Thanks to all for answering my questions about the different colored diaphragm materials. I do wonder if the brown stuff worked pretty well, why did they also come out with the blue one. Cost reduction? I'd love to get those engineers in a room and ask a bunch of questions about the tradeoffs they considered.

I knew the "flame speed travel has nothing to do with it" would elicit a comment from someone. But thanks for the answer: mostly naptha. I suppose it's available at Naptha Auto Parts???

Although it seems counter-intuitive, octane boost actually slows down combustion. This confuses people because higher octane fuels are always associated with higher performance engines. Well, high compression ratio is too. Only problem is that higher compression also causes the regular fuel to pre-ignite from compression and high cylinder wall temperatures. It's called pinging. So octane is added to SLOW DOWN the flame allowing the charge to fully compress, e.g. allowing the piston TIME to get close enough to TDC to deliver the power to the downstroke, not fighting the upstroke. It's a race between combustion speed and the piston. Also, octane smooths out combustion, delivering the power over a slightly longer time period. That's easier on the piston top and the main & rod bearings.

The other way to help knocking, pinging, or pre-ignition is to retard the spark. Your car does this by monitoring the knock sensors for preignition signature and computer-retarding the spark. This will only help to the extent the knocking isn't being caused by auto-ignition (high wall temps, etc.). Retarding the spark won't help if the fuel is igniting by itself. Like, lets say, you're just using the wrong fuel for your car. I have a Honda Civic SI with a 195 HP 4 cylinder high compression 1.9L engine. It's a pocket rocket, but you put regular gas in and you get less power because the timing gets retarded. It doesn't knock noticably though. A car that diesels when you shut it off is auto-igniting.

For the Saito, I indicated the crankshaft and the total indicator reading (TIR) is .001". So that's not the problem. Nosedragger, I'll experiment with different fuel mixes per your suggestion.

I also plan to put an APC prop on there and try it. I've been using wood props until now. At this point, one must cover all the bases. I have to admit I was astonished the vibration was still there after I removed my home made rod and bearing.

I got the Saito running again by making my own diaphragm. Yes, believe it or not I did it and it worked. Years ago I got a bunch of sample materials from a now defunct flex circuit company called Adflex. They were spun off by Rogers, in Chandler Az. I don't know if they're still in business (Rogers) but I have many sheets of some kind of glass impregnated thin membrane material. The color is beige, too. Looks similar to pictures of the brown diaphragm I see online, though I've never seen one in person. So I traced the old wrinkly diaphragm and cut a new one carefully with an xacto knife, scissors, and a hole punch. I can supply photos of this material if anyone is curious. I put a swatch of this stuff in some gas and it's sitting there as a fuel resistance test. So far no wrinkling. Time will tell.