mcx nytro knocking

[dicey]

so guys heres my problem i have a 09 nytro that i put a mcx 240 kit on about 1200 miles ago its always ran perfect from day one 12 lbs boost. well i take it out today for the second ride this year ,fire it up at the truck warm it up head out dont get 5 miles on the trail, just puttin along, the sled kinda misses a couple times then i start hearing a clattering kinda even knock ,i immedeatly come to a stop, the engine light flashes, and the sled shuts off ,but i fired it right back up no problem. we shut it back off pull the side panels ,and it has blown a little oil out the breather tube ,checked everthing, thats all we find so fire it up ,but still knocking, sounds like the engine ,we then towd it back to the truck . i get home drain the oil into brand new drain pan and there's lots of metal fileings in the oil ,i also pulled the mcx scavange pump and it seems fine ,so if anybody has any thoughts on what the heck please post.

 

[Thistledoo]

Center rod brg is toast.....

engine is savable....will need new crank, rod ect ect.

At least you didnt punch a hole in the block. then its junk. Make sure you clean out oil tank and pull screen outta the tank.

Lots of labor coming up.

 

[Lococoin]

Center rod brg is toast.....

engine is savable....will need new crank, rod ect ect.

At least you didnt punch a hole in the block. then its junk. Make sure you clean out oil tank and pull screen outta the tank.

Lots of labor coming up.

What would cause that bearing to fail so early?

 

[Thistledoo]

happens from dismounts when sled is on its side and low oil pressure shuts it down....over and over center rod brg is last to get oil and is the weakest link in that engine.

Do you have a tether on this sled and was it on there from day one?

I have experienced this first hand....not a good deal

 

[dicey]

no i do not have a tether ,over the life of the sled its been on its side mabey 4 or 5 times always shut off the key tho it never shut it self off

 

[Thistledoo]

Start yanking engine.....you have troubles.

rod brg is first thing to let go from detonation also....

if your oil has flakes....its done. Especially if you can hear the slight knock at idle.

Yank it and get ready for a big project.

 

[dicey]

happens from dismounts when sled is on its side and low oil pressure shuts it down....over and over center rod brg is last to get oil and is the weakest link in that engine.

Do you have a tether on this sled and was it on there from day one?

I have experienced this first hand....not a good deal

did yours have oil blow out the tank vent and what about a blown rod bearing could cause this?there was alot of brass looking flakes in the bottom of the engine where the oil pump is ,i am going to pull the engine, at this point i just pulled the front end to remove engine oil pan.

 

[Duke]

Let me know if you need any parts, I may part out a Nytro motor.

 

[Thistledoo]

Mine happened on the hill...heard the knock. Shut her down and flew it home.

Never started it again as I knew what happened. Re used block which was fine but crank was junk....

get someone who knows yammie engines it needs some thought as they use colors for brg tolerances ect ect....or get a good shop maunal.

By the time I got mine tore down and then gathered parts it took a solid 3-4 weeks.

 

[dicey]

Mine happened on the hill...heard the knock. Shut her down and flew it home.

Never started it again as I knew what happened. Re used block which was fine but crank was junk....

get someone who knows yammie engines it needs some thought as they use colors for brg tolerances ect ect....or get a good shop maunal.

By the time I got mine tore down and then gathered parts it took a solid 3-4 weeks.

thanks for the help,there must be other guys this has happened to,i cant believe this can happen just from normal use ,I have an xp as well with over 6000 miles on it, wheres the 4 stroke reliability?how can a guy feel confident . I bought this sled brand new at PG Yamaha and bought the turbo there as well all because i wanted a reliable turbo sled ,this didnt last as long as some turbo 2 strokes.I hope there is some obvious thing that made this go ,because i have been what i thought was overly careful with this sled,i am very picky with my stuff,would never loan it ,or run it if anything wasn't perfect,it has never ran for more than seconds on its side ,I do carve alot but i would think that a sled should be made to lay over,just dosn't make sense

 

[wilmot]

They should come with a shut off valve stock. Anyone with a 4-stroke yamaha better install one.

 

[julio]

rebuild

oft makes a great tether with a vent shut off so the oil doesnt drain out.

make sure you change the gears in the oil pump all that crap will have gone threw the pump and like a bearing with a nick in it will slowly go to crap on you. julio

 

[MRFUSION]

Crank 240HP out of your XP and see how long it lasts. We are installing tethers and roll over valves on all the kits we install. Yamaha is selling them as an accessory now, but it should be stock. My opinion. Shad

 

[boostedballz]

Has the oil light ever come on with that sled? I grenaded an Apex motor by running too close to the rev limiter causing a small amount of oil to blow out of the breather causing the oil level to drop slowly. A couple of cosecutive rides without checking the dipstick and my low oil light flashed once. I topped up right away but it was too late and my engine developed a self made inspection hole the next ride..... All it takes is one time for that bearing to heat up and eventually fail. With moving parts they all have an iminant failure date it's just a matter of maitenence, abuse, and sometimes pure luck that makes the difference between 1500 and 15,000 miles before it happens.

LL

 

[dicey]

Has the oil light ever come on with that sled? I grenaded an Apex motor by running too close to the rev limiter causing a small amount of oil to blow out of the breather causing the oil level to drop slowly. A couple of cosecutive rides without checking the dipstick and my low oil light flashed once. I topped up right away but it was too late and my engine developed a self made inspection hole the next ride..... All it takes is one time for that bearing to heat up and eventually fail. With moving parts they all have an iminant failure date it's just a matter of maitenence, abuse, and sometimes pure luck that makes the difference between 1500 and 15,000 miles before it happens.

LL

i don't think the oil light has ever been on ,i lost some when i first had it before the turbo once (about half litre)but dont recall the light
anyway sounds like i,ll have to come pay Chris a visit for a few parts soon.

 

[Thistledoo]

On mine I took the oil pump apart last and it wasnt good....replaced the whole thing with a new unit. Also make sure you replace all rod bolts ect ect


have you got it apart yet?

 

[dicey]

On mine I took the oil pump apart last and it wasnt good....replaced the whole thing with a new unit. Also make sure you replace all rod bolts ect ect


have you got it apart yet?

no going to try and get to it tomorrow

 

[MTN_VIPER]

dicey

When you get it torn down, besure to pull the valves on the cylinder(s) that have the bad rod bearing(s). What can happen if the rod bearing is spun and the crank is shot. The excessive clearance can allow the piston to travel father up into the bore and just "kiss" the valves. They may appear ok just looking at them, so what you'll want to do is chuck the valve in a lathe and check it for straightness.
A slightly bent valve can stick open, allowing the piston to smack it. Then each time the piston contacts the valve again, it bends it some more until the head of the valve breaks off and lunches your newly rebuilt motor.