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Old 11-16-2008, 01:12 PM
Motormac Motormac is offline
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Join Date: Sep 2008
Location: Ontario Canada
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Default Re: Decarbonizing without disassembly

Old Motorbike, you answered your own question, carbon knock is the result of carbon buildup on the valves of 4-6-8 cylinder engines, also carbon buildup on piston crowns is really bad too as the carbon thats sitting on top of the piston gets red hot in the combustion chamber and burns a hole thru the top of the piston.The best way to clean it is to disassemble the engine, but thats not practical in most cases unless you are disassembling it anyway for something else. The only real easiest way to tell if you have carbon buildup is to check your plug and shine a light into the spark plug hole.
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Old 11-28-2008, 10:12 PM
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eDJ eDJ is offline
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Join Date: Jul 2008
Location: Wayne National Forest
Posts: 531
Default Re: Decarbonizing without disassembly

I once made a water decarbonizer out of a bike water bottle and some fish aquarium stuff. It worked very well on an old Honda I used to drive around. I believe it was a 77 model that had points and a coil. (no CDI in those days)

The parts I used were a brass adjustable feed valve to regulate the amount of air and one of those cylindrical stones that makes a foam of bubbles. I had some plastic tubing and toothpaste size tube or RTV to seal this stuff with.
The stone was plugged into some tubing and a hole drilled in the flat sealing cap to pull it thru so the stone sit in the bottom of the bottle. The brass valve was RTVed to the lid and the tubing connected to one nipple. The other nipple had a small air filter I made for it stuffed with fiberglass. (all this stuff was fish aquarium parts) Then a larger hole was drilled thru the cap for a larger piece of tubing.....which would go to a vacuum tube to the carb. I cut that tube and inserted a windshield washer tubing "Tee" and plugged the tubing from the bottle
to it.

When I started the motor and allowed it to idle I barely backed out the adjustment screw till the water in the bottle began to bubble. It wasn't enough to effect the idle rpm and it was the setting for the operation I needed. This dampened the air going thru the bleed and was enough to
do an excellent job of decarbonizing the motor.

In time a head gaskett blew between two cylinders (this 1600 cc aluminum head motor was famous for this problem and was recalled numerous times)
The mechanic that fixed it for me asked about the little decarbonizer bottle
and remarked on how clean the head and piston crowns were. I was working loads of hours then and living in an appartment and had to farm out the repair.

I found a Radio Shack CDI unit in a yard sale and installed it on the motor later. The odd thing was that even with resistor plugs....when I used the decarbonizer bottle it would slowly cause the outer electrode of the spark plug to thin. If I turned off the water bottle it didn't happen. But when I ran the water bottle the plugs came out clean as the day they went in.

So, I would guess for a motorized bicycle that one of these could be set up and fitted like a "boost bottle" to dampen the intake air. I won't speculate on the long term
effects of using this thing on the bearings.
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