XS650 Top End Buildup

Before I started using the copper spray, I did use narrow beads of sealer applied to the gasket or head/cylinder surface. I would surround the cam chain tunnel, the 4 outside stud holes, and eventually, I added a strip across the front. I did that because I started to see a slight leak along the front of mine a few years after my rebuild. Applying it to the cylinder or head itself makes it easier to keep it out of that groove around the outer edge (red arrows below) .....

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Yes, the factory gaskets do have some pre-applied sealer along the front and rear of the cam chain tunnel. You can see it as the shiny, darker area on the factory gasket below. I suppose you could spread a bit more sealer around in those areas .....

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No, I wasn't saying that. It seems to be typical for a head gasket. It has the metal "fire" ring surrounding each bore, rest is stiff gasket paper of some sort. I don't know, maybe there's a thin layer of metal between the paper. I never "dissected" one down that far.
 
I agree with gggGary and have personally installed the gasket twice on my motor dry without any leaks. I would stop being cheap when it comes to your engine unless you enjoy rebuilding it more than needed. Get the copper spray and save yourself tearing it down and spending more on replacement gaskets the second time.
 
I agree with gggGary and have personally installed the gasket twice on my motor dry without any leaks. I would stop being cheap when it comes to your engine unless you enjoy rebuilding it more than needed. Get the copper spray and save yourself tearing it down and spending more on replacement gaskets the second time.
I'm not understanding what you're trying to say. If you've installed it dry twice without any leaks, why do you insist it must be installed with copper spray or else I'm implied to be a fool? You contradict yourself. Your tone is abrasive.
 
I'm not understanding what you're trying to say. If you've installed it dry twice without any leaks, why do you insist it must be installed with copper spray or else I'm implied to be a fool? You contradict yourself. Your tone is abrasive.

Let's play nice boys. All Bushy is trying to say is why chance having to do it again. Yes, maybe you can get away with no sealer but as 5T pointed out above, one of his started leaking out the front after a few yrs. Just to be safe, I always seal it.
RE copper: The reason for the copper is that in addition to sealing, it aids in heat transfer. Being an air cooled engine, I'll take all the aids I can get when it comes to heat transfer.
 
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Thank you for this thread which I am rereading. I bought my first Yamaha in June, 2019 as a 1974 650. I rode a friend's '72 and was hooked. I bought one a week later. It had a "frame off" restoration with blasted and repainted frame, and many new parts / components being new for the rebuild, but not the engine. Top end rebuild needed for sure. Soon I will rebuild it and this is such great info.
 
Still there? Good. Don't put them nice shiny jugs away yet. We need them now to check our piston ring gaps. Take your new rings (I always use new ones) and one piston. One at a time, slip a ring into a cylinder about a third of the way down. Now take a piston and insert it dome first. Push it against the ring to "square" the ring up in the cylinder. Measure the end gap with a feeler gauge. Take the same ring and do the same thing for the other cylinder. Decide which ones left and which is right and organize them appropriately.

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Do this for the top, second, and both halves of the oil control ring. The gap clearances are listed on Pg. 27. Remember, the smaller the gaps, the better the seal and the longer the ring life. An old hot rodder trick is to use the next oversize rings and then file/grind the ends 'till the gap is at the minimum value.

Once you're satisfied with your gaps, go ahead and install the rings... starting with the oil ring. Install the spreader ring, then the lower, and then the upper rail rings. Make sure the gaps in the rail rings are opposite (180deg.) each other and the gap in the spreader is about halfway between the two. Even when I'm using ring spreader pliers, I still wrap the grooves with electrical tape so that I don't scratch em'.

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Once the oil ring's in, move the tape up and install the second ring..... same for the top one. Take your feeler gauge and check for the ring side clearances listed on Pg. 27.

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Now you can either set that piston aside and do the other one, or go ahead and install it in the cylinder. I decided to go ahead and install it. Before you install it, make sure the inboard wrist pin clip is installed. Page 32 shows the correct orientation of the ring gaps. Give the inside of the ring compressor a good coating of oil and tighten it up around the piston. NOTE: If your piston is cocked in the ring compressor, your rings aren't compressed all the way. Tap the bottom of it with a piece of wood a few times and snug it up again.The piston won't go into the cylinder unless the rings are fully compressed.... and could possibly damage the rings and/or piston. Give the inside of the cylinder a good coating of oil, set the piston in the cylinder correctly oriented, and tap it into place. If you're using OEM pistons, there's an arrow on it that points forward. If there's no arrow, just remember that the larger valve pocket (intake) goes aft.

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There's several ways you can install the pistons. Keep in mind that at the beginning of this article I stated that this is how "I" do it. I have a good quality ring compressor that's served me well for over 30yrs. I'm comfortable doing it this way. The bottom of the cylinders have a slight bevel and some might feel more comfortable inserting the pistons from the bottom. Because of that bevel, you can literally use a couple pieces of wood to squeeze the rings together and insert the pistons without a compressor (it helps to have 3 hands here...;)). I've done it that way and it works. Do what works best for you with the tooling you have.

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After you get both pistons installed, tap both of them down (or up) 'till the wrist pins just clear the bottom of the sleeves and are parallel to each other.

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Cut 4 pieces of wood 4" long and tape or tie them to the front and rear of each cylinder.

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install the cylinder and let the wood rest on the base gasket. Don't forget to pull the cam chain through and tie it off.

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With the wood holding the cylinder height and the rubber bands holding the connecting rods centered, you should be pretty close on alignment. Rotate the crank and/or push the rods fore or aft slightly and the wrist pins will slide right in.

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Stuff a clean rag in there in case you drop the clips and go ahead and install the outboard clips. Once you're satisfied the clips are properly seated, double check em to make absolutely sure they're seated. Now go ahead and remove the rags, rubber bands, and pieces of wood, then apply a thin bead of sealant around the perimeter of the base gasket. Use your solvent of choice to clean up any mess you made, then work the cylinders down into place.

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If your pistons went down to BDC, hold the cylinders and work the cam chain to bring them back to TDC. I do this just to lesson the possibility of accidentally leaving something in the cylinders that don't belong there and because they need to be there for cam timing.

Next I installed the chain guide. The fastener holes are cut more towards one end (top). Slip the longer end down into the cylinder and install the fasteners. Screw the fasteners in by hand till they seat, then back 'em off a hair so you can wiggle the guide around easily. Pull the front of the chain up against the guide and wiggle the chain around until you're certain it's laying inside the guide properly. Eyeball the guide and chain so that you can center it up inside the chain cavity and just snug the bolts down. Watch the guide as you tighten. If you see it move one way or the other, loosen it up and try again. My eyeballs have been doin' this kind of stuff for close to 50 yrs. now. I trust 'em. If your not sure you can judge the center, put a piece of tape across the cavity and mark where the chain and guide should be. The bolts use copper crush washers just like the bushings do. Treat them the same (see above). Once you're happy with everything, go ahead and torque the bolts

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This is the XS/SR500 Frankenstein modded guide. You can read about how that was done here. I did manage to score an OEM guide for 115 bucks, but elected to use the modded one so I could see how well it holds up. Time will tell.....
Note: You can just as easily install the guide before you install the cylinder. In fact, some people who know a lot more than me about the XS say that you should install the guide first so that you can measure it top and bottom and make sure it's centered. I'm happy with the way I did it. Obviously, it's your choice as to which way you go, but if you're uncertain... I'd suggest you measure it and install it first.

At this point, I'd normally take the opportunity to put a dial indicator on a piston and verify the TDC mark on the rotor. My rotor's dead and I'm gonna have to replace it. So, instead of doing it twice, I'll check it through a plug hole when the engines back together.

I'm probably gettin' close to my character limit again, so we'll continue below. Next up: The head.
I just got my 706cc kit from cruseimage couple days ago and I was just wondering how u clock ur rings . I only can afford to do this bore and buy the kit once so I've gotta get it right the first time any help or thoughts appreciated.
 

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If you research this subject, you will find several recommendations. Most are very similar and all seem to have a couple things in common - stagger the end gaps and don't place any over the wrist pin ends. Here's Yamaha's recommendation .....

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Here's another .....

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'83 Heritage special motor...
Got a cam chain question. I just got a new chain from Mike's and it is lovely, riveted and endless.
I have my engine completely apart, cases split, crank out. Is it possible to slip the endless chain over the crank, button up the cases put the cam in without breaking the chain? My thought was to slip it on to the sprocket w/o the cam bearings in place then scoot the bearings on afterwards, of course double triple checking crank/cam timing.
Is this possible?? Seems like the clearance you would gain from the cam bearings being out would be enough to let this happen.
 
Yes, that's the approved method. Even with a new chain, there is enough slack to get the bearings in. Bear in mind that the bearings need to be tapped well in, up against the cams, so that they overhang on the inner side of the bearing mount in the cylinder head. I didn't push them in far enough and as a result the points & advance housings didn't seat fully against the outer face of the head. Now rectified.
 
Nice!!!
I did not relish the idea of breaking the chain just to rejoin it again once the top end was back together.
Especially with the crank out.
Ya, I've read about using the cam covers to push the bearings into their proper place before final head torque down; so that's on my checklist.
Thanks a ton for the quick reply!!
 
Jim, I just looked in the Yamaha factory manual for any reference to that oil baffle that goes in back of the head on my early '72 engine. I don't remember seeing it..now I see I didn't photo that side of the head. I'd better run to the machine shop before the head hits the parts washer and look. I just picked up my head halves. The baffle wasn't there. The head top had been off before. Getting it all just vapor blasted then back to machine shop. Not liking what I'm seeing with that cruising.... on ebay for those early .15 thick rings. Seems they've been having trouble with orders last 6 months..not un common now.
 
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Jim, I just looked in the Yamaha factory manual for any reference to that oil baffle that goes in back of the head on my early '72 engine. I don't remember seeing it..now I see I didn't photo that side of the head. I'd better run to the machine shop before the head hits the parts washer and look. I just picked up my head halves. The baffle wasn't there. The head top had been off before. Getting it all just vapor blasted then back to machine shop. Not liking what I'm seeing with that cruising.... on ebay for those early .15 thick rings. Seems they've been having trouble with orders last 6 months..not un common now.

Your ‘72 didn’t have one. They came along later, you’re ok.
 
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