Interesting engine problem

[Gary Dowler]

I was reading a post on another site posted by a flier. His OS 40 has, by his statements without any crash damage or ever being apart, taken to starting and running only backwards. He says it will not run normally.

What can cause this?

Gary

[Bill Adair]

Carbon buildup?

[Brett Buck]

Carbon buildup?

  Elvin magic?  OR:



    Brett

[qaz049]

I was reading a post on another site posted by a flier. His OS 40 has, by his statements without any crash damage or ever being apart, taken to starting and running only backwards. He says it will not run normally.

What can cause this?

Gary

Liner has rotated?

[Steve Helmick]

Since at least the FP series, OS engines have had a pin to clock the cylinder location, so that doesn't seem likely, especially without being taken apart. Engines usually start backwards from being over-primed, so I'd wonder if the throttle idle adjustment (air bleed) might have drifted enough to make it rich? It's either that, or the polarity has been reversed...  Steve

[Gary Dowler]

Since at least the FP series, OS engines have had a pin to clock the cylinder location, so that doesn't seem likely, especially without being taken apart. Engines usually start backwards from being over-primed, so I'd wonder if the throttle idle adjustment (air bleed) might have drifted enough to make it rich? It's either that, or the polarity has been reversed...  Steve

Don't ya hate it when people get their polarity reversed??

[Dan McEntee]

I was reading a post on another site posted by a flier. His OS 40 has, by his statements without any crash damage or ever being apart, taken to starting and running only backwards. He says it will not run normally.

What can cause this?

Gary

   Well, there is running ( popping, jerking, blubbering and not really spinning up and making power) and then there is RUNNING! Not enough information here. The direction it will run is pretty much dictated by crankshaft timing, correct?  If the liner was backwards, it might not even attempt to pop.Has he tried using a starter? Pinch off the fuel line and continue to attempt to start and see if it burns off the prime and runs correctly. Something is not right and we're not hearing the whole story I think.
    Type at you later,
    Dan McEntee

[Steve Lotz]

Maybe he put a reverse rotation prop on it.

[Perry Rose]

I had the needle set way too rich on on an Evo. .60 and it started backwards. Leaned it several turns and it ran properly.

[Dan McEntee]

Maybe he put a reverse rotation prop on it.

   You know, I have seen R/C fliers do that, and I did not consider it. Most look at the 'stick" that they are bolting onto their engine and as long as it goes on the shaft, that's as far as any inspection goes. Working in a local hobby shop for 35 years lets you see all sorts of stuff! An unknowing guy starts the engine, feels the prop wash going the wrong way and he thinks it's running backwards! This could be the situation, but still fits the lack of more information need.
   Type at you later,
   Dan McEntee

[Gary Dowler]

Just FYI, I have asked for more info from this guy, thus far no response.

Gary

[Brett Buck]

I had the needle set way too rich on on an Evo. .60 and it started backwards. Leaned it several turns and it ran properly.

   That can happen - it runs only backwards because running backwards pumps out the excess fuel on each stroke. Thats the most plausible explanation, given that the rest of the engine did  not change. Some engines run better backward than others. The original version of the PA51 were notorious for starting backwards and then running very strongly that way, far more than the 40 or the 61/65. IT was because the crank timing was much longer and closer to centered on TDC. That's also why it ran more smoothly across the break, and the "Aussie Crank Mod" made the 61 do something similar.

    Brett

[Dan McEntee]

   That can happen - it runs only backwards because running backwards pumps out the excess fuel on each stroke. Thats the most plausible explanation, given that the rest of the engine did  not change. Some engines run better backward than others. The original version of the PA51 were notorious for starting backwards and then running very strongly that way, far more than the 40 or the 61/65. IT was because the crank timing was much longer and closer to centered on TDC. That's also why it ran more smoothly across the break, and the "Aussie Crank Mod" made the 61 do something similar.

    Brett

    I don't think you will find any OS .40 with crank timing that wide. That's one of the things we don't know, which OS.40?? Supposed to be unmolested, not crashed and un-altered. I'm still curious as to what he means by "only runs backwards.". Does that mean it will throttle?  Even if a c/l version, will it needle? If so, I'll bet money on it having a pusher prop and he doesn't notice it.
    Type at you later,
     Dan McEntee?

[Dwayne]

    I don't think you will find any OS .40 with crank timing that wide. That's one of the things we don't know, which OS.40?? Supposed to be unmolested, not crashed and un-altered. I'm still curious as to what he means by "only runs backwards.". Does that mean it will throttle?  Even if a c/l version, will it needle? If so, I'll bet money on it having a pusher prop and he doesn't notice it.
    Type at you later,
     Dan McEntee?

My AX 46 will run backwards if the needle is to rich and I try and start it by hand, goose the throttle and it will quit, but will idle the tank out.

[Brett Buck]

    I don't think you will find any OS .40 with crank timing that wide.

   And more to the point, it didn't change since it was working correctly.

    Brett

[GERALD WIMMER]

Hello
As Brett points out unless something changed on the engine, some operating procedure must have changed even something small like being too rich by changing tank height.
The other interesting possibility the springs to mind  is he has an 'unusual' OS 40 like a 40H Rat Race or Pylon that has more radical timing .

My old Enya 60II (model 7032 the one with weird crank timing) would drive me wild with its desire to run backwards when flipped so I just resorted to the electric starting it , till I changed to the latter Enya 60III model 7033 with more normal crankshaft timing.

Regards Gerald