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Discussion Starter · #1 ·
Good evening community -
I have been able to find just about every answer by browsing this forum and others, YouTube, google, etc etc. However, I am finally stumped so I have officially registered and here is my first post!

This is a 1975 CB200T that I have 100% stripped down and (almost fully) rebuilt. I am about a week away from first start so I am really excited. The bike did not run when purchased. The intake valves were in decent shape and moved freely. Both exhaust valves were stuck open and had to be hammer-tapped out. All valves were scraped of deposits, brass wire-wheeled, re-seated with lapping compound and oiled to assure they all moved freely.

Tonight I began adjusting the tappets per the manual. At TDC I adjust the intake to .05mm and take the engine around 360 degrees to double check everything - no problems, everything moves smoothly. Now to the exhaust side where the problems arise: If I tighten the tappet screw close to the suggested .05mm I experience significant resistance rotating the engine on the exhaust stroke (valve opening). If I do tighten to the suggested .05mm I cannot even turn the engine through the exhaust stroke and I struggle to back out the tappet screw enough to rotate it. If I allow more play, I get significant resistance and it’s like something is interfering and then slips and then it’ll rotate fine until the exhaust stroke. If I leave about 1mm gap then no problems and it’ll rotate smoothly all the way. This happens with both of the exhaust valves.

This does not seem right. How much resistance if any should there be? Would I be ok running the engine with that much tappet spacing? What the heck might be going on the cause this?

Thank you all for your thoughts
 

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When I hear tappet adjustment it makes me think you are moving it a few thousands of a mm. I would not think tappet adjustment would make the engine stiff to turn over. How far are you backing the adjuster out? If you are backing it out all the way, the cam may not be properly timed and a valve is hitting the piston. This needs to be thoroughly checked out as a bent valve can result. You said the exhaust vales needed to be hammered out. When they were installed did they move freely before the valve springs were installed?
 

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I've not worked on a 200, but is it a 180? You need to do one side, then rotate the engine 180 and do the other side. Check through the plug hole and see of the piston is staring back at you, or not.

Edit: as above, could be cam timing/assembly issue
 

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Discussion Starter · #5 ·
I am trying to think back to when I dropped the camshaft back in. There’s a chance I didn’t get the “T” lined up when positing the cam, which would make sense. I am going to pull the head cover tonight and inspect and will report back. Fingers crossed no bent valves...
 

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Discussion Starter · #6 ·
Yep. Camshaft timing. Thank you for the diagnosis, guys.
I realized that when I originally dropped the camshaft in, I paid too much attention to the advancer knock pin and chain cog alignment and did not check the location of the rotor.
I readjusted all tappet screws and engine now turns smoothly through all strokes in both bores (much easier to monitor what's going on with valve cover off). The other positive is I can see the exhaust valves moving freely through the spark plug hole so they do not appear bent....but we shall see soon enough

Another note to self: do all these checks BEFORE strapping the engine in! This task did not seem too daunting until I realized the engine had to be pulled :mad:
Rookie mistake...live and learn
Thanks again
 

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You cannot see a slightly bent valve through a spark plug hole. And it does not take much to turn one into junk. You should do a compression test.
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