K&B 61 motor carb question
12-07-2005, 02:36 PM
#26
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RE: K&B 61 motor carb question
Sport_Pilot:
Yes, I like three bladed props. Several reasons, including less tip noise with the same engine load and pitch. Besides, they just look better. Efficiency is of no concern, our little planes are so overpowered that the loss is insignificant.
A power example - the Diablo pictured above, just barely above stalling speed in level flight can be pulled to vertical and accelerate straight up. More thrust is not needed.
Some might argue that I'm over propping the 61 with the 12x6 3b, but the engine does not overheat, and the plane flies fine. By keeping the rpm down it's also decreasing the noise.
If I can get a suitable three blade prop I will not run a two bladed prop. Even on the little ones. See the picture here? The Tiggerkitty has AMD 0.061 engines and three bladed props, the C-3/10 has Magnum XL46 engines and 10x6 MAS 3b.
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Frank:
If the plane flew well for your dad with the 11x7 I'd think you already had the prop you need.
Bill.
Yes, I like three bladed props. Several reasons, including less tip noise with the same engine load and pitch. Besides, they just look better. Efficiency is of no concern, our little planes are so overpowered that the loss is insignificant.
A power example - the Diablo pictured above, just barely above stalling speed in level flight can be pulled to vertical and accelerate straight up. More thrust is not needed.
Some might argue that I'm over propping the 61 with the 12x6 3b, but the engine does not overheat, and the plane flies fine. By keeping the rpm down it's also decreasing the noise.
If I can get a suitable three blade prop I will not run a two bladed prop. Even on the little ones. See the picture here? The Tiggerkitty has AMD 0.061 engines and three bladed props, the C-3/10 has Magnum XL46 engines and 10x6 MAS 3b.
---------------------
Frank:
If the plane flew well for your dad with the 11x7 I'd think you already had the prop you need.
Bill.
12-07-2005, 03:11 PM
#28
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RE: K&B 61 motor carb question
SP:
Back in the dark ages we'd go out with one pocket full of Top-Flite 10x6 wooden props. With the Barnstormer and a four bolt Fox 35 engine it wasn't uncommon the break a prop on landing. The props only cost 25 cents then, so it waswn't as bad as it is now. Another pocket, of course, had a bag full of new head gaskets for the Fox - they blew about as often as the props broke. The head gaskets were six or eight cents.
Bill.
Back in the dark ages we'd go out with one pocket full of Top-Flite 10x6 wooden props. With the Barnstormer and a four bolt Fox 35 engine it wasn't uncommon the break a prop on landing. The props only cost 25 cents then, so it waswn't as bad as it is now. Another pocket, of course, had a bag full of new head gaskets for the Fox - they blew about as often as the props broke. The head gaskets were six or eight cents.
Bill.
12-07-2005, 03:42 PM
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RE: K&B 61 motor carb question
Frank:
Sorry, you did say 11x6. Try a 12x6 then, with the radial cowling on the Beech the larger diameter should work better with more of the prop disc clear of the plane's nose.
Bill.
Sorry, you did say 11x6. Try a 12x6 then, with the radial cowling on the Beech the larger diameter should work better with more of the prop disc clear of the plane's nose.
Bill.
12-07-2005, 03:52 PM
#31
RE: K&B 61 motor carb question
I'm not sure but I think the blown head gaskets would put that at an earlier date than I (Mid 70's) I don't recall the head gaskets blowing, though the head bolt's have come loose, though once it builds up enough castor on the surface, bolts stay tighter than with locktite! I remember one time thinking someone must have come out with a dark brown engine, and foundit was just a Fox .35 with a fairly even but thick coating of castor. In fact I think the worst thing about that engine is the fact it had a cast on venturi that was a bit too short, so it spit fuel every where.
12-07-2005, 04:14 PM
#32
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RE: K&B 61 motor carb question
SP:
As I said, that was the older engine with only four screws holding the head. That was one of the first "Improvements" Duke Fox did to the 35 engine; by the early 60s all the "Four bolt" engines were history.
Excess fuel spray from the intake is still with us. That's why I tout the use of intake stacks, either factory or home made. See pictures of a Magnum GP 25 attached. No change in power, but the fuel economy goes 'way up.
Bill.
As I said, that was the older engine with only four screws holding the head. That was one of the first "Improvements" Duke Fox did to the 35 engine; by the early 60s all the "Four bolt" engines were history.
Excess fuel spray from the intake is still with us. That's why I tout the use of intake stacks, either factory or home made. See pictures of a Magnum GP 25 attached. No change in power, but the fuel economy goes 'way up.
Bill.
12-07-2005, 04:25 PM
#33
RE: K&B 61 motor carb question
Ah, the old Fox .35. It was my first "big" engine, bigger than a .049.
The first Fox .35 had a 4-bolt head and a 2-bolt backplate. The second year, 1952, as I recall, but that's a long time back, Duke changed to a 3-bolt backplate. I remember Air Trails had a review on the 1952 Fox .35 and the drawing was like a blueprint, blue background and white lines. I fell in love with that square cornered, ugly engine. I got my mom and dad to get me one for Christmas. Flew it for years on an All American Senior, then a Kenhi Wildcat.
The first Fox .35 had a 4-bolt head and a 2-bolt backplate. The second year, 1952, as I recall, but that's a long time back, Duke changed to a 3-bolt backplate. I remember Air Trails had a review on the 1952 Fox .35 and the drawing was like a blueprint, blue background and white lines. I fell in love with that square cornered, ugly engine. I got my mom and dad to get me one for Christmas. Flew it for years on an All American Senior, then a Kenhi Wildcat.
12-08-2005, 01:08 AM
#34
RE: K&B 61 motor carb question
....getting back on tract for a moment....( 
)....the last of the 6550 ringed
series came with the slightly smaller muffler. These engines put out a tad more
power than the early offerings. The later engines (Modeler Direct) would pull
the 11-8 prop nicely....the older engines turned the 11-7 1/2 to better advantage.
The engine in this ancient scratch built plane of mine is my original K&B .61.
It's on the third crankcase replacement, and 5th rebuild.
FBD.
)....the last of the 6550 ringed series came with the slightly smaller muffler. These engines put out a tad more
power than the early offerings. The later engines (Modeler Direct) would pull
the 11-8 prop nicely....the older engines turned the 11-7 1/2 to better advantage.
The engine in this ancient scratch built plane of mine is my original K&B .61.
It's on the third crankcase replacement, and 5th rebuild.
FBD.
02-22-2022, 12:58 PM
#38
I take that back... that's an OS carb in that pic in post #10. The .46 Magnum carb fits loose... one time I used one and I rapped some thread around the spigot to where
it would fit in... then used a thin layer of silicon and crammed it in there and tightened
it down.. I know it sounds Mickey Mouse but it worked like a charm. The Magnum
carbs were $36.95 back then. The Magnum .52 carb will work but it's just a hair too tight...easy to sand a couple thou. off with some emery paper.
it would fit in... then used a thin layer of silicon and crammed it in there and tightened
it down.. I know it sounds Mickey Mouse but it worked like a charm. The Magnum
carbs were $36.95 back then. The Magnum .52 carb will work but it's just a hair too tight...easy to sand a couple thou. off with some emery paper.
Last edited by Flyboy Dave; 02-22-2022 at 01:15 PM.
02-27-2022, 06:52 PM
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The K&B was designed by the great Clarence Lee. It was originally named Veco. It is one of the great sport engines of all time. It is still made by MECOA, so all parts are readilly available. The Perry carb was originally a German product before it was moved to the US. It is a brilliantly simplistic design that works very well. They are just different with the idle mixtere disc. The disc has an internal slot that is uncovered to control the idle mixture. It only takes small adjustments of the disc to set the mixture. By the way Perry carbs and pumps are also still made. I've used the carbs on other engines such as Fox. If you don't want them I'll take them.
