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smallz700r

Kx250 rattle

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Hey guys, i finally had time to take off exhaust pipe and see what it looks like.... I can put my finger through exhaust port and move piston side to side a little... Bike ran good but had super loud rattling noise i thought it was piston slap.... What do you guys think?20190912_103446.jpeg20190912_103852.jpeg20190912_103913.jpeg

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Need to take it apart.  These pistons crack on the intake side, from the cutout under the wristpin toward the boost port.  You can't tell anything from the exhaust port until the piston comes apart.

Pull that jug.  I'm guessing this thing has a ton of hours on it and it needs a top end regardless.

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Im about to Dan, im just worried it needs the cylinder plated and maybe even crank or connecting rod... the piston feels pretty loose in the cylinder. I just want it running good again! Any tips or cheap places for exchanging cylinders or anything... 

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This is a bite the bullet type situation.  You have no option other than doing it right.

The plating might be okay, you'll see when it comes apart.  If it is worn through above the exhaust port or at the top of the bore, it's done.  Good plating will go hundreds and hundreds of hours, it basically doesn't wear unless it eats dirt or is getting insufficient lubrication.

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14 minutes ago, turbo dan said:

This is a bite the bullet type situation.  You have no option other than doing it right.

The plating might be okay, you'll see when it comes apart.  If it is worn through above the exhaust port or at the top of the bore, it's done.  Good plating will go hundreds and hundreds of hours, it basically doesn't wear unless it eats dirt or is getting insufficient lubrication.

Crazy I mix my gas 30:1 to be safe, but i mostly hit freestyle ramps so really im not that hard on it, and I clean the air filter all the dam time.  Ive only had the bike a couple months so far but it developed a loud ass rattle... The only way Ill know if crank or rod is bad is too pull up and down on conrod correct?

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Yes sir.  Inspecting the bottom end can only be done with the jug off.  Usually cranks burn up before they make a lot of noise so there's a good chance the bottom end is alright.

Pistons do wear out, 100 hours is about the limit.  What I'm saying is the plating doesn't wear unless it's eating dirt or running dry.  Even with proper care, you need a new top end every 75-80 hours.  You just won't need to replate the cylinder every few times if you take care of it.

If you bought the bike used, it needed a top end already at the point.  After a few more months of riding on an already worn top end that piston may be getting ready to come apart.

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14 minutes ago, turbo dan said:

Yes sir.  Inspecting the bottom end can only be done with the jug off.  Usually cranks burn up before they make a lot of noise so there's a good chance the bottom end is alright.

Pistons do wear out, 100 hours is about the limit.  What I'm saying is the plating doesn't wear unless it's eating dirt or running dry.  Even with proper care, you need a new top end every 75-80 hours.  You just won't need to replate the cylinder every few times if you take care of it.

If you bought the bike used, it needed a top end already at the point.  After a few more months of riding on an already worn top end that piston may be getting ready to come apart.

Yes thanks Dan ! Definetely good to hear that about the cranks burning up, I been riding it for weeks with the rattle, im done now though gonna take it apart and send you pictures to see what you think. My 2002 cr250 locked up last year, so i sent cylinder to millenium and bought a piston from them also, got it back and put it together it cranked first kick and only rode for a shitty 5 mins before locking up again and ruining a brand new plated cylinder and piston. 400$  I was so mad i sold it pieces to a rich guy for 1200$ and went bought this kawi later that week and now this... Turns out a bearing was bad in the bottom the rich guy who bought it later texted me.

Edited by smallz700r

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Its a wiseco in there.  They don't crack up too easy but if you let it slap around too much eventually they'll let go.

How does the bore look?

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You can take the jug off without disassembling any of that, or you can use a pick and remove the circlip holding that collar onto the pull rod.

I bet the dowels are holding it.  Put the head back on with a plug in and turn the kicker over by hand.  That should pop the cylinder and head right up.

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You can take the jug off without disassembling any of that, or you can use a pick and remove the circlip holding that collar onto the pull rod.
I bet the dowels are holding it.  Put the head back on with a plug in and turn the kicker over by hand.  That should pop the cylinder and head right up.
Ok put head with spark plug back in and kick? Thanks dan!

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Maybe not kick it, you don't want to launch the jug.  Turn it over by hand, just hard enough to pop the cylinder loose.

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1 hour ago, turbo dan said:

Maybe not kick it, you don't want to launch the jug.  Turn it over by hand, just hard enough to pop the cylinder loose.

Bad news Dan, the jug and piston look good but there is a TON of up/down play in the conrod. I knew that was gonna be the problem, whats the cheapest way to fix? I know Im gonna have to have my local shop split the cases, but at least if I have the motor off the bike it wont be that bad. Thanks for your help man!

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Order up a Pro-x rod kit and find a local shop to rebuild it.  There are a few places that do it here in Albuquerque so I presume you should be able to find somebody up in MI.  Costs about $60 out here.

I would order up new, genuine kawasaki main bearings and crank seals too. 

Got some pics of the rod?  Usually they show discoloration on the big end when they start to go.

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44 minutes ago, turbo dan said:

Order up a Pro-x rod kit and find a local shop to rebuild it.  There are a few places that do it here in Albuquerque so I presume you should be able to find somebody up in MI.  Costs about $60 out here.

I would order up new, genuine kawasaki main bearings and crank seals too. 

Got some pics of the rod?  Usually they show discoloration on the big end when they start to go.

ill go take some pics now.

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