From: United Kingdom
Registered:
11/07/2008
Time spent:
0 hours
(Date Posted:09/16/2009 01:39:51)
Just rebuilt motor with a Honda CB125 RS head, has the cam bearings in the head. Works very well, no more tappet noises and valve/ignition timing seems more consistent. Engine definitely runs with a bit more poke.
Head is painted black so needs a bit of a sandblast and the mount sits at the rear so have to modify top engine mount, otherwise a worthwhile conversion.
I think this is the bike with this engine but cant be totally sure as bought just the cylinder head:
From: USA
Registered:10/01/2008
Time spent: 0 hours
Re:CB125 RS head conversion
(Date Posted:09/25/2009 16:35:13)
Sounds pretty cool, too bad you can't get roller rockers too and really reduce the friction in the head. What year bottom end did you attach the RS head to. I am just guessing, but I imagine the RS head probably had large valves and ports than the early two piece head. You wouldn't happen to know, would you?
Adam
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From: United Kingdom
Registered:11/07/2008
Time spent: 0 hours
RE:CB125 RS head conversion
(Date Posted:09/29/2009 12:26:16)
The bottom end was the one fitted to the XL when I got it,and has had a lot of abuse but still fairly strong, looks like the standard cases as I have another marked XL125 as a spare. The head design is very similar and I know the valves are the same diameter as I bent an inlet when the cam chain slipped and I swapped out another valve from the original head.The inlet valve was longer as I had to grind it to get a clearance but it definitely seated OK as after a light lap it sealed good.The rockers also needed a light grind off the underside cast line as they fouled the spring tops. The only other parts that needed further customising were the top mount and the points case which was slightly tight and just needed filing round to make it fit. I wish I had the picture from the original purchase but the head was definitely described as CB125RS, hope this helps. Paul.
From: United Kingdom
Registered:11/07/2008
Time spent: 0 hours
RE:CB125 RS head conversion
(Date Posted:09/29/2009 12:52:46)
Just to say as have been rushing this post in between doing other stuff, you also need the camshaft with the bearing on it that went with the head or maybe could convert a standard one.I think I just struck lucky, but most of it seems common sense, make sure nothing hits, got clearances, compression, timing, fire it up! Good luck.
