Flyer95

My Feedback: (1)

Hi, Yesterday I ran my brand new 120 FS surpass III with pump for the first time on a Diabolic 3D and wow this engine is strong turning a APC 16x6 @8500 rpm on the first tank after only 5min running time. Fuel contains 10% nitro 20% oil castor /syntetic blend.

My concern is that the engine seems to run a little lean "alot less smoke" in the midrange but the idle is rich with good smoke and so is the full throttle. There is no no adjustment on the regulator so what do you guys think I shoud do? Smaller prop or any other suggestions? I ran a total of 3 tanks thru it. Thanks

LuvBipes

My Feedback: (4)

I ran that engine for several yrs and a couple hundred flights. That prop (16x6) was the best compromise for me. If it''s idling reliably and top end is set right don''t worry about the mid range. I never had a dead stick with mine, never.

Be sure to set the top end at virtually max rpm, do NOT back off 300 rpms as is common with other unpumped 4-strokes. I used to back off only 100 rpms and the engine ran great.

2daysoff

I am running the same engine but no pump.. turning a 16X6 at 8300 RPM. what are you guys at on idle... also.. if I give it a quick movement from idle to WO no problem.. If I go pretty much instant from idle to WO the engine dies... This is my first four stroke so be gentle... is this normal? Or do I have some adjusting to do?

liquid_TR

richen your low speed needle for a quarter turn

Flyer95

My Feedback: (1)

LuvBipes, does your OS120 have a silicon tubing going from the camgear at the crankcase to the fuel inlet pipe? see picture.

I am gonna run this engine more today and try different propeller and will let you know how it runs.

Flyer95

My Feedback: (1)

Now I have run the APC 15x6, 16x6 and 17x4w and it seems like the 15x6 works best on the Diabolic 3D turning @9700 rpm. And now the midrange seems good and is not lean anymore.

LuvBipes

My Feedback: (4)

Flyer, yeah, that tube from crankcase to fuel inlet pipe is OS's way of venting the crankcase. It works and keeps the plane cleaner. I've tested it both ways (stock, and venting to outside of plane) and the engine runs the same.

Flyer95

My Feedback: (1)

Thanks! Now I have a total of 8 tanks thru the engine and have leaned the mixture and it runs great and very clean. Not much clean up work after one days flying!

skyriter

I am having trouble with an OS 120 III pumped. Seems it was running ok last year, but this year it does not want to rev up from about mid thottle seems to bog down. Will eventully rev up, but you have to really work at it. Have gone over all the adjustments and it just will not run right. Using new fuel (cool power) as well. Any ideas?

Bruce

Flyer95

My Feedback: (1)

On a pumped engine there can be two situations where the engine bogs down. It is "too rich" or "too lean". One way to find out is having the glowbattery connected to see if it can pass thru midrange without boging or surging. If the glowbattery solves the situation then the needles are "too rich" if not then they are "too lean" or the regulator is not supplying the fuel to the carburetor for some reason. And install a new OS-F glow plug to be sure the plug is not fouled from the last year. Are you using filters?
Have you been using ATF or afterrun oil during the winter? Because pumped engine usually can not tolerate petroleum based oils type. I know atleast YS and Perry regulators "glow version" can not tolerate these oils, however not sure about the OS-pump/regulator?

skyriter

Thanks for the info

Using a new OS-F glow plug, No filter in any of the lines, New fuel. Never used after run oil.
What seems to be happening is there is not enought fuel going to the carb to support the higher RPM. Did some more testing last night - ie changed both the low and high needles back to factory settings, Engine started OK, but now I have fuel coming out of the hole in the regulator body. Did not have time to finish testing with the low speed needle leaned out quite a bit. Not sure if having the low end really rich would cause fuel to come out of there - sprayed out pretty good. Will do more testing using your suggestions.

Will let you know how I make out. Thanks for the help.

Bruce