Carl,
The K&B 40's are pretty good. I have one in my YAK-YAK that I use in Super 52 Unlimited event. It likes to run in a fast 4 with an APC 11x5, 0.275 venturi and an ST NVA. I run Sig 5% 50/50 fuel. Some have run smaller props like the Rev up 11x5 cut to 10.5". If you do a search on this forum you will find lots of information. The only down side is it is about 1 1/2 oz heavier than the OS LA40.

I like the ability to flip the case to point the exhaust to the outside of the circle (I don't like looking at an ugly muffler hanging off out), it makes the fuse looks cleaner to me. Any muffler that fits the OS 20FP or LA will fit the K&B 40 (I use a tongue muffler from RSM).

Mine start well with a few choke flips then half a dozen flips, put on the glow driver and back flip - off it goes. Once in a while (if the glow driver is a bit low) I have to use the starter but not to often (because it's ball bearing it works well with the starter it that's your preference). I also use after-run oil at the end of the day, keeps the ring from sticking.

Best,         DennisT

Hi Carl,

Les McDonald won a World Championship using a Stan Powell prepped K&B .40.

BIG Bear
RNMM/AMM

Dennis
it still comesup zilch

Hi  To do what Stan did, you need to send the Sleeve out to be chromed, it will help if there is a slight taper honed into the fresh sleeve, then the sleeve needs to be sized just slightly smaller, 1 to 2 thou, this will make the piston fit better, and you will be able to get a ring with a tight gap. Then you should find a small front end, replace the bearings with a phenolic rear and sealed front, of good quality. If this is not possible, try to find one of the ones  BRODAK sold with a ABC  piston/sleeve, or finds anyone else who made them and has one for sale.  The get a 280 venturi/restrictor for it with a GOOD Needle Vavle assembly .
Most ALL stock one I saw , have too much clearance in the piston, and the ring was open too much on the GAP  stock/new.

Regards
Randy