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Honing Go-Kart Barrels

I used to race Go-Karts. I started off in the light class and had a Pirelli engine but the maintenance costs were to high. I then switched to the Clubman class which was a stock 100cc yamaha KT100S engine (thanks gtk for setting me straight on the engine model). No modifications were allowed and this was a cheap entry level of racing. However I was allowed any hone finish I wanted. Of course I chose a flex-hone. I would race my kart every fortnight at a race meet somewhere within Queensland and I didn't care whether it was dirt track or bitumen. There were many things that impressed me about the flex-hone when it came to race two stroke engines. 

1. I was impressed that I got a whole years racing from the engine with no tear down or ring replacement required.  A great testament to the flex-hone and Uni-filters.  You know I just got to plug this filter here because if your air filter is crap then everything the flex-hone achieves is thrown out the door, well for that matter any hone job is destroyed regardless of the tool used. Dirt will stuff that perfect hone job for you in no time. (see my Air Cleaners Compared review)
2. On the flex-hone website there is an article that talks about the gentle edge finish that the flex-hone puts on the inlet & exhaust ports of the barrel. Good reading if your into it. I believe this small almost unnoticeable chamfer gives longer ring life as the sharp edge of the port can no longer cause damage to the rings. Hang on, does this mean that the port timing has changed. NO, the chamfer is so small that it is almost unnoticeable and if it came under scrutiny from the officials, they will clearly see that no porting has taken place.
3. As mentioned in my article and other places, the ring seating is almost instant. A very important factor in race engines, whether 2 or 4 stroke. Can you imagine what it would be like if you had to run the engine in before you could give it some. I think not. All that is required is to bed the rings in, one lap around the track and that is done. Now let's go racing.

When the season was over, of course the engine got torn down for inspection. Well all I had to do was re-hone the barrel and fit new rings, replace the crank seals & bearings and put it back together ready for another year of low cost racing.

Flex-honing the barrel is easy. With the barrel held firmly in a vice or something similar, run the flex-hone through the barrel at low speed. If you have sufficient oil on the stone then very quickly you will see an oil slurry pattern in the bore. You need to adjust the up and down motion of the hone until you get the correct angle of cross-hatch. Hone for about ten strokes. Then flex-hone the bore from the opposite end of the bore or preferably reverse the drill. Run the hone a further 10 strokes. You are now done.

Let me tell you a very Hot Tip on how to now clean the bore. DO NOT use warm soapy water like almost everyone says. I have found an alternate method that is far better. This has been my little secret for years, well it was until now. The problem with water & soap is that by the time you air dry the bore, the atmosphere is already reacting with the metal and oxidizing it, causing a faint rust appearance. To avoid this I do not use water. After honing I use several rags to clean the slurry oil from the bore, then once the bore looks clean which it isn't, I get a can of Ardrox and spray the bore. I can't remember the full name of it but it is the cleaner part of a dye crack detection kit and comes in a spray can. This cleaner draws all the loose material from the recesses of the bore and brings them to the surface. Now give the bore another wipe with a new cloth and make sure you cover every sq millimetre of bore surface. Repeat again with another new cloth and that should be it. Now to test how good you cleaned it, take a perfectly clean white cloth in between your fingers and rub it in the bore as hard as you like picking several spots to check. The cloth will come out white. The bore will look fantastic and no sign of oxidation forming. Now you can coat the bore with some oil and start assembling. Happy racing.

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