k_n_browning

Ok I have the 55 be trying to run it on the bench.But can not keep the prop nut tight.Now how to fix this.

Mr Cox

Sounds like something else is wrong, they never throw a prop and please don't use an electric starter...

AMB

If you are getting a "kickback" that could happen, usually over-compressed can cause it and maybe too much fuel, with the compression set too high it can still fire. back off the compression screw 2 turns and start flipping, turn in a 1/4 turn at a time
till it fires on the prime, disconnect the fuel line to the carb first , when it starts and burns off the prime (should run a few seconds
then hook up the line , prime and flip that should get it going, then adjust needle and compression for smoothness martin

k_n_browning

Starting by hand.Only have ran 3 tanks in.Tryed to start it this morring to run it in some more.It seem odd to me the the prop nut is right handed threaded and the prop is turning to the left.Anybody know that the thead is on the shaft may try to get a plastic lock nut for it.Or the old hot rod way a peace of fishing line flat on the nut.

Mr Cox

All engines have right hand threads as far as I know, when the engine fires this will tighten the prop. The friction against a regular washer should be enough, are you handflipping off the prop or is the engine throwing the prop? With the correct and fresh fuel the compression will only be slightly higher than for a typical glow engine.

k_n_browning

coming off when hand flipping.this motor is realy tight at top dead center.I am waiting for some cox props to see if they will work better.Maybe the prop I am using.The hole had to be drilled out and a bushing to fit the shaft.Kevin

gcb

Might the bushing be a little too long and preventing the nut from being tight on the prop?

George

Mr Cox

Revups have some nicely shaped wooden props that fit well. They are available from brodak in 7x3, 7x3.5 and 7x4, and these covers the range of the PAW 55 well.
From cox the 7x3.5 is good, but hard to find. It does sound like the bushing is interfering. I believe all PAW engines are ran at the factory and they should not be overly tight, just a good fit.

k_n_browning

ok this is what I have found.When I get it to start it runs a few rpms and then it stops.And it stops at top dead center.That makes the prop come off.THen I have to rock it back and forth to free it up.If I turn it slow by hand I can feel it get tight just before TDC.

SGC

It sounds an awfull lot like its got a flooded crankcase and its stopping from hydraulic lock once it begins to run and throws the fuel up top.

Mr Cox

Well it should get a little tight just before TDC, but it should not bind of coarse. It may not actually be turning over during those few rpms. If the compression is too high then it will just rock back and forth at a low rpm. This can sound almost as if it is running but it is very quiet when it does that, I have had this happen to me on a PAW55 on the factory setting. Reduce the compression and when you get it to turn over you will hear a distinct change in the exhaust note.

It could also be hydrolocking as suggested, you only need to prime the side of the piston and it will fire on that. This is enough to find the compression setting and only then do you connect the tank, still using the piston prime though.

What fuel you using?

k_n_browning

well removed the head and all the little contra.the piston sticks at tdc

AMB

You could try removing the cylinder (unscrews) pull off. invert, put on a wood surface insert a wood dowl and see if you can knock it up with a little tap martin

Lube it with a little fuel or oil before trying

Mr Cox

That doesn't sound right. Were did you get the engine?
I believe that PAW are running their engines up to 10000rpm before they put them in a box.

Do you have any pictures, is it around the whole circumference or just at a high spot?

k_n_browning

No did not take any pics.It just sticks at tdc I can see a shiny spot where it sticks.Before I put the head back on I put the drill on the shaft and ran it with some oil for 10 min.Hepl a little but wont know untill later today.

k_n_browning

Ok a little oil and a little ATF 10 mins with the drill.Then a lot of turning by hand and trying to start and run backwards (did not know it will run that way).the prop stayed put runing backwards.Then started it the right way.The sticking is getting better run over 1/2oz of fuel.Now how much fuel before its run in?

Diesel Fan

If the hole in the centre of the prop is threaded in any way the act of flipping it over will make it unscrew itself - there should be no thread inside of the prop's hub at all.


But if the piston is sticking a TDC, and this is NOT a new engine then perhaps the liner has been removed (or moved) and it now resides in adifferentdegree of rotation than what it should be at.
If this is the case your 'running in' could actually run it out.

I have never seen a shiny spot on a PAW liner yet!

k_n_browning

No it is a new engine.And I was realy tight when I got it.I put a little 3 in 1 oil in it.And that seemed to help,then it seamed to get tighter after the 3 tanks of fuel.Then went to run it in some more the next day.And it would hang up at tdc.I think it is a couple problems.I think the bushing is too tight on the the shaft for the prop.2 the motor is sticking at tdc.I know it was sticking bad.Because when I removed the head and contra piston.If you moved the shaft by hand it would stick.I put the drill on the shaft with some AFT and oil.Ran the it on the drill for about 10 min or so.Put it back to gether and after messing with the setting it did start and run.I think it ran better this time than it did on the first 3 tanks of fuel.On this tank of fuel I did get max rpms.

AMB

Sounds like you solved the problem it was just super tight. I think MR Davis had mentioned spinning up a tight engine with the drill thing years ago ( I could be wrong on this) but think he stated this, on a tiny engine excess binding could cause this, just not enough
power the over come this drag it would "limber it up" doing this martin

k_n_browning

I am starting to hate this motor.Came home and it started up with out to much fuss.Let it cool down as per.The motor will start up only runs at a few rpms just like it ticking along.Cant get it to speed up at all.What am I going wrong?

Mr Cox

Sounds like too high compression, it doesn't turnover it only rocks back and fourth. What fuel are you using?

gcb

As Mr Cox says, it is probably prefiring from too much compression. Whenever this happens, just lower the compression a bit and it should kick over and run the correct way. If not, it will run backward a short time, then quit.

It may be too rich also. Once it is running, lean it out and adjust the compression until you get it at peak. You should reach a point where higher compression will not yield higher power. Decrease compression to just where power starts to lower RPM and run it for several one minute runs followed by complete cool down by air. At the end of the one minute runs stop it by pulling the fuel line. That should provide the fastest heat-cycle break-in.

Good luck with it.

George

k_n_browning

well new fuel mixed.differnt fuel tank need one that is for diesel.A little more tinkering.And It starts and restarts without to much fuss.Need a new fuel tank where do I get one?What are you guys using for fuel transfer and a prime bottle?

Hobbsy

My Feedback: (102)

I use a Sullivan fuel bulb for gasoline, the black one. I draw fuel from Davis metal can and push it into the third line in a fuel tank. I use Sullivan Slant tanks mostly with gasoline/Diesel plug in it.

http://www3.towerhobbies.com/cgi-bin...&I=LXFU53&P=SM

http://www3.towerhobbies.com/cgi-bin...&I=LXTXR0&P=SM

AMB

Hayes tanks work well, no changes needed for glow or diesel they go down to 2 oz. I like that small bung with the fuel draw and 2 nipples molded in front hence not messing with 2 or 3 brass tubes thru a stopper Thats all I use now and even replaced some tanks in my finished planes with them martin