Please help with OS 26 4 stroke
 

I can't get more then 9k out of it. I've changed the plug, fuel, 15% and 10%
checked the lines, clunk, and tank. Propped with a 10/4 and 10/5 same results,
idles fine, throttles up fine but not full power. The barrel opens all the way and
i'm stumped. please help!! Craig

RE: Please help with OS 26 4 stroke
 

About the only thing left is a new glow plug and resetting the tappet clearance. If it has a lot of run time, it could have buildup in the ports, exhaust mainly. Is compression good?

RE: Please help with OS 26 4 stroke
 

I did try a new glow plug, exactly the same results. Is there a little compression
tester or do you mean does it feel like it has good compression?

RE: Please help with OS 26 4 stroke
 

Compression, comparatively to what is was like when it was newer. 10k on a 10x5 is about all I would expect. It run a bit faster with the 10x4. Check the valves.

RE: Please help with OS 26 4 stroke
 

OK I'll check the valves. What do you think,10% or 15%?

RE: Please help with OS 26 4 stroke
 

Try a 9-6 or a 9-5 on it? They are loaded pretty hard with a 10-5 and just about will not pull a 10-6 without running hot or having mixture setting problems.

I have one and it runs very reliably but does not have the power of a Saito 30

RE: Please help with OS 26 4 stroke
 

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Nine K is about right for that engine and that prop.

Instead of reaching for higher rpm, try gaining more thrust by swinging more prop, such as an 11x4.

If the engine is new, it may gain a few hundred rpm as it acquires running time.

Please realize that four-strokes up to .30 in displacement are comparable to .15 to .18 (the latter is pushing it) glow two-strokes as far as power is concerned. The perfect model for these engines are .15 two-stroke powered models. Do not try to use these engines in models designed for a .25 two-stroke or you will be very disappointed.


Ed Cregger

RE: Please help with OS 26 4 stroke
 

I think it should do better than 9k when compared to these. My own FS-26 did about 10,500 on a Graupner 9x6. Looking at these posts there was some variability in the performance of this little engine.

http://www.rcuniverse.com/forum/fb.asp?m=630864
http://www.rcuniverse.com/forum/fb.asp?m=1508385
http://www.rcuniverse.com/forum/fb.asp?m=346354

An 11x4 will certainly give more static thrust. If you want to fly faster than ~40MPH you will need more pitch and less diameter. Especially, if you want to cruise at part throttle. It all depends on what kind of speed envelope you need for the model.

10 or 15% nitro will hardly be noticeable.

RE: Please help with OS 26 4 stroke
 

Don't use too much nitro on this engine, over 15% is a waste and will alter timing and performance a bit for the worse.
I got on mine 11300rpm with a higher compression ratio and 5% nitro on an aviomodelli 10x4 prop. ON regular use, it clocked a bit over 10000rpm, like Greg's engine.
Try using some castor oil on the fuel, it did wonders on mine!
Good luck!

RE: Please help with OS 26 4 stroke
 

Well, I adjusted the valves and it got worse...8700 I'll check the valves again. I can't
understand this, I took the plane on a fishing trip to Canada last year and it flew great,
take off on floats in about 150ft. Came home and tried it at a local lake and could'nt get
it off the water. Took the engine to a local guy to check out and he completely
disassembled it cleaned it replaced a valve and said it was fine. I reinstalled it on the plane
and it is exactly the same. I bought another one on E-bay and IT does the same. I'm
starting to think I have a bunch of bad fuel. I'm going to screw around with the valves again
and try to at least get back to 9k. I'll keep you posted.......Craig

RE: Please help with OS 26 4 stroke
 

Hi!
A 10x5 prop is prefect for the OS .26. Anything smaller is not going to work as good. You would expect the engine to rew 10000 rpm with a APC 10x5 or Master Airscreew "scimitar" 10x5 when using 5% nitro fuel. This is at sea level.
If your OS .26 is rewing only 9000rpm with a 10x5 prop either the cam is set wrong or the engine is worn out.

RE: Please help with OS 26 4 stroke
 

Set cam timing with the piston to the top. The mark may be like the picture or opposite and still be OK?

http://image2.rcuniverse.com/gallery...4/lg-21698.jpg