CB200 Cam Chain Sprocket on Crankshaft Align
 

Have split a Zongshen CB200 Crankshaft to replace a conrod.

I sadly did not note the Cam chain sprockets orientation on the crankshaft (doh)

HumanBeing fwd'd some great references:

http://www.ctx200.com/files/xl200_workshop_manual/
and
http://www.motorfans.com.cn/forum.ph...uthorid=343764

however am still not totally able to discern what I need to know:

Do I align a sprocket TOOTH or TROUGH to the crankshaft keyway at TDC??
(See pics)

Does anyone just happen to have a true side view of this area?

If it is like other Hondas, it is more based on the position of the flywheel, which you've already removed. As long as you're close to TDC, you can just mark a couple of places on the cam timing sprocket (up top bolted to the camshaft) to make sure that the chain goes back on aligned with where it was on the cam, and then mark the chain/crankshaft sprocket as well, that way you know that everything is properly indexed.

Effectively, as long as the valves are loose (i.e. you're properly at TDC), and the piston is pretty much at the top, which you could verify with a screwdriver in the spark plug hole, as long as everything is properly indexed to itself, and none of the valves are engaged, getting the exact tooth correct isn't that important, you just need to make sure that it all goes together the same way it came apart.

You could either use nail polish or a paint marker to mark both, make sure that they are free of oil so that the paint will stick. Additionally, have you considered just replacing the crankshaft? I haven't really tried to source a rod or a crankpin for one of these, but traditional Honda practice is to just replace the crank (also that has less of a margin of error).

The problem is that I didn't mark it before disassembly.

Additionally, because the cam sprocket must be pressed on, there is no way to reassemble the motor/top end to determine the proper alignment by "mocking it up".

Re-assembly order is: Press cam sprocket on crankshaft, assemble lower case, assemble top end, orient cam shaft to bottom end at TDC. thus my quandry; must know bottom cam sprocket to crankshaft alignment first.

I wish I could have found an entire replacement crankshaft but no joy.

Well, next time, make sure that you mark everything like that before disassembly, it makes things a lot easier! If the crank still has the sprocket on it, you can mock it up, you'll just have to reinstall the flywheel, and then put the top end back together. I believe that these run wasted spark, so it doesn't matter 'which' top that the cylinder is at when reassembling.

If it is like a Honda, there will be marks on the cam sprocket that align with marks in the head. Basically, if you get it at the 'T' mark on the crankshaft, all that you need is to properly align the marks on the cam gear and the head. Usually, the marks on the sprocket and cam are such that you can't easily screw it op. If you search online for an XR200 or ATC200 manual, it should show the marks that you need to see.

I think this is what you're looking for. This is the same as my Honda 200x
Attachment 11315

that is EXACTLY what i needed!
Thanks!

Any updates?

progress
 

So....turns out my donor crankshafts con-rod was 2mm shorter!
Unable to find the EXACT replacement the used good con-rod is otherwise a perfect match so i was forced to use it anyway despite the anticipated loss of compression. I'm not planning on racing so hopefully it should be livable.
with the info about cam chain sprocket alignment my machinist was able to press everything back together.
spent yesterday putting the motor back together.
new piston/rings and a hone job; we shall soon see how sucessful i am.....

Good luck. A thinner head gasket will help get the compression back up some.

Honda changed the deck height when they went from the 125 to the 185/200s (not sure how much), so I would think that if you got a shorter cylinder, like from a CB145 kit, you might be able to plug away with that, although I think that it's only a 61mm bore. They also changed the call chain length, so you might have to mix and match if you were to go with that option.

Another option might be to get a con rod from one of the aforementioned larger sized Honda motors, which, iirc, are a bit longer than the shorter stroke motors.

You might be able to get away with some Honda bond at the base, and no base gasket, or you could either deck the base of the cylinder or the head. You'd still probably have to play with call chain length of you decked anything though.

Rebuild Update!
Got it all back it together and have started the break-in!
Seems to have good compression and runs strong so far!
A couple more heat cycles, an oil change and it should good to go!

As you can see it's a real basic ride but not bad for a total expenditure of less than $400 and I've learned a ton!

BRAVO !!! :clap: