Ed_Moorman
Posts: 3684
Joined: 1/5/2002
From: Shalimar,
FL, USA
Status: offline
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Hey, Point Mugu, as I understand, you shouldn't run an SK engine rich. Ray Nano, the engineer, has said that even though the engines are ringed, they have tapered bores and must not be run rich or you can damage the engine. The cylinder won't open up enough and the ring will be pinched in the groove. The break-in given in their instructions is very much like an ABC break-in.
Here's what he said:
quote:
Ok, I’ve been avoiding this thread but I think a couple of things should be set straight. So this is the one and only time I will reply to it. If you choose not to believe me, that’s fine, if not that’s fine too... We sell over 150 engines a month, And I have been dong the tech support on them for 6 years. About 3% are returned with real problems, the rest of the customers just need a little help getting them dialed in.
1} Yes we have had a problem with sticking carbs, the clearance between the body and the barrel is too tight, and occasionally a deformation producing an edge at the venturi opening. The problem occurs in about 1 in every 75 motors. The new carb design is in testing now.
2} even though the engines are ringed we still run cylinder taper, so we need heat to expand the top for correct break-in. Four-stroking is bad in all our engines.
3} We did make the 75-90’s in both ring and ABC, the ABC has been discontinued, seems we can’t get people out of the old habit of four stroking them during break-in and they were scoring the cylinder/piston and eating crank pins.
4} Artisian’s post#43 is wrong. Several things happen when the engine runs out of port timing that are sometimes difficult to understand. It’s not the same as closing the throttle and restricting the air. Some of the symptoms are fuel leakage from the back plate gasket or the front bearing, the engine will go lean, and you will see excessive cyl. head temp. The reason for this is the crankcase takes a full charge but it can’t get it up through the ports to the top end. As the piston comes down crankcase pressure becomes excessive and it has to go somewhere. On occasion you will notice fuel that actually spits out the carb, or some of the other symptoms of reversion.
5} our engine are ported for a max RPM between 11,000 and 12,500 depending on the displacement. Short port timing allows the engine to produce more torque, but restricts RPM. They like larger diameter props.
6} We use a very hard chrome on the liner that takes longer to break in than most other engines, most don’t develop full power for several gallons of fuel, again depending on the displacement and SPFC.
8} there have enormous strides made in engine development and design in just the last couple years alone, partly due to metallurgy and a better understanding of flow dynamics. They are getting lighter, more powerful and more user friendly. What was standard just a few years ago no longer applies to some designs.
9} be careful what advice you take from the threads on the net, here or elsewhere. I can’t tell you how many times I have heard someone tell me “I’ve been doing it that way for 30 years, it’s always worked and I ‘m not about to stop now”. People with that attitude are idiots, avoid them. If it was true we would all be using AM transmitters and building our airplanes with Ambroid and carpenters glue.
I can tell you that I have broken in 3 SK engines as specified in the instructions and they all run great.
< Message edited by Ed_Moorman -- 7/23/2007 11:53:11 PM >
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Ed Moorman, AMA 553, KD4QBM, Revver Bro #156
R/C Report Magazine, Fun Aerobatics Column
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RE: SK ENGINES - 
