OK Cub .049

Thanks Bob, That is a nice looking group you have there ….. Actually the finish is just how I received it…. Looks like case may went through a tumbler or something at the factory…. I’ve read these later ones were a little hit and miss in quality control so I’m  just  glad I got it to run at all….

I had one of those 0.049A. Wore it out in one afternoon's flying (maybe 40 minutes?) all castor fuel snow on the ground so no dust or overheat. At the end of that day zero compression. Guess I got one with a soft cylinder?

The aluminum extension tube in the venturi stack is killing performance. It's like trying to breath through a coffee stirrer.

I got two like it when they were going out for the last time , decided to run one like to never got it started like you said needs to bee about flooded to start and run . Needled pretty good with not a lot of power , it started better after first run but still needs a spring if you ask me LOL Cleaned it put it back up for now !

Jim, Not sure why yours failed, But after reading up on them from a few sites on the net including here, It seems a random very few do wear out in a very short time… Others seem to have a decent life span… I don’t have enough experience with them to really know…. I only ran a few tanks thru mine and compression seems the same as when I started…It’s interesting to note that the Bee’s mounting screw pattern is the same as the Cub….. I’m guessing that was by design…

I don’t doubt Ken that the tube on the venturi is restrictive…. It is however .080 in diameter, larger than a Bee backplate….I may not be able to use that comparison though due to different  induction methods….I read somewhere one time (can’t remember where) they were installed as sort of a patch to help poor fuel draw or starting or something of that nature …. It does look like some kind of after thought …. The one on mine cracked the case a little when it was installed…

Thanks for sharing your experience Eric…. Sounds alot like mine…. Does yours have the pressed in venturi tube?

The venturi extension places the air intake higher than the exhaust ports, so that it draws clean air, not spent exhaust gas. I think on the Comet models it helped to keep the intake outside of the cowling

I have never had a OK Cub, but my guess is the most power-robbing part - as in COX engines with normal conversion heads- is the conventional glow plug whose thread gaps add to the compression space of the cylinder and reduce the compression ratio. It would be interesting to see how this engine re-energizes with a high compression Tee Dee head or let alone, a Kamtechnik turbo head...I am not sure if the OK Cub cylinder top thread dimensions allow the use of these, though..

balogh wrote:I have never had a OK Cub, but my guess is the most power-robbing part - as in COX engines with normal conversion heads- is the conventional glow plug whose thread gaps add to the compression space of the cylinder and reduce the compression ratio. It would be interesting to see how this engine re-energizes with a high compression Tee Dee head or let alone, a Kamtechnik turbo head...I am not sure if the OK Cub cylinder top thread dimensions allow the use of these, though..

Some of the later Cub .049s had a glow head that was interchangeable with a Cox one. The previous model Cub which used a standard glow plug had the same set-up as the earlier Cox heads, having the head seal at the top of the threads rather than the bottom. I'd suggest they would have had a huge improvement in performance using the later glow head.

I couldn't find the one I was running this was the other but I feel sure it's the same bought 2 at 1 time