Still patching last year's leftovers before starting any new projects. Trying to get a little more power for my Hyper Viper w/o changing engines. I have a Tee Dee .051 with the typical busted plastic carb body, thinking about putting the piston and cylinder on the sure start crankcase and back plate. Any thoughts about fuel draw through the sure start backplate and needle being adequate?  Is there a difference in the backplate and needle valve for a killer bee, i think those are still available. Any "hop up" thoughts would be helpful, would like to see around 18,000 rpm with a 5x3 prop staying with the sure start type backplate. Thanks, Ray

Quote by Larry Renger:
"As I recall, we found that the 5x3 black prop gave enough more rpm to make up the difference in diameter and produced the best flight performance.

Of course, a drilled venturi, Tee Dee piston and cylinder, and Galbreath/Nelson head would help too.

There was an article I did in the October 1974 issue of Model Airplane News (they actually did CL stuff then!!!) called "Super Tune your Super Stunter" telling what I knew then about making it perform extra well."

The Super Stunter has a backplate similar to the Hyper Viper but the engine had a single bypass cylinder. The one you have already has a double bypass like the Tee Dee so swapping is not likely to help.
Playing with the balance point could do a lot for performance and also trying to shave some weight anywhere you can especially around the tail feathers.

Larry is a good guy to,deal with but for several months now has been going thruogh some tough personal problems including a vehicle accident and a serious heath issue with another close family member. He has not been heard from in a while. When he gets back on his feet get the head from him. I hear they are the cats meow!

Robert

Not exactly sure about the name venturi, is it the fuel hole in the spray bar or the hole where the reed goes..

The venturi is indeed the air passage.  You need to remove the brass spraybar to do the drilling operation. 

First, remove the backplate from the engine and the sure start pipe unit.  Remove the reed valve and gasket.  Now, remove the needle valve and spring, then pull off the black Nylon seal.  At this point you can push the spraybar out the bottom of the backplate using the flat of a screwdriver blade so as not to damage the threads inside of the spraybar.

Drill out the venturi hole to match it's maximum diameter, thus removing the flat restrictor sections.  You can go about 1/32" larger diameter if you want even more power.  Clean the backplate thoroughly with soap and water to remove all plastic "crumbs".

Reinstall everything.  Be sure that the fuel jet hole in the venturi is pointing just out of sight to either side as viewed from the rear.  The ideal position is actually 15 degrees below straight across the venturi.  This position provides better fuel suction than the factory's straight down the pipe setting.

HI Ralph. That web site won't come up as printed> 

Ty, the above link has an error, try:
http://www.kittingittogether.com/

Drilling the venturi can be frisky bidness.

If you make it TOO BIG if won't draw fuel in stunts (or maybe at all). 

Be sure you drill to a known workable size and have plenty of spares on hand unless you have a UNdrill.