How do you know if an engine is siezed?

[Valver]

While riding my SM a few weeks ago.........

The bike made a whrrrrrrrr sound quickly followed by the back wheel locking up. When you push the kick start down it goes so far then sticks. It sounds like the piston is moving then hitting something. Its jammed solid but it does have a certain amount of movement.

Help!

[Cog Head]

have you tryed bumping it
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[Valver]

#well the back wheeel locked up at about 100mph so if that didn't turn the engine then nothing will. Don't think you could bump a 600cc single anyway!

[lilredmachine]

Doesn't sound good.

Could have been a cold seize, barrel constricts and traps the piston. You'll have to get the head off and take a look, but be prepared for the worst.
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[iCraig]

Very unlikely that you've seized a 4 Stroke Single, unless you've ran it along time without oil it in?

As for the piston hitting something maybe the engines dropped a valve or too?

[lilredmachine]

I would say it is infact very easy to seize a 4 stroke single, especially in a high end supermoto at 100MPH, or at least cause a lot of damage to the valvetrain.
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[stinkwheel]

My MZ 660cc single seized due to the conrod snapping in half.

Definately sounds like it is seized mate. To confirm, get a socket on the end of the crank and see if you can turn it all the way round. If it seems like it is coming up against an obstruction, you are going to have to strip the top end. If you can turn it freely, it could be something in the transmission (clutch/gearbox/chain).

At best you will have dropped a valve. At worst it is 'totally fucked' (that is an engineering term for what happens when a 4" diameter piston travelling at 6,000rpm comes to an abrupt halt whilst the rest of the engine is still doing revolutions for 100mph) with various degrees of fuckedness in-between. You wont know 'till you get in there.
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[LUXY DJ]

IF its a single cylinder then give it a compression test by putting finger in plug hole & then kick-starting it & your finger should either suck in or blow out but just 2 see if the compression is still there also knowing the piston IS still moving & also if it sucks more then once then its still being pulled down meaning its still attached to the conrod
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[Kickstart]

Hi

Does sound like it has seized.

Can you push it with the clutch in / in neutral? If so that should rule out the clutch and gearbox.

If it dropped a valve there is a good chance that it would not have seized solid. Enough momentum from the piston to smash the valve into a bent mess buried in the head. Pistons normally seize with heat and then free off when it cools down but not always. A snapped rod might well have occured, but these normally punch their way through the crankcases. Also possible that the cams have seized (old 4 stroke single Hondas used to do this quite well).

Afraid I think you need to start by pulling the head off the engine and having a look.

All the best

Keith
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[lilredmachine]

Is it possible for the piston to be ripped off of the conrod, say if it seized on the downward stroke? It could be the conrod hitting the severed piston which is still seized at the top of the barrel? A wild shot in the dark, but it may explain why it moves, but not to the full extent it should do.
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[Joey Bane]

it's hard to start.(we didn't know that our snowmobile was seized until we checked why it were so hard to start. it was really fucked)
you loose power.
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[Kickstart]

[Joey Bane]

[Valver]

I tried a ratchet on the crank and its not turning all the way. I thought it was siezed at the time but i parked it in the garage and walked away hoping that if i left it for a few weeks it might fix itself

Took the engine out today and i'll maybe take the head off later tonight and have a look.

[LUXY DJ]

no point in beating round the bush cause what it is...is what it is so you got to open it up to see 1st off then get it sorted a.s.a.p

get some pics of the results anyway
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[ZRX61]

Doesn't sound cheap...

[lilredmachine]

Yeah, we demand pictures of tortured thumper innards
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[Mr noOdles]

https://www.dansmc.com/seizure.htm

read this
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[quacker_boy]

[NSR Mick]

have seen it before where the cam chain tensioner fails and the timing slips causing the engine to only turn 3/4 one way then 3/4 the other

[Guest]

[stinkwheel]

[Guest]

I had a similar thing happen on a racing Super Six I was 'testing' on a disused airfield. Just got it flat in top and felt it nipping.

I got the clutch in and wobbled to a stop and my mate drove the van over. We whipped the heads off and it looked ok but when we tried turning the engine over only one piston was moving.

One had siezed at the top and the crank had kept spinning, pulling the gudgeon pin out of the bottom of the piston.

Then the gudgeon pin had slid across and got stuck in one of the transfer ports. The crank kept turning and the pin stayed where it was, wrecking one barrel and the conrod/big end bearing.

How we laughed

[Biker-Kev]

That sounds to me exactly what happened to my RS125. the thing seized so i ordered a full new cylinder and piston kit, took the old one off, binned it and fitted the new one. She started no probs and still going strong to this day.

I am no motorcycle mechanic but just giving you advice from personal experience

Kev
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[Kram]