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Discussion Starter · #1 ·
again the background,...3rd owner of a 79CX500C; I have no maintenance history, all 17.8K miles logged under one rider. I am assuming the valves have never been adjusted before. I have the Clymers and am following it step-by-step...I have the left side set to TDC, the TL is lined up with the arrow in the window. On to my questions...



Is it safe to assume that having the TL lined up with the arrow, that I am precisely at TDC? the reason I ask is because I had to back the adjusting screw off nearly 2 full turns to achieve the .004" snug feel between the rocker pin and the exhaust valve. I stopped and didn't touch the rest because that seems like an aweful lot of adjustment--maybe this is normal? I come from a 2-stroke world, no valves ever, and just wanted to make sure I was on the right track.



My thoughts are, that the piston is not at TDC and I am over adjusting the valve clearance?



Once the correct adjustment is found, what should the torque be for the 10mm hold down nut?



The plug I removed was black,...not crusty black, but not a nice golden burn either...just rebuilt the carbs...maybe I am a bit rich?



Does this sound right to you guys? I welcome any and all input!
 

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I would use a T-handled screwdriver and watch it as the piston goes up and down. When it's at TDC you will know. It is possible that the PO went nuts and did what they though. I have had several engines like this.



I cant remember the torque of those nuts but it's light like 6 pounds. To much and the threads of the tappet will either shread or the tappet will snap in half.
 

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Discussion Starter · #3 ·
I would use a T-handled screwdriver and watch it as the piston goes up and down. When it's at TDC you will know. It is possible that the PO went nuts and did what they though. I have had several engines like this.



I cant remember the torque of those nuts but it's light like 6 pounds. To much and the threads of the tappet will either shread or the tappet will snap in half.


thanks! we're having a bit of lake-effect here in Cleveland...not much accumulation--YET!



Just to confirm the direction of rotation is Clockwise when spinning the engine correct?--I think that I might not have been at TDC on a compressions stroke. I will go over everything again another night as I have had a long day.
 

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Clockwise when sitting in front of the engine with the ratchet set to tighten.



Have you seen Lucky's three videos on how to do it?
 

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Clockwise when sitting in front of the engine with the ratchet set to tighten.



Have you seen Lucky's three videos on how to do it?






Those videos are very helpful. Some things to note: Lucky was turning counterclockwise which you can do but you take the chance the bolt will unscrew. Clockwise is better.



What surprised me was how little movement there seemed to be in the rocker arms. Both the intake and discharge rockers ought to be able to move slightly if you're on the compression stroke. At TDC you're either on the compression stroke or you're not. If you are, the rockers both move and you can go ahead and check the lash. If they don't both move, then you need to roll the crank around one more time until you see the TL mark again (assuming you're checking the left cylinder first.).



I did not use a torque wrench when I tightened down the adjustment nuts; I just snugged them without being very aggressive at all. They're tight but not so tight I'll have trouble getting them loose the next time.



While you've got the left cylinder on TDC, go ahead and service the cam adjuster. Then move on to the right cylinder.
 

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I always thought you did the LEFT cylinder valves first.....as in left while sitting on the bike......
 

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doesn't really matter which side you do first, as long as they are both done, and on the right stroke - some people get thrown out when both sets don't move and think that they need to majorly loosen some overtight tappets - only to find out they are not on TDC for compression... roll the motor around a few times with a long t-handle down the plug hole - you will soon see when you are at TDC for either cylinder and then it's just a matter of picking it when both sets of valve rockers are loose or clicky...
 

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sorry bandit - I believe it doesn't make any difference if you do left or right- the cam chain tensioner don't care if its left or right at TDC as long as one is....I stand to be corrected...and apologise in advance if I'm wrong......



lol.you are not wrong,no appology needed,you are indeed correct.if you were not going to adjust the camchain,then it would make no difference,left or right first
 

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Quite few people have been caught out on not getting the TDC on the compression

stroke.

I turn the motor whilst watching the inlet valves on the cylinder I'm working on

When I see them start to close, I carry on turning it gently whilst looking down the inspection hole until I get TL or TR lined up with the pointer and check/adjust the tappets

Normally you'll find a small amount of play in both the inlet and exhaust at TDC

if they have been done correctly previously
 

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Discussion Starter · #12 ·
Thanks for such detailed replies all; this forum is great, and you all have quite a bit of collective experience--thank you for sharing. From what I have read and watched, I most likely did the common mistake and lined up the mark w/o verifying I was on the compression stroke. I may have been, but will double check this evening, confirm with a rod, and positive pressure from the plug hole;



I am glad I stopped because in light of 0.004 thousandths, my adjustment seemed to be way too much, and actually caught me by surprise. Maybe the valves were THAT overly tight...but I think I might be in error.



I will read up on the cam adjustment too. Will update my progress and thanks again all!
 

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When adjusting the cam chain it is important to turn the engine in the direction it runs, i.e. looking at the crankbolt on the front cover clockwise, this keeps the chain slack on the adjustment side. I was also taught to adjust tappets this way, its also easier to see which valve is opening or closing next.
 

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I always thought you did the LEFT cylinder valves first.....as in left while sitting on the bike......






You are absolutely correct... I don't know what I was thinking. You do the left side first and then the cam adjuster because they're right by each other.



I must have had my head up my ass when I wrote that. I've corrected my original post.
 

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Discussion Starter · #16 ·
is the adjustment of the cam chain tensioner covered in the Clymer's? 17k miles, not sure if mine has ever been replaced...after all of the reading I have done, is this one of the weaker points in this motors design?
 

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Discussion Starter · #19 ·
well I adjusted the valves, left to right, and adjusted the cam chain tensioner in between sides; I was definitely wrong in my first attempt and missed the compression stroke, so I am glad I stopped because the gap I had in the one valve I worked on was more than 1/16 of an inch off.



my shop is unheated, and its about 28 degrees out...am I wasting my time doing this since it is so cold out?



Maybe another way to ask, is will I have to readjust the valves, tensioner etc when it starts to warm up again? I have read that the bike needs to be dead-cold when doing the valves...
lemme tell ya, it was dead cold!



I do plan to run the motor for a bit and let it soak through a couple temperature cycles, let her cool down, and re-check the clearances...is this a good idea to do?



I did find that the left side was very tight on the exhaust, mixed bag for the intake, and there were significant clearance differences between each set on the left side. the right side however was very close in terms of the .004 & .003; a little tight no the intake. I went through them anyways to make sure the slight pressure feel of the gage was consistent with the left side adjustments.



I made my own inspection mirror from some stuff I had laying around the shop, and it was lights-out, and a bright LED shoved into the motor...it looked as though the tensioner was equal in thickness to the cam chain. I musta stared into that port for about 40 minutes!! It was helpful to have a copy of the opened up case posted by others to visualize in my mind what I was looking at.



I torqued the 10mm nuts to about 10 ft-lbs.
 

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for what i know the engine has to be stone cold to check and adjust the valves so dont run it and then check it because the readings will be off i do believe and as in my videos you notice how i say there can be a little play but must of us run the .003 for intake and the .004 for the exhaust so if you did them that way you should be great and to say about the torque of the nuts i just tighten them with a little past tight reason being is that they can snap and then that sucks so what i do is i grab the tappet and set it to were its needed and then tighten the nut and it works great every time but if you havnt watched the videos they are a good thing to watch seeing how i go step by step in there and yes there are a few things i did wrong but like what people have said on here they corrected me so all is good



i hope this will help you out
 
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