ORIGINAL: flyingagin
I have a K&B .65 that has ssen a few hours, not yet worn out. It was a later date I think like 95 +- a year or 2. idled and transition well. OEM carb. Going in my current rebuild project. I have proped more like a 4 stroke and in it's current ride propping it just the same. I have hade 2 K&B .20s and 2 .45s. All that is left is the .65.
I have used 12x6 and 13x6 on mine perfer the later
They get a lot of direspect, but I find those who do just don't understand the engines or try to use them in planes that they are just not suited for.
I remember seeing thos drones in the mags way back when.
I hadn't ran my sportster for a year or a little more. I had forgotten what it sounded like.. (They make noises you wouldnt think an engine should make, even after 2-3 gallons of fuel) I ran mine with 13" props after finding the 11 and 12" props didnt do the engine any justice. It'll turn faster than the MFG claims, but their good power is down low. Below 11k. I'm sure they will turn a 14x6 at 10,000rpm. Based on my runs today, I only lost 70rpm from the 12x6 MA-k and the 13x6 APC. This engine also has a high compression ratio and almost no blowdown period. Its got "poor mans 4-stroke" written all over it (along with burnt castor slime too)
It slimed the crap out of my test stand - bushing has a little wear on it. More than I remember, but the compression is still great and it has a good steady rpm at WOT. I peaked each prop, and then richened it 200rpm for about 2 minutes and swapped props.
My running .65 has no baffle in the stock muffler, and I found no muffler pressure to make it puke from the front bushing far far less.