRider;12798493]
Where I fly, Thornburg, Va.The right field is 750 feet long, the left is 500 feet.

What I'll fly Thursday
Thats a fantastic looking bike there, good health to enjoy it. A neighbour of mine loves his Harley Davidson. The Sig Fourstar will fly beautifully with that Saito. Kind regards Aidan

1200SportsterRider

That colour is rare, I had to get a plane and radio the match.

The LT 40 will fly with an FG 11.

easystar123

Yes indeed, I've never seen a Harley Davidson that colour before which makes it very unique. Lovey bike. I have to say there are things I've never done in life and three come to mind. I've never been on a motorbike, I've never been on a horse and I've never played golf and I'm surrounded with three golf courses lol. Also, I'm flying rc planes 38 years and there's a few planes I always intended getting but never did and one of those is the LT40 arf. That's a beautiful LT40 you have there and I love the colour scheme.