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This is what happens if you are overdue for a rebuild

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http://www.thumpertalk.com/forum/showthread.php?t=526278

**PICS ARE ON THE FIRST PAGE, SCROLL DOWN A BIT**

Totally my fault, went to long without a rebuild. My guess maybe 65 hours.

My parts list is nearly over $1000NZ now... new crank, rod, piston, rings, main bearings, barrel, need to split the cases to get all the bits of piston out.

Looks like I learnt the hard way. PAY ATTENTION TO SERVICE SCHEDULES GUYS!!

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What oil and what ratio were you using? 65 hrs doesn't seem that long.

I had over 250 hours on my stock top end before the piston went, and that was only because the radiators got plugged up with mud in an enduro and it badly overheated. There was less than 1 cup of coolant left in the engine and it was thick like honey, all the water had evaporated. The piston melted a little bit at the front and I lost compression. I put in a new piston and rings & coolant and rode 1000+ more miles before taking it apart again. This time I'm getting the cylinder ported and replated.

I'm doing the bottom end as well, if you've got any Q's, send me a PM. I'll be beginning reassembly when the rest of my parts arrive later this week. No problems so far. :thumbsup:

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I use 98 octane at 40 : 1 using motul 800. When we pulled it apart, the cyclinder felt very dry. I couldn't belive it. My only explanation was that it got very hot and burnt up all the oil before it went POOF?

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You might have got some of the dodgy motul 800 that was around in oz a few years ago. A few moto guys, go kart racers and my mates RS125 GP bike had huge engine explosions for no apparent reasons. I think Motul put the wrong label on the bottles or something like that, but of course the sales rep denied any such accusations. I now refuse to use it and am on the Shell Racing X2.

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My son and I ignored some gear shifting problems with his YZ85 and as a result have run into a major transmission rebuild. The bike ran a little low on oil which we missed!! Everyone tells me that it would have been worse in a four stroke.

I ride a YZ450 four stroke and am now paranoid with any noise I hear in the bottom end. What maintenance schedule do you recomend other than the regular fluid checks/changes and air filter?

YZ450vet

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That sucks big time! I blow up my Honda this spring:thumbsdn: , so im getting new bike after the army

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My son and I ignored some gear shifting problems with his YZ85 and as a result have run into a major transmission rebuild. The bike ran a little low on oil which we missed!! Everyone tells me that it would have been worse in a four stroke.

I ride a YZ450 four stroke and am now paranoid with any noise I hear in the bottom end. What maintenance schedule do you recomend other than the regular fluid checks/changes and air filter?

YZ450vet

If your asking about the maintenance on your 4-stroke, check your valves often and change your oil frequently. Also many overlook changing the cam chain once in a while which saves on crank wear and prevents timing jumps which can cause bad problems.

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If your asking about the maintenance on your 4-stroke, check your valves often and change your oil frequently. Also many overlook changing the cam chain once in a while which saves on crank wear and prevents timing jumps which can cause bad problems.

4 brokes are junk, get outta here :moon:

(jokes) :cheers:

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That's 'blown up'! Take that, all of you who say two-strokes are 'more reliable' than four-strokes!

I have both, and have never experienced such a failure on either so far.

Good luck with the rebuild!

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