What Fuel for K&B 40?

[Shawn Kuntz]

I have a K&B 40 R/C engine converted to control line.  I bought it in the early 1980's and never used it.  Can I use Sig fuel for Fox engines, 25% Caster, 10% nitro?  That is what I am using for my Fox engines.  I prefer to buy only one kind of fuel.

[Jim Thomerson]

I run Sig Champion 10%, 20% oil 50/50 in my K&B 4011's.  Your fuel should work fine.  The 4011's, which is probably what you have, are very strong engines, but you may have to fiddle with it; props, venturi, compression, etc. to control windup.  I have had 11 x 5 APC's work fine, or not. 

[Alan Hahn]

I might worry that the 25% castor might gum up the Dykes Ring at some point. I bet the norma Sig 50=50 castor-synthetic oil mix is a better choice. However I have no positive or negative evidence one way or the other.

[PatRobinson]

I have a Stan Powell modified K&B 40 and we used 7%, 8% and 10% fuel depending on temperature and humidity. The K&B needs all castor fuel of
22% to 25%. Using even partial synthetic oil made the consistent motor run
turn erratic.

There were some key points that turned the K&B into world beater that Les Mcdonald used to win his world championship.  1. Stan reduced the blowndown time between intake and exhaust to control the speed and
2. Stan found a source for great dykes rings that gave really great compression when you turned it over by hand. Most dyke ring engines aren't fitted to those tolerances and so when you turn them over you have very little compression.  Stan also varied head spacers as needed for conditions.

We tached the engine to 10,000 rpm to 10,500 rpm on the ground and the best prop we found was modifying a 12/5  Rev-up to an 11 5/8ths / 5 prop.
That extra 5/8ths of an inch increases thrust and helps to control speed.
A  Rev-up 5" pitch is actually closer to a 4" pitch on the pitch guage.

This was a "Hoss" motor that flew airplanes from 610 sq" to 660sq" and airplane weights from 50 oz. to 60 oz.  When K&B marketed their Stunt 40
they basically used Stan's modifications but I'm not sure they had the same ring fit so they never acheived the same performance as Stan's motors.

I hope you find this info useful. The K&B is one of my all time favorite motors.

                                                           Pat Robinson

[Will Davis]

I run Powermaster 22% Oil 1/2 synthetic, 1/2 Castor and 10% Nitro in My K&B 40 4011. I have used all or more castor , but too might be concerned with buildup on Dykes ring. I have used as low as 3.75 pitch gator Prop and as much as  12 inch diameter on a Imitation .Every plane will vary .

William Davis

[Shawn Kuntz]

My K&B 40 is an 8011.  I understand that the only difference between an 8011 and 4011 is the size of the front bearing.  All other parts are the same.  I think I will try the 25% Caster fuel that I use for my Fox engines.  Thanks.

[Bill Little]

I have a Stan Powell modified K&B 40 and we used 7%, 8% and 10% fuel depending on temperature and humidity. The K&B needs all castor fuel of
22% to 25%. Using even partial synthetic oil made the consistent motor run
turn erratic.

There were some key points that turned the K&B into world beater that Les Mcdonald used to win his world championship.  1. Stan reduced the blowndown time between intake and exhaust to control the speed and
2. Stan found a source for great dykes rings that gave really great compression when you turned it over by hand. Most dyke ring engines aren't fitted to those tolerances and so when you turn them over you have very little compression.  Stan also varied head spacers as needed for conditions.

We tached the engine to 10,000 rpm to 10,500 rpm on the ground and the best prop we found was modifying a 12/5  Rev-up to an 11 5/8ths / 5 prop.
That extra 5/8ths of an inch increases thrust and helps to control speed.
A  Rev-up 5" pitch is actually closer to a 4" pitch on the pitch gauge.

This was a "Hoss" motor that flew airplanes from 610 sq" to 660sq" and airplane weights from 50 oz. to 60 oz.  When K&B marketed their Stunt 40
they basically used Stan's modifications but I'm not sure they had the same ring fit so they never achieved the same performance as Stan's motors.

I hope you find this info useful. The K&B is one of my all time favorite motors.

                                                           Pat Robinson

Hi Pat,

Stan's engines were great!  They always did a real good job of having an intelligent stunt run.

AFAIK, the K&B (Brodak) 40 Stunt, #4055, IIRC, was very similar to Stan's set up although they were ABC, no ring.  I talked a good bit with Stan when these came out, especially as to how they compaired to his own reworks.  They are "close".

I have one of the ABC Stunt and one of the reworks.  I have not run the ABC engine at all. 

As to the fuel, I do believe the "all castor" was a factor in getting a steady run, much less variations.  Why?  I have no clue! LOL!!  I only need to know WHAT works, I'll leave the "WHY" to others. 

Bill <><

[Alan Hahn]

I have both a 4011 and a 8011 plus the Brodak/K&B 40 Stunt motor. If I recall correctly, the Brodak/K&B motor is a completely different beast than the 4011 and 8011.  These original two were of cross flow design with the piston having an intake deflector. The Brodak/KB version isn't even (I think) a schneurle design, much less a cross-flow, the intake and exhaust porting looks pretty weird! The piston is flat topped of course. I don't see how it can be a derivative of a reworked 4011/8011 engine (maybe I misunderstood the comment, or the rework was incredibly radical!)

[Bill Little]

I have both a 4011 and a 8011 plus the Brodak/K&B 40 Stunt motor. If I recall correctly, the Brodak/K&B motor is a completely different beast than the 4011 and 8011.  These original two were of cross flow design with the piston having an intake deflector. The Brodak/KB version isn't even (I think) a schneurle design, much less a cross-flow, the intake and exhaust porting looks pretty weird! The piston is flat topped of course. I don't see how it can be a derivative of a reworked 4011/8011 engine (maybe I misunderstood the comment, or the rework was incredibly radical!)

HI Alan,

Mike Garmon had a lot to do with the "design" of the Brodak/K&B 40, AFAIK.  Mike was very familiar with Stan Powell's engines, especially since Stan and Dave Hemstraught were flying them at the time around here.

I do not know "exactly" what all went into the "design" of the "Brodak/K&B 40", but I do know we were comparing the characteristics of them to Stan's engines when they came out.    I am pretty sure there was an effort to get a very similar run from the "new" stunt engine since it was to be an "out of the box" stunt engine.  Something the earlier Stan Powell engines definitely were not.  Of course, the Brodak/K&B 40 was an ABC, flat top piston engine and not the Dykes ringed R/C engines that Stan had to rework.  The purpose was to get a modern metallurgy engine out of the deal, and to do away with the Dyke's rings which were problematic at times.

Bill <><

[Alan Hahn]

Just for fun, here is a photo of the intake ports of the K&B4055 (aka Brodak K&B40). The angle cuts takes the place of the piston deflector in the old 8011/4011. So I guess it is still operating more of less as a cross-flow setup, so maybe it is equivalent to the reworked ones.

[Air Ministry .]

If your worried about the RING , the IRVINE 40 ( SE & RE ) ones a Dead Ringer   NOT the ABC one though .
These are the 80s Schneurle things , and are 20.000 rpm plus . Seem to have tougher metal .
They take up any slack , bar one which had none - compared to the K&B Ring . Wether they still exist ? ?    



That looks pretty much like a Thewper Tigre Transfer .

[Stan Powell]

The best fuel I have run in my K&B 40's in recent years is Powermaster GMA, which is listed as 22% oil (50/50 caster/synthetic).  I understand Powermaster has been sold and rumor has it the new owner has made some changes in the fuel, so I don't know how the bew stuff works.  Sig fuels, have run poorly (caster-synthetic blend, or all caster).  Back in the 70's/80's, we ran all caster, but the engine did gum up after a while.

The 40 stunt motor that K&B made for a short time was an ABC engine.  I evaluated one for a friend.  It was nothing like my modified engine in any way.  It was poorly made and had zip for power.

Thanks, Stan Powell

[Air Ministry .]

Strewth ; theres a cance this bloke will know what stan did . 

Was there a artical published on your mods ?
did they ' edit ' it or were there omission .

c'mon , whats the tricks , please. kind sir .

[Balsa Butcher]

I remember there was an article by Mike Garmon in the PAMPA Newsletter on his mods to get the K&B/Brodak ABC 40 stunt to run better. My guess it would be in the early 90's. Someone may remember it also. FWIW:Many of the older newsletter are available on line at the PAMPA site to PAMPA members. Hope the edition this is one that is available.

[Jim Thomerson]

I have to confess that I ran about 10 gallons of green cruelpower through my K&B 4011.  I quit and went to Sig, because it was turning my airplane green, and my friends were making fun of me.  I flew my K&Bs on my Agile Arrow, at 720squares, and 52 oz., and on my Humongous, same area and weight.  I have several K&B 4011s.  The only problem I had was one day there was black around the drive washer and the front seal was gone.  I swapped for another engine, and in a couple of flights, the same thing happened to it.  On to a third engine, again same thing.  I was losing enough fuel (all this with the Humongous) that I could not get through an OTS pattern.  I put in new front bearings from Boca, and solved the problem.

I'm a midlevel Advanced flier, and my K&B 4011s ran to suit me.  I did manage a 17th place in OTS with the Humongous at the 1999 VSC.

[Balsa Butcher]

Back in the WAM (Western Associated Modelers) days we ran a K&B Sport Race series using 4011 engines and Buster/Shoestring/Cosmic Wind racers. Replacing front bearing was was commonly done. Other than that the engines held up well. 

[Mike Keville]

The K&B .40 (#4011) in this Super Duper Zilch ran on 10% nitro/11% castor/11% synthetic from Excalibur Fuels (Mark Smith, Avondale, AZ).  Easy start; plenty of power.

[Timothy Payne]

I run some of my old US nitro engines (K@B 29 3-bolt, McCoy 29, Frog 500) on Model Technics Contest 10 (10% nitro, 18% oil).

From this I make up the nitro content to around 17% (model technics again) and the oil content to 25% (using normal castor oil).

Tip: add the nitro first then work out how much castor you'll need as the nitro will have diluted the original castor %. (Better to have slightly too much oil than not enough - especially in these older engines!)

This formula works well with either hot or cold plugs to suit weather/engine.


Good luck,



Tim

[Bill Little]

I never really took the time to run my "Powell" K&B 4011.  But it is still in perfect condition!  I envisioned it in a Hemstraught PT-19 since I saw how PaPa Dave's ran so well and really powered the plane nicely.  Always had great engine runs!

Maybe one day I will get the chance............. too many models and now less and less time!

BIG Bear
RNMM/AMM