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Vintage Smoke · March 29th, 2013, 02:10 PM

I like the mototune method as well EXCEPT for the initial start up. The way it was explained to me by an article I read from a piston manufacturer was that one of the ring's jobs is to transfer heat to the cylinder to be dissipated. A new ring is not perfectly round and/or in flat contact with the cylinder. This leaves very small contact areas for heat to transfer and only a small percentage of the heat that is supposed to be transferred to the cylinder does. They said that the ring will actually "microweld" itself to the pistons from the heat build up. In other words there will be tiny spots where the ring sticks to, then breaks free from the piston where it sits in the ring land. This creates imperfections between the surface of the ring and piston where they touch and will cause the ring to not be able to seal properly. Low compression will result. They had a bike that was a new engine build as their example.They also said that new rings did not correct the problem and piston replacement was the answer. Their recommendation was to "heat cycle" the engine on inital start up. In other words run the engine gently until it JUST starts to warm up, but before any real heat is put into the cylinders. Cool off the engine to room temp and repeat. I forgot how many times they recommended, but I do 5 or 6 cycles. I have used this method on many engines I have built and it works. Now for the bad part....for the life of me I can't remember what piston company it was so could post a link to the article. Sorry guys.

March 29th, 2013, 02:10 PM	#69
Vintage Smoke The 2 Stroke Ninja!! Name: Nick Location: Sussex, NJ Join Date: Feb 2012 Motorcycle(s): 2010 250R, 1977 RD400, 72&73 RD350 75 RD200 Posts: 79	Break in. I like the mototune method as well EXCEPT for the initial start up. The way it was explained to me by an article I read from a piston manufacturer was that one of the ring's jobs is to transfer heat to the cylinder to be dissipated. A new ring is not perfectly round and/or in flat contact with the cylinder. This leaves very small contact areas for heat to transfer and only a small percentage of the heat that is supposed to be transferred to the cylinder does. They said that the ring will actually "microweld" itself to the pistons from the heat build up. In other words there will be tiny spots where the ring sticks to, then breaks free from the piston where it sits in the ring land. This creates imperfections between the surface of the ring and piston where they touch and will cause the ring to not be able to seal properly. Low compression will result. They had a bike that was a new engine build as their example.They also said that new rings did not correct the problem and piston replacement was the answer. Their recommendation was to "heat cycle" the engine on inital start up. In other words run the engine gently until it JUST starts to warm up, but before any real heat is put into the cylinders. Cool off the engine to room temp and repeat. I forgot how many times they recommended, but I do 5 or 6 cycles. I have used this method on many engines I have built and it works. Now for the bad part....for the life of me I can't remember what piston company it was so could post a link to the article. Sorry guys.