15% ok,.. when you get up in the 18-20%, it raises the dynamic compression... I run 14%.

Running hot, too lean... 16-8, 17-6, 18-8 propellers?...

I see the earlier operators manual has a broader recommended propeller range 16-10, 16-12... 17-8, 17-10, and an 18-8... the later operators pdf shows a 16-8 as the recommended propeller, 16-8 for break in... my bad, the 14-6 is for the 100Ti.

Thanks for the offer Dave but my Plan is to make a simple "ring mount" with holes matching the firewall mount my ST 23cc has. This way I can use the "testbed" aircraft Im building to test them both... Once tested I might make a more "formal" mount.

I'm running a Xoar 18x8, engine was already broken in some, I finished the break in. Peak is 7150 rpm set slightly rich. Could be too much prop, I have considered that as possibly contributing to the excessive heat. Retarded timing can do the same thing, finishing the burn too far down the cylinder wall. The total oil content of my fuel is 17.5%.

If this engine can't turn a 18x8 I'll be getting rid of it. 16x8 is not going to do, a 17x8 might be ok.

I just edited my last post, the 14-6 was the recommended break in prop for the 100Ti, and 16-8 for the 200Ti... try a different prop, 17-8

Try an 18-6 and retard the timing... I tend to ignore the 2.5% castor comments ... whats your nitro content?

OK? I had not expected that. Unusual to see even firing inline twins due to balancing problems generally requiring balancing shafts.

Anyway, I stand corrected...

Clarence Lee was surprised at how smooth the 2200Ti ran, being an inline twin. He said it was one of the smoothest running twins he had testing, just as smooth as any even fire twin.

Oh, you're one of those.

15% nitro, it's all I have.

Oh, for smoothness, even firing Boxers and paralleltwins rival each other. For vibrations however, not really. At least not without additional balancing gear.
It simply is not in the geometry.

Over here smooth and vibration free are generally interpreted as meaning the same thing, in this context.
I'm experiencing very little vibration with my 200Ti.

well if it can't turn a 18/8 on meth, it probably can't turn a 17/8 on gasoline. how much prop do you need for the airframe you're planning to install this engine on?

Claims to be heat resistant up to 190c and also resistant against petrol.
https://blog.prusa3d.com/introducing...istance_69135/

most 3d printers cannot print nylon witout modification due to the high extrusion temperature required. also, nylon really sucks water out of the air and then the water boils off when printing which makes the prints porous and crappy unless you keep the nylon in a dry container even when printing. i'm planing on using asa and possibly abs depending on how difficult printing with those materials is. i'm just waiting a couple weeks for the temperature todrop so i can keep the windows open when printing with those materials.

No offense towards you intended ... I just don't use castor in 4 strokes... its a personal choice... but one particular flyer will use it to instigate an argument, and I refuse to be drawn in... I don't mind an intelligent conversation about the subject, just not used as a tool to ensue a conflict.

15% nitro is pretty hot for that compression ratio.... I can understand the "one mix for all" point of view., it makes it a lot easier to manage, especially when you run various glow engines often.... I only run the one engine on CDi / Methanol Glow fuel, so I have the one glow fuel mix for the boxer ,14% oil, 8% nitro, 78% methanol... I typically run between 5 - 10 % nitro in the glow 4 strokes.

Oh I wasn't correcting you.... I thought it was an odd fire as well until I read the review... well look at it this way... take the FA-300T, rotate both cylinders and crank journals up to 30 degrees of each other, reconfigure the cams and valve timing and voila, you have a 300Ti

Regarding balancing, if the crank, rods, and pistons are in balance, then you just have the dynamic in-balance from the power stroke ( rocking coupling ).... balance shafts on the 200Ti would have been quite something if they took it to that level... That would have been a true marvel in model engine engineering..

The Mitsubishi mighty max with the 2.6 4 cylinder had balance shafts, that was a nice little engine,

You'll have to forgive my spelling gentlemen... I just took my eye drops and my eyes are still a bit blurry... all errors corrected now.

Yes, I know the "flyer" of which you speak.

RE nitro: It's my understanding that nitro has little to no effect on engines equipped with CDI. A little more oxygen is brought in with nitro so a tiny bit more power is produced but I haven't heard of any other effects. My 200Ti ran on 15% nitro and GI with no evidence of detonation, even when overly leaned and using the Xoar 18x8.

7150 peak on CDI with a Xoar 18x8 isn't too bad. I don't want the 200Ti unloading over 9K so yeah, perhaps it could use a little smaller prop.

I may have problems with my glow engine test stand fuel tank. I've had three engines intermittently quit on me in the last week. They went lean all of a sudden, out of nowhere.
The 200Ti did that twice yesterday. Need to look into that.

Meanwhile, I think for the first time in 4 years or so, I will need to open up my boxer as it suddenly seems to develop an unbalance in temperature above 6500~7000 RPM (in flight).
Both cylinders rn basically near perfectly equal all the way from idle to 6500 where temperatures seem to slowly start to run apart, and at 7K there is about 10 deg C difference, at WOT (8200 in the air) that difference gets up to 20 degrees or more.
That in itself is not all that shocking, but it never did that before. What is more interesting, is that the cold cylinder basically does not follow the throttle above 6500 RPM (with todays temperatures it ran about 100~105 deg C and remains at that temperature all the way to WOT, while the other cylinder increases temperature with throttle.

That is a bit of a weird symptom, if I had to guess, there is either a blockage in the intake port or the intake runner.
Parkplugs are pretty clean, spark gap maybe slightly larger than 0,5 mm but not excessive, and as far as visible through the plugholes, the piston tops look fairly clean (I did not see any deposits on the piston tops).
But maybe it is something as silly as a leaking O-ring.
What is even weirder, is that I do not see deterioration of performance. It still does its leisurely 7500 on the ground and 8200 in the air, fuel consumption is normal, oil residue is normal. Starting is normal, basically everything is normal, only that load-related change in temperature difference.

Very curious IF I find anything, and if so, what it will turn out to be.

For what it is worth: the runhour counter passed 54 hours today (which means about 69 actual hours testbench included) and the last hour or so the engine was ran fairly hard because I was "calibrating" the fuel ROB indication (throttle dependent timer that counts back to zero, faster if the throttle is advanced, slower if the throttle is reduced, manual reset so its value remains even when the transmitter is switched of).
That works fairly well, I must say. It is not perfect, but good enough that I dare trust it. Done about 10 tests with either constant throttle (a few flightsboth high and low) and also with constantly varying throttle, and every time when the counter came to zero there was somewhere around 15~25% of fuel remaining.
Today alone I went through about a quart of fuel, and that is quite a bit...

If the valve lash is normal and a valve on that cylinder hasn't developed a leak that would be an interesting/strange problem. ASP boxer?

Which cylinder is hot? Is it the same one that ran lean before you modded the intake? I recall you drilled a couple air jet holes somewhere. Might one be clogged?

Valve lash is normal, the intake valve is maybe a touch wide but then I am talking 0,01~0,02 mm so really nothing;
I do not hear hissing, so I doubt it is a leaking valve. That cylinder has always had a slightly lower compression than the other one but that also is not really significant and has been the case from new.
oh... and yup... ASP. Still running very strong, just a weird problem. Without Telemetry I would not have ever known, because I can't tell by its power or running behaviour. It runs the same and pulls the same RPM as ever.

The airjet holes were done with the radial, not the Boxer.
My memory is blank about which cylinder was rich and which one was lean before that mod (I would really have to go through my notes for that) but the weird thing is, the one cylinder remaining basically constant in temperature while the other follows the throttle, would suggest a lean running cylinder (less fuel, less heat) which would mean that simply tuning a touch richer or leaner, at least one of the two should shift the bias: if the cold cylinder would be cold because of running a touch lean (it can't be much since the engine still ran nominal power) a bit richer tune would restore that cylinders temperature, and if it was rnning colder because of a rich conidtion a richer setting should increase the difference. Neither happened.
One click richer dropped ground RPM by about 200~300 RPM, but the temperatures as well as their difference basically remained the same.

That is why I suspect an obstruction: up to a certain throttle position both cylinders follow the throttle, up to the point where the throttle opening becomes larger than the restriction, from there one cylinder would run constant while the other follows the throttle. At least, that is my theoretical reasoning. Whether that reasoning is correct really remains to be seen.
A (partially) blocked exhaust would IMHO result in excessive rising of that cylinder's temperature.

As said, so far, I could just as well consult my ouji-board or crystal ball...
Tomorrow.... I will pull both heads and runners tomorrow

A blade of grass caught in one of the intake runners maybe?

First thing we do on the real ones if parameters change and other characteristics don't is suspect the instrumentation... ( 9 times out of 10 its the cause).. Is there a chance one of the temp sensors is having an issue?

Got my ignition setup done - Kinda a Morris mini motors setup using two rings... just the mount left now...