06 yz450 need some help

well i was out a glamis, bike ran bitchin till sunday. that morning i noticed it took about 15 kicks to start and at first it didnt want to kick over, like it built up pressure of some sort, then it went past it and got it started. i went on my normal ride and what not, came back put it in neutral and shot her off. few hours later i couldnt even kick the thing over when i went to go out again, it feels as is its in gear when im trying to kick it over but its not its in neutral ,my only other guess is that there may be sand in my cylinder causing the piston to get stuck if that makes any sense?

im hoping all i need is a piston and rings and not a cylinder but time will tell thanks for your help in advance

just ran across another post about the cam chain tensioner failing? the guy said it felt like the kick starter is binding which is exactly what my kick starter feels like.

It would be the chain failing in 90% of the cases, not the tensioner, but start by checking the cam timing.

would the chain cause the kick starter to feel like its binding? or the timing or both? when i get off work im goin straight to the garage.

thanks Rick

If the exhaust cam slips out of time because the chain is faulty, it could be nearly impossible to kick.

ok thanks grayracer, im on my way home and im gona start working on it. thanks again for the info and help

i took it apart, the timing is off, the chain is really loose and it did jump on me. now i talked to a guy at my local shop he said it could just be the timing chain but he thinks a valve may be bent to. i ordered a new chain..... For him to tear my engine completely down to see if there is any other problems is $140, then another $110 to put the new chain in. does this sound reasonable? he also said it would be a $100 bucks a valve if there bent.

thanks again

I would take the head off.....if there is any marks on the piston then yes, the valve may be bent...If you are good enough to get the bike where you can see a loose chain then you can go a little deeper and pull the head too...

If you are unsure about putting it back together then pay the guy to do that...

yea thats what i was thinking. im gona dig a little deeper this weeknd.

A cheap test is this:

Remove the cam chain and try to turn the engine over. As long as the cams are out, and the chain is kept from fouling around the crank, the valves will stay closed. If the engine has a bent valve, you won't have any, or at least very little, compression resistance, whereas if you dodged the bullet, it will seal tightly, and be quite hard to turn over. Bear in mind that it will hit compression on every stroke without valves operating, so it will feel weird.

thanks again i will give it a shot and get back to you guys by saturday night. thanks again

It would be the chain failing in 90% of the cases, not the tensioner, but start by checking the cam timing.

++1:busted:

i put my timing chain in, starts fine and sounds better but about after 20 minutes when i blip it a ton of smoke comes out of the exhaust, a little came out when i first started it, but about 20 minutes later it just like puffs outa there. maybe needs new rings im not to sure. any help thanks guys

Typically, If it's white/pale blue-white smoke (not steam), it's oil. If it blows one puff on startup, and then maybe when you open the throttle after a decel, it's valve guide seals. If it smokes continuously under a load, it's rings.

Typically, If it's white/pale blue-white smoke (not steam), it's oil. If it blows one puff on startup, and then maybe when you open the throttle after a decel, it's valve guide seals. If it smokes continuously under a load, it's rings.

yea its smokes continuously, thanks gray

constant smoke....did you take the barrel off?.....did you time the ring gaps right?.....check the end gaps?....I just did an engine that smokes, had great compression, passed the leak down test...had everyone stumped....so I took it apart and found the oil rings were worn to .065....should have been .010 .... and they had no pressure against the cylinder walls...just about fell through the barrel...I think they are a softer material than the sealing rings...the weird thing was the other rings were within limits???....soon as I changed the rings the engine ran perfect and no smoke...

constant smoke....did you take the barrel off?.....did you time the ring gaps right?.....check the end gaps?....I just did an engine that smokes, had great compression, passed the leak down test...had everyone stumped....so I took it apart and found the oil rings were worn to .065....should have been .010 .... and they had no pressure against the cylinder walls...just about fell through the barrel...I think they are a softer material than the sealing rings...the weird thing was the other rings were within limits???....soon as I changed the rings the engine ran perfect and no smoke...

did your smoke out of the exhaust, this is my first time in a 4 stroke motor what do you mean by ring gap and end gaps? thanks

when u say rings are you talking about the piston rings or like a little rubber o ring

He means piston rings, and specifically the oil rings. The end gap measurement is on page 4-46 of the manual, and should be a maximum of 0.020".

Even mor important is how they are assembled. The oil ring expander ring must have its ends butted together, and not overlapped, or there will be no tensione on the rings themselves. Then the ring end gaps must be located on the piston so that they do not align with one another. See page 4-48.

He means piston rings, and specifically the oil rings. The end gap measurement is on page 4-46 of the manual, and should be a maximum of 0.020".

Even mor important is how they are assembled. The oil ring expander ring must have its ends butted together, and not overlapped, or there will be no tensione on the rings themselves. Then the ring end gaps must be located on the piston so that they do not align with one another. See page 4-48.

will do tonight, thanks guys.

is it necessary to check the rings gap when installing brand new parts?(complate oem top end kit).

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