MyWay

What do you think about this motor? Is it any good? Is it worth anything.

William Robison

My Feedback: (3)

Ron:

No opinion on the Sportster 28. But as I've already told you, I do like the Sportster 65.

The 28 is a half sized version of the 65, so if you don't like one I would think you also wouldn't like the other.

Bill.

Richard39

My Feedback: (14)

MYWAY, I understand that you do not like the Sportster at all, something like it is worthless, etc.. please ship wothless engine to me and I will pay for shipping cost...

MyWay

Your too late. I tossed them years ago. Tried to give them away but nobody would take them.

jessiej

I have had excelent experience woth the Sportster 65 and 20 but do not own a 28.

I do not know if you have had any experience with the sportsters or not but you have expressed distain for the 65, so you may be best served to avoid the entire line.

jess

Boomstriker

I have a sportster .28 from years ago. It's no power-house but it's been one of the most reliable engine I've owed.
I bought a new .65 hoping to get the same- it was a POS. The crank had way more play in the bushing than any new engine should have. It wouldn't stay running, wouldn't hold a setting and didn't have much power at all. I gave it away at a swap meet.
I bought it around the time K&B was in financial trouble and was being bought-out. I just assumed it was machined and assembled by employees that were about to get laid-off because I've had good luck with their boat engines and others.
Kirk

Richard39

My Feedback: (14)

Myway... you tossed them years ago but you are asking for info on them now...why? you do not have them and you do not like them but you like to write about them because ??????

William Robison

My Feedback: (3)

R39:

Did I hear someone say "Troll?"

Bill.

AmishWarlord

My Feedback: (5)

LOL good one Bill, even though your dead the jokes keep coming!

I just bought a vintage NIB K&B Sporster 28 off ebay. I can't wait to get it on the test stand and break it in! I'm planing on putting it in a rebuild of my first RC plane.

blvdbuzzard

I have many gallons of fuel through a K&B .28. It is in no way a super duper power house. It does run very well. It has about the power of a Magnum GP 25 or the old O.S. FP 25. It did like a larger prop though and castor fuel. My .28 HATED Cool Power all synthetic fuels.

Buzz.

earlwb

I have several Sportster engines four .20's and a couple of .65's. They worked fine for me, no problems.
I haven't run them long enough to ascertain their longevity yet though.
With these engines, some castor oil in the fuel is a must, the engines have to have it. If you run 100% synthetic oil in them, they'll be junk real fast.
All castor oil fuel might be better but a blend of synthetic and castor oil works well.

1QwkSport2.5r

I have two .65's, and I might grab a .45 sportster that my local rc car hobby shop has on the shelf. My running .65 (the other is still NIP) was broke in and ran on SIG champion which is 20% oil 50/50 blend. It ran well on it, but it ran a lot better on 20% all castor. You may remember me berating the carb on my examples, but aside from that they will turn 13" and 14" props without sweating. I have no experience with the .20 or .28 sportster, but being in the sportster line I wouldnt expect it to turn much faster than 13,000rpm and even that would be pushing it. If the sportsters are treated like 4-strokes, they perform well. If someone expects to go real fast, then the sportster is not the answer.

I'll say even a 50/50 blended oil isnt enough castor. I think all sportsters should be ran on 25% all castor fuel, and no more than 10% nitro. Because of the low exhaust timing and near non-existent blowdown timing, the compression is quite high. I worked the compression ratio (effective; all ports closed) out to 11.3:1. I will have to remeasure it, but even at 9.5:1, thats too high for 15% nitro. Mine overheated on 15% but ran okay on 10% nitro.


I would like to own at least 1 of every sportster engine. If the .45 my hobby shop has turns out to be in good condition, I'll buy it and then only need a .20 and .28.

flyingagin

I have owned two .20s and two .45s. I still own a .65. All ran good. Like to be proped tall. Prop em like a four stroke. Must have at least 50% castor oil in the oil and need a total of 22% to 25% oil. I would not go more than 10% nitro.

earlwb

I think what messes up some people with the Sportster engines, was that K&B tuned the engines to turn larger props like a 4 stroke engine does. So if you prop the engine more like a 4 stroke engine, then the engines work well. If you try using smaller props the engines run Ok but just not all that well.
If I remember my little .20 engines liked 9 inch props and even some 10 inch props and the .65 liked bigger 13 and 14 inch props. Of course I don't know if MECOA kept the tuning like that or not.

If I remember correctly, I haven't looked at them in a while, was that K&B had chromed the piston instead of the cylinder (I assume that was a cost cutting measure by the accountants). So the max wear stress point is on the piston at/on the exhaust port side. So using castor oil is a must to prevent the chrome from wearing off fast. Also the engine uses a plain bearing support crankshaft and castor oil works good there too. I had taken apart a .28 once and it looked like the cylinder used something like a hardened aluminum inside bore (no steel sleeve) as well, so using castor oil would be wise.

I have seen guys wear out or destroy a Sportster engine using as little as one tank of all synthetic oil glow fuel before. Which might explain where we were reading or hearing about bad engines. But then when K&B was nearing its end of manufacturing and business, they might have gotten sloppy and quality control could have suffered.

bolar

My Feedback: (5)

A lot of people don't like the Sportster engines but note the bias against synthetic fuel. My .20, .45 & .65 Sportster's from the early nineties have run almost exclusively on synthetic fuel, and are running like new. 20+ years of flying and I still haven't worn out an engine, and I have done a lot of flying.

I haven't experienced a MECOA-K&B and have been wondering how good they are since the change. Maybe I'll try one when I finally wear out one of my Sportsters.

turbo.gst

My Feedback: (8)

I have a Sportster of every size. They are very dependable, mild mannered powerplants. I have used the 28 on a '20' plane with good results. I have never had a dead stick in some 20 years of flying that 28. It starts great, idles perfectly and has a smooth throttle transition. Its just not as powerful as most others in its class. Application solves that one easily enough. My favorite size is the 65, but I like all my Sportsters.

turbo

buzzard bait

I had heard about the large prop capability and so picked up a new .20 Sportster. I gradually broke it in on 10% nitro, 22% oil (1/2 castor) starting with a 9x4, very rich at first, then leaner, stop, cool down, do over. At first it seemed very sluggish to turn over and didn't really flip properly, with very little compression. I had to start it with an electric starter. As break-in proceeded, it got freer and compression improved, and soon I was hand starting it easily. I kept putting on larger props and stopped when I got to a 12x4...it ran beautifully on that prop, from idle to full power! Not very fast, but absolutely no sign of strain, overheating or any bad behavior. Transition from idle to full power was just fine. This could be a great engine on an old timer or a scale model of something like a Cub or a biplane. It was very quiet with the big prop.

It was such a pleasure I picked up a new .28 too. Haven't tried it yet.

Jim

AmishWarlord

My Feedback: (5)

LOL, dang a 12x4 on a .20 with running glow no less.

I wonder if it would swing a 20x10 if you put a Davis Diesel head on it.

buzzard bait

It actually makes me wonder why I have diesels! I read somewhere somebody ran it on a 12x6.

AMB

I do have the 20 with a Davis Diesel head, runs very well and very quiet with stock muffler martin

buzzard bait

Martin, do you have any stats for us? Props and rpms?

I guess this is getting a little far afield. Sorry.

Jim

cutaway

PAW claims their .29D can turn a 12x6 at @9K.

earlwb

That sounds about right for the PAW diesel engine. I have a PAW .29 and a Aurora .35 but I haven't tried running them yet. My anemic OS 40LA engine as a diesel conversion turns a 12x6 prop at around 8,600 RPMs.
The K&B .28 might be able to do that with glow fuel too.

buzzard bait

According to an old RC Report review the Sportster 28 did 8600 on a 12x4. My 20 did 7350 on the 12x4, but my notes say the engine still felt a little stiff, so there may be more to come.

I would guess that dieslizing would improve performance on the large props, but I'm not sure about that. Maybe as long as the glow version is not overheating the glow fuel does just as well.

My PAW 40 does about 7300 on a 13x6. I'd be surprised if the PAW 29 would turn a 12x6 at 9000. They gave rather optimistic figures for the 40 too. Maybe they do a little better on CL carbs than on RC carbs, and they report the CL figures.

Jim

earlwb

If I remember correctly the K&B Sportster engines tended to have smallish internal bore carburetors on them. So they had a stronger suction for fuel draw when running. This gives the engines a better more easy to install and easy to use temperament, which is especially useful for new people getting into model airplanes. The smaller bore carb would also allow them to run better with larger props on them too.

A higher performance engine typically has a rather large size or bore carb on it and the fuel draw is poorer meaning you have to keep the RPMs up more by running smaller props. Too large of a prop and the engine can't adequately draw fuel to run properly.
For example, the Chinese clone engines tend to be like that as the Chinese put on really large size or bore carbs on the engines and it results in the engines having a rather poor fuel draw then.