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Piston smashed into spark plug- now it won't turn over

  • Thread starter Thread starter petermatra
  • Start date Start date
P

petermatra

Guest
Hello folks

I'm a virgin GSer. Just got this bike. been riding her around for two weeks. I replaced the stator as that was completely shot/melted/shorted out. Otherwise the bike is in extremely good shape. well maintained.

While riding I heard a Ker-chlunk noise, and the engine quit on me. I could not figure out what happened. She wouldn't start up, or push start. I've done me diagnostics and noticed one of my pistons smashed into my spark plugs! :cry:

-I can hand crank the crankshaft only a three-quarters of a turn. But she completely refuses to budge any further. I can then go back the opposite way from which I came. All four of the pistons do move

-She seems to still shift gears ok as the lights change, but the wheel (or bike when pushed) will not turn the engine completely over

-Why is it still stuck???! something come lose like a rod? or the cam chain?

Please tell me there isn't a whole lot of damage. Thanks for all of your help.


Peter

1982 GS850GL[/b]
 
Sounds like the cam chain skipped or broke, and the pistons are contacting the valves.

You're going to have to remove the head to assess the damage, but the prognosis is grim.

Time to start looking around for a parts bike. Make sure you drain your carbs and store them properly if it's going to take a while.
 
See if we can give my best friend some help!

See if we can give my best friend some help!

Hey all,
Peter is my best friend from High school! He is the one that got me back into riding! :D

He was with me when I picked-up my '80 GS850G from Cycle Salvage in CT for $275!! :lol: I think he has been hooked on GS's ever since he took my for a ride when we got our bikes home. 8) He knew his previous ride a CX500 was no match for the mighty GS! :wink:


I was under the impression the GS 8-valve air-cooled engine was INDISTRUCTABLE!! Guess not! :(
 
Pull the valve cover and see if the cams are timed right with the crank at TDC with 1-4, if they are then it's not a cam chain problem. Also check your cam chain adjustment maybe it's too loose causing the chain to jump.

Pull all the plugs and try to rotate the engine again, if it hit's again you'll need to remove the head and see whats the problem is, drop valve, part of sparkplug, valve guide, bad crank journel, something sucked in through the carbs, etc, etc.

Also the only time a plug gets close the the pistion is when your using 13-1 pistons and a .005 base gasket. Sounds like there's something in there riding on top of that piston hitting the plug. Are you running high compression pistons???
 
woe is me

woe is me

To my knowledge the pistons are stock, and the plugs are the recommended plugs. Timing never changed from when I got the bike.

It looks as if that is the only way to see whats wrong is to dig deep in there huh and see whats NOT moving in there.

p

PS. thanks ahead of time for the replies
 
ouch

ouch

a roller bearing crank rod doesnt come loose, if its hit the piston against the plug, and not the valves, then i would say crank or rod failure myself
 
Re: Piston smashed into spark plug- now it won't turn over

You will have to remove the head and camshafts and take a look. You will have to know what the damage/if any is to the pistons in any event.
Removing the spark plugs might allow the engine to turn over, but that isnt going to tell you anything relative to possible internal damage.

Time to take a look see.

Earl



petermatra said:
Hello folks

I'm a virgin GSer. Just got this bike. been riding her around for two weeks. I replaced the stator as that was completely shot/melted/shorted out. Otherwise the bike is in extremely good shape. well maintained.

While riding I heard a Ker-chlunk noise, and the engine quit on me. I could not figure out what happened. She wouldn't start up, or push start. I've done me diagnostics and noticed one of my pistons smashed into my spark plugs! :cry:

-I can hand crank the crankshaft only a three-quarters of a turn. But she completely refuses to budge any further. I can then go back the opposite way from which I came. All four of the pistons do move

-She seems to still shift gears ok as the lights change, but the wheel (or bike when pushed) will not turn the engine completely over

-Why is it still stuck???! something come lose like a rod? or the cam chain?

Please tell me there isn't a whole lot of damage. Thanks for all of your help.


Peter

1982 GS850GL[/b]
Click to expand...
 
Bid Bang

Bid Bang

If you in deed did hit the plug with the piston, then you lost the big end rod bearing,if the gap is closed, if plug is damaged, and the airbox intact, then this is what happened, these motors are not bullet proof, every bike website claims that there Honda or Yamaha are bullet proof even if they jump out of gear or burn up the electrics, flatten cams or eat rockers and a host of other things that go wrong with all brands
 
true

true

as good as the roller crank gs/gsx lump is, its not bombproof, ive a gsx 11 motor with a rod through the cases after no 1 big end let go, and my mate did exactly the same on a gs850
 
I'd be inclined to lean towards a piston/valve incursion due to timing chain jump or failure. Pull that side cover and check that timing.

An additional check would be to see if the spark plugs will thread out of the head. If there seems to be undue resistance to screwing out, I'd stop until I had the head off to inspect, but I'll bet the plugs come out OK. If they do, then a quick eyeball to the electrodes will tell you if the piston has actually contacted them. I'd much more lean towards valves.
 
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