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Old Dec 27, 2012, 05:16 PM
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United States, WY, Gillette
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k&b 40

hey, i opened up a kb 40 this afternoon #0052563 this thing has a wedge top ringed piston with 2 ports in the piston 4 intake ports and 5 exhaustports it also has bearings.i was just curious but can sombody tell me what ive got?i dont think you can get parts for it can you?im thinkin its some kind of racing motor.if so is it worth something?6 bolt head and im thinkin its got a perry carb.thanks for lookin and any help you can give me.bobbelieve it or not it was on an old old swisal stick(no ailerons)
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Old Dec 27, 2012, 07:21 PM
Two left thumbs
Muncie, IN
Joined Sep 2006
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The K&B .40 used to be among the most popular engines. You can still get parts and new complete engines (when they feel like selling them) from K&B/Mecoa

The odd piston ring is called a Dykes ring. It's intended to provide low friction and high combustion sealing. A very clever design, IMHO. And if it's got a Perry carb it's an early one, and may have the small wrist pin. If so, upgrade to the new piston, rod, and pin if there's any wrist pin slop.

It's a good, reliable old engine. No power house, but if it's in good shape it'll last darned near forever.
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Old Dec 27, 2012, 07:47 PM
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USA, TX, Grapevine
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You shouldn't have any problems getting parts, if you need to, from MECOA for the engine. They still manufacture newer versions of the engine. But they haven't changed them all that much though. Those engines were more or less fairly high performance in their day. But they were not racing engines though. just good sport engines. They did use them in the restricted class of Quickie 500 Pylon racing though a long time ago. it was to level the playing field in racing so that everyone would have a similar engine without spending a fortune for a hot rare exotic racing engine.
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Old Dec 27, 2012, 08:27 PM
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There is a simplified control line racing event, Quickie Rat, which is a K&B 40 event. At least that is all I have seen run. The rules are such that when speeds reach the 110 MPH range, the venturi size dimension is tightened to lower the speed. I have several K&B 4011s and think that they are the ultimate development of that particular kind of engine design.
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Old Dec 27, 2012, 08:44 PM
Wichita KS
Joined Oct 2010
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K & B 40 engines

If anybody is interested, I have three of those engines and some parts I would like to get rid of. E-Mail <>

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Old Dec 30, 2012, 11:26 PM
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United States, WY, Gillette
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hey thnks guys for all the info .ive got a ring comin(maybe)hard to tell if the site works.but ive got a newer one to tinker about on a gremlin combat plane?
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Old Dec 31, 2012, 01:00 AM
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Israel, Ramat HaSharon
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Originally Posted by ratlm View Post
Hey, I opened up a K&B .40 this afternoon. Num. #0052563 this thing has a wedge top ringed piston with 2 ports in the piston 4 intake ports and 5 exhaustports...

Just to correct your terms and understanding...

The piston does not have 'a wedge', but rather 'a baffle' designed to deflect the incoming fresh mixture upward, to prevent it from just going across and straight out the exhaust port and to aid scavenging (pushing out the spent exhaust gasses in the cylinder).
There are just one intake port and just one exhaust port, but there are several 'bridges' in the sleeve, crossing each of the two ports from top to bottom, to keep the free-to-rotate ring in its groove in the piston. They are called 'bridged ports'.

Baffle-piston engines are rare now, with most manufacturers having adopted the Schnürle (or Schnuerle, if you cannot type the umlaut over the 'u') porting method. So, this engine is quite a relic.
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Old Dec 31, 2012, 05:52 AM
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Some pistons do have a wedge, rather than a baffle, the OS PET is one example.
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Old Dec 31, 2012, 06:57 AM
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kb 40

thnks for the help folks.
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