brokenenglish

Jon, The early Darts were all excellent. However, the company changed hands and many of the very late Darts were poor, and some were even non-runners when new. The biggest, and most likely, problem is excessive bore taper. A classic situation in which the pinch around TDC is mistaken for compression, and there's no crankcase compression around BDC, to pump the mixture up the transfer ports. Obviously, the only solution for this is a new piston and a properly fitted piston/liner assembly. Everyone should be warned - Stay away from late DC Darts (EWDEC production on the IoM), particularly, but not only, the gold head ones. Finally, this isn't theory or hearsay, I've been running Darts since the fifties (Allbon), and I've seen the above situation many times. Obviously, other checks are needed (fuel metering - NVA), but these are generally obvious to an experienced operator.

Manish, This question was resolved on FB by a former Irvine employee. You have an Irvine 20 diesel. Late in the production period, Irvine ran out of "20" crankcases, so they used some "25" crankcases, which are identical except for the marking, and they just machined off the "25" marking.

Running interesting old engines, mainly, but not only, diesels, has taken over as my main hobby over the last few decades. I still build and fly, but running old engines is easier and quicker. Great fun with more or less zero risk (no crashes!) Here's a very rare ED 2.49cc side-port and a beautiful McCoy 49 running on sparks.

Ignition improvers that replace amyl nitrate and amyl nitrite are well-known and readily available (and good!). However, you won't get a model diesel to run properly without ether. People have been trying, unsuccessfully, for more than 75 years. Forget it.

To go back to basics, it's the fuel surface that needs to be level with the spraybar (for zero head of fuel, positive or negative). In the OP, the fuel surface is higher than the carb, therefore you have a head of fuel, so it flows into the carb. Sorting out that point, logically, will cure the problem. If this tank positioning is inconvenient structurally then, as mentioned earlier, I would arrange a "uniflow" plumbing system, which I've done many times.

OK, everything you say is true but, for me, a 6x4 is just too small for this engine, particularly with zero running in. For me, the "various props" that you mention shouldn't go down to a 6x4, and this would appear to be confirmed by the fact that the engine didn't want to run on that prop. OK, I'll stop now! The engine and workmanship look superb.

Sorry , I thought it was obvious. It wasn't you that avoided a problem, it was the engine that avoided it by refusing to start on an insufficient load. I was simply questioning the idea of running an old design, side port engine, for the first time, on the smallest possible propeller. For comparison, your engine is similar to a Mills 75, but bigger, and I don't think anyone flies a Mills or an ED Bee on a narrow blade 6x4. Just sayin. Your engine looks superb, but surely trying to run a nice old side port engine on a tiny propeller serves no useful purpose. Just my opinion of course, and I'm fully aware of being a nit-picking ol' git.

I would question the idea of running an old design 1cc diesel, for the first time, on a 6x4 which is even short on blade area (APC). You're lucky the engine didn't start!

No Robin, the ED engine made by Webra was the 1.5cc ED Hawk (very similar to the Webra Rekord). I see the ED Pep being criticised, but I've had 3 or 4 through my hands and they've all been excellent runners. The common feature between the Pep and the Hawk is that neither was actually made by ED. The Pep was actually made by an ED sub-contractor in Brentford High Street and was subsequently transformed to become the ZA 92.

The Cox reed-valve configuration. No access to anything. No flexibility. Unpredictable and inconsistent running.

One point I thought of, but too late, is that your engine can't be a very early one because you mention removing the quickstart mechanism, and the early ones didn't have the quickstart gadget. I tried, unsuccessfully, to find the quickstart introduction date. In any case, this point doesn't change or invalidate any of the info you've already received.

Yes, there was the S-75, with the cutout, and the P-75, without the cutout.

The diesel is an early Oliver, sold as the Raylite Panther or Jaguar, through the Raylite Model Shop in Nottingham.

I ran a Mills 75 inverted for years, in a Mercury Tiger Moth with never the slightest problem (wish I still had the plane). People's opinions don't count for much. If you have doubts, cut a mount from a suitable piece of wood and try it for yourself. For me, there's no problem and I definitely disagree with the statement that Mills don't like running inverted. It just isn't true.

Great Planes "Ultimate" biplane. Here it is: https://outerzone.co.uk/plan_details.asp?ID=13254