davejerr

I'm having a problem with my O.S. 70 II surpass. I'm not getting full power in the high end. I've adjusted the needle valve several times but still no increase in power. I can't even do a loop without stalling. Any advice?

Ed_Moorman

My Feedback: (1)

What prop are you running?

May as well tell us your fuel and glow plug.

Gizmo-RCU

My Feedback: (27)

Check you valve lash, mine got sick when the setting opened up.....

chashint

Lots more info is needed, what plane is it, fuel, prop ....
What rpm are you getting at wide open throttle on the ground ?

My recommendations for a 70 Surpass ...
10 or 15% nitro (really does not matter)
Castor / synthetic blend or all synthetic oil
13x6 prop (Master Airscrew K series or APC ... does not matter)

With this setup you can expect peak rpm between 10300 and 10600 rpm.
Back it off 300 to 400 rpm by richening the HS needle.
It should pull a 6 lb plane straight up and it should fly up to an 8 lb plane through big loops.

forestroke

if its the 90 size extra you're trying to fly, you're not going to get too far. anyway, as said, put on the right prop and tach it on the ground. that'll tell us if your engine is performing. what you have it attached to, that's a different story.

davejerr

Sorry. It's an easy sport 40 with a 10x8 prop running 15% fuel.

chashint

Get rid of that prop immediately and use a 13x6 Master Airscrew K series or APC ... it does not matter which one.

May I ask if you bought the engine new ?

chashint

Here is a link to the manual, you really need to take a look at it http://manuals.hobbico.com/osm/fs-70...i-p-manual.pdf

forestroke

the prop is probably a bit too much pitch. 12 x 7 should be good for that engine and that engine should haul arse on that plane. anyway, tach it. that's the best way. how does it run on the ground? if it runs strong on the ground, maybe you're leaning it out too much. remember you need to back out the needle 3 click from highest rpm so that it doesn't get too lean in the air. good luck!

davejerr

well the engine is not new. it was crashed in a field and left there for a few days(we couldnt find it). But its been used at least ten times since and never had this problem until now. Will a prop with too much pitch actually slow the max speed of the engine?

moparcolt

My Feedback: (2)

I don't think that the pitch is the real problem I have run a 12X8 prop on my saito 72 for some time but a 10inch prop is too small for that motor, you may be revving it beyond its max rpm, possibly causing overheating. I also would suggest a 12X8 or a 13X6 . I have rus a 13X6 K-series prop on it and it really likes it.
Sitting out in the field probably didn't hurt anything, mine sat up in a tree all summer once, because the leaves were so thick I couldn't find the plane, and it is just fine. Get a tach and a different prop to start and see if it will spin the new prop to around 10,000 to 10,500 RPM and if that doesn't help start checking the valves and general condition of the engine.

NM2K

My Feedback: (14)

Yes, more pitch will slow down the engine, but will speed up the plane, unless the engine is grossly overloaded by the larger prop.

You are underpropping your FS-70 four-stroke with a 10x8. As recommended by others, a 13x6 (if you have the ground clearance) or a 12x7 or 8 would be better for the engine. If you must run a smaller prop on that model, a 10x9-10 or an 11x8 would be an excellent choice and would provide adequate loading for the engine

Check the valve clearance while you are at it, as others recommended. Also check the seal of the intake manifold to the cylinder head and the carburetor seal to the intake manifold. Sometimes air leaks develope after a crash. Most times they can be repaired simply and inexpensively.

While you are at it, check the run-out (wobble) of the crankshaft. You don't need fancy instruments to do this. Just use a fixed object against the crankshaft end (threaded portion) and slowly rotate the crankshaft for a full 360 degrees (remove the glow plug first). If there is any noticable daylight at any point while rotating the crankshaft, your crankshaft needs to be straightened or replaced.


Ed Cregger

rcdude7

My Feedback: (264)

That would be a good prop size for my .46 enya four-cycle. Do what these guys suggest, change the prop, 12X8, 13X6 are good choices.

FILE IFR

Are you sure the barrel of the carb opens all the way?