Hi,
Decided to make a seperate post for hopefully more views than my other thread. And to make the info easier to find, not all cluttered in one thread.
I am rebuilding my 1984 ATC200M engine now. I found that the aluminum cam journals in the head measure right at the very bottom of spec. 1.3411" Funny thing is, the camshaft itself is worn more than the aluminum journals! It measures 1.331".....that something like 0.005" below spec! Dont understand it, but I quadruple checked my measurements. As it sits it has 0.010" clearance between the cam and journal. I installed a good used cam that mics in spec, and shrunk that to 0.0045". Still too much clearance though, service manual specifies 0.003" max clearance.
I have also read the from the factory these journals sometimes came with more that 0.003" clearance....with brand new parts!! Certainly seems plausible, based on the measurements given in the manual.
As I see it I have a few options...
Option 1: Find a good used head. I believe I may have a good head off a 185S, need to mic it though. It does have a bunch of pitting in the combustion chamber, like from detonation or something. Head gasket sealing surface it intact though.
Option 2: Weld the journals and bore to spec on a mill. Have access to a machine shop who will do this for free! He does good work, and is the instructor at the machining program in a local tech college (where I go for welding courses).
Option 3: Bore and machine replaceable bearing inserts into cam journals. Unsure about this?? Seems possible, and would be nice to have something that replaceable.
Option 4: Install a ball or needle bearing on the opposite side of the cam chain. Exactly like Megacycle does, with their bearing plate, etc. Except I'm not spending $500 on it....I would make my own, or get it made at that machine shop. https://www.megacyclecams.com/catalog/Page22.pdf
Have also found a few guys over on Thumpertalk who have done this with XR200's and similar bikes.
https://thumpertalk.com/forums/topic...hy-not/?page=2
https://thumpertalk.com/forums/topic...omment-8715919
Any ideas, thoughts, or suggestions are welcome!! I'm curious to see if anyone has done this also.