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OS .35 FP reving up after a while.

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OS .35 FP reving up after a while.

Old 03-10-2008, 10:32 PM
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Default OS .35 FP reving up after a while.

I'm flying a Top FLite Tutor I profile with a OS .35 FP spinning a 10X5 Top Flite wood propeller. I set up my engine running rich on the ground (about 8500 rpm's). After about 2 1/2 minutes of flying time, the engine starts reving up and remains running very fast for the remaining to the tank. I'm using a 4 OZ uniflow brodak tank.
Any suggestions???
Old 03-11-2008, 02:51 AM
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Default RE: OS .35 FP reving up after a while.

Can you tell if the engine is an iron piston in steel sleeve, or an aluminum piston in a nickel-on-brass sleeve? (Different fuel needs according to the metals...)

What fuel are you using? (Too much or too little castor in the blend may cause problems...) An ABN 35FP should be happy on a 10%Nitro/11%synthetic/11%castor fuel, and should probably run in a low-2-cycle mode throughout the flight. The iron in steel version probably would like 22% to 25% MOSTLY castor fuel best.

Is the engine very hot after a flight?

I've heard of occasional inaccuracies in commercial fuel tanks - split or badly located fuel pickup tubes for example - that can cause problems. A crack in the uniflow vent tube inside the tank may uncover about halfway through the flight, and change the effective needle setting - usually a tad richer... A tank with the pickup tube or either vent tube not well soldered to the shell can suffer the effects of the tube 'whipping' around a small amount inside the tank shell, foaming up the fuel and affecting the setting -usually seeming leaner.

Do you see any bubbles in the fuel line while the engine is running? The could indicate a fuel foaming condition which could go worse in flight. Some cushioning under the tank might improve vibration insulation.

Of course, you could try different plugs, props, settings... Something that basic may just do it.

Luck!

Old 03-11-2008, 05:32 AM
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Default RE: OS .35 FP reving up after a while.

What you have is the dreaded "FP Runaways". These engines are not timed for stunt. The best thing I can recommend to do is to pack it up and send it to Lew Woolard or Len Newman. Lew does great work and has a fast turn over time. Len does good work as well, but takes a bit longer. It should cost about $40 or so to have that FP 35 running like a pro.

Jay
Old 03-11-2008, 11:51 AM
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Default RE: OS .35 FP reving up after a while.

My engine is the second generation of FP's, aluminium piston with nickel-on-brass sleeve.
I'm running 10% nitro, 10% Klotz sinthetic, 12% Klotz BENOL castor.
I have tried several tanks (with and with out uniflow system and with and without using muffler preassure) and the problem continues.
No foam through fuel lines.
Engine is not hot at all after landing, you could easily leave your hand on the cylinder head for as long as you want.
Old 03-11-2008, 11:53 AM
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Default RE: OS .35 FP reving up after a while.

What you have is the dreaded "FP Runaways". These engines are not timed for stunt. The best thing I can recommend to do is to pack it up and send it to Lew Woolard or Len Newman. Lew does great work and has a fast turn over time. Len does good work as well, but takes a bit longer. It should cost about $40 or so to have that FP 35 running like a pro.

Jay

Thanks for the suggestion Jay...
Do you happen to have those gentlemen's info, Phone numbers or e-mails??
Thanks again.
Old 03-11-2008, 08:05 PM
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Default RE: OS .35 FP reving up after a while.

Leonard Neumann
http://www.clstunt.com/

Lew Woolard
[email protected]

Hope this helps.

Jay

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