How to Drill out the Venturi on Plastic Backplates

Jaspur_x wrote:I have a few answers, but bear in mind I have never done anything with a plastic or horseshoe backplate,(yet, but soon will) so hopefully someone else can answer that better.
I did take notes on modifying a blackwidow or babebee. I`m not certain about the venom or killer bee, but the black widow did at one point have the largest diameter of the reed valve049`s, you could bore that out to .089", using a #43 drill bit and still hold reliability, but was advised not to go larger or sacrafice reliability and easy starting.
The plastic backplates, or at least the ones I have have the spraybar running through the intake port, therefore it should in theory be a larger diameter due to this interference of flow.
So bearing that in mind, my info may be of no help at all if your intake hole is already larger than that size.

If I didn`t help at all, maybe you have the info for your next project

Admin wrote:This is also better answered by someone else who has been doing it much more. You can remove the spray bar by removing the needle, and then remove the black plastic collar that is holding it in place (you should be able to get under it with a small flat head screwdriver or a small chisel if it is too hard to get between it and the backplate). You should also be able to push the spray bar right out once it is off.

Cox International wrote:Just use our red backplate:

http://coxengines.ca/product.php?productid=405&cat=25&page=3

as they are from the Killer Bee and already have the larger high-flow venturi hole.

Bernie
www.coxinternational.ca

Admin wrote:Are you sure it doesn't have a finer thread? My friend has a Killer Bee .051 and I remember noticing it has a finer thread then my regular surestart-product engine needles. I also tried it in one of my surestarts and I couldn't get it to turn in without ruining something. None of my post Estes ones have the finer thread valve. No, I'm not getting these backplates mixed up with the postage stamp backplates.

microflitedude wrote:I purchased the KB backplate, KB needle valve, and a few other small things today. I have done every thing I can to make a speed demon other than the insert head.

RknRusty wrote:Once I had a new KB backplate that had a loose spraybar that would turn when I turned the needle. Before I ever exposed it to fuel, I glued it in with JB Weld. I let it cure for several days, but it came loose again. Is there a better way to secure those? I had heard JB was the trick.

RknRusty wrote:

microflitedude wrote:I purchased the KB backplate, KB needle valve, and a few other small things today. I have done every thing I can to make a speed demon other than the insert head.

You mean like a Nelson head? I have a TD head you can use if you can't get one in time for Tach Race tuning.