Sportster 65 has dark gray oil in exhaust and some binding

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Sportster 65 has dark gray oil in exhaust and some binding

Postby Lardog » Tue Jul 14, 2009 11:47 am

Hello,

I own 12 to 15 K&B aero and boat engines and have always had great success with them. I have 3 brand new .65 Sportsters, and just put one on my Hangar 9 Twist 60. (I know - that's a lot of engines. What can I say, I love airplanes and engines...)

I ran 2 tanks of Omega 10% fuel through the engine while on the plane to break it in. (It stayed on the ground the whole time.) During the first fuel run, I was running pretty rich (based on the Sportster break-in instruction manual), and the was a lot of dark gray oil coming out of the engine. (I assume that's from aluminum being honed by break-in.) After that run, compression was very good and the engine was turning more smoothly. I leaned the engine a few clicks for the next tank, and it ran better and with less gray in the oil.

I leaned the engine another click or two, flew the plane for the next tankful, and the gray in the oil was almost gone. I still had a lot of oil on my plane, but it was pink (the fuel color) and the engine was running fairly well, but still pretty rich.

The next tank of fuel, I leaned the engine 1 click. Before flying I checked cylinder head temp, and it was around 185 at idle, around 230 at mid-range, and about 275 at full throttle. I flew the plane and the engine ran well and was alternating between two-stroking and four-stroking. (Just what I was going for.) It sounded great, and it was a great (though somewhat tame) flight.

The 3rd flight was with the same needle valve setting, and all was fine for 6 or 8 minutes. Then the engine lost a little power and sounded a little weak. I landed and the engine died when returned to idle. I found that massive amounts of very dark gray oil was again covering the airplane. I also noticed that there was some drag as I rotated the engine crank. It didn't feel like piston/cylinder drag, as it didn't change at BDC and TDC. It felt more like crank drag.

At home, I opened the back of the case, expecting to see where the crank was dragging the case or backplate, but it looked OK. There was quite a bit of oil in the engine, and it was very dark gray. The piston has a somewhat shiny ring around it near the top (top 1/8 inch I'd say) and the motor still has great compression.

Any idea what is causing the dark gray oil? Is my engine being damaged? What cylinder head temperature should I go for on this engine?

Thank you for your help.

Larry
Lardog
 
Posts: 4
Joined: Tue Jul 14, 2009 11:02 am
Location: Peoria, IL

Postby Lardog » Tue Jul 14, 2009 2:28 pm

Sorry - I'm a newb... :oops:

I meant to post this in the K&B engine Tech forum. I'll repost it there...

Larry
Lardog
 
Posts: 4
Joined: Tue Jul 14, 2009 11:02 am
Location: Peoria, IL


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