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Joined: 9/21/2007 From: las vegas,
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For kicks I Desided to send off my K&B MR. Lee for the pdp mods and stuffed it in my Model tech mach racer. I am wanting to keep the rpm down to the 12,500 mark. Right now its taching a little over with a 11*9 APC prop. Any suggestions to keeping the rpms down and not going with a larger prop as I cant do this since it will be to close to touching the ground.
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Joined: 12/17/2004 From: Martinsville,
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Go to a 3 blade prop and drop down to 10" while your at it........... http://www.masterairscrew.com/index.asp?PageAction=VIEWCATS&Category=12 Or even a 4 blade that can be expensive. I think the 10x7x3 would not go past 12,500, but none of my K&B's are PDP. The 11x7x3 would surely work...........
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I'd drop to a 10x9 or 10x10. One of the Jett .90's uses this same prop. Not that the Jett .90 has anything to do with your K&B .61.
I wouldn't expect massive torque from the Lee modified K&B .61 PDP.
Some of the earliest K&B .61's were screamers with an 11x7. The later editions were much more sedate. Fortunately, spare parts (crankshafts) aren't that expensive to replace, as long as you don't hole the crankcase.
Ed Cregger
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Thanks for the input. Ill try the 3 blade and see what that does. I didnt want to adjust the end stop cause we all know that 3/4 open on most two strokes is almost max rpm anyway, atleast all the ones ive played with. I have the throttle curve set on the transmitter so that have throttle is have the rpms, etc. ITs something to play with and Ill let you all know this weekend how it went
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I would tach it with a good 11x7 prop and use that RPM number as the baseline for other props. I agree with Ed that the crankpin is the thing you need to be careful about.
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Take the gear off and hand launch or make a launcher out of PVC and don't worry about the size of the prop. I have used the same launcher for different planes.
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I just returned from the flying field and I have to say that the engine is a very fine running machine. I have read people compare the k&b .61 to the new 40 size for power wise. I have ran mds .48 os 46ax and others in the mach racer and the k&b by far out does them all. I fly a p-51 with a magnum xls 61 and I would say its right there with it. I have to give MR. lee is due for building a engine back in the days that still has its place today.
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quote:
ORIGINAL: RSOSKE2
I just returned from the flying field and I have to say that the engine is a very fine running machine. I have read people compare the k&b .61 to the new 40 size for power wise. I have ran mds .48 os 46ax and others in the mach racer and the k&b by far out does them all. I fly a p-51 with a magnum xls 61 and I would say its right there with it. I have to give MR. lee is due for building a engine back in the days that still has its place today.
The old top of the line, baffle piston sixty engines, weren't that far off in power from some schneurle ported engines. Even though it is a baffle piston engine, it is still a .60 and it is usually capable of swinging more lumber than any highly tuned .40 - .52. We would all like to think that our newer smaller engines are more powerful than the older sixties, but, truthfully, they are not.
Ed Cregger
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quote:
ORIGINAL: Ed Cregger
quote:
ORIGINAL: RSOSKE2
I just returned from the flying field and I have to say that the engine is a very fine running machine. I have read people compare the k&b .61 to the new 40 size for power wise. I have ran mds .48 os 46ax and others in the mach racer and the k&b by far out does them all. I fly a p-51 with a magnum xls 61 and I would say its right there with it. I have to give MR. lee is due for building a engine back in the days that still has its place today.
The old top of the line, baffle piston sixty engines, weren't that far off in power from some schneurle ported engines. Even though it is a baffle piston engine, it is still a .60 and it is usually capable of swinging more lumber than any highly tuned .40 - .52. We would all like to think that our newer smaller engines are more powerful than the older sixties, but, truthfully, they are not.
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Joined: 9/21/2007 From: las vegas,
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I am starting to think that way. Went out again today and even the jet flyers were asking what engine im using, and they dont beleive its a old 70s. The older crowd at the feild remember when they used these and are thinking of going back to them after they saw the results. I like this better than my os engines by far. And its runs much better than them on the 5% nitro. I have had no trouble with the perry carb that the old timers said would have problems
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Mach racer and K&B .61 ringed PDP - 
