I could not resist, I broke down and bought a Mecoa Conversion Head for the 40FP ($22.00). It is a nice pretty blue head and is simple in construction and design.

Scrounged up an old gallon can of Davis Diesel at the LHS. It had been there so long that the owner just gave it to me for free as long as I would give him a report on how the conversion ran.

Installed the head, mounted the engine on the test stand and installed a 12-6 prop. Left off the muffler so I could prime and tweak the compression screw. Started the screw at the lowest setting and gradually started sneaking it down and flipping the prop until in started to pop. Hooked up the fuel line and applied the electric starter. Boom, it started right away. It was undercompressed (Blaa, burp, blaa, burp), so I tweaked the screw down until it evened out. Adjusted the needle for a smooth run and then checked the RPM. That thing was turning a 12-6 APC prop at 9030 RPM. I considered that excellent. It turns a 10-6 at 11900 RPM. Wow!!

Now, I have been reading all the post in this forum and was somewhat intimidated by diesels, but not any more. Just start undercompressed and sneak up on the ingnition point was all that I had to do to get mine running.

I can't wait to put this thing on a plane. I have a Kyosho BF-109 that I think I will try it on.

AJ, expect a couple of heads in the mail soon, a Tower Hobbies 75 and 46. I am hooked!!!

Great you got it down you are no longer a newbie (First try too you will have no problems) martin

I had read reports of exhaust being anywhere from clear amber to inkey black. Mine tends to be inkey black. I will try some homebrew next and see how it runs. Have to make a trip to John Deere this week for my ether.

I read several MSDS sheets for starting fluid this week and discoved that John Deere is in fact 80% Ether, the surprise was that Chevron Starting Fluid was listed as having 75 - 90% ether. Have not been able to find any Chevron Starting Fluid in my local area though.

I had inky black exhaust with Davis fuel when I started running a Tower 40 with an RJL head. As I ran the engine more and started flying it, the exhaust gradually changed to clear. I don't think it was a matter of being overcompressed at first (although that would be the usual cause for dark exhaust.) Try letting the engine warm up for maybe 30 seconds before you set the compression.

The contrapiston in my RJL 40 head came apart. The shelf below the O-ring groove was about 1/32 in thick, and this entire shelf came off and welded itself to the top of the piston and the face of the contrapiston. Major damage was bent rod and distorted case. Made a new contrapiston with a 1/16 in thick shelf and no further problems with the head.

Jim

Whats up w/ the davis fuel, my whole gallon has produced blackish/dark brown exhaust on an aurora .40 (ran again today after getting a new prop driver for it). The engine can be undercompressed and missing after warmup and it is still dark. I ran some of clutton's olde english and it turns amber exhaust???!@!@@ I even added about 6 oz castor to the davis just for extra protection and bumped my ether by ~10 oz (at this point gallon is only a quart). Anyone have any ideas??? His kero isnt even dyed as the fuel is clear and cluttons is, what gives ppl?

Just a guess you may have added too much castor the kero and oil does not evaporate. and a bad burn incomplete burning will be sooty
Also my irvines on davis abc amber oil out the stack however my ST 40 and 90 is black they run great however one of my irvine 40s black exhaust other 3 amber my new irvine XL 15 (see post) amber martin

If the fuel is really old, the ether content is probably lower than it should be. And, as a result you are running more compression than you should have to. Get some John Deere starter fluid and try a batch of fuel with about 10% starter fluid added. [8D]