Posted earlier that I was having some trouble starting my OS Max 60 FP engine, to which I received several replies (thanks), however, I am still having some issues.

The engine seems to be "getting stuck" at the top or bottom of the piston stroke. I did have a major hydro lock problem which I cleared by removing the glow plug, closing the carb, putting the starter on the spinner, and working the fuel out of there.

However, I still am unable to start the engine. One major irritant is that after a couple of failed tries, the stupid nut that hold the prop to the engine shaft unscrews itself and the whole thing comes loose and I have to take everything apart, re-assemble it, and try again. After 5-6 times doing this at 5-10 minutes a fix, it's annoying.

Does anyone have any suggestions as to what is causing the prop but to fall off or ways that I can fix that or my problem with it getting stuck at the top of the stroke?

Thanks!

oh, and one more thing...my prop is threaded onto the output shaft on the motor. Should I have drilled that out?

Hey
I haven't used the OS.. but i had similiar problems with a megatech ABC engine.
well it turns out the extra stiffness was due to too much oil in the engine. I took out the glow plug and turned the engine upside down and let the fuel flow out for about 5 minutes. Then connected the glow and hooked up the electric starter and it fired.
Hope that helps.. But if I am right the OS is not ABC so this may probably not help.

The OS engine is ABN, which is the same as ABC for all intents and purposes. OS juse uses Nickle instead of Chrome.

A new ABC/ABN engine SHOULD "get stuck" at the top of the piston stroke when cold. The piston and liner have what ammounts to an interference fit at the top of the stroke. Once the engine is warmed up, the liner expands more than the piston, and the fit is correct. If you losen up the fit while the engine is cold, you loose compression once the engine is running at temperature.

You should also try to avoid running the engine overly rich or at low RPMs before it has warmed up, and avoid extended cranking with an electric starter. Both of these will tend to wear the piston/liner fit more than you really want it to be worn.

As for throwing the prop, you might want to get rid of the spinner and go with a spinner nut, as it makes it easier to take a look at things. Generally, though, it sounds like you just aren't tighening down the prop nut enough. If it continues to be a problem, you can add a second prop nut as a jam nut. A lot of 4-stroke engines use this, as they are prone to throwing props when they backfire.

Which brings me to the possibility that your engine is backfireing. If the glow plug you are using is too hot, or you have too much nitro in the fuel (or a few other things too), the engine can fire too soon, and kick backwards, throwing the prop. Since your engine is brand new, and sounds like it has a lot of compression, this is certainly possible. Try this. Set the electric starter aside for the moment, and use a chicken stick. Prime the engine, put the glow starter on the plug, and then flip the prop BACKWARDS against compression with the chicken stick. The engine might "backfire", which in this case means fire in the correct direction, and start up.

I'm not sure how new you are to the RC world, so you may already know these things. When I started a few years back, I didn't put the prop washer on before the nut, as in spinner backplate, then prop, then washer, then nut, then spinner cone. I tightened that nut down so many times, but it still came loose until someone asked me where the washer was, which fixed that. If you use a spinner nut, all you need is the prop, then the spinner nut.

Is the engine mounted inverted?

Do you disconnect the muffler pressure line when you refuel? If not, that will flood your engine sometimes.

Thank you all for the suggestions so far...

Here's a couple of things...

To vegassky:

I will try again to empty the cylinder, perhaps I just didn't get it all out before.

To Montague:

I did get the engine started once. When I did, the prop moved quite freely and fired up. After I did, I ran it at full bore to break the engine in per manufacturer's instructions.

I'd add a second jam nut to the shaft, but it's too short, unfortunately...I was thinking of dropping a lockwasher on there to see if that helped.

I'll also try the chicken stick trick.

To autopilot:

I am extremely new to the R/C world-most of the time, my forte is computers

I have the prop stuff attached to the shaft in the order you describe, so that's most likely not the issue...

I don't understand your question about the engine being "inverted". What does that mean?

I actually have to pull the fuel tank out when I refuel (major pain in the butt), so I don't think that's the problem either.

Thanks, all for the help so far...

Hmm, I really suggest taking the plane to a local club to get some help. I suspect the problem is really something simple that will be obvious to someone looking at it, but really hard to pick out over the web.

Taking the fuel tank out to refuel? That doesn't make sense. Usually, you just unplug the fuel line from the carb or remote needle valve, if the engine has a remote needle, and pump in fuel from there. You unplug the muffler vent line to keep from filling the muffler full of fuel when the tank is full. If you can't easily reach the fuel line because the remote needle is too close to the fire wall, you can put a fuel filter or bit of brass tubing in the line to serve as a place to pull the line off to fuel.

This isn't the best picture, but it's what I had. If you look carefully behind the engine, you can see a little silver thing with fuel tubing going to it. That's the fuel filter. Because I can't reach the carb on this plane, I put the filter in there so it sticks up, and I fuel by unplugging the line from the filter instead of the carb.

is your engine mounted upsidedown(glow plug facing dow)

Hey Montague,

I have to admit, you are pretty spot on about me needing professional help. The issue is really that I need to find someone who lives near me (Detriot Area), and will help me for nothing or next to nothing.

I looked at a few R/C clubs in the area, but they all want you to be AMA and some others have dues also-I'm willing to pay, but not before I have an engine that starts-the whole chicken and the egg syndrome.

The reason I have to yank the tank out is that the fuel line is smaller then the nozzle on my fuel refilling thingy. The hobby shop I go to seems to have an idiot in there who keeps selling me the wrong parts (don't get me started on the battery he sold me to start this thing that was WAY underpowered). I need to make an adaptor that'll go from the too big size to the smaller one, apparantly...

Also, to autopilot, my engine is not inverted

All I can say to you guys is thanks for the help so far-I'm really frustrated with incompentance in being unable to start this thing and with the service I've recieved from my hobby shop so far (they won't help me with the starting problem).

I had similar problems with my O.S LA at first.

Take out the glow plug and open the carb and take off the fuel supply line. Turn the engine over and spin the prop by hand forwards and backwards a number of times.

Set the engine/plane in the sun or at least outside for say an hour and come back and hook up the supply line and put in the glow plug. This time let's all the extra fuel evaporate.

However many times you been turning over to prime cut that in half or not at all if you have an electric starter. Put the ignitor on and start spinning the engine - may take a bit. Once it cranks your set.

After I did that the first time I never had a problem with too much fuel accumulating and causing the lock and the prop to back off.

Ask them if they have the introductory pilot program or anyone qualified to instruct it.

Our club has it and it allows an instructor to instruct you at first without you being in the AMA but the club and you are still covered by insurance.

We always have people come out on Saturday with a new plane that they help out for free and the introductory instructor (we have 2 and almost always 1 is there on Saturday morning) will take you up on a buddy box with HIS trainer plane.

At least that's how it works here. If your regular instructor turns out to be one that can do the intro program you won't even need AMA till you start to solo or join the club. Mine is (even tho I have AMA) and I haven't joined the club yet and I'm about 1 flight away from a solo.

Well, you need three things to make an engine run : fuel, air, and spark. Make sure your glow plug is good by taking it out and hooking it up to your glow plug igniter, this may tell you if you buned up your plug, and will also tell you if your battery power is sufficient. It sounds like you're getting fuel - watch it come up to the carb through the fuel line, either by turning the prop counterclockwise by hand with your finger over the carb, or when you've got the starter on the front starting it. Air comes through the carb, but unless you've adjusted the low end needle, you should be okay there. General rule of thumb with the high end needle, when you're not sure, is all the way in and then two turns out. Check with your instruction book on their specs to be sure, though.

Make sure you've got the lines hooked up right from the tank to the plane, and that the screw in the middle of the tank assembly is tight, and appears to be airtight.

Let us know how it goes.

Thanks, Borzak

That's really good information, at least I now know what questions that I should be asking so I don't sounds like a total idiot

I'm going to give this thing another shot. God willing all the great advice I've gotten here will bear some fruit!

i had a hell of a time today starting my plane cuz i was dumb adn set in on a hill facing down whoops anyway i must have filled the entire thing with fuel, so i dumped it all out and she started up in about 5 seconds. flew great all day that i flew too.

maybe you have your tank a little to high up in your fuselage. i had that problem with my other plane, i dropped it down to where it should have been(i followd instructions to the T for where to place it) and it starts much better now

Back to the part of the prop coming loose, make sure you torque the nut down reeeal tight. Use a socket set or one of the hobby-style 4-way wrenches.