So, what I was hoping to be a simple bearing swap to install the R1 frontend into our YZF600R, became a bit more involved. Going from the old style to the new, Yamaha made the necks around an 1 1/2" shorter in length. The only way around this little problem is a stem swap. Pressing the R1 stem out is fairly simple with a good hydraulic press.
Make a note, if you need to attempt this process, stems typically press out through the bottom to be removed. Also there's a circlip attached at the bottom end of the stem to act as a stop when it is pressed in place. The lower bearing race needs to be removed before the stem can be pressed out. Otherwise it will hang up on the tree and you can potentially bend the stem or the lower tree. Little trick I picked up some years ago. Put the whole lower tree in the freezer the night before you press it out. Have a propane torch handy and heat up the tree only as you start to press the stem. As the tree gets hot the metal expands faster then the cold stem. Should help release the stem easier.
So that was the easy part. Removing the stem from the YZF tree took a little more work. Where the R1 is two pressed together aluminum parts, the older all steel design of the YZF is first pressed together and then welded. The weld on the bottom of the stem looks small, so I had first tried to grind it away. This proved to not be the case. The weld in this case penetrated well into the tree. In the pursuit of custom, we sacrificed the tree. Which wasn't a big deal since this tree was tweaked from a crash some time ago.
With the center free, a little massaging with the grinder to knock off the hard corners and miscellaneous studs. I was able to start turning the excess material down.
Just as I was starting to get down to the diameter I needed, the rest of the tree came away from the stem like ripped up paper. Great! Although, I was optimistic. The lower bearings are the same size, maybe the seat of the stem is too... Negative! Went to test fit it and it slid right through with about 0.002" clearence. Back to the drawing board...
At first I considered the idea of making a spacer, but then reality set in and it would be so paper thin by the time I got down to the size I needed that if the lathe didn't tear it apart, the press would. Then it hit me. Weld it up and turn it back down. We've been making camshafts like this for a century, what's the difference.
So now we have a finished product. Press everything back together and bolt it all up with original bearings. More updates soon.
Make a note, if you need to attempt this process, stems typically press out through the bottom to be removed. Also there's a circlip attached at the bottom end of the stem to act as a stop when it is pressed in place. The lower bearing race needs to be removed before the stem can be pressed out. Otherwise it will hang up on the tree and you can potentially bend the stem or the lower tree. Little trick I picked up some years ago. Put the whole lower tree in the freezer the night before you press it out. Have a propane torch handy and heat up the tree only as you start to press the stem. As the tree gets hot the metal expands faster then the cold stem. Should help release the stem easier.
So that was the easy part. Removing the stem from the YZF tree took a little more work. Where the R1 is two pressed together aluminum parts, the older all steel design of the YZF is first pressed together and then welded. The weld on the bottom of the stem looks small, so I had first tried to grind it away. This proved to not be the case. The weld in this case penetrated well into the tree. In the pursuit of custom, we sacrificed the tree. Which wasn't a big deal since this tree was tweaked from a crash some time ago.
With the center free, a little massaging with the grinder to knock off the hard corners and miscellaneous studs. I was able to start turning the excess material down.
Just as I was starting to get down to the diameter I needed, the rest of the tree came away from the stem like ripped up paper. Great! Although, I was optimistic. The lower bearings are the same size, maybe the seat of the stem is too... Negative! Went to test fit it and it slid right through with about 0.002" clearence. Back to the drawing board...
At first I considered the idea of making a spacer, but then reality set in and it would be so paper thin by the time I got down to the size I needed that if the lathe didn't tear it apart, the press would. Then it hit me. Weld it up and turn it back down. We've been making camshafts like this for a century, what's the difference.
So now we have a finished product. Press everything back together and bolt it all up with original bearings. More updates soon.
No comments:
Post a Comment