Old School OS 61 SF -pumper help please
07-02-2006 | 09:14 PM
#27
Senior Member
Joined: Sep 2004
Posts: 613
Likes: 0
Received 0 Likes
on
0 Posts
From: Wpg,
MB, CANADA
RE: Old School OS 61 SF -pumper help please
ORIGINAL: Skypilot_one
That sounds bad.
That sounds bad.
It never use too, it started all at once while it was running, of course at WOT.
roltech
07-02-2006 | 09:20 PM
#28
Senior Member
Joined: May 2002
Posts: 1,045
Likes: 0
Received 0 Likes
on
0 Posts
From: Phoenix,
AZ
RE: Old School OS 61 SF -pumper help please
I don't think you should be losing fuel from either of the two screws......the inside of the cowled-in area of my pattern plane was never wet. I have no idea why those holes are in those screws, but I remember OS warning the consumer to never adjust them. So I didn't.
Clair
Clair
07-02-2006 | 10:14 PM
#29
Senior Member
Joined: Sep 2004
Posts: 613
Likes: 0
Received 0 Likes
on
0 Posts
From: Wpg,
MB, CANADA
RE: Old School OS 61 SF -pumper help please
ORIGINAL: Azcat59
I don't think you should be losing fuel from either of the two screws......the inside of the cowled-in area of my pattern plane was never wet. I have no idea why those holes are in those screws, but I remember OS warning the consumer to never adjust them. So I didn't.
Clair
I don't think you should be losing fuel from either of the two screws......the inside of the cowled-in area of my pattern plane was never wet. I have no idea why those holes are in those screws, but I remember OS warning the consumer to never adjust them. So I didn't.
Clair
roltech
07-03-2006 | 06:42 AM
#30
Senior Member
My Feedback: (3)
Joined: Dec 2004
Posts: 1,486
Likes: 0
Received 0 Likes
on
0 Posts
From: Martinsville,
IN
RE: Old School OS 61 SF -pumper help please
The fuel coming out of the airbleed hole means you have a pinhole in the diapham. Just like a 4 stroke needs a crankcase bleeder air hole the pump on the backside needs a bleeder hole.
07-04-2006 | 09:43 AM
#34
Senior Member
My Feedback: (4)
Joined: Aug 2003
Posts: 592
Likes: 0
Received 0 Likes
on
0 Posts
From: Callahan,
FL
RE: Old School OS 61 SF -pumper help please
A pinhole in the diaphram is definitely NOT normal and probably cannot be repaired. I think the time may have come for you to go ahead and take the pump apart and take a look at the innards. Be sure and notice where ALL the parts are supposed to be and be very careful to not tear the diaphram or lose any parts, then eyeball the diaphram looking for holes. I don't know of anyway to repair a diaphram and don't know if other OS pump diaphrams will fit. If you can't repair/replace the diaphram it may be Perry pump time.
Good luck.
Regards,
doubledee
Good luck.
Regards,
doubledee
07-04-2006 | 12:31 PM
#35
Banned
RE: Old School OS 61 SF -pumper help please
The diaphram is toast. There is no point in taking it apart because you can't get parts for it anyway. Besides, disassembling the pump will usually ruin it anyway. What probably happened was that the opening weren't plugged and the pump diaphram dried out. That's why OS says to keep the nipples plugged.
07-04-2006 | 06:30 PM
#36
Senior Member
My Feedback: (4)
Joined: Aug 2003
Posts: 592
Likes: 0
Received 0 Likes
on
0 Posts
From: Callahan,
FL
RE: Old School OS 61 SF -pumper help please
I disassembled mine (OS120FS), cleaned it, and reassembled it and it works fine. I am not recommending taking a working pump apart. It is clear that the pump in question is shot, so nothing lost by takingit apart and finding out what is wrong. Maybe something can be learned, heaven forbid. I would sure as heck take it apart and have a look before I put out the bucks for a Perry pump or give the engine up as a lost cause.
Regards,
doubledee
Regards,
doubledee
07-04-2006 | 10:34 PM
#37
Senior Member
Joined: Sep 2004
Posts: 613
Likes: 0
Received 0 Likes
on
0 Posts
From: Wpg,
MB, CANADA
RE: Old School OS 61 SF -pumper help please
Thanks guys! I'm thinking of putting a perry pump if I can't get it going, I will take it apart if all fails. one way or another that motor will run again.
roltech
roltech
07-05-2006 | 09:05 AM
#38
Senior Member
My Feedback: (4)
Joined: Aug 2003
Posts: 592
Likes: 0
Received 0 Likes
on
0 Posts
From: Callahan,
FL
RE: Old School OS 61 SF -pumper help please
roltech,
A word of advice. When you attempt to lift the diaphram off the pump use a single or double edge razor blade to gently slip under the diaphram to help break it free from the pump. Razor blade only, other blades are too thick.
Regards,
doubledee
A word of advice. When you attempt to lift the diaphram off the pump use a single or double edge razor blade to gently slip under the diaphram to help break it free from the pump. Razor blade only, other blades are too thick.
Regards,
doubledee
07-05-2006 | 10:50 AM
#40
My Feedback: (11)
RE: Old School OS 61 SF -pumper help please
On the O.S. pumped engine: Any high-speed needle setting more than 1-1/4 turns out from closed will be EXTREMELY-RICH. More than that, and the engine will be so rich you'll be lucky to get it to run. When properly-leaned, it will be about 3/4-turn out from closed.
The hole in the one screw is the hole for the regulator. If you have fuel coming out through it, then the regulator diaphragm is either holed, or the small cone-valve assembly isn't fitting into it correctly.
Here's the setting procedure for all O.S. pumped engines:
http://www.osengines.com/faq/faq-pumped.html
The hole in the one screw is the hole for the regulator. If you have fuel coming out through it, then the regulator diaphragm is either holed, or the small cone-valve assembly isn't fitting into it correctly.
Here's the setting procedure for all O.S. pumped engines:
http://www.osengines.com/faq/faq-pumped.html
07-05-2006 | 04:13 PM
#42
My Feedback: (14)
Joined: May 2002
Posts: 4,878
Likes: 0
Received 0 Likes
on
0 Posts
From: Gales Ferry, CT
RE: Old School OS 61 SF -pumper help please
BAX,
Does that include engines with four nipples on the pump and two nipples on the carb like the engine in this thread?
I have taken the 91 four stroke pump apart and cleaned it for a friend but it didn't look like this pump.
Does that include engines with four nipples on the pump and two nipples on the carb like the engine in this thread?
I have taken the 91 four stroke pump apart and cleaned it for a friend but it didn't look like this pump.
07-06-2006 | 10:02 AM
#43
My Feedback: (11)
RE: Old School OS 61 SF -pumper help please
The carb-setting procedure is the same for ALL of the O.S. pumped engines. With the pump, you don't worry about the engine leaning as the level of fuel in the tank drains.
The pump/carb system used by the O.S. Max .61 SF/RF system had four nipples on the pump and two on the carb. The pump had fuel in, fuel out, the "S" port that used vacuum from the carb, and the "R" line that returned excess fuel to the tank
The carb had two nipples. The one right at the needle valve took fuel from the "OUT" port of the pump. The nipple that was lower and inboard was connected to the "S" port of the pump. If you look into the carburetor, you can see a small hole in the venturi just behind the butterfly valve. When the vacuum of the carb changed with throttle setting, it would affect when the pump started returning fuel to the tank. This lowered the fuel pressure to the carburetor at lower throttle settings and helped give a more-linear response to throttle.
The pump/carb system used by the O.S. Max .61 SF/RF system had four nipples on the pump and two on the carb. The pump had fuel in, fuel out, the "S" port that used vacuum from the carb, and the "R" line that returned excess fuel to the tank
The carb had two nipples. The one right at the needle valve took fuel from the "OUT" port of the pump. The nipple that was lower and inboard was connected to the "S" port of the pump. If you look into the carburetor, you can see a small hole in the venturi just behind the butterfly valve. When the vacuum of the carb changed with throttle setting, it would affect when the pump started returning fuel to the tank. This lowered the fuel pressure to the carburetor at lower throttle settings and helped give a more-linear response to throttle.
03-07-2026 | 04:37 PM
#44
Junior Member
Joined: Apr 2025
Posts: 1
Likes: 0
Received 0 Likes
on
0 Posts
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!
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!
03-07-2026 | 09:05 PM
#45
there are 2 very tiny holes in the carb butterfly take it out clean the butterfly with choke clearner from auto store until you see a fine spray coming out. Reassemble it should idle fine after that. If you have the original manual i need the exploded view of the rear pump.
I think the engine in question has been thrown out a LONG time ago.
