1QwkSport2.5r

Nice looking plane, AW. Looks like something I wouldn't mind building. Someday I'll have a .20, .28, and a .45.

I'm considering building another airboat big enough to hold both of my .65's until I get the Mig drone RTF.

Sport_Pilot

While this is true, it is very small. You will need a mike to measure the differance in wear from front to back and side to side in anything but the most worn out engines.

52larry52

My Feedback: (1)

I recently aquired a K&B Sportster .65 as part of a lot of seven used engines that I purchased. I had no idea what it was untill I researched it on this thread. It came with both rear cover plates. I removerd the one with the mounting ears to peak inside (nice and clean) and installed the standard one to fit the engine into my test stand to bench run it. I pre lubed everything inside with after run oil before running the engine and the bench test went very well. It's a good runner and was no problum to tune, ran a full tank of fuel thru it. It did leak exhaust residue at all the muffler assembly joints so after cleaning it up for storage I sealed all the assembly joints with a small neat coating of high temp silicone including the rear cover plate with the mounts which is the one to be used in the airplane. OK, here's the question.....I unknowingly left out the rear cover gasket when I reassembled it using just the high temp silicone. I found the gasket a week later and figured out it belongs to the K&B sportster. Is it needed for thrust spacing agianst the back plate or is it just there for sealing? Should I put it back in just to be safe? EZ to do, just four bolts add the gasket and reseal with silicone. I am looking forward to flying this engine in a Balsa USA phantom II bipe which I aquired partially completed in the same lot as the engine. Thanks for all the info I picked up from the previous posters on this thread.

earlwb

It is there for sealing. If it was really needed for thrust spacing you would have noticed it when you put it back on without it and turned the engine over.

spaceworm

+1` except sometimes the crank pin will rub the backplate when using an electric starter if the gasket is not installed. If you hand start then no problem. In any event, once the engine starts the propeller will pull the crank pin away from the backplate if the pin rubs only when pushed back against the backplate I would personally re-install the gasket. Your call though.

earlwb

There is normally a really thin steel washer that goes on the engine in between the drive washer and the crankcase front end.
Don't forget to put it back on. It is used for the electric starters so the drive washer doesn't wear into the front of the crankcase.

52larry52

My Feedback: (1)

earlwb and spaceworm, Thanks for the feedback. Yes, I do use an electric starter so I've set the engine out on my workbench and will reinstall the gasket tomorrow. The thrust washer is still there up front too. Thanks again for not letting me get lazy, I knew it should be put back in, I just sometimes need to be told!

1QwkSport2.5r

The crankpin will rub on the backplate with or without the gasket in, when the engine is idling with only 1 thrust washer installed anyway. At least mine does. When rpm is below 3000 on my .65, the crank moves in and out and gives that distinct "chatter".. Using two thrust washers made it move less but it still needs one or two more thrust washers to stop doing it altogether..

If the paper is already soaked with oil, it will probably leak oil. If you are going to use a gasket, I'd cut new ones. I use my All-in-one printer/scanner to make gaskets.

spaceworm

The crankpin rubbing on the backplate will create aluminum particles that will contaminate the glow plug element and cause the plug to fail. Also, any metal in the engine is not a good thing. A look at the exhaust oil will often show shining particles in the sun that likely is metal. I think that the pin rubbing the backplate under any condition is not right and should be further investigated.

1QwkSport2.5r

Has anyone tried running a high pitched 11" or 12" prop on a .65, something in the ballpark of 11x11 or 12x11? I cant find any APC props in pitch over 8" in the 11" and 12" sizes, though I did find an 11x9 that I plan to try.. Wondering if its worth ordering a 10 or 11" pitch prop....

NM2K

My Feedback: (14)

APC sold 11 & 12" diameter props with 11 & 12" of pitch some time back. However, they were not listed in the sport prop listings. They were listed as pattern props and they were not cheap.

It should not be difficult to find some used ones for sale at much reduced prices.


Ed Cregger

1QwkSport2.5r

I'll keep my eyes open when I visit the hobby shops. Thanks for the tip, Ed.

earlwb

I had acquired some of those 11x10 and 11x11 props a while back on clearance sale at one of our local hobby shops.
The size was popular on the old Drone .29 engines way back when. The engines didn't rev up high, so you needed a higher pitch prop, if you needed the speed.
I used some years ago on a plane that didn't have the ground clearance. It worked OK, but the landings were faster as the higher pitch prop doesn't help the plane to slow down though. It was on a pattern plane design anyway, so the landings being faster wasn't a problem. But it could be for some planes though.

turbo.gst

My Feedback: (8)

I have used 12 x 8 & 12 x 10 on my Sportster. As Earl says, they don't slow down on landings. I like using them when flying in high winds.

dennis

My Feedback: (90)

Did anyone ever see or have in their posession a K&B Sportster 91. They were made for the military and I'm trying to mail down the info as to it's accuracy. I thought I could mail it by the stamp on the backplate but 65's have #2 #7 #91 on the examples that i have. I'm curious because i wasn't aware of any casting changes to the case and cylinder throughout the production run but there could have been. The picture with the 4 thick fins is a 65. i havent checked the bore and stroke of the other but it is decidedly different with other subtle differences. Supposedly used by the military when they were using the foam floggers for shooting practice.

1QwkSport2.5r

There was never a sportster .91. The engines with the :91 on the backplate were the military engines, were .65ci, and they tend not to throttle well with the supplied carb because they werent designed to throttle well. I have two of these engines, :91 backplate stampings, .65ci displacement. Early sportster .65 engines had tall cooling fins and later engines had shorter fins to keep heat in the engine. With either a civilian sportster carb or a perry, they are sweet running engines. Use 0-5% nitro and 25% castor if you want it to run best.

dennis

My Feedback: (90)

Thanks for the information, It's really appreciated.

dennis

1QwkSport2.5r

I'm a Sportster fanboy. Always willing to share/help.

AmishWarlord

My Feedback: (5)

Did you guys see this .45 Sportster CL engine with spark ignition on ebay?

I was tempted but just got another car "2010 Subaru Outback" and don't have the funds for a shelf queen engine.

http://www.ebay.com/itm/150914188442...84.m1423.l2649

Anyone here buy it?

earlwb

It wasn't me. It does look pretty nice though. I am sure some vintage free flight guy got it for a big free flight plane. At least I hope they plan on using it and not putting it on a shelf for display.  I would have likely used a electronic CDI unit for ignition myself on a conversion like that.

1QwkSport2.5r

That engine didn't come from the factory like that, I'm pretty sure. Someone added the extra "junk" on. Sorry, spark ignition isn't right on a glow engine. IMHO.

I can't tell how many fins are on the head, that could be a .65. I think there's 12 or 13 fins on a .65 and 10 on a .45 I think.

earlwb

One thought about that  spark ignition K&B Sportster engine is that it probably does best running methanol fuel instead of gasoline. K&B shaved off a lot of the cooling fins on the head to improve its performance as it was running a little too cool as a glow engine. So as a gasoline engine it will likely overheat. But for free flight it wouldn't be a problem running either gas or methanol as the engine wouldn't run long enough for it to get too hot.

1QwkSport2.5r

I dont think Gasoline will handle the oil content needed by that engine, at least to keep it in suspension anyway. I could be wrong though. If it is in fact a .65, and it were mine, and I was going to try running it on gasoline, I'd try to find one of the early heads with the tall fins.

I'd never run it on gasoline though. The above is completely hypothetical.

jeffie8696

Those foamy target drones were hard to hit. And they flew full throttle the whole time.

1QwkSport2.5r

I'm surprised they were hard to hit. They're freakin' huge! I have one that needs to get finished to be flightworthy, but man is it big. Its longer than I am tall, and almost as wide. 5'7" WS and Fuse is 5'9" long. I think the sportster might be a little too anemic to fly it "well", though it will work. It might be a good candidate to run my ST S90 in.

The videos I've seen of them flying on YouTube shows them flying pretty slow with a .65 and 12x6 RevUp wood prop.