Mentor 140 Problem

[vicenterc at comcast.net]

Robert,

I have the same engine.  I agree that needs at least 17-10 prop.  In cool weather will need 17-12.  I am running a 3-blade prop.  My Mintor has been running very well in the last three years.  I will suggest that you check the following:

1.-  Low end usually has to be in the lean side.  I am almost all the way lean.  

2.- If #1 won't fix it and you have very hard time to set up the middle range, you will need to check the internal o-ring in the carburetor.  I have the same problem long ago and the o-ring was bad.  It is very easy to cut the o-ring during assembly.

3.-  I don't think that glow plug is critical.  I always use OS F with good results.  I also agree that pipe length is important but should not be that critical.

Good luck,

Vince Bortone

-------------- Original message -------------- 

Robert,

The Mentors I've seen run swing a much larger diameter prop. I would at least try a 17-12 and see how that works. The pipe tuning may be for that size prop and 17-8 is turning up too much. Adjusting the pump is the last alternative I would try.

Good Luck.
----- Original Message ----- 
From: Robert Schofield 
To: discussion at nsrca.org 
Sent: Sunday, May 08, 2005 4:15 PM
Subject: Mentor 140 Problem


I need advice. I have been trying to dial in a Mentor 140 for 6 or 7 months. I have about 7 or 8 gallons of fuel thru it. It took forever to get it to run half way right but it finally started to work. I have it in a test plane because I still don't trust it. After break-in I tried to fly it but it would surge at any low power setting. The people I got it from sent me a new pump and carb. It will now idle well but mid-rang is so rich it will 4 stroke. I was told to lengthen the pipe, which I did. It was set at 1/2 in. between the header and front of the pipe. By the way the pipe is the aluminum pipe from Mentor. The header is a 30mm. rise from Mentor. 
I leaned the low end and set the pipe at 3/4 in. spacing. I also leaned the top end. I have tried lean and rich on both top and bottom. It always runs very rich mid-range. I am using 15 % Cool Power. 17x8N APC. RPM top is 8800. I richened it to 8400, 8500, 8600. Idle is very good and reliable. When I pull verticle, that is when it leans out and runs like it should, however blowing the top of the box at 80 mph ain't cool.    
I was told to lower the pump pressure, which I have not done yet. 
I have run YS,OS,Supertiger, Hano's for 15 years, but this is the most flustrating thing I have ever seen.
The power is scary, however I would like to have throttle control instead if a "parked and gone" switch. 
HELP
Bob Schofield    
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