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Well it should stop at TDC, either Firing or overlap, as this is when the connecting rod angle is straight. While turning it even 20 degrees may make it want to move, but really it should stop and hold anywhere. The valve spring tension, pushing on a cam lobe, shouldn't be enough to turn a motor over. Even with high performance triple springs.
If you roll the motor over, while feeling the rocker arm for clearance with your hand, do you feel it increase beyond the setting of say .005"? If it gets sloppy then you must have set it when the Cam lobe was not on the base circle. Finding TDC firing position, should ensure that the Cam lobe is on the Base Circle and ready for adjustment.

Your Profile doesn't say where you are at. Maybe state where you are, there could be a helpful member near by, maybe?

Here is a quote from the 305 forum: www.armbell.com/kz400/viewtopic.php?t=72...t=valve&mforum=kz400

"I never bother about where the engine is in its stroke when adjusting the valves. When the inlet is open, the exhaust is closed and I adjust that - and vice verse. And with the spark plugs out, it is easy to rotate the engine with the rear wheel once a gear is selected."
So this is another way, if the cylinder you are wanting to adjust has the EX valve pushed down/ open. Then you should be able to adjust that cylinders IN valve clearance. Maybe this will be easier for you?

I was actually reading that very post (and many others) last night, wondering if it made sense.
I also tried his rear wheel thing thinking it may help me stop at TDC, but maybe I need to try a higher gear. It sure doesn't work in first. Normally I post over there but there are so few 305 owners it can take days to get a response, if you get one at all.

Did you try to Feel the play as you rotate through the cycle? Did it change and get looser somewhere else besides at the mark where you adjusted it?
I can't explain why the motor won't stay in place where you are thinking TDC is, as it should.
Is that page from the manual for the 305 and not the 400? Seems the two are different, according to that post on the armbell forum.

I havent gone all the way through checking it at various points, but I KNOW there are places where it is MUCH looser just by random checks. Right now its at one of those places, I can stick the .203 in easily on both intake and exhaust. I could probably stick two in there. But since I wasnt at TDC I didnt know what, if anything, could be concluded from that.

Yup that page is definitely from the 250/305 service manual. The 400 is quite different, I also learned last night reading old messages there. .

Well look back a page here where I posted the cam lobe picture. See the area called the "Base Circle"? That would be the loose spot you are on now. This is where I would set the clearance.
Give it a try and see.
I don't know it is possible for another model, say 400, components have been fitted to your 305. It sounds like the TDC mark might need to be checked to be sure that it is correct. Back to either a screw driver/ Dial indicator down the plug hole. Or perform a positive stop, this is inserting a tool into the plug hole, uses the threads, goes down to touch the top of the piston stopping the motor from turning. A mark is made when it touches/ stops turning. Then rotate the motor in opposite direction till same, stops. Then divide between the two marks= True TDC.

I'll try it tonight. I need a break. Thanks for all the feedback, will let you know what happens...

I dont think anything has been modified on the bike. It was a one owner bike basically. It has occurred to me that I skipped links on the cam chain when I cranked backwards, but I dont know the likelihood of that, and the bike runs fine except for the noise.

I'm just wary of that which I do not know. if I set the clearance when they are at the loosest and its not at the TDC mark, I will know if I set them too loose because they will be noisy. Is it possible to set them at the right spec when not at TDC mark, and have them be quiet but cause damage? Thats my only reluctance, because I dont fully understand this stuff. If it cant cause damage and I have nothing to lose but loose valves which I will hear, then I'll go ahead and set them like that. I guess another ay of putting it is, if I set them this way will the clearance be less, more or the same at TDC when it fires? It seems thats the important thing.

You could verify the cam timing for both piece of mind and to assure it did not jump when turning it backwards. Look in your manual and it will show you how to remove the valve cover and verify the marks. It will also give you a chance to inspect the chain and guides, etc.
I can also tell you another quicker way to see if cam timing is on right. It involves finding the TDC mark, and this time using the "Overlap" of the cam. So both the intake and exhaust valves will move slightly. Splitting the overlap, so the IN and EX valves are just open slightly, and even amount, should be within 2 degrees of TDC. Only if you had Dual cams and adjustable sprockets, or performance grinds might change that. Also if the cam chain is stretched or off a at least 1 tooth will also change it. Split overlap, TDC.

to inject my useless $0.02...

My 550 clymer manual has me rotate the the crank and check clearances when the cam nose to pointed 180 deg away from the bucket.

My 750 manual has me always stopped at 1,4 tdc or 2,3 tdc and measure the cams... they aren't 180 deg pointed away, but all different angles......

Not sure which is right or wrong.


PS-had a 73 Honda 500 four with rocker arms and tappets. Once you got the stupid engine port hole cover things off it took 5 min to adjust your valves. pretty slick.

Both methods should put the cam lobes on the Base Circle. Most books would have you do say a V* like that, adjust 1/2 the engine and then rotate crank 360 and do the others, all lined out as to which ones.

I'm wary of getting deeper inside-the bike runs good and I want to ride instead if I can loose this noise without going there. What I hope to find peace of mind on is "If I set them this way (not at the TDC mark) will the clearance be less, more or the same at TDC when it fires? It seems thats the important thing."