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ttr90 intake valve bent 2nd time Help!

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recently aquired a 2007 TTR90E for $100. I check it out and just needed the carb cleaned really bad. it was running for a good 2 weeks then one time I took it out when the kids went inside and I wouldn't say I went nutz but the next day no compression and intake valve bent colided with piston. 

 

So I took the time to rebuild the top end piston, rings valves, springs, etc. I finally put it together and it fired right up kids were pretty pumped again. Following the middle of ground breakin I did a 4 heat cycles one day then the next day warmed it up and did one power cycle 2nd gear 3/4 trottle to marry the rings to the cylinder. I let it cool then I went to fire it up and boom tap tap noise on from the intake rocker and no compression. Bent intake valve again. I am at a loss. yeah I could get new gasket and valve and fix it again but what the hell is happening to it??!?!? its a 4 stroke the valve should be completely closed by the time the piston hits the TDC.  I think I read somewhere posible chain tensioner. but I just checked the timing and everything is spot on. 

 

kids are bummed I am bummed not sure what to do. 

 

Also when I rebuilt the top end I cleaned it squeaky clean. I could eat off the parts. moly lubed everything moving new seals etc etc. just sucks. 

 

any help would be awesome 

 

 

 

 

 

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I figure I would add to the post just for my own reference. I figure I had some time and took the head off and it was the intake valve bent struck the piston most likely on a cold start since you can see the nick on the piston. I figure the valve is getting stuck. I popped of the spring and sure enough it was hard to take the valve out sticky. Also on the top of the it seemed coated with like sticky residue. Burned oil maybe? So I decided to go the route of clean the head and put the valve back in and redo the timing. So i put it back together the timing is check mark on cam matches the single mark on the rotor not the double mark. The last thing before I fire it back up is the gas tank seemed pretty nasty so I ordered a new petcock and drained the old gas. I guess we will see. btw the timing chain seems pretty tight. 

 

https://goo.gl/photos/YW6Xz6SugXsASBuB9

Edited by dirt_chuck

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A few possibilities,

 

-timing chain could be stretched (even if the tensioner makes it feel tight)

-worn / damaged timing gears (cam / crank)

 

-worn / damaged valve guide inside the cylinder head, binding the valve from returning to it's fully seated position

Edited by mlatour

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Thanks for the reply, 

 

The cam gears looked good no single side wear etc but did not check the chain or crank gears. Being a shade tree mechanic I don't have the puller for the flywheel to get at the chain and really didn't want to take it to the shop $$ I cannot imagine what they would charge to replace the chain $11 and gear. 

 

I changed out the petcock and cleaned the carb again we will see how long she runs. Both times the valves bent I road it , maybe its my bad luck I'l stay off of it this time. 

 

The strange thing that I cannot get over is that both times it was after I rode it a bit hard and let it cool completely and when it struck the piston it was on start it seemed. Time will tell. 

 

Thanks again.

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Buy the correct puller, under ten bucks.

http://www.motionpro.com/motorcycle/partno/08-0027/

Confirm this is the correct one first!!!!!!!!!!!!!!!!!!!!!!!

 

New cam chain, new tensioner. Install the tensioner properly, it can easily be done wrong and over tension the chain.

Inspect the cam chain guides for wear

Inspect the valve guides for damage

 

 

Fix it right once.

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Buy the correct puller, under ten bucks.

http://www.motionpro.com/motorcycle/partno/08-0027/

Confirm this is the correct one first!!!!!!!!!!!!!!!!!!!!!!!

New cam chain, new tensioner. Install the tensioner properly, it can easily be done wrong and over tension the chain.

Inspect the cam chain guides for wear

Inspect the valve guides for damage

Fix it right once.

ImageUploadedByThumper Talk1447881766.057256.jpgyou need this style puller which is essentially a steering wheel puller to remove the flywheel, The bolt holes to remove the flywheel are in a triangulated pattern, on these bikes aswell as the ttr125, this isn't like a flywheel on a yz250 that has a large threaded hole around the crankshaft snout. Edited by yzdude250f
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📎ImageUploadedByThumper Talk1447881766.057256.jpgyou need this style puller which is essentially a steering wheel puller to remove the flywheel, The bolt holes to remove the flywheel are in a triangulated pattern, on these bikes aswell as the ttr125, this isn't like a flywheel on a yz250 that has a large threaded hole around the crankshaft snout.

Thanks for catching my mistake. :thumbsup:

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On 11/16/2015 at 5:43 PM, dirt_chuck said:

Thanks for the reply, 

 

The cam gears looked good no single side wear etc but did not check the chain or crank gears. Being a shade tree mechanic I don't have the puller for the flywheel to get at the chain and really didn't want to take it to the shop $$ I cannot imagine what they would charge to replace the chain $11 and gear. 

 

I changed out the petcock and cleaned the carb again we will see how long she runs. Both times the valves bent I road it , maybe its my bad luck I'l stay off of it this time. 

 

The strange thing that I cannot get over is that both times it was after I rode it a bit hard and let it cool completely and when it struck the piston it was on start it seemed. Time will tell. 

 

Thanks again.

 

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