YFZ Crank

[Bigun55]

Allright i got a 2007 YFZ 450, i got in in the fall of 06 and sence ive had it, i have went through 3 rebuilds (crank messing up) a water pump rebuild and a transmission rebuild, one question i have is, has any1 else had anything but trouble out of theres, or did i just get a lemon? and the other question is, i have heard some people that say to put at WR 450 crank in them, and it keeps them from reving so high and they dont lock up all the time.Is this true? If so im gonna completley redue my yfz and fix it like that so i can have something to ride and not have to worry about it messing up every single time i get on it. Thanks, Please anyone throw in there opinion on what they think about it, or what i can do to fix it.

[Bigun55]

Hmm, so can nobody help me?

[TilltheEnd]

im interested in this myself b/c i just picked up an 07 yfz that was used but in great shape.

[Dustin075]

I'm on my third motor myself. I threw the rod threw the cases both times. I now have to WR crank and so far have not had a problem, but the motor only has like 5 or so hours on it.

[daddio]

I've heard of people putting the WR crank in pre 2006 YFZ's to get them to 450cc's. But since the longer stroke 2006 came out, most people use the YFZ crank, because it has a larger wrist pin.

We have 4 YFZ motors, and we have only had 3 crank problems. One was a stroked '04 and the other was a Carrillo crank pin that failed and the third one was a worn out '04.

However, I have updated all our motors to the '07 oil pump and squirter, and I clean the screen in the oil tank once a month.

[Bigun55]

How about anyone else?

[2 fast for you]

i have two 04 motors with wr cranks. and i dont think they turn up any less. the one exception to that would be my hot rod wr crank motor i dont think that it turns up as quick. o yah i got my yfz a week after they were reasled and my motor only blew up once and that was when a rock went though the case and the cheap plastic skid plate (i had an aluminum one coming and that showed up later that day).

[THORrider350]

Originally posted by 2 fast for you
i have two 04 motors with wr cranks. and i dont think they turn up any less. the one exception to that would be my hot rod wr crank motor i dont think that it turns up as quick. o yah i got my yfz a week after they were reasled and my motor only blew up once and that was when a rock went though the case and the cheap plastic skid plate (i had an aluminum one coming and that showed up later that day).
now that blows

[Ride1Rob]

WR cranks aren't any more reliable and have no bearing on fast the motor revs out. Like said before, alot of guys (including myself) went to the WR setup to make the bike a TRUE 450. I have since gone back to an 06 crank b/c the WR setup is more wear on the cylinder b/c of the angle at top and bottom stroke. That is weird that you've had this many problems with the bike as I got mine in Feb. of 04 and have had 2 motor rebuilds. One b/c it was time, and another my JE highcomp piston cracked and broke a peice on my rod.

[Bigun55]

I honestly dont understand why its done that, but it has, I mean i like yfz and everything, i just wish that it wouldnt mess up EVERYTIME i ride it, its a leaking antifreeze right now, it is something all the time on it. But this winter im gonna tear it down and redue everything on it, and then ill just hope for the best. BUT i bought a CRF a couple of months ago, the yfz has only been rode once sence then lol

[ztobias]

I have an 04 and its raced hard and so far its only been rebuilt completly ounce and i'm gettin ready to tear into it again because i can hear the cam chain slapping.......not to be rude but how hard do you ride it and how often is the oil changed i change myne after every race or atleast every 2 rides....

[nicker71]

I have a 05 that I bought new. Never had anyproblems with it. I race XC and this is my 4th year with this motor. I replaced the top end last year because it had a lot of hours. I run a gt thunder +1mm piston kit. I also change my oil often, about everyrace or everyother race depending on conditions. I dont use special high dollare oil, just the cheapest atv oil i can find on the shelf. And I clean my uni filter every race. Maybe that the key, or I have just been lucky.

[daddio]

Originally posted by Bigun55
I honestly dont understand why its done that, but it has, I mean i like yfz and everything, i just wish that it wouldnt mess up EVERYTIME i ride it, its a leaking antifreeze right now, it is something all the time on it. But this winter im gonna tear it down and redue everything on it, and then ill just hope for the best. BUT i bought a CRF a couple of months ago, the yfz has only been rode once sence then lol

The leaking antifreeze sounds like the waterpump seal. This seems to be a part that is a total crap-shoot. Sometimes they last for years, sometimes you have to replace them alot, then all of a sudden they last for a long time. I have 4 YFZ motors, and they all are different with that seal.
Most of the time, people with continous problems, are usually putting the new seal in backwards.

I also change my oil after every race.

[Bigun55]

Well now were its a leaking at is out of the bottom of the antifreeze bottle, or thats what it looks like anyway. I'm not no harder on my yfz than anything else ive ever owned, The oil is changed in it, every other ride.

[Bigun55]

Well ive got another update on the yfz, i was going to change the oil in it. Even though i changed the oil in the lsat time i rode it, and it has been rode about 5 miles at the most sence the last oil change, i took out the oil filter and saw metal shaving all over the filter, stuck a rag back in there, and got all kinds of metal shavings out. Im guessing crank bearings? But I'm not sure? and would that also mean that im gonna have 2 redue the crank?

[Ride1Rob]

WOW! This thing does sound like a lemon. There are many things we can speculate on for the shavings. The only way to know is to tear it apart.

[Bigun55]

lol, i swear i belive its a lemon, but i guess ill go take it to the shop and tear it down, i just know its gonna be 500 or more to fix it, and oh boy im lookin so forward to that:( . But oh well i guess. If you ride you might as well expect dissapointment lol

[Dr89]

i just gotta ask....are you doing all the work yourself? because if the engine's just getting thrown back together with stuff out of spec, even just by a tiny bit, your going to have problems.

im not criticizing your mechanical skills lol, just askin if theres any possibility that that's the case?

my 05 has a hot rods crank and has been doing well for over a year, and its been ridin very often and i dont go easy on it. the initial rebuild was done at a dealer before i bought it so the cause is unknown to me, but since then all i've had go wrong was a blown head gasket, but i replaced the 12.5:1 piston with a 12:1 and have been good since then.

but anyways, it COULD be a lemon, but thats a whooole lot of problems in a very short amount of time...so im just curious as to who's doing the work on it ya know.

[Bigun55]

lol, no i aint breaking the motor down myself, lol i could proubably do it, but i really dont wanna try it, im takin it 2 a local shop, the guy thats runs it is one of my dads friends, and im gonna let him look at it.

[Toadz400]

Man, I didn't know the YFZ's ever had a crank problem. I bought my '05 brand new back in '05 and I've never touched the engine besides the cam mod and oil changes. I've got countless hard hours on it and it still runs like a champ.

Have you ever cleaned the screen in the bottom of the oil tank? I know if it gets too clogged with shavings and other deposits it will reduce oil flow.

[Bigun55]

Well now i live in a very small county, there are 5 YFZ's in it, i actually got mine first, then one of my buddies got his, and so on, well mine messed up first, crank siezed, one of my buddies had the same thing to happen a week later, and another one of my freinds run his dry on oil, and it messed up, which you know you cant blame the quad for that one, that was just his own stupidity lol, and the other two are in top shape, never had bit of trouble what so ever out of them. But i dont know, im takin mine next week to get the motor broke down and see whats wrong with it this time.

[Toadz400]

That's crazy, sorry to hear about your bad luck. I've been thinking about rebuilding mine but I think I'd rather not touch it while it's still running great.

[daddio]

Originally posted by Bigun55
Well now i live in a very small county, there are 5 YFZ's in it, i actually got mine first, then one of my buddies got his, and so on, well mine messed up first, crank siezed, one of my buddies had the same thing to happen a week later, and another one of my freinds run his dry on oil, and it messed up, which you know you cant blame the quad for that one, that was just his own stupidity lol, and the other two are in top shape, never had bit of trouble what so ever out of them. But i dont know, im takin mine next week to get the motor broke down and see whats wrong with it this time.

Not to doubt your abilities, but I have to ask because I've seen this happen before..................

When you change oil, are you removing TWO drain plugs (one from the motor and one from the tank), then adding approx 1/2 a quart of oil to the motor, and 1-1/2 quarts to the oil tank?

[Bigun55]

Yes that is how the oil is changed in it, But i havent ever cleaned the screen in the bottom of the oil tank, i guess that could possibly be my problem

[daddio]

If the screen gets clogged with debris, then it will starve the engine for oil.

A friend of mine is tearing his engine apart for the first time, and found borings from the machining process inside. :rolleyes:

If you have already had this much problems with your motor, I would completely disasemble it and flush out everything, including the center hole of the crank, that lubes the rod bearing.

[Toadz400]

Originally posted by Bigun55
Yes that is how the oil is changed in it, But i havent ever cleaned the screen in the bottom of the oil tank, i guess that could possibly be my problem

I think that is what causes the majority of crank failures in YFZ's. I've always kept mine clean and I've had 3 years of hard riding on it with great luck.

[Bigun55]

Yeah i guess whenever i do redue it, its gonna be worked on from the ground up, everything in it will be new, but god i hate 2 know how much this is gonna cost lol.