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my newest motor blow up leaves me stumped

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riding this afternoon and the bike lost compression, bogged out and started tapping, pulled in the clutch and hit the kill switch immediately and walked it home. got home to find out it bent the right intake valve and cracked the guide. the seat and head surface is okay but the valve seems to have tapped the piston ever so slightly. valves were in spec so it is to my belief that the keepers or the retainer failed and the valve pulled through the retainer, snagged the piston and bent. the spring has an ever so slight wear mark that the valve spring retainer seemed to be eating at it, the retainer snapped clean in half and ive never seen this happen nor do i have a good explanation of why it did. with the exception of a valve float or failing retainer/keeper

i have some WMR cams in it and heres the specs for all you cam profilers out there:

valve lash: .004

valve lift: 0.360

duration: 266 degrees

duration @ 0.050: 244 degrees

lobe center: 106.5

intake opens 15.5 degrees before TDC

intake closes 48.5 degrees after BDC

i dont believe a .360 lift cam is so aggressive that it would snap a retainer? the valve bucket is totally fine. i know crower sells a .380 cam with an 18 degree advancement and its not snapping retainers in half. somebody help me figure this one out. heres some pics to have fun looking at

IMG_4271.jpg

IMG_4272.jpg

IMG_4273.jpg

IMG_4274.jpg

IMG_4275.jpg

IMG_4277.jpg

makes me kinda mad cause my motor blew up 2 short rides after i just got my rg3 works a-kit..... :bonk:

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Those questions are beyond my comprehension. I just wanted you to know that I am bummed for you. Good luck with the rebuild, man.

Chris

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Are those OEM retainers? With that cam lift and what looks to be a pretty fast ramp.. Id be using some light weight billet Ti retainers. For strength as well as a lighter valve train.

If aftermarket retainers whose? and did you use new cotters?

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its all OEM besides the cams and springs. the springs have a large amount of hours though so maybe they just floated? but the piston didnt tap it very hard by any means. ill have to look into the billet retainers if i want to continue running these cams. i would like to because these things make HUGE power. more than my pro circuit cams

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large amount of hours on oem or heavier valve springs is just asking for float... by the way hell stock cams on these bike are still agressive so huge amount of hours on any valve springs is running the risk of floating the valves if you ride at any clip..

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large amount of hours on oem or heavier valve springs is just asking for float... by the way hell stock cams on these bike are still agressive so huge amount of hours on any valve springs is running the risk of floating the valves if you ride at any clip..

do you agree that a valve float would be the culprit? it happened mere seconds after i started the bike and didnt even exceed half throttle thank god, if i was higher up then it probably woulda been worse. i wasnt sure if it was the retainer that failed first

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the following pictures can explain this:

worn guide gave intake valve enough side to side play to snag the valve slot in the piston, bent the valves and the piston came back up and the bent valve tapped it on the center of the crown. intake valve seemed to have been tapping the piston, i learned today that the 2010 piston is 0.05mm taller from the piston pin to the top of the crown, i was running the 2010 piston in my 2009 which may also be a cause of this too.

IMG_4282.jpg

IMG_4283.jpg

must have been a comination of 0.05 taller piston, the higher lift cams (cause i had no valve tap on the stock cams and ran the motor on stock cams and 2010 piston for 8 hours no problems) and a worn valve guide. should have it up and running in no time :bonk:

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It´s 0.5 mm taller.

Time to replace all parts in the head. Leave nothing old in.

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is the 2010 piston higher compression? If you want to run a higher compression piston (which you should with bigger cams) then i would go to a forged piston that had a higher dome with bigger valve reliefs so that the valve doesnt make contact.

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It´s 0.5 mm taller.

Time to replace all parts in the head. Leave nothing old in.

already on it, only things im leaving is the bare head and the cylinder. its getting new guides, valves, springs, retainers, spring seats, keepers, seals, 5 angle valve seat job, new piston :bonk: any clue what the side to side play tolerence for the 09 rod is?

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hahaha! sorry for laughing but it seems funny that only a few days ago I was saying there was some sortof reason there is a requirement for a thicker base gasket on running a 2010 piston in an 09.. Guess this would be the afteraffect of why..

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hahaha! sorry for laughing but it seems funny that only a few days ago I was saying there was some sortof reason there is a requirement for a thicker base gasket on running a 2010 piston in an 09.. Guess this would be the afteraffect of why..

yup you sure did. problem was, i put the piston in like 8 hours ago and it ran fine on the stock cams :bonk: but after 2 hours, the WMR cams went wrong. seems to me like its okay to run the 2010 piston on a 2009 with one gasket but is cutting it very very close, swap the cams and then it goes bad. not sure if im gonna put a 2010 piston back in, probably gonna stick with an 09 piston

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the kx is really tight on intake valve to piston clearance...so I'd guess the piston is the culprit.

I always thought it was 1mm taller - never measured side by side...but maybe what I am thinking is crown is 1mm thicker...

Really good cam set ups for that bike push the edge of valve to piston clearance..and with stock valve springs it becomes a major issue if it floats at all.

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the kx is really tight on intake valve to piston clearance...so I'd guess the piston is the culprit.

I always thought it was 1mm taller - never measured side by side...but maybe what I am thinking is crown is 1mm thicker...

Really good cam set ups for that bike push the edge of valve to piston clearance..and with stock valve springs it becomes a major issue if it floats at all.

yea i measured side by side and its 0.05mm, remember 2 base gaskets if you ever decide to run a 2010 piston in an earlier year. i measured the base gasket and its 0.05mm thick so its perfect fit!

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