Help with OS 120 Surpass pumped

[Bruce Richards]

Hi,

I have just got hold of a second hand OS 120 Surpass witha pump. I have never used a pumped engine before and I have no instructions for it. So far I have been unable to get it to run are there any tricks to getting it going. I have a variety of 2 and 4 stroke engines which I have no problems with.

There appears to be no low end needle on the 120 so how do you adjust the low end throttling?

Any help or suggestions most gratefully received.

Bruce 

[Tim Mackey]

Apologies for linking to another forum...but rather than write all this lot, try HERE

[Doug Ireland]

Don't you have to remove the pressure feed to the tank with a "pumped" engine?

[Engine Doctor]

Hi Bruce. What Mk of Surpass do you have ,as they have different types of pump and carb and require different plumbing ? If the pump is made of aluminium and mounted on the crankase backplate then it is a Mk 11 .The mk 11 had a small cam type screw to adjust the low end and this is extremely sensetive.  If  the pump is small and   made of plastic ,still mounted on the backplate ,then its a Mk111.This has a low end adjuster screw fitted  on the oposite side of the carb to the needle. Niether engine uses a pressure nipple on the exhaust and both require that the tank is vented . The Mk11 has a fuel return ,to the tank , and this MUST be free flowing or the motor WILL stop suddenly and can throw the prop. The MK111 does not need a fuel return but tank must be vented to atmosphere. I have both types and have found them ultra reliable . I run them on 10% nitro  and once set up need little or no adjust ment . DO use an OS plug F type glow plug . Hope this helps.

Regards

E.D.

[Bruce Richards]

Thanks Timbo and E.D.

By you description I have a Mk11. Where is the small screw to adjust low end? Is it in the pump or on the carb?

Bruce

[Engine Doctor]

 Sorry about not answering your last post,you have probably found the idle mixture screw by now. Its on the side of the carb and sits in a small "U" shaped metal plate.

Regards

E.D.

[Dave Atherton]

Hi Bruce

The Fs-120  Mk 3 ... The factory settings are :::    Set the throttle to the fully closed position, Then carefully rotate the mixture contol screw clockwise untill it stops.  Finally, turn the mixture control screw back exactly 2.5 turns.

If you turn the engine over with a starter you should get fuel coming out of the exhaurst. then take the starter off ,put the glow on and start it with a stick.

I also have a OS,Fs 91, I had trouble starting this engine, after removing the tappet cover a found one of the valve springs had broken.  It might be worth checking  your 120.    If it is broken its easy to fit a new one

Hope this helps

Spanish Dave

PS  You have checked the plug,!!    good luck

[Bruce Richards]

Dave hi

thanks for your help. I did get the engine started and it ran very well. All I did was clean up the fuel tank and fit all new fuel pipe and off it went.

I may also have changed the plug can't remember now.