Author Topic: K&B 40 Engine (Read 6427 times)

Steve Dwyer · « **on:** April 26, 2016, 05:29:59 PM »

I recently bought a NIB K&B 40 control line engine, there are no operating instructions with it. The box has the number 4055 C/L on it, I have looked thru the K&B information at the MERCO site but cannot find anything on this 4055 engine. I've reached out to them but they are slow. I'd like to know if it is the older style steel engine that must have a high castro oil fuel similar to the old Fox engines or is it the newer style mixed alloy engine that uses a synthetic blended fuel. Looking into the exhaust port it has a ringed piston. Is a ringed engine reliable, what's the best method to run it for the best longevity? It's a beautiful engine but a little beefy compared to my OS LA 40 or my OS 40 FP engines and weighs a couple ounces heavier. I haven't found much written about it, is this a good engine? What about it's power and how does it compare to a 46 size or larger engine? Is it a good performer and where is it best used?

If anyone has the break in and operating instructions I'd appreciate getting a copy from you. Any information regarding the performance I can expect would be good to know, K&B MERCO shows two 40 size engines which are presently not available?? Is this a boat anchor, I didn't pay a lot for it, it came by way of an estate sale.

Will appreciate your input,

Steve

George Truett · « **Reply #1 on:** April 26, 2016, 07:20:30 PM »

From what I have seen, your information seems to be conflicting. I have a 4050 version which is the RC engine with ABC piston/liner and a special tuned exhaust. It's a great little engine for the money but I don't know how good it would be for stunt. The 4055 is supposed to be the venturi equipped version of that engine. I have several of the old 4011 with the ringed/baffle type piston. Can you take the head off and see if you have a flat top piston?

Air Ministry . · « **Reply #2 on:** April 27, 2016, 01:13:55 AM »

They do do a ringed version of the beefy nose , baffled .

think it was the one I tried for ' the wind ' in my High Loading

MB3 Martin Baker .

Used a 10 x 4 3 blade , and had it wound up some , with a pumper backplate .

It still came on & off under load & downhill , respectively . Pump was to keep the gas up to it in rough Air .
Surprised the run wasnt much differant without the pump , setting was close , say 1/8 turn max. differance .

Steve Dwyer · « **Reply #3 on:** April 27, 2016, 05:36:36 PM »

Matt and George,

The box clearly says 4055 (handwritten) it could be a mistake and should be 4050. The piston is a flat top and there are what appears to be 3 piston rings. The back plate has a location in the casting for a hole to be made but there is nothing to indicate a pump should be attached. I cannot send photos with this message my camera is set for too large a picture, if you send me a personal message with your email address I'll send you the photos to help you identify this engine. I found one running on a bench on u tube but their was nothing describing what fuel to use. still wondering if this is an ABC engine?

Steve

George Truett · « **Reply #4 on:** April 27, 2016, 05:50:54 PM »

Steve,

I just looked at 2 of my K&B 40s, the attached picture is a 4011 ringed engine of which they sold tens of thousands I'm sure. You can clearly see the baffled piston. The 4050 is flat top and ABC as the 4055 should be. I think what you are seeing are grooves (maybe to carry oil) and not actually piston rings. I have the original 4050 manual which I can scan for you but honestly it has little of value in it. They recommend K&B 500 fuel which is long gone. K&B never listed the oil content but it was believed to be around 18% and at least part synthetic. K&B had their own synthetic oil they called X2C. I would use a good quality castor/synthetic blend of 20% total oil or more if it were me. George

Steve Dwyer · « **Reply #5 on:** April 27, 2016, 07:34:51 PM »

George I think we are on to something here, looking under a magnifying glass the 3 grooves at the top of the piston appear to be just grooves and not rings as you said. The cylinder sleeve appears to have a brass color on the outside when looking into the exhaust port while the inside of the liner is silver, the top of the piston is definitely flat unlike the photo you attached. So you are confirming this CL 4055 is an ABC engine and I should use a blended fuel. What percentage ratio of synthetic and castor should I use? I have a good deal of fresh 5% nitro 29%castor I use on my old Fox 35s. Will this gum things up? How high a % of nitro would you recommend? I probably don't need the operating instructions, do you recommend I run it 180 degrees richer (with a lot of smoke) than optimum setting for a tank or two to break it in?

Appreciate your help,

Steve

Air Ministry . · « **Reply #6 on:** April 27, 2016, 07:57:10 PM »

Keep it in a TWO STROKE ( ABC ) read supertigre pamphlet .for pinch fuel line trick .

50 / 50 C / Syn.

Steve Dwyer · « **Reply #7 on:** April 27, 2016, 08:09:16 PM »

George,

I'll order some fuel tomorrow, last question how would you compare the K&B 40 to the OS 40 FP and OS LA 40 or is it closer in power to the OS LA 46?

Steve

George Truett · « **Reply #8 on:** April 27, 2016, 08:21:38 PM »

Steve,
I have never flown a K&B 40 on a CL stunt model though I have flown many R/C. I think it is heavier than the OS, I can weigh them tomorrow. I know the 4050 surprised me on a Delta model I had. Not in the class of a Nelson or Jett but well beyond the old 4011. I don't think you'll ever get a 4-2 break on a 4055 but running a lower pitch prop at a 2 cycle might work for stunt. When I recently got back into stunt I decided to go with the OS 40 FP on 40 size airframes and I have been happy with that decision so far.

Steve Helmick · « **Reply #9 on:** April 27, 2016, 09:17:59 PM »

The #4055 was manufactured for Brodak, by K&B, not MECOA. Can't say if the cylinder is the same as the #4050 or not, but I always thought it strange that a 3-port (intake) engine would have a single bypass. Funky!

Yes, I had one, and flew it awhile in a Humongus. I wasn't too impressed with the power, but perhaps had the wrong prop on it (Taipan 11-5). I pulled the K&B and put in an OS .46LA and it was MUCH more power (11.5 x 4 APC). Anyway, the OS was lighter and more power (I ran a MACS Muffler on it), and the K&B went away.

You might see if Brodak can provide any information on props and fuel, but rest assured that it is an ABC and will be happy with any good fuel, meaning 20%+ oil, some of which should be castor. See Randy's pinned articles at the top of this forum!

Steve

Steve Dwyer · « **Reply #10 on:** April 28, 2016, 05:25:47 PM »

Thank you all for your help finding out what I needed to with this K & B 40.

Steve

Dave Holtsclaw · « **Reply #11 on:** April 28, 2016, 06:17:13 PM »

This is from the instruction sheet from Brodak
Fuel 5 to 10 percentnitrowith 24 to 29 percent caster oil synthetic is not recommended
Prop10X6 or 11X5
The engine should be run in a fast four cycle and break into a two cycle when the nose of the model is pointed up. The engine is ready for flight when it will hold a two cycle setting with no signs of sagging
Fuel tank should be 1/4 to 5/16 in above center line of engine
For airplanes up to 660 sq in wing spans to 58 in weight to 55 oz
My engine is nib and has all the instructions as I bought it new from Brodak. Hope this helps you out.

George Truett · « **Reply #12 on:** April 28, 2016, 06:59:08 PM »

Dave, Are you certain your engine is the ABC version?

louie klein · « **Reply #13 on:** April 29, 2016, 05:43:33 PM »

I have 2 of these motors in great shape that needs venturies and nva's. Would you be able to give me the spec's on the ventury and what type of nva they have. Much appreciated-Louie

Steve Dwyer · « **Reply #14 on:** April 29, 2016, 06:08:10 PM »

Gents,

I received a response from K&B regarding the engine and the fuel, the 4050 was the RC version and the 4055 I have is the control line venturi version both identical engines except for the carburetor and both are ABC engines. Refer to the following link regarding the recommended fuel. http://www.mecoa.com/faq/fuel/fuel.htm Essentially for this engine they recommend 20% oil at a 50/50 blend of synthetic and castor.

Thanks again

Steve

Dave Holtsclaw · « **Reply #15 on:** April 29, 2016, 07:48:30 PM »

Yes it is, this is from the instruction papers that came with the engine. It said 4055 K&B 40 ABC I looked afain and there is no ring

George Truett · « **Reply #16 on:** April 29, 2016, 08:32:04 PM »

That is really odd, I just can't see using 29% castor in an ABC, ball bearing engine.

Dave Holtsclaw · « **Reply #17 on:** April 30, 2016, 08:31:12 PM »

Doesnt sound right to me. Thats whats on the instruction pages. Ive had good luck with all synthetic

Steve Dwyer · « **Reply #18 on:** May 01, 2016, 07:34:07 AM »

Steve,

It sounds to me as thou the K&B 40 is not much on the power, especially when compared to a lighter OS LA 46. Makes you wonder if poor performance was Brodak's reason for getting away from it. I wonder if anyone out there has a positive experience with the 40? Was this a late 70's into the 80's engine? Funny K&B shows it is still offered but not in stock or "in progress" ?? I'd did hear from a gent a while back the 40 was used for racing seems confusing for sure.

Steve

George Truett · « **Reply #19 on:** May 01, 2016, 09:09:11 AM »

Steve,
The original ringed K&B 40 goes back to the 60s. They went through several upgrades, the front end changed from a slim pinned arrangement to what they have now. They began offering the PDP mod probably in the 70s trying to hang on when Schnuerle porting began to show up on model engines. They were good engines in the day and used in a lot in one engine only events like regional Q-500. There was a rear intake version that ruled R/C Formula 1 prior to the ST G-40. They sold many of them over the years, simply outclassed by more modern designs. I got my first 4050 with ABC piston/liner probably in 96. On a Diamond Dust delta (R/C) it was a great, relatively inexpensive engine choice. With its tuned muffler it was lighter and faster than current sport engines of the day like the OS. Like most of the engines offered by MECOA, it is an old design kept alive mostly by nostalgia, in my opinion.

Steve Dwyer · « **Reply #20 on:** May 01, 2016, 10:52:41 AM »

George,

Thanks for the background on the K&B, so it had it's day when compared to the early OS engines, interesting. I'm almost finished with a Mickey Pratt kit Primary Force silk and dope job, I plan to use a new OS FP40 I bought and converted over using a RMS ST needle valve assy. venturi and head gasket. I haven't run the K&B yet, it's a beautiful looking nicely built engine but it's heavy compared to the OS FP and possibly a bit too heavy for the Primary Force. I have on the docket to build a scratch built Pathfinder Profile it's up there in Sq. In. area perhaps this would be a good fit or should I plan to install my OS 46 on it? What models did the K&B find itself on in it's heyday. Thanks again for spending time on this subject.

Steve

George Truett · « **Reply #21 on:** May 01, 2016, 11:10:19 AM »

Steve,
I have probably owned 20 or more K&B 40s and another 5-10 of the racing 6.5 which came later. They were good, even great engines in their day, especially the 6.5. Having said that, I have never flown a K&B 40 (or 6.5) on a CL stunt plane. I did a search on the forums and found where some reported success with your engine (4055). I weighed mine and found it over 2 ounces heavier than an FP 40 with no muffler on either. I think if you were persistent in experimenting with props/fuel, etc., you could be successful with it. I think more people are probably having more luck with the LA 46 these days on stunt planes. Again, just my opinion. George