I find the described throttle barrel issues interesting 🤔 Thousands of flights from the 140 to the 200 and I've never had fuel leak from, or any running issues attributed to the barrel. Apart of course from an incorrectly machined one I had ages ago.
As such, I can't really see adding extra O rings to be a benefit. Maybe it does? However I'm not going to modify anything unless absolutely needed. Until then, keep on keeping on 😬

PS. Rapicon - 9% oil, 33% nitro 👌💪😃

Yes, I gave up on modifying the original. I believe the barrel to body clearance was just too large and was swamping the metering action of the tapered slot in the barrel against the fuel port in the bore at the low/idle position.

I'm a decades long cool power user in a variety of engines but picked up a 2nd hand nitro heli (OS105HZ-R) that came with a few extra litres of fuel that was mixed with Klotz KL-198. To cut a long story short, I replaced all the engine internals at 32litres, then zeroed the "clock" and using mainly coolpower blue oil and sometimes purple, changed the rear bearing at 50 litres, and then both bearings and ring at 80 litres. I then swapped to using KL-198 oil and I'm now at 190 litres (110 litres on the same bearings and ring) and I still feel no need to change the bearings. I feel that in that engine, the way I use it, I suffer less bearing rusting between flying sessions and I'm keen to run this DZ200cdi with it to see if I get less rusting inside with it as well. Running wise, the OS 105HZ-R doesn't seem to care what oil it's turning into smoke and it's fuel consumption is about 65cc/minute. I've never tried the KL-200 but the SDS says it's about double the viscosity, 23.3cSt @100degC vs 11.1cSt @ 100degC for the KL-198.

I use scales and mix using weight as well for convenience reasons. The specific gravity of the Klotz is fractionally greater than 1, but close enough for me to call it 1. The specific gravity of cool power is/was about 0.98.

Got 5 x 13 minute flights in this afternoon in very blowy (25km/hr) conditions. Didn't touch the main needle but tweaked the pump 1/8turn leaner for the last two flights. Currently running 30% nitro, 12%oil and 58% methanol and will drop that oil back to 10% oil after a few hours. Just happy to be flying a decent fixed wing plane again..

Soo, in regards to oil.

I was using Cool Power MV until I switched to Rapicon in 2017. With Cool Power I was replacing bearings at around 50 - 65 litres through the engine. With Rapicon, it's now around 110 litres. It's also worth remembering that the bearings are the same size as is used in the 140 and gone from 15.5" to 22" props.
I found with CP internal rust was forming relatively quickly when left sitting. With Rapicon, it can sit for months and no rust forming at all. I don't use any form of after run oil, just drain the tank and run the engine until it stops. It would be nice to know what oil is in Rapicon.

8 flights today with no issues, only changed the muffler header O ring. O rings don't last as long as the Hatori ones did.

Now sitting here deciding whether to replace the bearings before going to Shanghai for the Chinese WC this weekend

That's interesting results you're getting with the Rapicon fuel.
110 litres is a lot of hours by my reckoning, but it's easy to rack up the hours practising F3A

Best of luck in Shanghai !

Thank you.

Around 44 hours flying time.