OS FS-91 / pump; runs when needle valve fully closed?  
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All Forums >> Glow Engines, Gas Engines, Fuel & Mfg Support Forums >> Engine Manufacturers Direct Support Forum >> O.S. Engines Support >> OS FS-91 / pump; runs when needle valve fully closed?
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OS FS-91 / pump; runs when needle valve fully closed? - 7/8/2008 7:20:03 AM   
AeroFinn


 

Posts: 33
Joined: 6/13/2007
From: Turku, FINLAND
Status: offline 		Hello everyone,


I am having some tuning problems with my O.S FS-91 II /w pump engine:

The other day the engine was running rich so I started to tune it by turning the needle valve step by step clockwise to lean out the engine;

Now the problem is that I can fully close the needle valve and the engine still keeps running ( a bit on a rich side) ??

So my question is should I replace the needle valve or is this a regulator problem? Should a properly functioning needle valve cut totally the fuel supply when fully closed?

I appreciate any input, thanks

artto

EDIT: I checked the needle valve; it seems to be ok so I am thinking the problem might be broken regulator or something that enables fuel to leak into the carburator..Is this possible?

I also checked Tower Hobbies' parts listing: There was only the whole carburator body available and no rebuilt kit for the regulator..is this really the case? Why not rebuilding te regulator like with Y.S engines?

< Message edited by AeroFinn -- 7/9/2008 8:46:58 PM >
       Post #: 1

RE: OS FS-91 / pump; runs when needle valve fully closed? - 7/10/2008 3:49:31 PM   
Bax


 

Posts: 12457
Joined: 4/26/2002
From: Champaign, IL, USA
Status: offline 		If you turn the needle valve clockwise until it stops, and the engine continues to run very rich, then you have a damaged needle seat in the carburetor body. The needle seat in your carburetor is built as part of the carburetor body, so you need to replace the carburetor body to effect a repair.

_____________________________

Bill Baxter, Manager Hobby Services/Futaba Service/North America
3002 N. Apollo Dr. Ste. 1 Champaign, IL 61822 USA
Service Phone: 217 398-0007
Email: hobbyservices@hobbico.com

(in reply to AeroFinn)
       Post #: 2

RE: OS FS-91 / pump; runs when needle valve fully closed? - 7/10/2008 5:48:10 PM   
AeroFinn


 

Posts: 33
Joined: 6/13/2007
From: Turku, FINLAND
Status: offline 		Thank you very much Bax!


I appreciate your kind reply; so if I understand correctly what you say the theoretical alternatives the fuel enters into the carburetor when the needle valve is turned clockwise until it stops are:

1 .either damaged needle seat or

2. damaged needle valve?

So the regulator really can not play any role in this case?


thank you again

(in reply to Bax)
       Post #: 3

RE: OS FS-91 / pump; runs when needle valve fully closed? - 7/11/2008 4:40:03 PM   
Bax


 

Posts: 12457
Joined: 4/26/2002
From: Champaign, IL, USA
Status: offline 		The regulator works when the needle can be properly-set.

_____________________________

Bill Baxter, Manager Hobby Services/Futaba Service/North America
3002 N. Apollo Dr. Ste. 1 Champaign, IL 61822 USA
Service Phone: 217 398-0007
Email: hobbyservices@hobbico.com

(in reply to AeroFinn)
       Post #: 4

RE: OS FS-91 / pump; runs when needle valve fully closed? - 7/11/2008 11:05:31 PM   
AeroFinn


 

Posts: 33
Joined: 6/13/2007
From: Turku, FINLAND
Status: offline 		Thank you, Bax!

(in reply to Bax)
       Post #: 5

RE: OS FS-91 / pump; runs when needle valve fully closed? - 7/21/2008 7:40:57 PM   
AeroFinn


 

Posts: 33
Joined: 6/13/2007
From: Turku, FINLAND
Status: offline 		Hello Bax!

I am still having problems with my OS FS-91 / pump;

I checked the needle seat in the carburetor body and it looks just fine? (as is the case with the needle valve)

Can the pump (if damaged) cause fuel leakage into the crankcase? If this happens the fuel would find its way to burn..

I still appreciate very much if you have time to answer to my question so I know if I should consider ordering a new pump, as well.

However, as the engine runs rich it seems the pump is supplying fuel appropriately.


thanks again,

Artto

(in reply to AeroFinn)
       Post #: 6

RE: OS FS-91 / pump; runs when needle valve fully closed? - 7/22/2008 3:45:37 AM   
Live Wire


 

Posts: 3793
Joined: 11/20/2002
From: Sterling , CO, USA
Status: online 		Well I have the 91 with out the pump doing the same thing needle all the way in and still runs rich, with no visable damage to needle or seat. You very seldom have to adjust the carb but all at once this comes up.

_____________________________

Larry K AMA 36417
WACO Brotherhood #34

(in reply to AeroFinn)
       Post #: 7

RE: OS FS-91 / pump; runs when needle valve fully closed? - 7/22/2008 5:08:03 AM   
AeroFinn


 

Posts: 33
Joined: 6/13/2007
From: Turku, FINLAND
Status: offline 		Hi Larry!

Sorry to hear yours is doing the same as mine ; so have you checked the pump to find out if it leaks fuel to crankcase? Or have you yet changed some parts, like the carburetor body or the needle valve?

cheers, artto

(in reply to Live Wire)
       Post #: 8

RE: OS FS-91 / pump; runs when needle valve fully closed? - 7/22/2008 11:48:10 AM   
AeroFinn


 

Posts: 33
Joined: 6/13/2007
From: Turku, FINLAND
Status: offline 		Larry,

I just realized your version was without the pump..

Anyways, good luck with attemps to find out the cause for the problem,

regards, Artto

(in reply to Live Wire)
       Post #: 9

RE: OS FS-91 / pump; runs when needle valve fully closed? - 7/22/2008 3:32:19 PM   
Bax


 

Posts: 12457
Joined: 4/26/2002
From: Champaign, IL, USA
Status: offline 		The pump shouldn't leak fuel into the crankcase, but we suppose it could. That could cause fuel to get into the combustion chamber through the oil-recovery lines.

_____________________________

Bill Baxter, Manager Hobby Services/Futaba Service/North America
3002 N. Apollo Dr. Ste. 1 Champaign, IL 61822 USA
Service Phone: 217 398-0007
Email: hobbyservices@hobbico.com

(in reply to AeroFinn)
       Post #: 10

RE: OS FS-91 / pump; runs when needle valve fully closed? - 7/25/2008 1:35:13 PM   
AeroFinn


 

Posts: 33
Joined: 6/13/2007
From: Turku, FINLAND
Status: offline 		Thank you again,

Bax!

(in reply to Bax)
       Post #: 11

RE: OS FS-91 / pump; runs when needle valve fully closed? - 7/26/2008 4:21:14 PM   
Peter Frey


 

Posts: 17
Joined: 2/26/2003
From: Stuttgart, GERMANY
Status: offline 		Hi,

I wrote this before but somehow my answer was deleted: If you blow inside the fuel inlet nipple of your carb and close your needle valve ther should be more resistance the more you close your needle. When the needle valve is fully closed and air is still going through you either have a bad needle or more likely a bad valve seat.

this works for non-pumped engines maybe it´s also valid for pumped ones.

Hope this helps

Peter

(in reply to AeroFinn)
       Post #: 12

RE: OS FS-91 / pump; runs when needle valve fully closed? - 7/26/2008 10:21:37 PM   
AeroFinn


 

Posts: 33
Joined: 6/13/2007
From: Turku, FINLAND
Status: offline 		Thank you Peter!

I will do the test


(in reply to Peter Frey)
       Post #: 13

RE: OS FS-91 / pump; runs when needle valve fully closed? - 7/27/2008 1:02:28 AM   
Live Wire


 

Posts: 3793
Joined: 11/20/2002
From: Sterling , CO, USA
Status: online 		Peter
This is some thing I can not understand. This motor seemed to never need tuning. No crashes or need to bottom out the needle then it seemed to get rich all at once. Even tried different fuels, and different hobby members advaice no luck. Then it came to a all new Carb. and still no luck. Going to check the cam and see if it jumped

_____________________________

Larry K AMA 36417
WACO Brotherhood #34

(in reply to Peter Frey)
       Post #: 14

RE: OS FS-91 / pump; runs when needle valve fully closed? - 7/28/2008 3:54:18 PM   
Bax


 

Posts: 12457
Joined: 4/26/2002
From: Champaign, IL, USA
Status: offline 		This is not a discussion forum, nor is it a forum where anyone can chime in with answers to peoples' questions. Per RCU rules, this is a Support Forum, which means that people may post questions to be answered by the service representatives of the engine manufacturer, in this case, O.S. Other posts will be deleted, regardless of whether they are correct or not. If you are not representing O.S., you cannot post an answer to peoples' questions.

_____________________________

Bill Baxter, Manager Hobby Services/Futaba Service/North America
3002 N. Apollo Dr. Ste. 1 Champaign, IL 61822 USA
Service Phone: 217 398-0007
Email: hobbyservices@hobbico.com

(in reply to Live Wire)
       Post #: 15

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