On your pic CB rebuild 039 it looks like the top ring has a piece missing. That probably indicates a worn bore.
Jensen is right. Measuring things is the best way to understand what is wrong. Buy a digital caliper and get some measurements. Clean all of that oily black crud off the top of the piston and you will see markings which tell you what size they are. The one in my pic is 0.75mm oversize...
You have done the difficult bit in taking the thing apart. All that is required now is the interesting bit. Clean and check the condition of the parts, work out what to replace by measurement. Reassemble with care and all of your new-found knowledge. You do not need to rush.
Understanding what is worn / broken and why can save you a ton of money. There is plenty of free advice here and numerous books you can read.
"A wise man learns from his mistakes. An even wiser man learns from everyone's mistakes.... "
Have fun - it's good therapy.
G
The Superhawk from hell...Thanks G-Man!
I am going to buy the gauge and measure today. I am wondering if you or others have an opinion on this kit: http://bore-tech.com/product/358cc-big-bore-kit I am sure it is fun, but are there reliability issues? Also, are you saying the gap in the top ring here is not supposed to be there?  CB77 rebuild 039 by Jrlovvorn, on Flickr Thanks everyone for all the help! Change of plan. The bore gauge is $150, plus shipping, and not available at retail anywhere.
I am pretty sure I can get the machine work done for that, and if I dump a couple hundred just to measure, and then a couple hundred to have it bored, I am wasting money. That just leaves the question of .25, .5, 1.0, or the big bore option. THe gap just looks too big to me. Does it close up if you squeeze it back into the groove?
It's still a good plan to clean off the top of the piston as this (along with the condition of the bore) will tell you what is the next size you need to go to. You don't need to buy a bore gauge. One of these is a very useful tool for many jobs in the workshop, it will save its cost many times over. http://www.amazon.com/s/ref=nb_sb_noss_ ... al+caliper. You can use feeler gauges to check the clearance from piston to bore. http://www.amazon.com/s/ref=nb_sb_noss_ ... eler+gauge G '60 C77 '60 C72 '62 C72 Dream '63 CL72
'61 CB72 '64 CB77 '65 CB160 '66 Matchless 350 '67 CL77 '67 S90 '77 CB400F Thanks, I started cleaning, and no marks on the top of the pistons.
I have a digital caliper, but that will only tell me the measurements at the top and bottom, and won't tell me out of round, will it? Also, I think I found one problem, at least. LM wins again - the valves are a mess. I am no expert, but I found that, no matter what position the cam is in, I have these evil eyes staring back at me from inside the left side exhuast. I rotated it all the way twice, and although the right side got dark off and on, the left was always the evil eyes... I think this means the left exhaust valve is never really closed, which I assume is the likely source of the white smoke?  CB77 rebuild 049 by Jrlovvorn, on Flickr Sorry for all the questions, I really am way out on a limb here! What does it look like if you slacken the adjuster on that valve? If you have been running them tight the valve seat may be burnt. Not sure that would produce the smoke you mentioned earlier.
There's so much oily carbon on your pistons that the bike has been clearly burning oil. What do the bores look like? Any scoring? Why are you worried about out of roundness? Pistons are never round. It's difficult to diagnose these things from 3000 miles but it shouldn't be too difficult to fix.. If you send me a Pm with your email I have a really good motorcycle workshop book in PDF. G '60 C77 '60 C72 '62 C72 Dream '63 CL72
'61 CB72 '64 CB77 '65 CB160 '66 Matchless 350 '67 CL77 '67 S90 '77 CB400F Valves were running pretty loose. After the smoke started, I tightened them up to spec. No change.
I think I am going to stop fiddling with the head and just pack it up and ship it to Ed tomorrow. I was thinking out of round as to the cylinder, not the pistons - sorry. I don't see deep scoring, but then again I have no idea what I am looking at! I did measurments with the digital calipers, and I will post them in a bit. I think I did it very well, as the numbers seem odd to me.
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