New Rider, Old XS650 - A Begining

[Shadow24v]

double checked the timing with a timing light when i did the ignition upgrades. Had to adjust it then as the timing was way retarded after the upgrade.

Is there most likely going to be more damage or can this be fixed with possibly just 1 piston replaced? Doesn't help this happened when I'm half broke and my DD is down for major repairs as well. Guess when it rains it pours...or something like that

Also, it appeared that i was losing a fair bit oil out the right PCV hose prior to the failure. It probably wasn't connected well enough and came off the connection to the airbox. not sure if that means anything though.

 

[Shadow24v]

A little more info for diagnosis. I pulled these plugs the night before last when i changed the pilot jets. These had about 100 miles or so on them. R;ight plug is righcylinder and left is left.

 

[Shadow24v]

Been doing some thinking... I think i might be able to get away with getting a used piston from the local bike salvage yard and doing a quick and dirty piston swap for only the cost of the piston and a gasket set... I know its not necessarily the BEST way to do it, but unless i become independently wealthy overnight, I'm sorta stuck with low-cost for now...

 

[mouser]

stock piston?

 

[Shadow24v]

probably, I'll make sure once i get a chance to pull the motor apart.

 

[Shadow24v]

Well, it has been over a year and a lot has changed. got a new job and moved 5 states, but now I finally have time and a place to tear down the old XS650 and see what internal part was sacrificed in the pursuit of speed and riding bliss.

Got quite a bit torn down today, and have only 2 bolts left holding the engine in (I think...). Hopefully I can pull the engine by myself, but I'm not sure. Any advice on a single person motor pull would be appreciated .

I did have a bit of oil dribble out the header on the side that I believe has the holed piston. Also, are the retaining collars on the headers not supposed to be able to come off? it looks like they can't get by the metal shoulder on the part that goes into the head and they can't get past the support bracket on the lower part either...

 

[Dennis]

collars should stay on the pipe

 

[XSLeo]

On the engine mounts, lets start at the top and work down, the upper mount is held to the frame with two bolts and to the engine with two bolts, no need to separate the four pieces of each mount.
Around to the front is a mount with two bolts in the frame and one in the engine. At the rear is a mount composed of two pieces that bolt to the frame with two bolts, the engine one bolt. Below this mount is a bolt that passes through mounts that are part of the frame and the engine.
It's best to remove all the bolts and mounts.
At the very bottom under the engine is one long bolt that passes through mounts that are part of the frame and the engine. This is the last bolt to remove and the first to remove.
Once you get all the electrical, fuel, clutch, throttle, etc. unhooked I use a floor jack to left the engine straight up to clear the bottom mount. while holding the engine as straight up as possible.
Now it will practically fall out of the frame.
It weighs about 165 lbs so be careful. I lift it out on the right side using the kick start and the exhaust port as hand holds. Have an engine stand or a cart of some sort ready to set the engine onto.
Once you have it out of the frame mount it in an engine stand. This will allow the engine to be in a stable upright position to work on it.
In the XS650 TECH section there is a thread on handmade tools. There are several engine stands in there as well as engine pulling ideas.
One I like is the the tool with a U shape that bolts to the front and rear engine mounts on the engine, has a long handle with a T on the end to allow not only lifting but you can twist the engine forward and back. It has a loop to hang it from a lift or chain falls or even a chain around a rafter. I think a heavy duty office chair with wheels under the tool to act as a fulcrum would work well too. After you lift the engine, you can just roll it out sideways from the frame. This would work for those who don't have anything overhead to attach too.
I think it was Retired Gentleman that used a pair of pipes bolted to the engine mounts that stuck out a few feet on both sides of the bike. It needs two people or supported by something on one end as in the first tool. Again an office chair one wheels would work well.
Leo

 

[Shadow24v]

xsleo - thanks for the pointers! I didn't get a chance to read your post until AFTER the motor was already out and mostly disassembled! I lucked out and once all the motor mounts were out, I was able to tilt the motor to the right a bit and lift it out of the frame using the kickstarter and the points housing. then I brute lifted it onto the worktable. Didn't realize it was that heavy...


As for the tear down and diagnosis...
Engine out - via brute stupidity...i mean young strength

and up on the workbench, via same method as above

Some ill omens in the oil filter

rockerbox off - only thing concerning is what look like grooves where the cam bearings were. can't feel any grooves though...

and found the source of those metal pieces in the oil screen...good old front cam guide is FUBAR

Not sure if the tensioner guide is still ok though, got some decent grooves in it. (also found the lock nut for the tensioner set was MIA)

and initial diagnosis of a holed piston confirmed. Interestingly enough both pistons had a fair bit of carbon buildup too...

blowout from the underside, looks like it not only melted through, but also had a pressure fracture event as well.

Hopefully the combustion chambers clean up ok. not sure if the aluminum spatter from the piston is welded to the head yet...

and where we are for now...in pieces

I did measure the top two rings (in their respective bores) and got some odd readings. from what I can tel from the Clymer's manual, spec is .2mm to .8mm. Also, the replacement pistons I have are 954 stockers and the # on the one good original piston is 953.

good piston
ring 1 - .711
ring 2 - .203

bad piston
ring 1 - .559 carbon stuck
ring 2 - .406

Also, I think someone was in at least the top half of the motor at some point, there was sealant all around the advancer housing and some of the valve cover plates had sealant on the o-rings.

Lastly, since I have the motor/trans torn down this far, is there anything else I should check? Is there anything that would drive further dis assembly and inspection of the motor and trans? Ideally I wanted to adjust the cruising rpms, but I was going to start with a sprocket change first. Funds permitting though, I may spring for Mikesxs' 5th gear as well...

I should start compiling a need/wish list at this point I think...

 

[Johnt3]

Hey,ya got to do what ya got to do. I like the "via brute stupidity...i mean young strength".
Hey are you still looking for a seat? I've got one that's off of my '78 special that's a king queen with a sissy bar to match.
It's yours for free if you want just pay for shipping.
Here's a couple pics of them.

 

[Shadow24v]

Johnt3 - you have a PM

One thing I didn't mention in my last post is that I was considering re-running the piston rings on the replacement pistons. my theory is that there would be very little break-in as the rings would still be in their respective bores. I did look into the Honda ring solution, but most of the kits are now $50 or more anyways, which is close enough to make getting OEM replacement rings feasible.

i also noticed that both sets of pistons have some scrapes in the piston skirts. I don't think this really affects how the motor runs' but would it be worth smoothing them out with some emery cloth or very very fine sandpaper?

I need to start cleaning parts i think, to really see if there is any other damage to the main jugs, head etc. What works well for you guys to clean carbon and greasy oil dirt off of parts?

 

[Shadow24v]

I checked a theory of mine as to the original cause of the holed piston. My theory that my ATU was worn excessively seems to be right. the ears on the ATU weights mic'd in at 3.3mm and 3.4mm, far from the 4mm spec and snug fit needed.

 

[XSLeo]

The head is an aluminum casting around a steel combustion chamber. Those aluminum spatters on the head will just come right off.
On cleaning the carbon off, some use oven cleaner, paint stripper. Me I use elbow grease.
In your Clymers book page 70 explains what the number on the piston is and how to use it and the number on the sleeves below the cylinders. They are what the piston and bore were when new.
If you back up to page 69 and start reading just below pic 78, step 5 it tells how to measure your pistons. The ones you have will be wron at least a bit. The 954 was the size when new. They will be smaller now. Measure the bore as described on page 66.
Now after you measure and find thew difference in size that's the clearence with those pistons in those bores. If it is with in specs, .0020-.0022 inches or .050-.055 mm, then they will work.
On the specs you listed on the piston rings, is that the end gaps of the rings when put down in the bores as on page 72, pic 87?
If so they are a bit on the big side. The cost of rings isn't much compared to tear the engine down to replace them when it burns excessive amounts of oil.
I would buy a first over set and grind the rings to get the gap right.
On the tensioner side cam chain guide It does show some wear. If you have the one from the engine the pistons came from you might want to use that one if better.
They do hold up better than the front guides. I think it's because it don't get the stress the front one gets.
On the rest of the engine, some will reccomend you split the cases and do a good job of cleaning out the bits of the piston that came down when it holed.
I might agree especially if you want Mike's Fifth gear. If not I might just flush it a few times with a cleaner of your choice. I might used kerosene.
Your Clymer book tells how to check the rods big end play and small end play. You can check the crank runout without splitting the cases.
Just read the book and check everything it talks about.
Leo

 

[Shadow24v]

Thanks againg for the wealth of knowledge XSLeo.

I looked but wasn't able to find any stamped markings on the sleeves indicating their original bore size on the lower or top portions. Is there a specific spot they are usually stamped on? I also have to go out and get a better caliper, mine only goes to .1mm, which I don't think is accurate enough.

I don't have a spare engine, I picked up the pistons off ebay cheap a while back hoping to keep costs down.

I did check the piston ring gaps as shown in the manual (squaring in the bore with the new used piston). I was a bit concerned with the gaps as measured. (used feeler gauges incrementally until one wouldn't fit, then wen't one size down).

 

[XSLeo]

It wasn't stamped into the sleeves but written on with a white ink? The numbers were about half way down the sleeves below the cylinders. Either on the front or rear of the sleeves. Just can't recall right now.
If they had the same spec as the ones I have had apart it will be something like 003. That would make the bore 75.003 with the pistons being 74.953. Subtract the piston from the bore and get .052 clearance. All the ones I have had apart were set to .052 mm clearance at the factory. That's right in the middle of the .050-.055 spec.
What they were new has little bearing on what you have now.
You might want to take them to a machine shop that does engine work and let them measure them for you. They have the tools and experience to properly measure them.
With the measurements you can determine the clearance and tell if they will work. As well as the out of round and taper of the cylinder.
Most places won't charge much to measure this, most will just apply this cost to anywork that needs to be done.
I had a second over rebore done by a local car speed shop used by most of the local racers. It cost me $35 per hole.
Another place is Lawn mower repair place. If they don't rebore them selves they should know a good place.
On the ring gap the ones you list at .711 is very close to the .8 mm spec. I would replace them. The gap is about at max and the old rings are much weaker than new ring. They won't push out against the cylinder walls as hard as they should.
A good hone with new rings won't cost much but will work much better than the old rings.
Leo

 

[Shadow24v]

Hmm, Ill check again, but I didn't see any white writing.

I may do that, but I am comfortable with telescoping bore gauges, micrometers and calipers just lacking some of the tools since moving (can't borrow them from my father-in-law anymore due to distance).

With a re-bore, would 1st or 2nd over pistons be needed or can the 1st or 2nd over rings on stack pistons work? (I'm guessing if not, it would be due to excessive piston to bore clearances).

The bores "look" ok, so if they mic out ok, I may just go with new rings. Although, if its cheap enough, having a quick hone done might not hurt, especially with new rings.

 

[XSLeo]

I wouldn't worry to much about finding the sleeve numbers. They won't apply anymore.
As far as who measures, as long as it's done right you will find out what you need. Using a stock piston with a first over set of rings works if the stock piston clearance is a bit on the big side of the spec. But in this case with the piston being a bit larger than your stock piston, a ligt hone might gdet the bore a big big too. The stock size rings might work but be toward the larger end of the gap spec. Maybe even be to much. That's why I suggested getting the first over rings and grinding them to fit.
Years ago cars came in .020 steps in piston over sizes. Often the bores were not worn enough to need a rebore but worn enough so stock rings wouldn't work well. They sold rings in .010 steps so you could use the stock pistons, the new rings and do a 1/2 step oversize.
Using the stock pistons and grinding the ring gaps to match the bore is along the same lines.
Those specs on the oversizes may have been .010 and .005. Been along time since I did a lot of engine work. Around the mid 70's
Leo

 

[Shadow24v]

that all makes sense actually.

It will be a good while until I have everything cleaned up, parts acquired and ready for re-assembly though. If I can get the tools cheap enough, I'll measure it myself, but if the cost is low enough at a local shop, I may go there instead.

I'm also considering stripping the frame down for some refresh, and contemplating re-wiring the bike as the current harness is a bit "crunchy" and has a few issues (and working on rounding up all the parts for a PMA swap, plus LED lights)

 

[XSLeo]

With all the wiring changes you are thinking of, then a rewire is a good option. It gives you a good chance to remove all the unnessary crap the factory put in.
Leo

 

[Shadow24v]

Worked on trying to split the case today. I THINK i got all the nuts/bolts but it still won't split. I am stuck at the moment trying to get the clutch bolt off (have to get a 29mm socket and a 2nd set of hands). Is there anything hiding that keeps the halves together?

Also got a quote from a local shop, $10 to mic the bores, $15 per bore for a hone but $50-$75 PER BORE for an overbore!