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temp siezure 08 Yamaha WR250f?

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Ok so im away on holidays son rings and says he siezed his bike in 40c heat...

his mates dad a qualified mechanic comfirms its a siezure...

I get back pick bike up...

kickstarter wont budge. Electric start wont budge...

Put it in neutal, all roles well...

Put it in gear its all locked up

Pull off side cover and turn crank with a spanner... At first its kind of firm, but quickly losens, then feels totally normal...

I replace fluids and give it a gentle kick...all feels good...

I remove ignition plug and turn over on electic starter...all feels and sounds good...

I give it a start and it starts first go...

I give it a few gentle idles and promptly stop it all seems good...

There was absolutely zero metal particals in the oil we drained...

So my question is this...

Whats your thoughts...what happened and is it likely to fully siezure

Should we just rebuild top end... Or run it and see what happens..

Anyone got any idea what happened,mhow to tell what happened or if its going to implode...

It could have been a starter gear siezure, but we couldnt find any evidence...form what i can see with side casings, bore and bottom end look fine... But i have no idea if ring or piston is damaged..

Should i do a leak test?

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Yea I feel like at a minimum do as above stated to be safe. Just at least inspection of cylinder, piston/rings, cams, etc. If nothing looks wrong, guess do a set of rings for the heck of it haha. Could probably cop a good feel of the ole crank with the cylinder off too. Inspections would cost ya a top end gasket kit whereas if something IS wrong inside it could end up costing a whole lot more.

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Hi guys , i pulled the side off and looked at bottome end throught the gap... Saw purple colouration on the crank right at the bearing .....so im assuming its horendously cooked..

I decided to remove engine, pulled top off, looks good....bottom end bearing is very purple ....so doing a bottom end.. And rings...

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Cant put it back together as havent found reason for seizure... 

 

The kick starter was locked solid initially... And twice while idling it it stopped unusually fast at a high idle....once slightly warm...

 

Bike shop reckoned by symptoms described its a bottom end bearing...  ?? 

I have already ordered and paid for a gasket kit and rod kit  from usa  so will split it and take a look... I havent checked the bearing free play yet.. 

Edited by condog_aus

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Check the cam chain, tensioner and valves. Not only check the marks but also confirm the lobes look correct, 2 and 10 O'Clock

Engines do not seize rock solid then free up as if nothing happened. You have some sort of mechanical issue, perhaps the cams, perhaps a chunk of metal getting caught in the gears. Bearings or a seize, are terribly noisy.

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Ok so got crank out and its 100% a siezed bottom bearing...

Strangely its rather free, then locks up... One or a few of the roller bearings must be jamming, broken or collapsed...

Thanks for help.. Now to get a press or get it presed by shop for the replacemnt

pS does anyone know where that solo 10 mm bearing in the impellar side of case came from...

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Ok so got crank out and its 100% a siezed bottom bearing...

Strangely its rather free, then locks up... One or a few of the roller bearings must be jamming, broken or collapsed...

Thanks for help.. Now to get a press or get it presed by shop for the replacemnt

pS does anyone know where that solo 10 mm bearing in the impellar side of case came from...

Guessing you're talking about the one for the clutch, and it goes in the hole in the center of the clutch... see link

 

http://www.motosport.com/dirtbike/oem-parts/yamaha/2008/wr250f/clutch

 

part #22 is what I am going to guess it is. A lot of people dont see it come out then dont know where it came from.

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Been away again...but finally got it all back together today... 

 

Problem is it feels tighter than usual and when i press the starter it screams rather than turns the engine... 

 

Im wondinering a few possibilities and after suggestions before i hit the tools again...

 

Im pretty sure i got the rings in correctly, but perhaps not,,, im also certain i have the timing right...thats an easy check... not 

it

 feels tighter than usual the whole way through the cycle  

 

the crank was pressed together by the yamaha shop and felt good , though the tiniest bit firmer than i expected when i turned it by hand... but not enough to be this firm... 

suggestions welcome 

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So worked it out and just posting incase anyone else has similar issue

 

The tight feeling was the timing chain tensioner

 

As i was inserting it , it must have popped out ans thus was way to tight and fully extended , after fixing that, I put it back together and its running perfect. 

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