Top End Notes Part 4 - Break In

Well, we've got over 5 hard hours on the new top end with zero oil useage and nothing caught in the catch tube. All seems good. I thought I'd wait for results to post my procedure as it was a bit unusual.

1) As previously posted, I used a 2-3/4" 180 grit aluminum oxide ball hone under running water to hone the cylinder to a nice uniform cross hatch. Total hone time was about 10 - 15 seconds. I didn't get any good pics, but the cylinder ended up looking a lot like mikerides33's.

2) Cleaned the cylinder with brake cleaner repeatedly until a new white paper towel showed no sign of honing residue.

3) Cleaned the piston and rings thoroughly with brake cleaner.

4) Assembled the piston/rings and installed them into the cylinder.

5) Pushed the piston/rings up and down in the cylinder 50 times through the entire stroke on my bench top. (Push piston down to table top, flip cylinder, push piston down, flip....) I was very careful to push the piston up by pressing on the center of the pin and down by pressing on the center of the piston top.

After removing the piston from the cylinder, I noted some extremely light scuffs on the exhaust side of the piston skirt and cylinder. So....

6) Repeated steps 1 - 5 and removed piston/rings again.

7) Performed one last 5 second hone on the cylinder and thoroughly cleaned the cylinder as above.

8) Put a very light film of synthetic oil on the piston skirts below the rings. Then I dripped a small amount of oil into the ring grooves and rotated the rings 360 degrees to fully distribute the oil in the grooves.

9) Assembled the top end as usual with the cylinder dry and the light coating of synthetic oil on the piston skirt/rings.

10) With the no oil in the crankcase, we slowly kicked the engine over approximately 25 times.

11) Filled the crankcase with oil and rotated the engine over for approximately 10 seconds using the e-start while holding down the kill button. We did this to get the oil fully cirulated before startup.

12) Bike fired on third attempt. Ran the bike at idle for a minute or so to listen for "death sounds" and shut it off.

13) Took the bike to our ride area, cranked the bike and idled it for three minutes to get it fully warmed. Shut it down and checked the oil.

14) Told my son to hammer it up and down through the gears basically like we did during the first break-in.

So far, so good.....

Good job thank you for all of your posts on this new top end. They were done very well.

Sounds good Skip. Are you sure it was a 2 3/4" ball hone? That would fall right through.

Sounds good Skip. Are you sure it was a 2 3/4" ball hone? That would fall right through.

I read that you should use a hone 10% smaller than the bore in several places (Eric Gorr among them). I was a bit concerned that it would be too small, but it turned out to fit just right.

I'm sure the 10% smaller rule would apply to the 2 strokes because of the ports to snag, where the 4 stroke have none.

I squeezed a 3 1/2'' flex hone in there and ran it under the faucet. Back and forth 6 times and then 6 times in reverse.

Great write-up as usual Skip. We need more like this! ??