Is it my muffler?

[tdevince]

Hello, I have an older Xcell 60 (1992 vintage) with an OS 70 SZ engine and a 60K carb. (3 needle adjustment). I have a Hatori SB 1 for the muffler. The problem I have is trying to get the engine to stay running in the mid range. It idles OK, and if I punch the throttle I can get past the mid range and have it run on the high speed needle. The mid range adjustment seems to make it too lean or too rich. The symptoms are as I increase throttle to hover, (just about the time it starts getting light on the skids) the engine increases smoke output, the engine studders then quits. As I lean the engine with the mid range needle, it just quits without the studder. Last night I took the engine apart (removed the head) and found losts of oil in the muffler and engine. So I'm wondering if my muffler is causing the fuel to have too much pressure such that I don't have fine enough adjustment with the mid range needle. Is the SB1 too small for the OS 70?, what muffler should I try? By the way, I was previously able to get it running, but then the following day, with no changes to engine setup, it starts exhibiting this problem again.

Thank you,

Tom DeVincentis

[DavidH]

Tom,
Just my opinion. I think that muffler is too small for the 70. We used that muffler on 60 size engines. But once the 80/90 engines appeared and the new larger mufflers. There were a lot of pilots that used the SB 15 on the 60 size engines. Those engines ran so much better with a muffler with a larger volume cannister.
I think if you try a different muffler with more volume you will find out the same.
The SB1 is a great muffler. My opinion it was borderline in volume size for a 60, so a 70 probably puts it way undersize.

David

[tdevince]

Thanks David, I'll get a SB15 on order (all I see is the SB15 FH, which I assume is the same thing).

Thanks

Tom

[Fox222]

tdevince,
Did you try another glow plug? If it ran one day and not the next, it is usually the plug. Sometimes the plug looks fine but still does not work properly so I would try a new plug first.
The other thing that will cause this type of behavior is the fuel system such as clogged filter, hole in line or debris in carb.

[tdevince]

Fox,

Thanks for the help.

I've tried 3 different glow plug manufacturer's, replaced my fuel lines, cleaned my filters and tanks (main tank and header tank), verified klunks are clear, and cleaned the engine/carb. All to no avail. I'll try a new muffler, if that doesn't work maybe I should go electric.

Tom