79 xs650 Special - No Spark... But 12v. help?

That could be a 'good' sign. The previous owner may have already dumped oil in that cylinder, trying to unstick rings and/or do a compression test. And now, all that oil is in the exhaust (not showing on the plug), and burns/smokes when the exhaust heats-up.

Takes quite a bit of running to burn-out oil in the exhaust. Or, could remove the right exhaust and flush it out with your favored solvent...
 
With a car at least, it can smoke bad from bad rings for a long time before it gets bad enough to foul the plugs and show oil on them. Putting new rings in shouldn't be such a hard thing. Shouldn't take more than a day...if you start early in the morning. Plan everything out ahead of time. If it turns out to be that.
 
Thanks guys! I was wondering is there some way for oil to get into the exhaust OTHER than past the rings? Like a stuck valve?
 
If you have it running, I might suggest just running it. The thing is with most bikes that set can develop lots of things. Sticky ring and valves can be just a couple. The valve stem seals could have broken on that side and allow excessive oil in. They can, with a few special tools and techniques, be replaced with out pulling the engine.
A search will find them.
As mentioned oil can accumulate in the exhaust and take awhile to burn out.
I might just run it awhile, a few hundred miles, watching the oil consumption.
I would also buy, borrow, rent a compression tester. It can reveal a lot of information on your engine.
Finding some one with a leak down tester or buying, building your own will reveal even more.
Leo
 
Not a stuck valve, but bad valve stem seals, but that usually gets better as it warms up rather than worse. Internal head gasket leak into a cylinder, so try re-torquing. But everybody's going to say rings is the most likely way to fix it.
 
Thanks, as always........I will try to run it again for sure......I was just worried about doing further damage........any thoughts on that?.......Of course I'll keep an eye on the oil level.

Leo, I guess I can Google it, but what the heck is a "leak down tester"? I've never heard of that.
 
Leak-down tests are traditionally done on aircraft piston engines, quite revealing, and establish go/no-go for engine/flight certification. The tester hose is screwed into a plug hole, compressed air is hooked-up to the tester, passed thru regulated orifices, and pressure retention is read while at TDC. You can also hear air escape to help determine problems...
 
Please bear in mind that I've been giving you the optimistic, rare, 1% fat chance hopeful scenario.

Xjwmx and xsleo are giving you a reality check.
 
UUGHHH.bad news......:( I did the thumb over the spark plug hole test,,,,,,,,left side, my thumb pops off the hole when engine is cranked.........right side...NADA........no compression. I guess I should have done that sooner! :doh: OH, well........Suggestions on how to proceed?
 
Pabeye said:
UUGHHH.bad news......:( I did the thumb over the spark plug hole test,,,,,,,,left side, my thumb pops off the hole when engine is cranked.........right side...NADA........no compression. I guess I should have done that sooner! :doh: OH, well........Suggestions on how to proceed?
Click to expand...

Check that your valve gaps are normal with a cold engine. That will ensure you don't have a valve being held open.

If valve gaps are OK, then you likely have a hole in the piston, that the PO failed to mention.....................sometimes PO's are forgetful. You need to do a top end re-build. If the engine has high milage, then it was due for a re-build anyway.
 
You can look in through a plug hole and often see a holed piston.
Before you do a tear down, pull off the valve adjuster covers, turn the engine and watch the valves. Watch to see them open and close. Arte they all opening and closing ok.
Engines always have one valve open. With one valve open and the engine sets very long a bit of rust forms on valve stems. This bit of rust can hold a valve open.
With the carbs and exhaust off rotate the engine watching the valves to see when they are open, spray penetrating fluid in through the intake and exhaust to coat the valve stem. Now with the adjuster covers off spray around the valve springs.
I might also take a foot long length of wooden dowel, 3/4 inch or so in diameter. With the valves closed, place one end of this dowel on the valve adjuster. Hit the other end of the dowel with a hammer.
This very quickly opens the valve and lets it snap closed. This can often break the rust loose on the valve stems.
Once you are sure the valves are fully closing retest the compression. Another thing you can try is loosening the valve adjustment up a bit. Like double the standard adjustment. This will help insure the valves fully close.
Some have had good luck on cleaning the valve head and seat by reaching in through the intake and exhaust ports with brushes and solvent.
All these things may help get things working before you tear down. Might save you a tear down. If you still need to tear down all these things don't cost more than a bit of time.
Leo
 
XSLeo said:
You can look in through a plug hole and often see a holed piston.
Click to expand...

SPOT ON LEO! Now I know why she was blowin smoke! I was able to see a BIG hole in the top of the right side piston when it was at TDC. The one a + note the valves seemed to be opening and closing correctly. .........Let the removal and take down begin! (What would cause such a thing? I want to prevent same after the rebuild!


Next question: Best source for parts like pistons, rings and what ever else the beast might need. And any hints about removal and take down that I will not find in the shop manual Thanks in advance.
 
Too hot a plug, too low an octane fuel, too advanced timing. All these things can do it. Most likely a combination of things.
Often when a piston holes on the XS650 the gas is low octane, the timing advance unit has not been maintained and sticks full advanced on a fast run on the highway.
The high speed run with the stuck advance, the engine starts to knock because the fuel burns poorly. Going this fast it's hard to hear the knock.
The knock creates a hot spot on the piston dome. If it stays too hot too long it burns a hole.
One of the best ways to prevent this is to properly maintain the advancer and run higher octane fuel.
There are several places online to shop, Mike's, 650central, Ebay, As well as many online parts sellers like boats.net.
There are several specialty shops like Hoo's Racing that sell parts too.
Up in the XS650 tech section you will find many links to engine rebuilding. Reading through the home made tools threads will help you come up with special tools that people build to help them do engine work.
Leo
 
Thanks Leo..this will be a first for me! Never tore an engine down before..but Hey, maybe at 63 yrs, maybe ya can teach an old dog new tricks! Fingers crossed!

Should BOTH pistons be replaced or just the broken one? Thanks!
 
Once you get it apart, you may find some damage to the cylinder walls on that side that holed. That would require a re-bore with over-size pistons. That would take two.
 
I think the bike is stripped down enough to pull the engine. Exciting stuff........

IMG_4598_zps0682ecac.jpg


Hopefully this weekend I can get another strong male (my son in law ) to help take it out. I have another friend who is sending me the shop manual......NOW all I need is some good luck and more advice from you guys!

A SCREWie question: The carbs have a drain plug at the bottom. It's brass and they are all chewed up. Need to be replaced. I found some short bolts that fit but they are steel not brass.........any suggestions.......use the steel ones? someplace to buy brass ones? Thanks


AND while we are at it, the rubber boot that protects the wire that connects to the alternator is shot. Where to get something like that or do we substitute a spark plug boot or something like that......as always thanks in advance.
 
I think I might have hijacked this thread.......sorry...........

Had some time to work on the bike today....got the engine out..
ALL BY MYSELF! For those interested w/o side covers and w/o oil it weighs in at 125.....exactly the same weight as my dog!


IMG_4616_zps93135fc2.jpg


Oh, and here is "the dog" Lola by name! I pick her up too.....to help get her into the car.......
IMG_4421_zps0e876eb7.jpg
 

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