OS 91 FS II Problem
08-11-2004, 09:02 PM
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OS 91 FS II Problem
Hello all,
I have an OS 91 FS that I bought brand new last fall, that now has about 1 1/2 gallons of fuel thru it. well my problem that I now have is, while I was flying today the engine died and I had a succesful deadstick landing, well after I refueled it I was going to make some adjustments to the fuel mixture, when I went to turn the prop back to the backwards stroke to use the started I soon found out that there wasn't any compresion on the engine! Is there anything I can do to fix this or should I send it in for service, it should still be under the warranty?
Thank you
Tony
I have an OS 91 FS that I bought brand new last fall, that now has about 1 1/2 gallons of fuel thru it. well my problem that I now have is, while I was flying today the engine died and I had a succesful deadstick landing, well after I refueled it I was going to make some adjustments to the fuel mixture, when I went to turn the prop back to the backwards stroke to use the started I soon found out that there wasn't any compresion on the engine! Is there anything I can do to fix this or should I send it in for service, it should still be under the warranty?
Thank you
Tony
08-12-2004, 12:00 AM
#2
RE: OS 91 FS II Problem
On the OS 91 Surpass (most four strokes for that matter) if you have the carb completely closed, The engine will apear to have no compression. The OS doesn't have as much compression clockwise as it does counter clockwise anyway.
Try it again with the carb opened up.
Enjoy,
Jim
Try it again with the carb opened up.
Enjoy,
Jim
08-12-2004, 01:15 AM
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RE: OS 91 FS II Problem
there isn't any compresion wether or not the carb is open or closed, besides there was compresion before the flameout.
Thanks for the reply
Tony
Thanks for the reply
Tony
08-12-2004, 10:00 AM
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RE: OS 91 FS II Problem
A sudden loss of compression in a four-stroke engine could signal a broken valve spring, trash getting inside the engine between the valve and the valve seat, or something worse. Yes, the trash can be in the engine compartment and suddenly get sucked into the intake midway through a flight. We've seen pieces of grass, seeds, and other types of trash stuck there. Occasionally, a valve spring breaks, and the valve stays open.
If the valve's not sealing, no compression.
You can most certainly send the engine to the shop to see what's gone wrong.
If the valve's not sealing, no compression.
You can most certainly send the engine to the shop to see what's gone wrong.
08-12-2004, 12:38 PM
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RE: OS 91 FS II Problem
Tony:
Complete agreement with Bax.
If you want to check it yourself, and maybe save yourself the delay of sending it and waiting for its return, take the rocker cover off, turn the engine until you can see both valves closed, set the crank in position to adjust the valves.
Press the valves open one at a time, if you feel a big difference in the spring pressure you've probably broken one. This is very rare. Be careful as you let the valve close, you can disengage the push rod from the adjuster, making the valve stand open.
Next check the valve clearance. If you find one with zero clearance you might have had an adjuster nut a little loose, Reset the valves and check compression again. This is only if you find a tight valve.
If on the other hand you find a valve loose, don't reset it - you've probably gotten Bax' bit of trash on the seat.
Pull the engine out of the airplane. Hold your ear next to the intake or the exhaust, depending on which valve you found loose. Turn the crank rapidly, if you hear a hiss or a whoosh you have a valve standing open, and probably a bit of trash on the seat is doing it.
Clamp the engine in a stand, pull the plug. Then, using a blow nozzle connected to your air compressor blow in the plug hole while you tap the valve end of the rocker with a plastic screwdriver handle. If it's the intake be sure the throttle is fully open. Often this will knock the trash loose and blow it right out of the engine. Things to watch out for: Be careful with the blow gun, don't damage the plug threads. While tapping on the rocker you can also disengage the push rod, just as you could when pushing the valves open by hand.
If you get the compression back, you've saved the postage cost and the waiting time, if not you haven't wasted a lot of time anyway, and the next step is pulling the head. Under warranty, I'd let Bax and company do the job. They are usually pretty fast, it won't take too long.
Regardless of the result of your testing, get on the phone to Tower (Bax' people) and order their catalogue number BRUG3104 and BRUG3204. Cost is about $5.50 total, you will get the Bru-Line air filter and two spare elements. You won't suck any more trash in. Actually, if you send the engine for service, save a few bucks and let them put the filter in with the engine when it comes back to you.
Hope this helps.
Bill.
Complete agreement with Bax.
If you want to check it yourself, and maybe save yourself the delay of sending it and waiting for its return, take the rocker cover off, turn the engine until you can see both valves closed, set the crank in position to adjust the valves.
Press the valves open one at a time, if you feel a big difference in the spring pressure you've probably broken one. This is very rare. Be careful as you let the valve close, you can disengage the push rod from the adjuster, making the valve stand open.
Next check the valve clearance. If you find one with zero clearance you might have had an adjuster nut a little loose, Reset the valves and check compression again. This is only if you find a tight valve.
If on the other hand you find a valve loose, don't reset it - you've probably gotten Bax' bit of trash on the seat.
Pull the engine out of the airplane. Hold your ear next to the intake or the exhaust, depending on which valve you found loose. Turn the crank rapidly, if you hear a hiss or a whoosh you have a valve standing open, and probably a bit of trash on the seat is doing it.
Clamp the engine in a stand, pull the plug. Then, using a blow nozzle connected to your air compressor blow in the plug hole while you tap the valve end of the rocker with a plastic screwdriver handle. If it's the intake be sure the throttle is fully open. Often this will knock the trash loose and blow it right out of the engine. Things to watch out for: Be careful with the blow gun, don't damage the plug threads. While tapping on the rocker you can also disengage the push rod, just as you could when pushing the valves open by hand.
If you get the compression back, you've saved the postage cost and the waiting time, if not you haven't wasted a lot of time anyway, and the next step is pulling the head. Under warranty, I'd let Bax and company do the job. They are usually pretty fast, it won't take too long.
Regardless of the result of your testing, get on the phone to Tower (Bax' people) and order their catalogue number BRUG3104 and BRUG3204. Cost is about $5.50 total, you will get the Bru-Line air filter and two spare elements. You won't suck any more trash in. Actually, if you send the engine for service, save a few bucks and let them put the filter in with the engine when it comes back to you.
Hope this helps.
Bill.
08-12-2004, 05:21 PM
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RE: OS 91 FS II Problem
Well guys here is the news after further investigation into the problem, and after removing the valve cover I quikly figure out that the exhaust side valve spring is broken!!! bummer.
Bax, I cant find my reciept for the engine, so about how much will this cost me to have repaired, also Im good at working on automotive engines and I was thinking about maybe doing the repair on my own to save a few bucks, all of the parts are available thru Tower.
thanks to all that replied.
Tony
Bax, I cant find my reciept for the engine, so about how much will this cost me to have repaired, also Im good at working on automotive engines and I was thinking about maybe doing the repair on my own to save a few bucks, all of the parts are available thru Tower.
thanks to all that replied.
Tony
