Found out why I had ZERO compression

[bobber bill]

no explanation other than FML needed:

somehow, the rest of my motor seems ok

time for big bore ?

 

[inxs]

time for big bore ?

- would solve some issues - dont forget to resolve the original problem too

 

[jay760]

I've got a piston in the shed vertually the same as that, do you want a matching pair?

 

[gggGary]

Ouch! Do you know what caused that?

 

[bobber bill]

running lean? thats my guess

also, this motor was much more difficult to turn over with the kickstarter compared to my other motor. is this an indication of any problem(s) in the bottom end? i sure hope not

 

[Travis]

Those images are huge! Over half a megabyte each. People will dial up probably won't bother to wait for them to load.

 

[bobber bill]

dial up ? whats that ?!

 

[inxs]

dial up ? whats that ?!

-

 

[Travis]

Okay, I'm going to assume you know what dial-up is and that was a joke.. Forget dial-up, even though a lot of people still have it. Think about the mobile users. Those images are over 500kb and are about 1,907px × 1,268px. The site is scaling them down to about 800px × 532px for most browsers. 800-1000 pixels wide on the longest side is about as big as you need for things like this and then the images will usually be under 150kb and will load faster for everyone. Read this http://www.xs650.com/forum/showthread.php?t=48

 

[dlabkeeg]

Dude, I think you got a hole in one of your pistons.
Aren't you glad I'm here. I'm so full of............ knowledge.

 

[angus67]

lightening holes are so passe...... imagine finding this in a supposed runner.

did I win!??!?!?

 

[bobber bill]

Yes, it was a joke. Very sorry if i offended any dial-up users

Images are now re-sized for everyone's viewing pleasure

YIKES! Supposed runner eh? shame on the PO then

Also, fabbed up a valve spring compressor tonight and pulled the valves apart only to find out that my springs are out of spec. Damnit! guess I gotta order new valve springs along with everything else.

 

[Travis]

Cool.. sorry to be the picture nazi...

You should post a picture of the valve spring compressor in the homemade tools thread

 

[retiredgentleman]

If the engine is 70 to 79 with the mechanical ATU, they are known to wear excessively causing the the full advance timing to increase beyond the "full" timing mark. The overly advanced timing puts holes in pistons. Be sure to check the ATU timing operation after re-assembly.

 

[msmary]

i recently had the same thing happen. when the head gaskets weaken they sometimes blow "temporary" oil leaks at higher rpms. but not at lower ones go figure. Make sure you check your top of connecting rods while your in there high heat can make the damn wristpins swell just enough to loosen up the top of em .

 

[bobber bill]

If the engine is 70 to 79 with the mechanical ATU, they are known to wear excessively causing the the full advance timing to increase beyond the "full" timing mark. The overly advanced timing puts holes in pistons. Be sure to check the ATU timing operation after re-assembly.

How exactly do I do this ? thanks

 

[retiredgentleman]

Google is your friend..................just google "timing XS650". Here's a link to one site that has the service manual:
http://www.knucklebusterinc.com/tech/XS650.pdf

Buy a Haynes or Clymer manual................you must have one to work on these bikes.

 

[Tomterrific]

Low octane fuel cheapskates. Use premium at the pump, it only costs 20 cents more and who knows when your engine will start to detonate itself to death. (I do but the path it takes to get there is to long to narrate.)

As mentioned, you need to check timing with a light at full advance. Timing that is too advanced is a sure way to get detonation and the subsequent damage. Don't be dumb, listen to a guy who always owned bikes with points for 43 years and screwed up more than he can remember.

Tom Graham

 

[twinsarehot]

Oh boy, so after getting an eerie feeling that my compression had dropped since the last time I checked it, I retested the compression. Right side fine, hitting 120ish, left side (my problem side) gets ZERO?!?!!

What should I do before I drop the engine and tear off the head? Perhaps my tappets are incorrectly adjusted/stuck? The bike was running before and without any tell tale moment of failure stopped working.

Another symptom of my bike is that there is gasoline backfire out the intake of my left carburetor (detailed here: http://www.xs650.com/forum/showthread.php?t=1872). By backfire I mean small puffs of unburned gasoline.

Bill sorry for the thread jack, but I NEED HELP!

 

[gggGary]

Throw some compressed air in the plug hole. That should tell you where the compression is going. There are only three possible places, intake, exhaust, or crankcase. possibly you just have carbon on a valve seat. Or a stuck valve. I just tore down a perfectly good GS1100E to find just carbon on the seats. (it did need seals and gaskets). I swear one of these days I am going to rig up a water injection system to clean out the carbon every so often.
Stable as of today
Runners
83 XS650H
97 VT1100 Shadow A.C.E.
98 VT750 Shadow A.C.E.
81 CSR305
79 KZ1300 (6 cylinder)

non runnners
about 4 or 5 XS650's
KZ305