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Cylinder/head Damage (with pictures)

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Hey everyone, cracked open the cylinder today to put in a new top end and discovered some disturbing things...

Here is the head:

Head.jpg

Here is the top of the piston(NOTICE THE GROOVE IN THE SIDE):

Piston.jpg

Here is they cylinder:

Top View:

CylinderTop.jpg

Bottom View:

CylinderBottom.jpg

They cylinder is what im most concerned about, you can see it looks like a little chip of aluminum stuck in the groove. You can also see a groove in the piston that corresponds to where that chip in the cylinder is. That groove is about 2mm deep in the side of the piston. Weird thing is, I was riding the bike last week and it wasnt low on power or anything, ran just fine, started on the 6th kick. But the head is peppered and the top of the piston is shot. No damage to the bottom end from what I can tell.

Do i need to send this in for repairs or could i slide by with a new piston and pretend it doesnt exist? I was planning for a dune trip this weekend...

let me know what you think.

Edited by Chikang
forgot to caption pic

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Looks like you left a wrench inside the jug when you buttoned it up. Or an elephant.

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Looks like the rod bearing failed. Good time for a 300 kit, but don't forget to address the bottom end problem. PM sent.

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Looks like the rod bearing failed. Good time for a 300 kit, but don't forget to address the bottom end problem. PM sent.

:thumbsup:Agreed

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i put it back together today and it runs fine. just fine, you would have never known there was damage unless I had taken it apart. I dont understand it.

I'm gonna go with a 300 kit from eric gorr, the bottom end is perfectly fine, not play in the rod at all. Also no scoring or scuffs on the crank.

I cant believe this thing runs, and it runs well. So i'll let everyone know how the dunes are. :bonk:

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Looks like the rod bearing failed. Good time for a 300 kit, but don't forget to address the bottom end problem. PM sent.

YES!! thats exactly what has happened!

take a flaslight and rotate the crank up n down and i bet youll see in consistency in the lower rod bearings.

please take our word for it, redo the crank, same happened to me. i checked the play and it all seemed great. i put it back together new topend ran super good too. hour later and it happened again.

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Wow, you are a keener chap than I. The potential for major and extensive damage if you run it like this is very real. This is repairable. Just my opinion. Good luck.

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agreed , this happend to me , one of the circlips came out and wedged its self in the barrell , can almost guarantee you will regret not getting the cylinder sorted , believe me itl cost you more when it goes again than what it wouldve if you fixed it this time

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Drain your Oi-l Run a magnet thru it.Ive had Reed screws-Rags-Power-valves-Rocks-Neighbors Cat LOL-35+yrs of Dirt/Street Bikes. Sometimes I get lucky sometimes I turn Gears into Metal washers.Ive passed Reed screws with just Small Clylinder grooves. I would Re-ring and get a few more rides out of it.

But-in due time-So the fouled plug would start. So wiether I would Sleeve/Seal I Just could'nt waste the $$$$$ and Labor knowing that there is something still bouncing. If you plan on keeping this bike for awhile-Go in for surgury-Good Luck.-Happy N-year.

juststuff013.jpg

Smash.jpg

DrewsRM157.jpg

MyYZ025.jpg

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Drain your Oi-l Run a magnet thru it.

What exactly will that prove? The transmission is completely separate from the engine crankcase.

Chikang -

Is this your first time in this bike's top end? I ask, because maybe this is damage from a previous owner. Could be the plug dropped a ground strap and long ago passed thru the engine.

Or, if it is fresh damage, it's been pretty well covered. My guess would normally be rod bearing, but typically it's bigger indentations from what I have seen. Plug ground strap you'd notice, because the bike dies as it happens.

In any case, that's going to need a replate. If it were my bike I'd do it before running it and making the damage any worse. But if you are doing a 300 and it's all getting bored out anyway.....

Lets just hope it's not the bottom end and you get more catastrophic damage.

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Your right Adam, I didnt notice that before. Looks like someone ground the edge of that port to "deburr" it so nothing would catch on it. Almost looks like a ring broke judging by the amount of material missing from the top of that port to me.

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Guess I should have been more specific--Drrrrrrrr-LOL.What I meant is that I have had Top-end failures do a number on the crankshaft-not by things trying to squeeze past the seals-LOL,but Heat transfer-warp-Super play.

Check rod clearances up/down-side/side,still --the apperance of your crankcase oil can tell you alot---I would just hate to see you run a new piston kit with the Cylinder in your Pic.

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Those lines running up the cyllinder and the side of the piston mean that some bearings have failed in the bottom end and the little metal pieces worked theyre way ip your jug and gotten in between the head an piston, thats why the head and piston have those markings in them, complete motor rebuild is required

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i disagree , this also happend to me but it was not any pieces of metal from the bottom end that tore into my piston and jug it was one of the circlips in the piston so really what im sayin is it couldve been anything that caused this

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