I have a os 120 surpass II with pump and I need plumbing instructions and if this is a good motor. The motor looks like its in good shape and it has good compression any help would be thankful

It is a good engine.

There are some guys on here that know how to plumb it. They will eventually be commenting.

Here is the manual's plumbing instructions. Send me a PMwith an email address and I'll send you a copy of the manual

What the manual doesn't ' show is how to fuel and defuel the engine. You can put a splice in the line from the clunk to the pump and make it accessible outside the cowl. That is the easiest way. Make sure the Vent line is open while running. Make sure you plug it at the end of the day.

There is a pump failure mode on this engine that allows it to start and run, but run rich. When you tune it, it's OK but smoking like crazy, the suddenly it stops. What is happening is the seals on the pump shaft are not initially sealing and you are pumping raw fuel into the crank case and as the vent of the crank goes to the intake manifold, you have a second path for fuel to the engine separate of the carb. I strongly suggest you set the engine up on a test stand and make sure you have a transparent line from the vent to the manifold, and of the right size. Get the engine running and watch the vent line for a bubbly flow of fuel heading up the line to the manifold. You will also see fuel leaking out of the nose bearing.

A permanent fix for this is to replace the little seals in the pump. I haven't located a source yet, but it wouldn't be a hard job. If you need to fix that, PM me and I'll give you as set of instructions and things to watch for.

My engine had this problem. Iwas reading some post here on RCU about another problem with the engine and that was an over rich idle due to excessive pump pressure. The fix for this was to put two T's in theoutput and return lines off the pump and connect them with a smaller diameter line. Igave this a try on my engine and it is working as a fix for the leaky seal also. Something to keep in mind in case you have problems.

Iwasn't able to hook up a choke as the motor mount I was using didn't allow for the pull rod. Ididn't need it though as the engine is one of the fastest starting engines I've seen. You will need a big starter though, one for a large spinner.

Tuning the engine is different in that you find the peak on the high speed and then leave it there. The pump prevents it from leaning out when it unloads in the air. Set it for peak RPMand you are done.

As W8ye said, it is a good strong running engine. You should enjoy it.

Don

I just found I could upload a PDFfile so I loaded the full manual. Now to see what it looks like.

Don

It worked.

Don

Benchmark APC 16 X 6 at 9000 rpm

Those are the numbers I got on both the Surpass II and Surpass III

Don

 Thanks everybody all this information was a great help and does anybody no if you can bypass the pump and use it whithout the pump

You need some way to get fuel up to the regulator on the carb.

You can use a Perry vibrator pump

You can use a check valve in the muffler pressure line to the tank.

I would use the pump if it is working. The pump is driven by the crank and if it doesn't have fuel flowing through it, things are going to wear out quickly and break. You don't want the drive disk falling into the crank. It would likely blow the whole bottom end out of the crank case. The fuel is the lube for the pump.

You can pull the pump apart and take the shaft out which will eliminate the drive from the crank, but you will have a hole that needs plugging. You can't use a stock back plate because the crank has the extension to drive the pump and it will interfere with a back plate other than the pump.

Hummm, you just gave me an idea. You could build a diaphragm pump and use the shaft hole as the crank pressure feed. I've got to look at this a bit. That may be easier than replacing the seals on my pump..

Bottom line though, use the pump if it isn't giving you problems.

Don