Engine Seize

Yeah, I did it. I forgot to tighten the oil drain plug on the frame this morning after an oil change. Rode out and the plug must have fallen out as I was raging across a long (3 mile) whoop section and I did not notice the oil leak. Well it the engine started to act tight and I slowed to stop and it seized when I pulled in the clutch.

Ok, trucked it home and washed out the oil passages, filter ect. Refilled with oil after it cooled and it will now turn over but not start. Lubed the piston/cylinder and it all turns like normal but will not start although with a tad of throttle it sputters and backfires. Changed plug. No Start.

Any thoughts?

Azemon <----- DUMBAZZ :thumbsup:

ok...If it's a manual decomp engine (400/426):

can you kick it all the way through the compression stroke?

If you can kick it through I'd guess that piston/ring/barrel damage has occoured causing a loss of compression.

If you can't kick it through:

Maybe the lube you put in the bore is also preventing it from starting, instantly fouling the plug. Pull the plug, put it in 3rd gear, hold the throttle wide open and push the bike around the back yard a few times. This will vent the barrel. Refit a new plug and give it another go.

It is a WR450 and the kickstarter and elec. start crank the engine over just like before. I only put light/small amount of lube in so no prob with hydralic lock. Seems to act like before the sieze just no start.

Need whiskey for this one.....ACK

wasnt talking about hydraulicing. The oil you put in there could foul the plug. sounds like you need to do a leakdown test next

Oh, gotcha Bro,

Nope not a fouled plug. Changed it and got the same. I am bummin' thats for sure.

I am really puzzled by the back fire. When I try to start with choke or no choke or hot start then no difference. When I crack the throttle then the back fires.

Hating life at this point.......

Such a dumb mistake......


Maybe you spun that infamous woodruff key on the flywheel during the seize knocking the timing off? :thumbsup:

also kick the bike until the oil starts to leak through the loose oil line/cylinder connection bolt

that way youll make sure the oil is in the head

I drove my previous KTM without a drop of cooling water (unavare) for more than a mile, first heating up the engine and then pulling it on the streets with no damage but sure the oil is the first in line in cooling and lubing

Okay, you can kick it, and the e-start turns it over. The plug is okay but you get back-firing with both methods.

Sounds like you've got a spark.

I'm suspecious of the timing. When the bike seized the timing chain may have slipped. This would account for the back-fire and the not running. If you aren't real mechanically inclined, find someone that is. Get into the engine and check the timing chain. :thumbsup:

The engine may turn but with no oil you may have 'burned' some of the bearings.

Your manual is really good on giving you instructions on the engine. Take you time and go over it. :devil:


I would agree it sounds timing related, maybe it stretched the chain a bit??

Thanks for all the replys Bro's. I am going to dig into it this morning. I also suspect the timing is off so I will start there.

This is not how Sunday mornings are supposed to be. WHAAAA!!!

sounds like you've got a stuck valve. maybe not enough to hit the piston, but enough to screw things up. if an exhaust valve is open a bit, it will allow the fuel charge into the exhaust. when you get a spark, pop, it lights up. with the auto decomp cam in the 450's it'll be hard to tell if a valve is open. i know that's kind of what the decomp feature does on a 450, but when the engine spins any faster than starting speed the valve closes. yours may not be.

Ok, I checked the timing marks and the cam marks line up perfectly with the head. The rotor mark was off just a tad so I figured that the woodruff key may have sheered or bent. Removed the rotor and the key is fine. Sheesh. All this 'cause I forgot to torgue the oil plug. ARGHH. Checked valve clearance, all good. Gonna check piston, rod, crank next. Also check for stuck valves as you said. All this AND it is the start of football season!! WHAAAA!

It that happened to me, I would have the piston out, check rings, the bore etc. The valves, timing etc. (also w'key as mentioned above). Even if you are able to get it going, you cannot be sure of the damage done and you would not want to find out when you are 40 miles from your trailer or home. Sounds major but the only solution in my view.

Well Sox it is starting to look that way. I am gonna pull the head and cylinder next. everything else looks ok. Another interesting thing, my rotor has 3 timing marks on it. The cam timing marks, when flush with the head, line up closest to the 3rd mark.(when rotated counter clockwise).

Not sure which one to use. Book says nothing about it. Shrug.


I sure hate to see you going through all this by email analysis, sounds like it may not be a simple thing but some stuff just doesn't add up. IMHO if you ran the bike without oil and it stuck you should bite the bullet, pull the motor and go through it completely. To think that it stuck and din't do any damage is denial as far as I can see. Good luck, sorry this happened to you, but don't kid yourself. there is not one person on this forum who couldn't have made the same mistake, so don't beat up on yourself, just fix it.. :thumbsup::devil:

It's one hell of an expensive mi$take...I'm sure you won't do that again.

Good luck. :thumbsup:

You guys got that right. Gonna watch a football game and bite the bullet. Yank it out and break it down.

Oh the horror!! :thumbsup:

Good education on the 450 engine though!!

I'll keep ya'll posted....

Well gonna need a new piston for sure. Galled it up and froze the rings. Cylinder has some residual piston aluminum ion the walls but no cuts. Might be able to clean it up and reuse. Lower end all good. Looks like I may get off cheap. Only about $500 for a piston/rings and cylinder.

Yeah, I will not do that again.....

Thanks for all the input gang. Let ya know when it is running again.

Aze :devil::thumbsup:

Life. All the other four letter words were taken....

Well, at least the engine is new instead of old, tight, and greasy. (like a...uh....never mind.....). :thumbsup:

Post the list of parts you need on the forum. These guys are good at finding deals....

Muriatic acid will remove the aluminum from your cylinder walls,

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