Twin Spark Plug Cylinder Head Prototype!

GoldenMotor.com
crmachineman

crmachineman

New Member
May 24, 2012
259
2
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New Hampshire
Well, I just had to make one!

This head has the same combustion chamber contours as the single spark plug version. The counterbores for the spark plugs are 1.0 " diameter, so I had to use the spark plugs that have a 3/4"/19 MM hex. I'm very happy with how it came out. The ignition I'm using is a battery powered DC fired CDI feeding two separate coils. I think I will use two CDIs and two coils soon. I just came back from a test drive. The engine runs superb! The power seems to be slightly higher that with the single plug, but I can't really tell without more elaborate testing. I think I will try to make another prototype with slightly higher compression, as I feel that the twin plug arrangement can allow for higher compression. Of course I tested the head at top speed for long periods, and there was no signs of detonation.

I don't have any of these for sale yet, but when I do, I will make a submission in the "Swap and Shop" section. I have to work out some production issues first before I start making them in production.

You can see in one of the pictures, I'm running the new version of the intake plenum, which is basically a shortened version. This new version seems to have better high speed performance.

-Fred

zpt
 

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dmb

Active Member
Dec 4, 2010
1,354
3
36
lakewood ca
now put a compression release on it and see how good it stops. if you never used one it will really impress you with the engine braking. no more worrying about steep hills and cheezy brakes. it will sound like a truck jake brake and work the same way. and a great way for racers to stop brake fade and cool a hot motor by expelling hot gasses from the combustion chamber. truly a racers edge used on all the 2 stroke tt racers from years ago. dennis
 
tooljunkie

tooljunkie

Member
Apr 4, 2012
663
5
16
Manitoba,Canada
thats real nice.
a patient guy with a file and various grits of sandpaper could make that head a work of art,not saying it isnt already.
pretty soon gonna build your own jug?
 
crmachineman

crmachineman

New Member
May 24, 2012
259
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New Hampshire
Well tooljunkie, it's true these heads can get a bit of hand finishing if one desires. I would say filing the edges of the fins would be a good start. I do a little hand finishing on each one, but it's only to take off the bad burrs that could cut you.

Hey DMB, I removed one of the spark plug wires to see how it would run with only one, and it seemed totally fine! Now, let me pick your brain a little...
I only about jake brakes and compression releases from a theoretical standpoint. I have no actual experience using one on a motor bike. I see a lot of chainsaw compression release units for sale for very low price, that's good. What kind of work is involved to get a compression release operational. Don't you need a cable to control it? Maybe I'll buy a chainsaw compression release and study the design and see what I can come up with. I'll need a little time on that cause I need to make a lot of heads! Maybe one of you guys can figure that mess out for me! LOL.

-Fred

laff
 
Crazy Horse

Crazy Horse

Dealer
Feb 20, 2009
1,153
3
36
USA
Fred, I'm following your work on the 2-smokes!

OUTSTANDING!!!!

I'm impressed with what you are producing for the 2-smoke community, and I might just have to try one of these new products of yours.

Any chance of producing a complete engine?

Jerry, @ Cherokee Motor Bikes is rumored to be looking for a buyer for his business. He has produced only a couple of the V-Twin 2-smokes. Yes his engines are very expensive.

But hey if someone has the resources and wants to have a V-Twin that is proportionate to a motorized bicycle Board Track or Flat Track style Tribute build, then why not!

He has the cad drawings everything is turnkey for his design both the Single Cylinder and V Twin / Two Cylinder. Also he is selling his machines as well.

I wish I could buy him out, he has another business that is his primary business and he just doesn't have the time to invest into the engines
now.

Here's the V-Twin Engine video Link:
http://youtu.be/L5SwXtBwJgQ?hd=1

http://cherokeemotorbikes.com/

Peace C'H.
 
tooljunkie

tooljunkie

Member
Apr 4, 2012
663
5
16
Manitoba,Canada
the stihl saws/trimmers at work use the decompressors.
it would be difficult to activate one of them,it would need to be held down as it pops up as soon as engine fires.
a lever on a pivot wouldnt be difficult to make it cable activated,but it would ugly up the fine cylinder heads you are turning out.
a spring loaded doo-dad thats somehow activated by a double pull brake lever would be the bomb,it could decompress at first stage of braking,then activate the rears.
 
CroMagnum

CroMagnum

Member
Sep 2, 2011
148
1
16
Los Angeles
crmachineman said:
The ignition I'm using is a battery powered DC fired CDI feeding two separate coils. I think I will use two CDIs and two coils soon.
Click to expand...

You might be able to just use one CDI and one coil.

Most 4-cylinder motorcycles use only two coils, with two spark plug leads each. If you look a single lead coil one side of the secondary is grounded. Instead what the 4-cyl bikes do is put a spark plug lead on both sides of the secondary so they both spark at once. Of course that means you get a spark on the exhaust stroke too, but that doesn't matter.

Scrounge up a coil from a GSXR, YZF, or CBR and you can simplify the parts count.
 
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dmb

Active Member
Dec 4, 2010
1,354
3
36
lakewood ca
bigblue beat me to it. there you go! i'll be supprised if your head and the compression release dont take off because thats what these motorbikes need most. a engine brake! being that most use bike coaster brakes and a cheezy rim brake. good luck dennis
 
crmachineman

crmachineman

New Member
May 24, 2012
259
2
0
New Hampshire
Crazy Horse said:
Fred, I'm following your work on the 2-smokes!

OUTSTANDING!!!!

I'm impressed with what you are producing for the 2-smoke community, and I might just have to try one of these new products of yours.

Any chance of producing a complete engine?

Jerry, @ Cherokee Motor Bikes is rumored to be looking for a buyer for his business. He has produced only a couple of the V-Twin 2-smokes. Yes his engines are very expensive.

But hey if someone has the resources and wants to have a V-Twin that is proportionate to a motorized bicycle Board Track or Flat Track style Tribute build, then why not!

He has the cad drawings everything is turnkey for his design both the Single Cylinder and V Twin / Two Cylinder. Also he is selling his machines as well.

I wish I could buy him out, he has another business that is his primary business and he just doesn't have the time to invest into the engines
now.

Here's the V-Twin Engine video Link:
http://youtu.be/L5SwXtBwJgQ?hd=1

http://cherokeemotorbikes.com/

Peace C'H.
Click to expand...
Yeah, I've seen that video. It's very clever what he did! I think you would have to beef up the clutch on that twin. Both crankshafts drive a single large bevel gear and clutch, so I would imagine this unit would have some clutch problems if you were to actually drive it. Maybe it could be solved by putting a more powerful spring for the clutch.

I wonder if it's possible to make a vee-twin where both cylinders share a common crankcase? You could even do a fork and knife connecting rod arrangement just like Harley does. Both cylinders would fire almost at the same time, the difference in timing would be determined by the angle between the two cylinders.

Have you ever looked into those gorgeous opposed twin RC aircraft engines? That kind of engine would be terrific on a bike! Low vibration!

-Fred

laff
 
Hoze513

Hoze513

New Member
Nov 24, 2011
262
0
0
42
Joliet, illinois
Keep up the good work CRmachineman. You are making lot of needed product, that we don't have. Also lots of great stuff for a newbie to read. Thanks
 
BigBlue

BigBlue

Member
Nov 29, 2011
781
0
16
California
Moto said:
SO RAD! Found this picture on the internet it might be of interest to you. If I remember correctly they used two super rat cdi's.
Click to expand...
That would seem correct. I found a post from camlifter trying to run 2 coils off one magneto and would only fire one plug. My guess the magneto doesn't produce enough amperage to fire both coils.

See post #17

http://motorbicycling.com/showthread.php?t=27732&page=2

Chris
AKA: BigBlue
 
crmachineman

crmachineman

New Member
May 24, 2012
259
2
0
New Hampshire
Oh yeah, look at that!
You can see in the picture there is a splice on the HT wire to supply both spark plugs from one magneto/coil. I guess that would work, but they may have had to close the spark plug gap for each spark plug. I worried about the same problem you mentioned Big Blue, which is why I only use the magneto to trigger a DC fired CDI. The CDI is powered by a small battery and the CDI feeds two coils; one for each spark plug. With the set up I'm using, there is plenty of energy for the spark plugs.

That does look like a nice job on installation. Nice job on the motor mounts.

-Fred
zpt
 
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dmb

Active Member
Dec 4, 2010
1,354
3
36
lakewood ca
DUDE!!!!... don't leave me hanging on the compression release! i've been watching everyday for a report back. dennis
 
crmachineman

crmachineman

New Member
May 24, 2012
259
2
0
New Hampshire
Hi dmb
Well, I've been busy making the standard single plug heads, but the good news is that I'm finishing up. I'll be resuming work with the twin plug heads soon. This head set up will be the one that will have the optional compression release. I think I will make a twin spark plug model with a third tapped hole for the compression release. There is enough room for that. It will be a totally sick head quite frankly. I will definitely run it soon on my test bike which just got clocked at 54 MPH running the twin plug head!

-Fred
xct2
 
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dmb

Active Member
Dec 4, 2010
1,354
3
36
lakewood ca
WOW! just what i need for that super rat that's been sitting on the shelf for a long time. i've been afraid to use it.
 
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