qazimoto

My Feedback: (1)

That's the way it begins, first you buy one, then another and the next thing you know you have three hundred and they dominate your life. :-)

Mr Cox

I'm glad to hear that you got it running and welcome to the club, it is an addiction.

And don't run engines indoors, for long, the fumes and smell will take forever to get out...

Unimogdriver

Yes i it is really kind of addictive, like driving A Unimog once you have driven you can't get enough.
Yeah I let it run for like 4 minutes max. But I am a little worried about the Bearing, I took off the propeller and when i turn the crankshaft, i can feel some very slight resistance in the bearing when wiggling it between TDC and BDC, it has no radial play and if the propeller is on and i turn it the same way I can't feel anything. I don't know if this is normal for such a bearing when it is turned very slowly or If the bearing has to be changed. I know that a bearing has to build up a hydrodynamic lubrication film, but I don't know if this slight resistance is normal. I have seen that they list the bearing on the PAW site, but can it be done by myself, and are there any special tools needed?

Lou Crane

To your original post -

Diesels respond well to a very sharp flick. If your fuel is good, as the other replies stress, and the prop is as PAW recommends, the problem may come down to flooding or insufficient compression and comp or fuel settings. - Given a good sharp flick...

The indicators on the settings are good! Sometimes a flooded diesel feels unresponsive to flipping the prop when it is flooded. Make sure it is not too wet before going further. If you can, turn the engine to the side and flip several times with the fuel needle closed. That helps pump any excess fuel out the exhaust. (Upright, the excess may remain in the crankcase.) Lower the compression, flip several times, and when it feels like it might want to start, ease the comp up gradually. If nothing, open the fuel needle slightly and try again.

At some point, you may get a pop or so. You may even need another SMALL prime. Draw fuel to the spraybar - your fuel tubing should allow you to see that. Flip several times. Choke until the fuel reaches the spraybar, plus about a quarter prop turn to get fuel into the crankcase,

Increase comp gradually until it pops. If you are close on needle and comp, it should pop and fire for a few seconds. Note the way it stops. You probably have the fuel needle closed too far. Open it slightly and go through the choke-prime procedure again. The engine may - likely will - need more comp to keep running. Be gentle. If it does try to keep running, try first a bit more comp. Then the fuel needle - again gradually. When it runs more steadily, tweak each adjustment until it sounds like it will keep going.

Running unevenly does not hurt it, if it is a bit rich and under-compressed. Let it warm up several seconds before trying to get it smoother. Run the fuel needle in until it doesn't increase RPM. Tweak comp and play with the fuel needle again. You'll soon find a comp setting that clearly sounds labored - back off a hair and play with the fuel needle. If too lean it should sag and quit unless you richen it enough to keep going soon enough.

You'll get there..

In my experience, first runs on a new diesel are the most frustrating. Later, it gets so much easier.

qazimoto

My Feedback: (1)

Your bearing is more than likely perfect. You're probably feeling some minuscule slop in the rod and the tightness of the piston in the top of the liner. You can fit a replacement bearing yourself but any work on a new PAW really should be done by the factory. It's just so easy to make things worse on your first diesel.

Unimogdriver

Lou, thanks for your good explanation I will surely need it when running it in and experimenting to find the best setting. Yeah it is kind of frustrating, but I already got better at it, it is a good learning curve. Yeah I hoped so because with the short run time and1/3 of oil shouldn't harm it all, but I will watch out when running it in, if something is strange, was just a little worried because the engine is so small and I don't want to destroy it. In case it gets harder to turn I will pack it and send it to the factory, because they have the tools and know how for such little engines. Thanks to all of you.

Mr Cox

If you only feel a bearing problem with the prop off, it sounds to me like the crank-pin might touch the backplate with the prop off...?

On some of the PAW engines the axial play is a little too large and the crank-pin can hit the backplate when the prop is pushed towards the engine. This comes from small uncertainties in the machining of the prop-driver (mainly the conical part), as stated in the manual if I remember correctly. This is easily fixed by placing a small brass shim behind the prop-driver.

I only have one of the .55cc ones and it needed a shim, as have some of the larger ones too.

Unimogdriver

Hello, yes when i push the shaft in then that happens, but I don't see a big problem here, because of the prop pulling it outwards while running. If i push it in then there is a real resistance. My resistance is more like you can feel the balls in the bearing roll over, it is not stuck or anything. I think i will see when it is run in for a few minutes if anything changes or not.
Mr Cox are you the one with the nice YouTube videos of the PAW's?

qazimoto

My Feedback: (1)

How many times do you run the engine with the prop off? That's the only time when our friend can feel the problem. A brass shim behind the prop driver is going to make his "problem" worse not better if the cause is blackplate rubbing. A gasket behind the backplate screw thread will remove any doubt. Plain bearing PAW's can have what seems to be excessive shaft axial end float. Twenty five years ago I tried shimming it out with the washer behind the prop driver but eventually decided it didn't matter. My TBR PAWs don't have any endfloat.

Mr Cox

On a CL engine it doesn't matter much as the crank is always pulled forward by the prop. But on an RC engine that is trottled down the crank is indeed pushed inwards by the underpressure in the crankcase and lack of prop trust. Sometimes, just above idle, and RC engine can really slam the crank back and forth in the crankcase. The solution is very easy with a shim or two behind the propdriver.

Putting shims behind the backplate when there is excessive axial play will indeed stop the crankpin from hitting the backplate, but the crank will still slam back and forth, and that is not good for the connecting rod.

If the axial play of the crank is not excessive, then one cannot shim behind the propdriver (of coarse) as that can eliminate the axial play completely and then cause other problems. In that case one would simply put an extra gasket behind the backplate.

As far as I remember all the single ballbearing PAW engines that I have had to be checked for this potential problem. A brass shim behind the propdriver will also prevent the aluminium propdriver from rubbing/galling against the aluminium crankcase.

I don't think that I ever posted any video of the .55 PAW, but I have a very short video of a bench run with a PAW .061 (1cc) here (spinning a Graupner 7x4 prop);

https://www.youtube.com/watch?v=JQQjS2wu-T8

Unimogdriver

Mr Cox then I have mistaken you for the guy named Brian Cox with lot's of videos.
So this will be my new test-stand for the summer to run it in. The C-Panel will contain the throttle mechanism. Didn't draw it because it is already finished in real.

qazimoto

My Feedback: (1)

Nice!

maxtenet

Hi Unimog,

Check out this information. It is the best I have found for new diesel owners. Very Complete info.

http://carlsonengineimports.net/FAQ.html

Good luck,
Max

Unimogdriver

Hello guys,
thanks for all the help today was day I let it run in, it works really great on my test stand. I will take a video and link it here in the the next days. But i already have a photo of it. Now i figured out how to use it, it starts at the first flick now.

Unimogdriver

In my opinion it runs pretty smooth and powerful.
Here is the YouTube link: https://www.youtube.com/watch?v=YNOE...ature=youtu.be