2007 RMZ 250 cracked case!!!

hey everyone i have a 2007 rmz 250 with a posey motor, i have a crack along the left AND right side of the breather tube behind my kickstarter... its cracked all the way through screwing up the idler gear... which the cover that supposed to be on the face of it fell off inisde my motor and wedged itself in behind my clutch basket, all that happened was a couple gears got shaved a hair... just wondering what would be the best option to do. I need new cases anyway but the shop i took it to estimated 2200 to 2300 without even seein what was inside. help please!!

Just happened to my 2008 this weekend. have you heard of others or any dealer support?

damn dude, iv found like 8 or 9 other ppl having the same problem, i took my motor into my dealer to see if they could contact suzuki and see what they could do, no word back right now but ill let you kno.

Just had this problem after rebuilding my 2007 RMZ250. The problem is definitely in the automatic decompressor on your exhaust cam. It is supposed to hold the Left exhaust valve open when you initially kick the bike from the piston being in the top dead center position. If it doesn't hold the valve open you will be compression locked at just prior to top dead center. Guys typically kick the bejesus out of their bikes at this point and crack the cases because they were never designed to be kicked this hard. That is why Suzuki won't make this claim good. The decompressor has a very light spring attached that as the piston drives down the cylinder it shuts the exhaust valve(due to centrifugal force on the decompressor from the cam spinning). This in turn allows the piston on its upstroke to build compression properly(which it couldn't do if the valve was still open). The problem with your bikes is one of two things. If your left exhaust valve clearance is excessively large(I set mine at 0.008 of an inch plus or minus 0.001 of an inch) the decompressor cannot make enough contact with the top of the valve stem to actually partially open it. The other issue that may be the case is that the decompressor spring has an issue. It can have a couple of different issues:

1) Spring is broken-this stinks because you can't buy a new one that I know of and have to buy a $288 exhaust cam from Suzuki(Hotcams and other aftermarket cams DO NOT come with the decompressor or spring)

2) Decompressor has some grit in it-remove it by pulling the allen head the holds it in place, clean it, lube the area where the decompressor contacts the cam gear face with a SMALL amount of moly paste or bearing grease, reinstall, ensure you either take a digital picture of how the spring attaches or take a real good look before pulling the allen. It took me a minute to put mine back on.

I would pull my rocker cover(I know there are no rockers on most mx bikes) and see if the decompressor operated smoothly with my finger. Mine hung up with some crud in it after my stock(man they are crap) clutch basket lunched itself. If it operates smoothly(mine sometimes operated smoothly and other times not so it might be worth taking apart anyway and cleaning/lubricating) I would check valve clearances(you are in there anyway and it makes the bike start SOOO much better with spot on valve clearances on this model bike). Good luck.

-An intelligent man learns from his own mistakes, a wise man learns from other's mistakes.

As an aside Suzuki has updated the cases a couple of times. The new cases have webbing added to strengthen the case. Make sure if you do rebuild you bike you get the new cases. Look at part numbers for 2007/2008/2009 and get the latest cases you can find.

I appreciate the informative reply on why the cases cracked. I had an 07 do crack last year and an )8 this year crack. In addition I know of two other 08 thats cracked the case since mine did in early april.

I don't put much hope in Suzuki coming through on this either.

yeah i got no help at all, suzuki said it was to old and was a race bike, so i went with just buyin a motor off eay and swapping heads so i could still run the posey head... i am now trying to sell it and lookin forward to buyin a 2011 rmz250

My case just cracked on my 2008 RMZ 250 :foul: .  

 

I didn't realize it was cracked and 99% of the oil leaked out over a practice session and 2 race motos.  It started making a screeching noise so I shut it down and then realized the crack.  Surprisingly the top end piston/cylinder and most internals were still in good shape.  The kick starter gear was loose because of the case crack and the kick start idle gear would contact the top part of the case when kicking over.  This felt like TDC

 

The new (and revised) case just came in.  Hopefully this doesn't happen again.

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