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Engine basics => Engine set up tips => Topic started by: Angelo Smyth on April 12, 2020, 07:20:23 AM
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Ok - I have a brand new K&B .20 that as far as I am aware, has never been run (looks new in every regard). Normally, I like to perform some break-in engine runs on my test stand for new (or new to me) engines before considering it for installation onto a plane. However, I've run into a serious problem - whenever I tighten the prop nut, the crankshaft counterweight gets pulled so tightly against the inside of the case, that it will no longer rotate. Loosening the nut to a point where the assembly will rotate only makes the prop slip. There's some discernable crankshaft end play that I hadn't noticed before - is there a fix for this such as placing a thrust washer on the inside face of the counterweight? Anyone else ever had this issue?
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Are you sure it's the crank disk? I had an old K&B .09 that the prop driver would bind on the front of the case when the prop was tightened down. I took some off the case snout and then it was ok.
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If you would, try this...........
being that the crank threads are 1/4" dia AND the glow plug threads are 1/4"
take a Plug washer and put it on the crank shaft right behind the prop driver and install the prop and tighten down the
prop nut.
See if that works for you.
I have had to do this a few YEARS ago when I was running Picco .21 Racing Marine engines.
Carl
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According to the parts breakdown, there should be a prop drive shim, is this there on your engine? This is what Carl is using the glow plug washer as an on hand replacement for.
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If you would, try this...........
being that the crank threads are 1/4" dia AND the glow plug threads are 1/4"
take a Plug washer and put it on the crank shaft right behind the prop driver and install the prop and tighten down the
prop nut.
See if that works for you.
I have had to do this a few YEARS ago when I was running Picco .21 Racing Marine engines.
Carl
Thanks -I'll try this and report on the results 🙂
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According to the parts breakdown, there should be a prop drive shim, is this there on your engine? This is what Carl is using the glow plug washer as an on hand replacement for.
Yes, the original prop drive shim is in place. After I had the issue, I removed the prop and the prop drive to verify that the shim was actually in place.
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Are you sure it's the crank disk? I had an old K&B .09 that the prop driver would bind on the front of the case when the prop was tightened down. I took some off the case snout and then it was ok.
Interesting, as I had not considered the case snout end of the equation.
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Interesting, as I had not considered the case snout end of the equation.
There should be rub marks on it, back of the thrust washer or front of case, if that is happening. Carl's test seems pretty good, take off the thrust washer, tapered cone, and slip a glow-plug washer on there, put it back. If it is binding up on the case or front bearing, that will fix it, if not, then its probably the crank being pulled up against the rear bearing, presumably because its missing a part to space the two journals, or one of the other bearings is not seated.
If it's new from the factory, call up MECOA and see if you can get it replaced.
Brett
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I had a K&B 60 do the same, I ended up dismantling the engine and with a emery board I carefully removed some material from the case snout.
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Take a Sharpie or other marker and mark up the end of the case and the back of the prop washer. If something is rubbing it shows by clearing off the marker. Probably just some flashing or something on a case or prop washer casting. I think both are cast aluminum on these? haven't looked at mine in a while.
HAPPY EASTER!!
Dan McEntee
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I had a K&B 60 do the same, I ended up dismantling the engine and with a emery board I carefully removed some material from the case snout.
Report: the addition of any sort of shim / washer to the snout of the engine (and it didn't matter where I located the extra shim on the snout; whether before or after the prop drive) made no difference....whenever I tightened up the prop nut, all I did was to bind up the rotating assembly. So, in the end I removed a very small amount of material from the snout. I did this in stages and it took several tries, but the rotating assembly finally freed-up so that I could actually tighten the prop nut like normal. I'm happy to report that it's first engine run on my test bench was successful! Thanks to all who had some input here and Happy Easter!
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Report: the addition of any sort of shim / washer to the snout of the engine (and it didn't matter where I located the extra shim on the snout; whether before or after the prop drive) made no difference....whenever I tightened up the prop nut, all I did was to bind up the rotating assembly. So, in the end I removed a very small amount of material from the snout. I did this in stages and it took several tries, but the rotating assembly finally freed-up so that I could actually tighten the prop nut like normal. I'm happy to report that it's first engine run on my test bench was successful! Thanks to all who had some input here and Happy Easter!
That's how I did it as well, a little at a time, so glad to hear it worked for you. y1 <= #^
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Wait til you get and engine that won't draw fuel even choking it. Found out the spray bar had not been drilled. Opened with smallest bit I had and then had to face off the needle body so I could lean the engine out. It was an LA 40 of all engines. D>K
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So, the OP has a "K & B 20". Keeping that in mind, 90 % of the help on here is useless. The K & B 20 is a bushing (actually crank running directly in aluminum case) engine. There are no "Bearings" to seat. There is no drive cone. The prop drive seats against a shim washer that seats against a step on the crank. Unless of course, it's not "actually" a K&B 20