New stage 2 racing cylinder head available!

Hi everybody!
I just finished a tiny initial run of the newest CR Machine cylinder head. Sorry, it's not for the 49cc engine. It's for the 66 cc engine with 8 MM studs.
I came to realize that it is impossible for one cylinder head design to allow optimal performance for every engine configuration.
This head is designed for highly advanced race engines. Engines like this have enhanced port size and flow characteristics, and employ large, well tuned exhaust systems. Because of this, a lower compression version is needed. Simply adding another gasket is a compromise. Instead, the stage 2 head has a different, taller combustion chamber shape and a wider squish band. The head has been tested in our test bike and passes with flying colors. I was able to get beautiful results from a stock ignition system.
Here is the link to my ebay store if you want to take a look at it there.
http://www.ebay.com/itm/Motorized-b...es&vxp=mtr&hash=item1e71f5ab9f#ht_1148wt_1111

I'm not done yet either, soon a twin spark plug version of that head will be available soon, God willing. It will have the same combustion chamber design as the stage 2 head, but with 2 spark plugs. That head will be the stage 3 version.

-Fred

Hi Lowrider
There is detailed information about the heads in my ebay listings. Yes, the stage 2 head has a different chamber shape and size. The stage 2 is basically lower compression than the stage 1. Which one is the best for your setup is dependent on what kind of intake and exhaust you run. For example, if you run a stock intake manifold and stock exhaust, the stage 1 would be right. Even if you run a moderately effective expansion chamber exhaust, but stock intake, I would say the stage 1 head would still be the right choice.
When you are running a really good exhaust system coupled with a high flow intake, then the stage 2 head becomes necessary in order to prevent detonation from happening.
Thanks for the great questions!
-Fred

Hi Huffydavidson.
Sorry about the lack of PMing you. I don't really know how to do that! Well, I think they will be ready soon. I've stopped making the heads for a few weeks now, as I'm working on other machining projects for other industries right now. That is wrapping up, so I'll be making heads again soon, and they will be the twin plug models. I have not been in contact with Dave Rust from Arrow Motorized Cycles in a while because I'm sure He is still really busy moving shop. Anyway, he is running engines that breath such high volume, I have a suspicion that he may have detonation problems even with the stage 2 head. So this is where the stage 3 head will come in..... The stage 3 head will have the same combustion chamber as the stage 2 (same compression), but with the additional spark plug, it will be harder for detonation to occur.
Now, about what to do with making a twin ignition system:
I suppose you could try splicing the spark plug wires, but I suspect that the energy will pick one spark plug to go to. I could be wrong, but I prefer to know for certain that both plugs are firing when the engine is at full throttle.
The answer I came up with is to use a DC fired CDI. There are AC fired CDI's (which are more common), but I simply don't know how to hook up to a china girl 6 volt generator. The magneto/generator of the china girl motors is very limited in output, so that is the primary concern regarding a twin ignition system. This is the reason why I chose to use a DC fired CDI. So, the DC fired CDI requires a 12 volt battery. You will have to find some kind of 12 volt battery that will fit on your bike somewhere. When I ran the first twin plug prototype, I used a single CDI unit to power two coils. I probably ran that set up for maybe 20 hours of driving time and didn't have any electrical problems, so I think one CDI can reliably support two coils. I'm preparing my bike for running the DC fired CDI again, just in time for the new stage 3 heads. When I have it done, I'll take some pictures of the installation, so you can see the kind of battery I found, where I mounted it, and so on... The electrical work is pretty easy and simple. I have some DC fired CDI's in stock that I will make available soon for folks like you who will want to try this. Of course, I will supply the electrical wiring diagram too, so you can construct the ignition system.
One more thing I would like to say, since I'm writing about the DC fired CDI;
it makes a very strong, high energy spark. Again, the limited output of the china girl magneto provides a weak spark for just one spark plug, so two plugs is not going to work out so well with the stock ignition set up.
I appreciate your gear headedness!
-Fred

Hi.
Well 160 psi sounds like pretty high compression. But if it works without giving you any detonation problems, great!
You could try to splice two spark plug wires, but like I said, even with your Jaguar box, you are still relying on the output which the magneto can produce. I suspect the limited output of the stock magneto will not adequately supply both spark plugs with a hot enough spark, but I certainly could be wrong because I have not tested that idea. Another idea would be to have your Jaguar unit power two separate coils, one for each plug. Again, the system would be powered by the stock magneto, which may not be adequate. I think you should try it though, since you have the system already in place.
Thanks
-Fred

Okay,
Well, to the best of my understanding, detonation is when some of the fuel mixture spontaneously explodes. This causes immense shock to the engine, transmitting powerful stresses to the entire engine. I have personally put a nice 1/4 inch diameter hole right in the center of the piston. I have also destroyed several wrist pin bearings as a result of detonation problems. Most of those problems happened when I was running the stock cylinder head. Detonation will occur when the flame front does not complete the burning of all the fuel mixture quickly enough. The flame propagation must be completed before the pressure rise in the cylinder reaches the point where remaining un-burnt fuel mixture will detonate. For this reason, there is a limit in how high we can run our compression ratio, as a high compression ratio will increase pressure, and therefore increase the chances of detonation. A twin spark plug cylinder head will initiate two flame fronts; one on each side of the combustion chamber. This will shorten the amount of time it takes to complete the burn of the fuel mixture, and therefore will reduce this risks of detonation. Detonation will sound like a rattling or rumbling noise. It will most likely happen when you are climbing a long uphill with a hot engine. Pulling off the side of the road after a fit of detonation, you will notice your engine hotter than usual. Heat is one of the main byproducts of detonation. During detonation, the pressure rise is so fast, it can't produce much work to the road wheel at all; instead, it produces a lot of extra heat in addition to the intense stress to the bottom end components.
Often, achieving the best power is when your engine is close to, but not quite experiencing detonation.

Hope that explains it a bit!
-Fred