Hello, folks. Just acquired several airplanes and engines today, and along with the lot came a K&B engine with no indication as to size. It is fairly large physically, only four bolts securing the head, weighs in at 13.8 ounces, and has stamped on the left mounting lug "J2900045 and "made in USA" just above the lug. It has in large raised letters "K&B" on the right side of the engine above the mounting lug. That is all of the markings on the engine. It has a huge (wide)carburetor, and the head is as large as most 60's and 70's I've seen. Do any of you K&B folks out there know how to determine the discplacement of this engine short of measuring its bore and stroke?

Without a picture, I will take a guess. It sounds like you have an K+B Sportster engine, maybe a .65 .
Does it look like this, the older version did not have the remote needle valve assembly shown here. It may have the backplate engine mount that was included with the engine.
The Sportster series was made in a .20, .28, 45, and .65 .

At a weight of 13.8 ounces and with that lug number ending with, 45 I suspect it is the Sportster .45.

I also suspected that, but I checked both of my .65 Sportsters. They are both older versions, but just had "A 65" stamped on the right lug. Not a long set of numbers like he has, so I am not sure if what he has is a serial number or product number. Mine were made when K+B was still in Downey California and have the needle valve on the carb. Thats why I gave him a list to choose from.
Jollypopper, the Sportster series engines have a muffler that is a long and thin and is a two piece design. The mounting bolts go through the engine case, then through a seperate mounting flange and then into the muffler chamber. The Sportster engines are not by any definition a "High Performance" engine. They are however, very long wearing reliable engines. Feed it a high castor based fuel, 5-10% nitro and most importantly, prop it like a 4-stroke. These engines will produce lots of torque, not high RPM's. I have said for years that the .65 Sportster would be the ideal inexpenive engine for a Senior Telemaster or Senior Kadet. Its perfect for a big floating trainer thats not supposed to go fast!
If you try to push RPM's or mount it on a performance or 3D airplane you will be disapointed. It is what it is, a good long lasting reliable engine, not a fire breathing monster.

Way too large for a Senior Kadet. I thought a TT .46 was too much power. I had that engine pointing down at what looked like a 30 degree angle down before it would stop climbing straight up on full power.

That is a characteristic (and a preferred one) of most flat bottom trainers. When the student gets in trouble he adds power and lets go of the sticks. The airplane levels itself and it begins to climb. The Kadet was designed that way.
I have flown a Senior Kadet with the .65 Sportster and it was a perfect match. Large prop, (14x5) turning 8,600 RPM and idling at 1,700 RPM. Just because the left stick goes all the way up, doesn't mean you have to push it that far. I could take off at 1/4 throttle and it looked like the airplane was flying in slow motion. It would do BIG SLOW LOOPS all day long at 1/2 throttle. With that big prop idling so low I could stop it dead in the air with a little headwind.
The Senior Kadet is a big, lightweight trainer. The .65 with a big low pitched prop would pull it through most windy conditions with very little effort. The heavier engine weight also helped its flight characteristics in the wind. My kadet had some downthrust but nothing extreme.
Your TT .46 (if its like any of the the 5 I have) is putting out pretty decent RPM's at full throttle and is trying to pull the airplane at a much faster speed. Thats why you are getting all the lift.
The Sportster .65 is all low end torque with a big prop, power not speed. Thats why I said you need to prop it like a 4-Stroke. If you try to treat the Sportster series of engines like current production ABC smokers, you will be disappointed. Its a puckety-puck kinda engine that really shines on big lazy, slow flying airplanes, and will last a lifetime.

It was designed to climb when power was added with a .40 engine, not go over on its back in a large egg shapped loop!

It flies perfet with a .40. With the .46 I was wasting the engine flying it around at 1/2 throttle. A .65 would be a larger waste. A plane ole K&B .40 works just fine, though thinking about a slightly hotter .40 for hot days.

Thanks for the replies, guys. The engine looks identical to the one CCRC1 has pictured with the exception that the needle valve is in the side of the carb instead of on the back plate. For some reason, I believe that this is a .45 size engine, but it is massive for a .45. I have a Tower .46 in my collection and I thought that thing was physically big, but this thing is even bigger. I just went out to the shop and got a digital caliper to do a couple measurements on this thing. The crankcase just under the mounting lugs measures 1.435 inches (36.4mm) and across the head measures 1.807 inches (45.9mm). That just seems huge for a .45. Funny you guys mentioned a Senior Kadet as that is exactly the airplane I was thinking about using it in.

Jolly Popper, here's a few shots of my .45 Sportster. Note the 45 stamped on the edge of the right mounting lug. Mine will tolerate 5% nitro max. My head measures 1.780". My under the lugs measurement is the same as yours, 1.435".

A little more info on the Sportster series JollyPopper. There is no sleeve in the cylinder. If you score the cylinder somehow, it's throw away time. Being a loop scavenged engine, an idle bar plug seems to work best.
And like CCRC1 said, lots of castor for this plain bearing engine.

All of the Sportster series were kinda large. If you think the .45 is big, wait until you see the .65
TimC is correct about the glo plug also. Mine seem to like the K+B long w/idle bar. I have had the best luck with 5% Sig fuel with 20% all castor.
If you need parts, they are still available from Mecoa
http://www.mecoa.com/

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I have flown a friend's Kadet Senior that had ailerons added and most of the dihedral removed. It was powered by a K&B .65 Sportster and was not over powered at all, surprisingly enough. Yes, downthrust is needed with any flat bottomed airfoil equipped model that hasn't had a bit of positive incidence added to the horizontal stabilizer, ala the Goldberg J-3 Cub.

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All of my Sportster engines are schneurle ported. Not a baffle on a piston anywhere. <G>

Mine is kit built and flies fine with a .40. I added strip ailerons and took out some of the diehedral. Seems to fly slightly better than the ARF. At leas the ARF I saw with a .40 did not seem to climb as well, or maybe they don't have the technique down, for if you pull up too steep as though it had more power it will bog down. But if you let it build up some airspeed and gently pull up it will climb out very well. Makes a better trainer that way. Lots of modelers seem to think you should jerk the model off the ground, works when overpowered, but teach's bad habits. And yes I increased the down thrust with a .46, the stock downthrust seems sufficient with a .40. With a .46 and the stock downthrust with a 11-4 prop it would do a hans off loop with no down trim. It was probably a bit tail heavy at the time.

It does seem to climb poorly on 95+ degree days, but then only when right over the runway or close to the ground. I think a .40 that is slightly hotter than the K&B or maybe a 50 sized four stroke would be ideal.

You are correct on the measurement of the head, TimC, it is 1.780. I was reading the caliper inverted and must have transposed the 7 and 8. I guess we can be certain that this is a .45 now, and I will treat it as you guys suggest with 5% nitro and 20% castor. This thing seems to be in very good condition, probably an 8 on a 10 scale. There is virtually no darkening on the side of the pistion, has very good compression, and the bearings are silky smooth. Probably be a good engine.

Artisan, it's been four or five years since I've had my Sportster apart. I guess I got it mix up with one of my other K&B's. Thanks for the correction.

The Mecoa site advises you can identify the .45 by counting the cooling fins on the engine case. The .45 should have 10.
By the way if you are a K+B fan you should spend some time at their web site. It is loaded with info and advice. It also has a very good question and answer forum.

All of the K+B Sportsters were Schneurle ported engines.
They are still in production and all parts are available. You can even get a replacement older style carb if you need one from Mecoa.

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I don't doubt what you are saying one little bit. My last one was powered by an HP .49 VT, which is probably even less powerful than your two-stroke .40. I could have used a bit more power on days when the grass was getting tall, but, once airborne, even the low powered HP .49 VT could be throttled back to under half throttle for training purposes.

I was amazed at how well the .65 seemed to work on this model. The owner used a very large diameter, low pitch prop on his .65, now that I think of it. It made it really easy to spot land it because of the drag of the large prop disk. An unexpected plus, that would have worked just as well with a smaller engine and a similarly large diameter, low pitched prop.

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The only reason that I know, Tim, is that I bought what was supposed to be a K&B .61 from a fellow modeler a while back and it turned out to be a .65 Sportster. I took a gander in the exhaust port and there was no baffle there. If it were not for that experience, I would probably have agreed with you. You can't remember everything.