Hobbsy

My Feedback: (102)

Thanks H man,The prop pictured on the 1.20 is a 15x7 three blade, that should be close to a 15x8 two blade. The care package we discussed is on its way, enjoy.

I rigged up the throttle today using my swing lever rig, it's slick and smooth operating. The servo is 537 bushing JR, I may swap it for BB one.

hsukaria

Thanks FDF. Just not experienced enough to "feel" the difference between a bushing and BB servo on throttle. Would that be noticeable? Or is it more for long term durability?

Hobbsy

My Feedback: (102)

My biggest complaint is that this particular servo is noisy and doesn't center very well. To me quiet equals quality. I have an old ACE Data Master to test servos, it also has an inline milliamper meter, the digital servos are battery hogs, I like the three pole, (Armature) HiTechs, they hold center very well and are easy on the battery.

NWCORSAIR

My Feedback: (8)

I have a os fs 120 pump and have a problem. It starts fine, runs fine, and then after a few minutes running will drop back to idle, no throttle control. Any suggestions.

NM2K

My Feedback: (14)

I agree. a 14x7 three blade prop is way too large, regardless of what the engine manufacture states, unless the engine is being sold as a "stroker", Don't mind me and my wacky Toshiba coffee soaked keyboard!

Ed Cregger, NM2K

Bax

My Feedback: (11)

You may have a problem with the pump/regulator system, especially if it's a few years old and has been run infrequently.

NWCORSAIR

My Feedback: (8)

What is the fix?

Bax

My Feedback: (11)

Try running it for several tanks' worth of fuel to see if the pump/regulator system needs to loosened up. They can get dry and not regulate properly. The only other solution is to replace the carb/regulator assembly. If it's bad, you'll likely have to locate something online. The pumps and carbs for the FS-120 Surpass I and II are no longer available from O.S., but might be found through an internet search. Neither of those two engines are supported by O.S. any more.

Sport_Pilot

Bax, What is the material used on them? I believe some have repaired similar regulators no longer supported by cutting the right material to shape and gluing a small metal plate where the spring or valve rests against it. Also cutting down a larger one made for some other regulator or pump.

Bax

My Feedback: (11)

We have no idea what the material is. We never disassembled the pumps, since they were not repairable by anyone other than the factory. Some pumps could not be disassembled without destroying them.

Hobbsy

My Feedback: (102)

When I installed the new Boca Bearings in the OS 1.20 Surpass I did not remove any of the seals/shields. I had a change of heart and disassembled the engine and removed the rear most seal/shield, now he vent gurgles as it should when the engine is rotated. It acted like the crankcase vent was blocked with both seals in place. I got it timed correctly both times.

Hobbsy

My Feedback: (102)

Alpha .56 sorted out. I had struggled some with a new OS .56 Alpha with the engine surging and almost quitting. I got busy and let it sit in the box a while and decided to see what I could do with it today. When I put it in the box I had pulled the high speed needle out for safe keeping. Today I happened to look in the needle socket and saw two pieces of black dirt, one big and one little. The little one was in the metering hole, the larger right beside the metering as if drawn there by the fuel flow. I flushed the metering hole with PB Blaster, (with the carb off the engine), it was handy. The reults.

OS .56 Alpha
Prop==Bolly 12.5x6
Fuel==WildCat 10% with 18% full synthetic
Plug==Fox Miracle
Exhaust=Stock
Max rpm=10,380, rock steady
Idle======2,000
Excellent engine

szempruw

I'm rebuilding 2 older OS MAX .50 FSR engines and I can't find piston rings. Frank Bowman no longer making them. I have email into Caber Engineering in Italy. Original part number is 25103405. Anybody have any ideas where to get?

SuperNash

Try this guy, I don't see a 50FSR ring listed but maybe he will make to spec:

http://www.ebay.co.uk/sch/gaviscool/..._sop=12&_rdc=1

Aresti-RCU

My Feedback: (1)

I need to change the bearings of my OS 120 Surpass III. Can somebody guide me in the process? I am concerned mostly on how to remove the piston pin and the camshaft and how to put it back together with the right timing. Putting the piston back in the sleeve is also another concern (not breaking the piston ring!)

SuperNash

This...

https://www.youtube.com/watch?v=S_HrTCCO-GY

...is for the FS 52, but all the Surpass series are constructed the same way, and the timing is set just the same.

Once you have the head off, the pushrods can be removed. Then the cam cover comes off, and the cam will just fall out.

Piston pin comes out the back of the engine. If you pull the liner, it will exposes a hole, through which the pin can be removed.

It seems from many peoples experience that the pin may be gunked up, and it may need some cycles of soaking in methanol / heating, especially if the engine has been run on a castor mix.

Aresti-RCU

My Feedback: (1)

Started with a 56 alpha, got the engine disassembled but the bearings are stuck in the crankcase...more heat?

knuckleball

Reference:
OS FS-52 Four Stroke RC Glow Engine Disassembly
https://www.youtube.com/watch?v=S_HrTCCO-GY

Heat gun or hair dryer works very well on the case to get it hot. As shown in the video a surface like wood is needed. If more than the crankshaft is needed for removal use a brass or similar or steel punch and a small hammer to tap around the bearing(s) to push out. ONLY tap on bearing NOT case..

the Wasp

My Feedback: (1)

oops,,
can any one here help me in this post here>

http://www.rcuniverse.com/forum/glow...-question.html

thanks, big time !
Jim

Dealspeed

My Feedback: (17)

Count me in for the OS club, by far my most favorite engine maker.
here is my list of OS engines
OS 46ax x2
OS 55ax
OS 50sx
OS 91fx x2
OS 25fx x2
OS 46la x2
OS 25la
OS 120ax

Hobbsy

My Feedback: (102)

My OS Alpha .56 is almost installed in a GP Cherokee 40, gotta lot left to do in making the cowl opening neater, connecting the throttle. The RotoFlow 10 oz tank is roughed in. I discarded the stock 11 oz tank. A .56 four stroke will run a long time on 10 oz of fuel. The TurboHeader fits right in the rear corner of the cowl.. I will cut the Dubro extension off to make it look better. The prop is a Xoar 12x6 the spinner is a Kavan backplateless spinner from Hobby-Lobby, can't get em anymore.
The instructions call for 4 and 15/16" from the firewall to the face of the prop driver, that is wrong. 4 and 3/4" is more like it. I was fortunate to have an extra 40-70 mount as the first was not usable with the holes so far out.

Hobbsy

My Feedback: (102)

What was the OS engine designation for the bushed fourstroke 70, Thanks, Dave

Bax

My Feedback: (11)

The O.S. FL-70 was a non-ringed four-stroke engine, but did have a ball-bearing-supported crankshaft. O.S. did not make a bushing four-stroke engine. Even the old FS-75 used ball bearings.

Hobbsy

My Feedback: (102)

Thanks Bill, I lost it to another buyer anyway, I'll get another chance one day. I definitely misunderstood about bearings.

controlliner

What is the most running time you have logged in on your OS Alpha four stroke engine? I'm concerned about the valve seats on these engines being plated instead of having bronze inserts. I notice the valves reciprocate directly in the bare aluminum of the head as well...sigh... cost cutting?