Bill Adair

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Hi Folks,

This may not interest most of you, but for you MK-17 diesel owners it's something to keep in mind.

I recently worked on a friends MK-17 diesel, and continue to be amazed at the quality of this low cost engine.

The problem was that the head (Muff) insert was loose, and rotated with the comp screw preventing any further adjustment of compression once the engine was running. Checked around the forums, and the consensus was that the insert was swaged into the muff. A circular indentation around the button seemed to confirm that was the case. This engine was purchased new from Ed Carlson so I called him, and he agreed that the button seemed to be swaged in place on the spare Muff he had in stock.

Gave the muff and comp screw a thorough solvent cleaning to remove all the lube, and inspected the button closely to see if re-swaging was practical. The button turned freely with a two finger grip, but surprised me by backing out when rotated anti-clockwise. Removed the button with no effort, and noted traces of a grey material on the threads. Solvent (Acetone) cleaned it up nicely, and I reinstalled the button with J-B Weld.

The cylinder liner does not appear to be indexed mechanically, and practically falls out if not held in place with finger pressure. Unfortunately, the needle assembly on this engine had been tightened improperly, so that the detent spring was hooked under one cylinder fin, and popped the liner out as soon as the cylinder mounting screws were loosened. Reinstalled it after cleaning, but had to eyeball the liner position to the best of my ability.

Now the engine is running great again, and with no apparent loss of compression due to mis-alignment of the liner and piston.

Bill

fiery

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I have just run in my third example, and concur with all comments made. I picked it up for $40 plus $12 shipping from Bulgaria NIB. An absolute bargain. And it came with a sickly green nylon 8 x 4 prop which fits perfectly.

It is very nice, but was full (and I mean not just a little) of iron machining grit which I have always (perhaps incorrectly?) called 'swarf'. Take care to remove all of this before turning the engine over, let alone running it.

The late Ron Chernich's site has a great review (I think by Ron himself) of the engine, which pretty much sums up all you need to know.

You need to go to the drop -down index under "finder" and there you find an array of excellent reviews, including the MK-17

http://modelenginenews.org/

One other thing. My MK-17's are not happy hand starting with usual 7 inch or 8 inch props with the 5 mm large bore red venturi insert. They like biege 3.5 mm insert. Perhaps it is due to the climate (heat) and humidity where I am. They also reputedly throttle quite well if you wish to fit an R/C carb such as may be found on on O.S Pet .099 or similar.

qazimoto

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The much lamented Ron Chernich was a trickey bloke, but he left a "backdoor" hint to his page and article indexing system.

Try this direct link to the MK-17 article.

http://modelenginenews.org/cardfile/mk17.html

Bill Adair

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Fiery,

Thanks, that is an excellent review of the MK-17 engine, and I've filed a copy in my notes for future reference. The article included a reference to the comp screw insert being pressed into the anodized head (muff), and I wonder if that might really be the case with some examples? I understand they were manufactured at several locations in the USSR.

Mine is still NIB from Ed Carlson, but I was able to satisfy my curiosity about the MK-17 by running my friends example from new. He was brand new to diesels and our flying club at the time, so when he saw me running some of my half-A diesels he asked if I would help him get his running. I had it running in short order after finding the right comp and needle settings, and was totally impressed with the handling. It had the large venturi installed, but started easily here at sea level in spite of that. In defense of my friend - the diesel running instructions he was following were hopelessly incorrect.

He now wants to fly his on a proper sized control line sport airplane, and has asked me for recommendations. Something with ample nose momeaccommodatemodate the rear intake engine would be nice, and an even longer tail moment to balance the extra weight of the MK engine. May have to kit bash a simple profile for him unless someone here has a recommendation for, and/or good experience with a suitable design for this engine.

Bill

Bill Adair

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Ray,

Thanks for the direct reply to the MK-17 articles.

Took me a while to figure out that Ron's engine index list included engine reviews, and not just engine pictures as the first few engines I looked up seemed to indicated. <G>

Bill

qazimoto

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Yes Bill the engine reviews on Ron's site are top notch.

He raises a few interesting points about the MK 17's USSR manufacture, particularly the fact that while large numbers were made it's not a Metric sized engine as one would expect.


Further he pointed out that some of the dimensions were very American. I think that the shaft thread was 10:32 (or similar). The answer to me is clear, the engines were made on US equipment supplied in vast quanities to the USSR under WW2 Lend Lease.

See: http://whatreallyhappened.com/WRHART...6315/lend.html

for an example list of stuff sent.

The comp screw assembly as described by Bill is particularly neat. I wonder if it would be possible to wire the castellated part to the comp screw to prevent it moving as is often done on fullsize aircraft?



Ray

fiery

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Thanks Ray! I could not work the link out.

One other thing. It has to be said that you should not expect PAW quality. The screws ... one of my slot-head back plate screws had to be twisted off with small mole grips when the slot burred when a correct size screw driver was used to remove it with only reasonable force. Made from 'butter metal'. Luckily it did not sheer under the head. I cut down one of the supplied mounting bolts to replace it (thanks for that tip Mr. Owen!). Gorilla force must have been used to tighten them up at the works. On reflection I should have spot heated each back corner of the case with a propane torch before attempting removal of the screws.

An excerpt from a comment by Adrian on the 'MARZ 2.5' thread, which I suspect also is applicable to some (if not all) MK-17's:


[RE: MARZ 2.5

qazimoto

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You can usually (but not always) pick up the hidden direct link on Ron's pages by doing the following.

On the page that you want the link for (on a PC) do a "right click" on the Mouse.

A small menu will appear.

Select "View Page info" and "left click". It will load the page information on the screen.

A few lines down from the top of the page you should see the actual page address. It will end in the file name which in this case is mk17.html. He always uses the engine name in the file name.

Highlight the whole name (eg http://modelenginenews.org/cardfile/mk17.html ) and press down both the Ctrl and the C keys simultaneously.

This should copy the address into the PC clipboard ready for use.

As I said this doesn't always work on Ron's pages, sometimes he hides this address as well.

Ray

Bill Adair

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Ray,

That lend lease list boggles the mind! <G>

Never heard your assumption about the MK-17 being made on US equipment, but that certainly makes good sense.

Noted also a variety of nuclear materials on that list, and that is a great surprise to me, given the Russian willingness to change sides when the going gets tough.

Interesting comment about the castellated comp screw insert, but the only MK-17 engines I've seen don't seem to suffer the wandering comp screw problem. Mine and my friends engines both have unfinished (irregular) surfaces on the tip of the comp screws, and that is usually effective in preventing that problem.

Castellated nuts were in wide use this side of the pond, but usually with a cotter pin through a hole in the shaft to keep the nut from backing out.

Bill

qazimoto

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Bill,

since the Manhattan Project was still secret I doubt that it would have been weapons grade Nuclear substances..

My best guess would have been Nuclear Materials for Medical X-Ray, and the non destructive testing of Aircraft components.

I believe that British built WW2 Aircraft used wired castellated nuts extensively to prevent the same unwinding or loosening in use.

Some of the recent Eastern European engines also have the Castellated comp screw insert. Thinking about it, it offers a simple method of tightening the comp screw thread by a gentle squashing of the tabs with the screw removed. It's also a way of replacing a worn out internal thread. The old insert can even be easily machined out if necessary.


The superb Ukrainian made Parra T4 3.2cc diesel with a Mk-17 style tabbed comp screw retainer and a Brass comp screw.