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dillon0990

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All,
After finding black plastic when removing sump filter I determined it was at least time to replace the front cam chain guide. Following the popular youtube videos, I remove cam cover, head, and at first did not plan to remove the jugs. However, It lifted off the gasket and found the gasket to be in pieces, some stuck to the case and some the jugs, so decided to move forward. At first the cam guide looked good and only edges came off, but once I got it out I pulled on the black plastic and it was just sitting there, not even attached.

I knew I could remove the cylinders without pulling pistons out, but decided I came far enough. Might as well take some measurements, replace rings as needed, and other parts as needed (I am on a budget, well the wife says so). No compression issues before parking it. Failed to check before taking apart.

As of today I will be dropping the pistons and jugs to a machine shop to measure. If in spec for piston/cylinder clearance (0.050 to 0.055 mm piston/bore clearance), they will do a light hone. I checked end gaps of stock rings on one side and were in spec, but on the edge of limit. However, when remove rings from second piston I broke one. I will now buy 1st over rings and grind to minimum ring gap.
Current piston size for both L/R are 74.962 and bore is 75.013 (0.051 clearance when new). Thoughts on best 1st over piston ring sets?? where to buy?

I have seen some people discuss using a feeler gauge to determine if bore/piston clearance is in spec and if a .004" fits its probably out of spec, but I think it is flawed or misunderstood. Pistons are measured at the skirt perpendicular to the piston pin 10 mm from bottom. There is no requirement to measure the top of the pistons. With my piston in the bore I can fit a .006 " feeler gauge at the side, but from the bottom at the skirt, I cant even squeeze a 0.002" in. This leads me to believe the piston and bore are in good shape and in spec. THOUGHTS???

Cam chain is still intact, but thinking if I have everything apart I should replace it. I don't have the right tool, but think I may try the ball peen technique. I tested valves by placing them valve side up and using first gas and then tried again with water. No leaks at all, so I doubt I will mess with the valves/heads. Keep it or replace it????

Replaced clutch push rod bushing yesterday and will do seal once I get some gasket cement. It had a bad leak there.

I purchased the new clutch springs and allen head spring retainer bolts from tc bros. Friction disks look pretty good and were not stuck together. steels had no rust or anything and straight. Plan to leave them and see how clutch works once in the bike. (pretty easy to replace disks later if needed).

For reference, this is a 1977 xs650. owned by my dad for 35+ years. has been sitting without running for 10+ years, but ran when parked. the carb floats had pin holes, but then it sat until I decided to take it and convert to brat style with monstercraftsman brat kit.

I will update when I get measurements back. I pray I don't need a bore or new pistons.
 
Thanks for the links, I will check them out.

So I dropped off my pistons and cylinders to machinist. He is the best in town and has been doing it for many years. He does a lot of engine work for racing bikes and cars and works with our local motorcycle shop a lot for normal daily driver engine builds.

He said the piston to bore spec of 0.050 to 0.055 is a pretty standard spec for a lot of bikes. He also said not to stress over it to much. He is going to do a full measure and give me the numbers. If in spec he will deglaze. He said for a normal daily driver even slightly outside the 0.055 is NOT going to be an issue as long as ring gaps are good and the cylinder is straight without any tapper or wear damage.

Thoughts on this?
 
The .050-.055mm spec is the new spec. Wear limit is about twice that, up around .10mm or so. It's probably a good idea to replace the valve guide seals. They're rubber and 30+ years old after all. Ask your machinist and he'll probably agree. Your machinist can probably handle that work but I'm not sure what he'd charge. For about $20, you can get a nice valve spring compressor and do it yourself. Just pouring liquid into the combustion chambers isn't the best test for valve leaks. It will only show really big ones, not the little ones. To find them, blow compressed air into the intake and exhaust ports while the liquid is sitting in the combustion chambers. Watch for streams of bubbles around the edges of the valves .....

dAyCZVL.jpg


scTVevw.jpg


mLxDTcb.jpg


EmVtx11.jpg
 
I thought I had seen in the manual (not in front of me) a larger clearance from wear, but don't see many people discuss it. I pretty much see people saying if not 0.050 to 0.055, bore and get new pistons and rings.

Thanks for the input on checking valves for leaks. If valves are all good without leaks and I pull them to replace valve seals, will they likely still be good, or will I need to check again or lap the valves? I would of course put the valves back in the same spots they came from. thoughts on best valve seals to buy?
Are the rings from mikes good for the pistons, or should I look somewhere else? I have read in several threads that you like buying 1st over and grinding.
 
If the valves aren't leaking then you could remove and re-install them without lapping. But here's the thing - the valve sealing lip and the valve seat in the head just normally develop pits through use. If they're not leaking, that just means they haven't pitted up quite enough yet to do so, but they will eventually. The exhausts are more prone to this because they run hotter. Often when testing for leaks, the exhausts will have some but the intakes won't. So, it's usually a good idea to "freshen" the seats up with a little hand lapping when you have one of these apart.

Yes, you should have valve guide seals if you got the full Athena gasket kit.
 
Help. For some stupid reason I slid the old inner clutch pushrod into the hole with my new clutch push rod bushing. Now it wont come back out. with the old push rod I tilted the engine and it came right out. The new pushing is a little more snug. Ideas? Tried finding a magnet at my local menards, but the end is too big to go into the hole. I already have the new one piece long push rod from mikes, so I would like to get the old one out. Worst case I just go with stock and put the ball and short rod in.
 
When reinstalling the pistons to the connecting rods, do you only replace the retaining clips you removed? I figured if the clips on the other side were not removed, they should be good to stay in. About to order a new pair and wasn't sure if I should order two pairs. I also ordered a valve spring compressor to replace valve seals.
 
dillon0990 said:
When reinstalling the pistons to the connecting rods, do you only replace the retaining clips you removed? I figured if the clips on the other side were not removed, they should be good to stay in. About to order a new pair and wasn't sure if I should order two pairs. I also ordered a valve spring compressor to replace valve seals.
Click to expand...
The clips don't wear, they just lose tension when removed and reinstalled. If you didn't remove the inboards, you don't need new ones.
 
I may try that if the magnet does not work. Thanks!

I received good news that my cylinders and pistons are in good enough shape that I will not need a bore job. He is going to deglaze the cylinders and I will start putting this thing back together once I get rings and my new cam chain.

Pistons were within 0.001" of each other. Bore taper was 0.002" from top to bottom. My piston to cylinder clearance at mid/bottom of cylinder was 0.002" and at the top 0.004". His recommendation was to deglaze and put some new rings in. I think I should be able to get quite a bit more life out of it. The engine has 18,000 miles on it. Maybe in a few years I will do a big bore kit. For now I am going with it and hope to get on the road before winter.

I replaced my clutch bolts and springs yesterday. Man they are so much better than the Philips head originals. I have a lot of gasket cleaning ahead of me. O have read to just buy some gasket remover and lacquer thinner and get a plastic scrapper. Any other thoughts? I started with a metal blade, but I was scratting the surface of the head, which I know I don't want to do. With a little scuffing, small scratches be OK or do I need to try and remove any scratches in the sealing surface???

I will continue to post once I get moving.
 
Small scratches are OK Metal scrapers are fine and probably needed. The trick is to grind off any sharp corners. I have a selection of repurposed metal scrapers at the bench, all have rounded corners. My most used are probably broken hacksaw blades, ground at an angle, wrapped in duct tape for comfort. grind about a 30 degree angle. finish on an oil stone, pull the edge through a block of wood to remove the "feathers".
A trick; once you get under some gasket down to the metal, is to rock the blade. this often starts to lift gasket ahead of the blade edge. Often as not I get float bowl gaskets and sometimes other gaskets off intact with careful rocking to separate the gasket from the metal. I grind my float bowl removers from stainless steel strips out of old windshield wipers.
 
Last edited:
I got my cylinders and pistons back today and look great. A little cleaning and everything should be good to start going back together. I plan to reuse the front cam chain guide/tensioner, which seems to be acceptable from what I have read. I have not removed it, and probably wont.

I got my inner clutch pushrod out today with a small magnet. I then pushed in the new seal. I got it a cocked half way in, but I carefully worked it back straight and was able to drive it the rest of the way in. I found no signs of rubber that scrapped off. The new one piece push rod from mikes seems to have worked great. Went in nice and snug in the seal. Before replacing the seal, bushing, and rod I could grab the old one and wiggle it back in forth. Now the rod doesn't move at all and is so much more secure. Lets hope it stays that way once I get the engine running with oil.

Now the wait for rings and cam chain. Still need to start cleaning gasket surfaces and separate the cam chain.

Should I replace the thin o-rings at the bottom of the cylinders?? I assume they are in my athena gasket kit?
 
dillon0990 said:
...The new one piece push rod from mikes...
Click to expand...

Be sure to at least polish that part of the pushrod that runs in the bushing and seal.
Then, smear some grease on the rod, helps to protect the rod and seal.

dillon0990 said:
...Should I replace the thin o-rings at the bottom of the cylinders?? I assume they are in my athena gasket kit?
Click to expand...

Yes...
 
I don't know what/where you've been reading, but the front cam chain guide pretty much always needs replacing. It's the rear one that doesn't. Carefully inspect yours to make sure the rubber strip isn't coming unglued. The rubber strip usually doesn't get worn out, it simply comes loose and sometimes even falls right off.

Keep a good eye on your Mike's pushrod. The one I got apparently missed the hardening step during manufacture and the ends were very badly dimpled by 10 thousand miles, to the point that it was ready to start shedding metal chips .....

iUDEG9e.jpg


Needless to say, I won't be using MikesXS pushrods anymore. I swapped in an old original. If you shop eBay, you can find N.O.S. long rods for about the same price as that P.O.S. from Mike's .....

https://www.ebay.com/itm/NEW-CLUTCH...130?_trksid=p2349526.m4383.l4275.c10#viTabs_0
 
My bad, I was talking about the rear one. The front one is the only reason this top end is getting done. So I take it that means I am good to not piss with the rear one as long as it is in good shape. Good to know about the mikes pushrod. I hope I didnt make a mistake by using it. I will keep an eye on it for now and replace later if needed.
 

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