Need info on a K&B 40 size engine - RC Groups
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May 21, 2006, 04:53 PM
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Starguard's Avatar

Need info on a K&B 40 size engine

Does anyone here know anything about these engines? How reliable are they and how do they hold up performancewise?
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May 21, 2006, 07:55 PM
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The 8011 was great. The 4011 was a hit and miss kind of engine. This depended on who owned K&B as it changed owners a lot. Performance wise? What do you mean? It only put out about 0.8 HP at 15k rpm. It was a very reliable sport engine. I ran mine on 15% nitro and used Top Flight 9 x 6 props.


P,S. 8011 had a bushing for the front bearing. The 4011 had two ball bearings.
Last edited by Konrad; May 22, 2006 at 06:00 PM.
May 22, 2006, 12:36 PM
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I've got a 4011 and it has been very reliable. It doesn't have much compression even when new because it has a dykes ring. It was my first engine and everyone told me it was junk because it didn't have any compression. Once started and broken in, you'll get plenty of use out of it.
May 22, 2006, 05:53 PM
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Dyke ring are low-tension ring and rely on cylinder pressure to push them against the cylinder to make a seal. A good dykes ring should feel bad to a slow hand flip.

The problem with some K&Bs is that the crank case seals were not very good and the rods had too much bearing clearances. This had a lot to do with the (some) owners wanting to use too high a tool feed speed in a vain attempt to increase profits. Engines built when modelers ran the company instead of venture capitalists are very good.

As you learned hand-cranked compression means nothing. A set in (broken in) dykes ring will still feel bad compared to a SAE D ring. But the dyke will give more power, as there is a lot less drag from the ring against the cylinder. One needs to give K&B credit for using the dyke ring. Most engine manufactures did not use the dykes ring for fear that they would loose a sale to those who would say, "it was junk see it has no compression". K&B had a well-earned reputation for strong well-mannered engines prior to the venture capitalists.

Last edited by Konrad; May 22, 2006 at 06:00 PM.
May 22, 2006, 06:40 PM
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My 4011 will windmill in flight, power off!!!
But it does produce the proper amount of power when it's running.
May 22, 2006, 06:43 PM
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Thanks guys
Jun 20, 2006, 12:27 PM
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In reference to post #2, Both the 8011 and 4011 have front and rear bearings, The bearings on the 8011 are smaller diameter. See the exploded view at

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