I have an OS 61 sf-p....the one with the 4 way pump on the backplate. The pump has 4 nipples: from tank to pump, from pump to carb, a return- from carb to pump, and return- from pump to tank. Judging from the engine manual it appears that there are two holes/vents/nipples in the backplate. This engine sat on the shelf for about 6 years and I tried running it. Engine runs great, but won't idle. I notice air bubbles coming from the pump, but not from the tank.

I sent it to Hobby Services for repair, and they sent it back two weeks later, saying there is nothing they can to, because the engine has been discontinued in 1998. They also said the pump is all metal, and vitrually unbreakable, and that I should simply run fuel through it to "limber" it up again. And of course, two tanks later...same old bubbles that don't go away.

My question is, because the carb opening diameter is huge and requires (won't run without one) a pump to pump fuel in and a pump to pump fuel out. Can I just get a couple of perry pumps? If not, does anyone want to buy the engine at a really great price? It is a great motor that has about 10-12 lbs. of thrust and has more power than a OS 61 FX; and with the pump working, it would idle at 1800rpm and I have never had a deadstick. All in all, it has about a gallon of fuel through it total. Paid about $260 for it from Tower in 1997 and have original reciept.

Thanks for any suggestions!

technoheli ....welcome to RCU....

Try cleaning the carb real good, and running some more fuel through it before
you give it the "Heave-ho toss". It might just heal itself.

Flyboy Dave.

Do as Flyboy Dave says, Just keep running fuel through it and it will possibly fix itself. If after a period of time it doesn't straighten itself out send it to me. I will give it a good home.

Regards,
doubledee

I have a downloaded manual for the pump used on the SF61. If you want me to send it to you, PM me. It may be of value or not. I think I downloaded it from the OS website, so it may be available there too. A friend of mine has the same engine that until this spring was still new. He bought it around 1991. It runs great. I got the manual to find out how to connect the fittings of the pump to the tank, etc.

George

Give it a chance! I bet is is gunked up a bit inside which would restrict fuel flow at lower throttle settings--- remember it only takes a speck of dirt to wreak havoc with fuel draw. Those are darned good engines I would run the heck out of it before I sold it to Flyboy Dave, because he would show up and have it running perfectly and rub it in...

Run it then run it some more- Heck try some different props. and plugs and give us some stats!

Welcome to RCU!

James

Good stuff I have the same engine and have the same problem, could you post the OS link to download this manual and the how to connect the fittings to tank etc.
Thanks

roltech

Like this ?

As noted, give it time on the test bench, and make sure it is plumbed correctly.

Even though it is a pumper, tiny bit of fuel foam can cause havoc. When they go through the pump regulator, the bubbles accumulate, and can cause larger air bubbles in the carb feed line.

And I too will get in line.... if you decide to get rid of it I owned 4 of those at one time.

Bob

Put me in line too!!!!!!!! I have two NIB Enya 60XLF-GP engines waiting to go on the test stand.

Here is the link to the manual for the pump:

http://www.osengines.com/manuals/72502000-manual.pdf

George

A perry pump will work fine.

Thanks a Bunch
Now I find out there's lot of things I should not of done, as taking the pump apart???
But now I know.

roltech

Are you saying that you can replace the OS pump with a perry pump? if so that's great! Did you try this?

roltech

Yup, I did it on an OS120 surpass.The pump went bad. Sat without covering the nipples for 5 years and that ruined the pump. I plugged all the nipples and used a Perry Oscillating pump. about 25 bucks these days. I use that pump on any model where fuel tank position is in question.

If you download the instructions you will also see the recommendations for storage. I didn't and it sat for years and never worked again. I tried all the suggestions and the pump just didn't work. Perry solved the problem

Is the pump on the 61 a diaphram pump or gear pump? !20 diaphram might go bad but gears last a long time.

Well that's good news! however the motor I have is a .61 and not sure how I would hook-up a perry pump? is the return line from the carb used with the perry pump? and can we use the same carb? If not what has to be done? to convert. I would appreciate all the info I can get, this motor was stored for many years also, I can get it to run at WOT but wont run past halfway down to idle it shuts down.

roltech

roltech,
Just keep running it, there is a good possibility that as you put fuel through it it will loosen up all the gunk that is in it and well eventually work fine. Or, spend the money on a Perry oscillating pump and find out later that you didn't need to buy it after all. At least give the fuel passing through it a good try.
Regards,
doubledee

It's a diaphragm pump and the diaphragm will dry out and that's that. The perry pump only has one output and that goes to the carb.

His carb has two lines, one would have to go back to the tank.

You say it won't run below the midrange to idle, is it going lean or rich? You can pinch the line from the pump to the carb to find out.

I tried many things but not the pinch line thing, would I have to run at WOT to try this? because lowering the throttle some, the motor cuts out?

roltech

I didn't know the engine died at any setting below full throttle. Your post stated it died below half throttle. You did take the pump apart, was there any foreign matter in it? Did you turn the painted adjusting screws? Are you using a filter and have you checked to make sure it is clean?

I read thru the instruction manual again. With the needle three turns out can the engine be made to run rich? Do you have fuel flowing thru line D back to the tank?

I noted that the pump is used under license from Perry. Maybe you could contact Perry/Conley and see if they have any info on these old pumps.

It dies if I lower the throttle past half way. I did not turn the painted screws, thought it was factory settings, the filter is clean,
it will only run with needle setting 1 1/2 turn from stop, and you can see the fuel returning from the carb to the pump, I did take the pump apart to check if anything was obstructing the flow, but did not find anything, I use a very small amount of petrolium jelly to rub gently on the diaphragm, I reasembled it and tried it again with the same result. Now I will check for fuel flowing thru the D back to the line, I don't have the motor at my place now, I took it too our LHS and see what they could do with it. They know this motor and said they will check it out.
Thank for the info, I will post the results.

roltech

I ran one of these back in my pattern days, a rear exhaust version. Strong, strong engine. Still have it, in fact. To think along a slightly different line, I wonder if the idle adjustment may be messed up on your carb. I don't remember the details of that carb, but I imagine there is an O ring involved, and it may be dried up. Worth playing with, perhaps. I think one of my pattern buddies had a problem with his, and we filled the tank with denatured alcohol, took the plug out of the engine, and spun the engine with a starter, which caused it to run the alcohol through the pump and engine, blowing it out of the plug hole. It seemed to clean out whatever had gotten into the pump, and ran fine thereafter. Maybe worth a try.

Good luck. Don't give up on it yet, it is a fine engine. Clair

azcat,

That is an excellent idea.

Another thing when last testing, there was fuel coming out of the pump screw, the upper one "with the hole in the center", does anyone know if fuel should come out from there for some reason? as yes I can tell this is a strong motor, just by the compression.

roltech