Twin Spark Plug Cylinder Head Prototype!

[crmachineman]

Hi. Actually, I'm glad you dug up that old thread.
Well, the twin plug head will be available soon. Right now I'm making the stage 2 heads which are lower compression than the first series of heads I made. So, now those heads will be called the stage 1 heads. I've decided to make the twin plug head, a twin plug version of the stage 2 head. Once that head design is in production, it will be called the stage 3 head. If twin plugs are used, it will be able to safely operate at the highest actual compression. There are some, like Arrow motorized cycles, who are running extreme engines that require even lower compression cylinder head due to the amount of "supercharging" those engines have from the use of highly advanced intake and exhaust systems. But instead of making a third single plug design head with even lower compression, I thought it would be better to simply add another spark plug. This additional plug will hasten the completion of the burning of the fuel mixture, thus preventing the deadly detonation.
I'm a little unsure about what kind of variations of this twin plug head I should make...
I certainly want to make some heads that actually have three spark plug holes; two for spark plugs and one for a compression release. One would go right on my bike as soon as it's ready!LOL
I'm kinda guessing about this part though; Most people probably won't want a head with three holes, so I think most of them will be twin hole designs, so either you run one spark plug and a compression release, or two spark plugs and no compression release.
Well, anyway, that's my current plan of what will come next.
I've got a ebay listing for the stage 2 heads. There is a image of the combustion chamber, which will be the same shape that the stage 3 head will have.
Thanks for your interest in my products!
-Fred

 

[SpeedWizzard]

I think that's great. you should ask around about the three hole design, post in a few threads asking who would buy one, then figure out the numbers and if it's worth it. and variation wise, you should do a low compression and high compression version?
Thanks for the great reply.

 

[crmachineman]

Hi everybody.
I've received a few requests for a wiring diagram for the twin spark plug head that will become available soon from CR Machine.
I'll try to get some pics of my simple installation, but the wiring diagram is really the most important info. I've been using a DC fired CDI to power the coil/coils.
I have found that a single CDI unit can reliably run twin coils. The coils I use are ones you would find for a small scooter, not the original equipment units we get with our China girl kits.

Hope it's helpful
-Fred

 

[borntofli]

It seems to me if your building a twin plug head and there are no consumer friendly options of getting spark to those 2 plugs you should be in that market also.......I'd buy a twin plug head, but no sparky, no buyee.....

 

[crmachineman]

Ah hah!
Yeah, that's kinda funny. It's partly true, indeed.
I've got so much work in the shop machining, it takes a while to cover all the bases. Actually, I was hoping an electrically inclined person here on the forum would put something nice together. I've been thinking about it myself too. The one annoying problem that I have not been successful in solving, is obtaining the appropriate electrical plugs to fit the CDI. What I had to do was break off the white plastic housing and solder wires directly to the CDI. It works fine I guess, but it looks a little low tech.
Well, if worse comes to worse, and people want me to make turnkey kits, which allow you to simply plug the wires in, I can make up a few units and sell them on ebay. No problem. I already have two of the CDI units in stock, just for that possibility.

-Fred

 

[Huffydavidson]

Ok Fred, now that you what CDI & Coils to use, we'll have get Draco. to come up with a home built modified CDI like he did the Jaguar . on to the next level . I all want out generation 4 head is dual spark plugs compression release high compression and water cooled and can we make the compression release optional nitrous jet injector? I can't wait to see the design .

 

[crmachineman]

Hi. Well, I don't know any particulars about this CDI, except that it is a DC fired unit. It is a common unit which I've seen sold by several vendors on ebay. Take a look at the picture of it, and I'm sure you will spot the identical one if you search for scooter CDI's on ebay. There is a number of coils that should work fine as well. To be honest, I'm not an electrical expert, like some on this forum, so you won't be able to rely on me for tip top support in this area. You have a picture of the CDI and the schematic. I hope that is good enough for now.

I will try a three hole cylinder head design, but I just don't know if that is going to stay. All these holes will eliminate some of the cooling fins; I'm a little concerned about that. It is a possibility that the twin plug head will only have two holes, so if you want to run the compression release (which I am not making right now), you will have to run just one spark plug.

-Fred

 

[crmachineman]

At last, the production twin spark plug head is here!

Well, we've been talking about it for a while, and now they are finally coming off the line!
Within a couple days, I'll have some available. I will start a thread in the swap shop, with details on what they will cost, availability and such.
I've tested it, and sure enough, it works excellent. The bike wasn't detonating at all when I was running the single plug version, so it really is not improving MY performance, but if the engine was tricked out to the max it would probably save it from detonation.
The compression release works really well as a rear brake. Sounds just like a big truck using the jake brake!
I've included a few images of my bike, showing the components for running the twin ignition. Earlier in this thread, I put up an image of the schematic. I'm working on full ignition kits, but with this information, you will be able to build your own.
Hope you like it!
-Fred

 

[BarnstormCyclewerks]

Nice work Fred!

 

[ivan H]

Hi, reading posts re using a decomp valve 4 compression braking. Seems there's misconception. A jacobs or"Jake Brake" works by; exhaust valve closed during intake & compression strokes, (the compression stroke gives the braking effect) then the exhaust valve is opened at TDC of compression stroke so compressed air is expelled so it doesnt force the piston down, like power stroke. It then closes again & the cycle is repeated. A decomp valve simply will not achieve the same result. Cheers

 

[crmachineman]

Hi Ivan
Hold on now.. Decompression valves have been used in two stoke bikes for many years. They aren't very common now, but they used to be common on dirt bikes of the past. I've been enjoying increased braking ability by using it. It's just the plain truth; I'm not making this up! It sounds just like a jake brake, and it helps slow the bike down. Not by a wee little amount, but by a significant amount you can really feel. I have a simple coaster brake in the rear, and just a small drum brake in the front. The addition of the decompression valve is allowing me to stop twice as fast. Now, I can leave the coaster brake just for emergencies.

-Fred

 

[ivan H]

I know they've had them for yrs, as a starting aid/hi comp motors, & they'll slow u, kinda like rolling along with the plug out will, but not like a "compression" brake, which really work well. I did a quick search, back when 2 strokes did flat track people tried it, but opening the cylinder2 the enviroment isnt good & again they found systems that only vent outward was the way 2 go. Outta phone screen, 'nother post

 

[ivan H]

I also found manufacturers of both chainsaws & decomp valves say not 2 use while the motor is running as damage will result. But each 2 there own, & inovation is a good thing. I just by into increase automotive output, increase braking, & bike brakes aint that costly. Cheers

 

[crmachineman]

Hmm, well ok.
I really like how it helps me stop, and it gets attention, like a horn!
-Fred

 

[ivan H]

Ha, yeah I read of that use when I searched them. Seems people were trying 2 get the compression braking effect of a 4 stroke by this method on 2 strokes. I can c that it would help with a coaster brake. (man, put some disks on ur bike, safety, or at least V brakes) If u could desing 1 that dumped @ the top of the compression stroke u'd get tthe full effect of, but complexity would probly make it not feasable. Cheers

 

[dmb]

ivan,it's plain to see that you've never used one. i have many times, when air cooled 2 strokes were the norm. the motorcycle 2 stroke compression release's work very well, sounds like a jake brake [40 years of using them]it is like a decompression but bigger and does not suck in air[1 way] oh! and i wished the jacobs brakes on the old 2 stroke detroit diesels worked half as good as these motorcycle release's work on these motors. i told CR in thread#2 how good they work as a brake and i think every 2 stroke with a coaster brake should have one. and they work really good unflooding motors. dennis

 

[ivan H]

Ur right, I havent used a decompression as a brake on a 2 stroke, nor a coaster brake since infants ats school. A Jacobs, or "compression" brake on a diesel with 18;1 compression ratio, yes. Ur entitled to think ur decomp gives the same result. I choose decent brakes, but each to their own. Cheers.

 

[dmb]

your the one that thinks these are DEcompression releases and they are NOT. and your the one who said they are not jacobs brakes when no one said they were. CR said they sound like one and they act like one in real life TRUE. i agree with your brake upgrades but really should not remark on things you know nothing about. [2 stroke compression releases only] i agree on most of your answers on 2 stroke port and piston upgrades but your wrong on this one. thanks dennis

 

[ivan H]

ok, well I stand corrected, tho a search of 2 strke compression release has dirt biike forums showing diagrams calling them decomps also, & showing them, whether in head or cylinder, doing the same release of, or decompressing of the compression stroke as the chainsaw's, mentioning the use of to assist inadequate 60's/70's drum brakes & warning "not without problems" of damaging the release. I noticed some mechanically connected to the kickstart mechanism, fascinating Cheers

 

[dmb]

correct. some big bore 2 strokers had a type of compression release for starting[dt360]. but i cant remember any factory issued one's although almost all had a extra plug hole for use. back in the 60's and 70's most desert racers in so.cal had one on their bike. but they went away when the water cooled bikes came with one spark plug hole. oh they were not bullet proof but not chineeze junk either.