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Yz85 melted piston, bottom end fine?

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Hello, first time posting on the Yamaha forums here. So I've got a 94 cr250 and my buddy wants to get riding so we picked him up a 2004 yz85 for $500 with a blown top end (no compression). owner claimed he was selling it because his son liked quads more and never rode it, sons friend was going to buy it,took it out for a test drive and said the kid didn't shift and it seized right up. Well after getting it home and inspecting it we found out that their was straight gas in it 😡. So we ordered a already reaplted gem cylinder and a pro x piston kit, should be here next week. Owner claimed it was not ridden very much which I believe the bike looks extremely clean! What I want to know is if the bottom end is still useable as I believe there are not many hours on it. I checked the side to side play at the journal with a feeler gauge and its in spec(0.60mm) and no up and down movement whatsoever, rod does not look bent at all. It would be his first bike and he's really excited to get it running but I don't want to install the new parts only for it to go kaboom. Thanks for any help! 

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That will have aluminum in bottom end big time.  Has to be split,cleaned new crank bearings seals atleast.  You just try and wash I out I bet won't last long at all. Ran with no oil figure everything goes to bottom end first.  You need all new crank bearings and seals.  but if you re use crank clean bearing out real good with weaver brake parts cleaner then litte air. Pre lube good with your brand of twostroke oil

Edited by Motox367
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They did a good job melting that one down .....do you have a picture of what the bottom end of the rod looks like ? Obviously with that much damage to piston /old cylinder at least some metal got into the bottom end . It's a crap shoot to just put it back together depends on what it looks like down in the bottom end the right way to do it is split the cases but I know that can be expensive depending on what you find but it can also be a waste of money on new piston and cylinder if you have to buy it twice .

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2 minutes ago, harry showerman said:

ok, do you think I should still split the cases and clean everything?

Yes new crank bearings and seals :thumbsup: but your call. I've seen this so many times it's impossible to get all the aluminum out of crank bearings.  Goodluck

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The seller perhaps claimed it was not ridden much but he's likely not the original owner.

By the boot scuffs on the RH clutch cover, that bike's got over 50+ hours.

 

As many suggested you need a cylinder re-plate and complete tear down & inspection of the bottom end,

would be shame to wreck a new top end by taking a gamble on the bottom end being okay

(especially since this isn't a mild seizure, lots of aluminium got shaved off)

 

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If mine I would do it all but with that said running straight gas I bet it locked fast and melted fast all together.  Motox367 certainly has my respect on his thoughts. Keep us informed!

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On ‎8‎/‎4‎/‎2017 at 6:58 AM, Smoking 2's said:

:thumbsup:

Read first paragraph

stating that it was strait gas does not explain how he knows. :banghead: 

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If he's ever seen mixed gas before vr's straight it would be easy to decifer. I guess I'm assuming a bit!:facepalm:

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3 hours ago, Smoking 2's said:

If he's ever seen mixed gas before vr's straight it would be easy to decifer. I guess I'm assuming a bit!:facepalm:

You do know what ASSuME means. Hahaha, :lol:

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4 hours ago, Smoking 2's said:

If he's ever seen mixed gas before vr's straight it would be easy to decifer. I guess I'm assuming a bit!:facepalm:

that was PART of my question. if the oil is colored its very easy but many oils are brown which makes it next to if not impossible to tell.

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