New Killer Bee cranks

Here is the first video.

Nice engine, what were your fuel, prop and cylinder setups?

SIG champion 25%, cox grey 5x3 prop, Bernie's TD cylinder, teflon reed, and Killer Bee backplate.

I'm trying a different reed today to see if I can get it close to 20k.

Jason

I cant get that cylinder, piston combo to spin as fast as the Sure Start cylinder with shortened piston.
Still working on it, had problems with teflon reed went back to mylar.

I've had good luck with the new Tee Dee piston/cylinder using a full size lightened piston.

Great video! That thing looks and sounds great!

Do you lighten the pistons yourself, been trying to think of a way to do that.

Was running the engine in the video again today testing different reeds and I could no longer hold a needle setting. While looking for air leaks I found the crankshaft side to side play was excessive. While turning the engine over slowly I can see air bubbles leak out from between the crankcase and the drive washer. I pulled it apart and I did not see any of the gold anodizing worn on the inside of the crankcase bore. I can only assume the crankshaft is worn to the point it cannot seal anymore. I did notice a light grey oil coming out from the front of the crankcase while running the engine. I will get a measurement of the crankshaft to see if is worn down.

I installed the old version HD crankshaft in the same gold anodized and I am now able to hold 19.1k. I will load a video later tonight.

Ok here are the HD crankshaft measurements that have the air leak in the front. Front measures .217" and the back measures .216"

A babe bee crank front and back measure .2177"

A new made in china HD crank front and back measure .218"

Using SIG champion 25% with 22% oil.

I will run a few tanks through the other engine that has the new HD crank.

crankbndr wrote:Do you lighten the pistons yourself, been trying to think of a way to do that.

There was a machine shop across the parking lot from me at work that did it but I watched his machines get packed up and moved out last week. All I did was to take an example piston and a few standard pistons in to Ed the machinst and asked him to make the standard pistons like the example piston. I think I paid ten bucks a piston. It was sad to see him go.

Bob

Here is the video with the made in china HD crank in the same gold crankcase. Mylar reed, Cox grey 5x3 prop, and SIG champion 25%. Nice solid 19.1k.

That's super! It is difficult to turn that prop that fast. Nice job!

Here is my other killer bee clone with the USA HD crank installed in my custom turned crankcase. TD #4 cylinder, killer bee backplate, Mylar reed, and medium insert head.

Cox grey 5x3 prop and SIG champion 25%. Nice 18.2k out of this setup.

Good steady runs Jason. Now lets see some 25K+ TD's

Hmm... My KB clone got 18.5K with a defective crank.

We are aware that the cranks have a little more play than an OEM Cox Killer Bee crankshaft. The vendor who manufactured them did mention that they have a slightly smaller diameter than the approximate 0.217" of the Killer Bee specifications. Having said that, this should be consistent across the board, with all USA crankshafts within the appropriate tolerances. In further production runs of these I will ensure the diameter is increased slightly.

Before listing the crankshafts for sale I test ran a number of these crankshafts, and the results were positive. They improved performance and provided consistent runs.

One potential reason issues may arise is that there is both the crankshaft and the crankcase. If the crankshaft is at the lower end on the tolerance scale and the crankcase is on the higher end, it may result in 'extra' play. Since many Cox parts are interchangeable (especially reed valve engines) these crankcases can vary in age from the 1960's to the present. The varying in tolerances has changed slightly over the years.

In every manufacturing run there will be defects. It may be a machining error or grinding or something else entirely in this case. I am sure most of our forum members can attest that if there is ever an issue from a product we sell the issue will be resolved. If anyone buys something and is not 100% satisfied, it will be corrected.

Best Regards, Matt

Cox International wrote:And we concur with Matt.

The cranks seem to be of genuinely good quality and, should any have manufacturing defects, we also stand 100% behind what we sell and will replace any product that has issues.

please edit: "should NOT have any defects..."

happydad

Permit me to rephrase this:

And we concur with Matt.

The cranks seem to be of genuinely good quality.

Should any have manufacturing defects, we will replace such as we also (same as Matt) stand 100% behind what we sell.

Does a killer bee crankshaft increase rpm or simply tolerate high rpm better?

JPvelo wrote:Does a killer bee crankshaft increase rpm or simply tolerate high rpm better?

It's lighter, so in a perfect world it should be faster.

I got a brand new Killer Bee style crankshaft in the mail yesterday from Bernie (Cox International). I weighed it - and a stock one. My scale is a cheapo digital job that costs all of fifteen bucks.

Surprisingly, the Killer Bee crank weighs MORE than a stocker.
Stock cranshaft - 4.50 grams
Killer Bee crank - 4.84 grams

But the Killer bee has a much heavier web at the connecting rod pin. The killer bee also has a lightening hole drilled in the pin.
Overall I think the KB crank is just a sturdier version with about the same if not more rotating mass as the regular crank.
When the standard cranks fail, it is usually the pin that separates at the web where the metal is thinner than the KB crank.
I broke a crankpin off on a diesel conversion babe bee years ago. The increased torque snapped the stock crankpin.

So here's my take on the KB crank : If you soup the engine up enough with other parts, the crank will not fail like the stock one. I don't think it makes it go any faster.
Please excuse my crappy pics. I use a $40.00 camera and I just point it, shoot a bunch of shots and hope for the best.