w0mbat

My Feedback: (1)

I have an OS 120 surpass without pump that was mounted in a plane and hasn't been flown in about 5 years. Before I tried to start it, I took off the carb, backplate and head to make sure nothing was gummed up. The engine was perfectly clean on the inside and has very good compression. (the engine only has about 10 runs on it) I put it on the test stand and connected the fuel lines but am not getting any fuel to the engine when I turn the prop by hand unless I choke the engine and turn the prop 20-30 times. The only way the fuel will easily feed from the tank is if I turn it with an electric starter. The problem is that I can crank on it for a minute or more but the engine will never start. The only time it starts and runs for a few seconds is when I add fuel to the carb manually.

I have taken the following steps:

Changed and inspected the glow plug. It glows red when I remove it and use my igniter.
Removed the carb and inspected it for obstructions. Carb cleaner runs through it without any problem.
Checked the tank and clunk for any obstructions. Fuel flows freely when I blow in the tank.
Adjusted the valves to factory settings on the compression stroke
Adjusted the low speed needle to factory settings and tried all other settings - same with the high speed needle

When I turn the engine with the starter and turn the throttle to full, fuel drips from the carb but the engine doesn't even fire at all.

Anyone have any suggestions?

mvarzoni

How old is your fuel? have you stored it properly?
Are you sure it is suitable for 4st engines?

Hope it helps.

Campgems

First thing I would try would be to remove the high speed needle and then blow into the muffler to tank line.You should get a good flow of fuel out the high speed needle hole. This will tell you if your clunk to carb line is working. Now put the high speed needle back in and close it, then open 3 1/2 turns and again blow into the muffler to tank line. You should see fuel dripping out of the mouth of the carb, assuming the engine it head up mounted.

Now set both the high speed and idle per the instruction manual. and see how that goes for getting it started. Here is the link for the manual
http://manuals.hobbico.com/osm/fs-120s-e-manual.pdf
The cab inital setup is on page 15

An O.S"F" plug is a very good choice for this engine. Omega 15% Nitro. 10% should be OK, but the idle will suffer.

if it still won't start, check the cam timing. Rotate to TDC without a glow plug, then pull the cam cover. The dot on the cam should be pointed either at the rocker arms or away from them on a line down the push rods. This will "not" be 90 degrees to the crank.

If you are still in trouble, then use some after run oil on the valves stems, and the rockers, just to make sure you doin't have a binding valve.

Once you get it to run, then use this method to tune it in


This is the sequence I use and has treatedme well.

Set both needlesto the inital setting in the manual.If you don't have the manual post and I think I have a digital copy I can send you.

Now, with the engine running and warmed up a bit, and the glow driver off,open the throttle to full, and slowly lean the high speed for maximum RPMthen go to the rich side by 300 to 400 rpm.

Adjust the throttle to the lowest setting that will allow the engine to keep running and then without the changing the throttle, slowly lean the idle mix for maximum RPM.

Go back to full throttle and again adjust the high speed needle.

Back to idle, this time the idle speed should be considerably less that the first time, but again set the throttle to the slowest speed that will keep the engine running, and again very slowly, IE1/16 turn at a time, and remove the screw driver after each adjustment, adjust for maximum RPM.

Now work on the transistion. Run up the engine then go to full idle and let it run for 10 seconds or so the jam the throttle full open as fast as you can move the stick. If the engine dies, open the mixture screw 1/16 a turn and try again. If it bubbles and slowly gains RPM, then go lean on the idle by 1/16 turn and try again. The engine should jump from full idle to full throttle in less than two seconds. One second should be your goal.

Don

w0mbat

My Feedback: (1)

Yeah, I checked the position of the timing mark and it is pointing at the rocker arms. I also took out the needle valve and was able to blow fuel through the carb. When I install the needle valve with 3 turns out, I am only able to blow fuel into the carb if it is at full throttle. It's been so long since I ran a glow motor, I don't remember if that is correct.

The only thing I was questioning is the glow fuel. My fuel is about 4 years old and was stored with the lid in place. I'm starting to think that I may have bad fuel even though I have ran fuel that was older than 3 years with no problems. The only thing is that the motor still starts when I add fuel to the carb manually.

Campgems

I just modified my first post and gave a link to the manual. Ithink that if you follow the steps I gave and start from the factory start point, for both needles, you should be able to get it running even with old fuel. Maybe not peaked, but running, The O.S. engines are contankerous if the carb is out of balance. Actuall all engines. It is really important to set thigs up per the manual to start.

Don

Campgems

I missed this on the first read.

Sounds as if the idle is set way to lean. You won't get much fuel out of the carb blowing into the vent at 1/4 throttle, but you should get some.

Don