Yamaha Anyone Know When rebuild The YFZ450

[firedowg]

My buddie blew his 450 up last summer when he talked to Yamaha they said that you have to do piston and rings at 30 hours and check the valve clearance. Becouse the 450 is a bure bread race machine was there excuse for the 30 hour rebuild. Valves i can see but the piston doesn't seem right. If this is the case I should have stuck to my 2stroke. When this piston let go it tore the pin right out and bent the rod,valves and destroyed the cylinder i just think its going to cost a awful lot to keep the 450's on the trail or dunes at that rate.

Anyone have any answers

[2fun]

My buddie blew his 450 up last summer when he talked to Yamaha they said that you have to do piston and rings at 30 hours and check the valve clearance. Becouse the 450 is a bure bread race machine was there excuse for the 30 hour rebuild. Valves i can see but the piston doesn't seem right. If this is the case I should have stuck to my 2stroke. When this piston let go it tore the pin right out and bent the rod,valves and destroyed the cylinder i just think its going to cost a awful lot to keep the 450's on the trail or dunes at that rate.

Anyone have any answers

Thats a bunch of crap! There is NO WAY you have to change out the piston and rings at 30 HRS.

Maybe if you are a racer or something, but give me a break. How many hours did he have on the motor?? I use synthetic oil in mine, and I don't even plan on THINKING about changing any of that stuff till it gets to be around 100 hrs or so. Sounds more like Yamaha guys not wanting to take any kind of responsibility for their products. An easy way out if you will.

Checking the valves before then I can also see, but piston and rings..........NO!

What kinds of mods had/has he done to it? Is there any chance HE messed something up??

[onyx]

sounds like a combination of unfortunate events such as running to lean ,timing to

advanced and bad fuel source,if he installed a rev box that takes it up to 11500rpm

i believe it. not a normal situation even racing it ,to break that motor.....solid bike

i have a 05 yfz 450 it takes everything i throw at it with a smile

[firedowg]

He Had the high compression Piston gyt Cam's and pipe but him and my self put it togeather and we've been at this stuff for about 10 years each so I'm sure that we did it right he had about 40 hours on those mods when it blew "NO REV BOX" my 450 has the same mods with about 10 hours and no problem yet

[2fun]

You say about 40 hours with those mods. How many hours TOTAL on the piston and rings?

[firedowg]

same amount he put the high compression gyt piston in at the same time

[2fun]

same amount he put the high compression gyt piston in at the same time

Should that set up be run with higher octane fuel?

[SANDDOG]

Hey, I'm In The Middle Of Replacing My Piston And Rings.i've Got Over 100+ Hours On The Old One And My Piston Still Looks Like It Could Finish Out The Season. Perhaps Your Buddy Ran His A Little Lean And It Got Too Hot. Anyway, I Wouldn't Wait As Long As I Did But You Could Go At Leasat 60-70, Maybe More If Your Ride Is Running Properly.

[firedowg]

i know the thing was not running lean I just think that it was one of those thing that could happen and it did and yamaha didn't want to take the responsibility for it. So until i hear other I'm just gonna keep driving mine like i stoled it.

[jmics19067]

seeing a lot catastrophic engine damage on the YFZ at work. when they blow up they blow up big time. WE have 3 jobs right now that are at the tune of 2300$. with your old 2 stroke say the banshee you could run it till siezed or till it made no power and it generally only costed you a top end kit and reboring the cylinder. THis YFZ is something different it is appearing to make a lot of power right until it destroys itself. $2500 new head new crank new cylinder and everything in between (1 exhaust valve is 95 $). This thing is a very high strung race engine .

When Yamaha recommends its 30 hour rebuild ( which is in my mind conservative meant for the protection of Yamaha at national level racing) it doesnt nescesarily mean replace all parts .... but you should inspect /and measure everything then replace anything that is questionable.If the 30 hr inspection/rebuild is done properly you should never run into the truly expensive problems.

[firedowg]

What about the high compression piston should u just replace stock with that at 30 hours or stay stock

[jmics19067]

I would stick with the stock compresion ratio. 12to 1 is pretty stout and taxing reliability already.

[2fun]

seeing a lot catastrophic engine damage on the YFZ at work. when they blow up they blow up big time. WE have 3 jobs right now that are at the tune of 2300$. with your old 2 stroke say the banshee you could run it till siezed or till it made no power and it generally only costed you a top end kit and reboring the cylinder. THis YFZ is something different it is appearing to make a lot of power right until it destroys itself. $2500 new head new crank new cylinder and everything in between (1 exhaust valve is 95 $). This thing is a very high strung race engine .

When Yamaha recommends its 30 hour rebuild ( which is in my mind conservative meant for the protection of Yamaha at national level racing) it doesnt nescesarily mean replace all parts .... but you should inspect /and measure everything then replace anything that is questionable.If the 30 hr inspection/rebuild is done properly you should never run into the truly expensive problems.

From the looks of your post, I am assuming you are a Yamaha Mechanic?

If so, are we supposed to replace the cylinder studs everytime we remove the head since they are torque to yield bolts?

Sounds expensive to have to do that every 30 hrs??

[firedowg]

ok than what mods would you do ive just got the gytr pipe know and we ride mostly dunes and trails here in michigan i was goin to do the cams before summer

[jmics19067]

From the looks of your post, I am assuming you are a Yamaha Mechanic?

If so, are we supposed to replace the cylinder studs everytime we remove the head since they are torque to yield bolts?

Sounds expensive to have to do that every 30 hrs??

yes I work at a dealership but I am far from having all the answers ,personally I rebuild from the ground up every winter on my own toys if they have seen a lot of use that year. I probably won't follow the 30 hrs myself on my wr450 bike but then again I do not ride against the rev limiter, have less wieght and less traction that the bike has to work against compared to a quad . this thing is new to me and I am a little leary of the ti valves since they are not really noted for longevity compared to steel so i wll be keeping an eye on valve clearance closely. MY wr 400 was a strong runner and I ran it a lot... had it for 1 1/2 years both winters I dismantled for inspection and only had to replace the rings the second time so you could say that it was a waste of 2 top end gasket sets. I prefer to think of it as piece of mind for the following summer.

. seeing these quads in the shop with expensive damage is scaring the hell out of me since I have basicly the same engine in my bike Mind you it is only 3 out of 20 - 25 we sold and these things are fairly hammered , found sand in the air boot going to the carberator on one,another one was stolen and recovered after blown up and the third one doesn't look much different than the stolen one.can't really blame it on the engine but it is still scaring me and making my wallet pucker up

I would replace the head bolts on torque to yield bolts just like I would replace the head & base gaskets relatively cheap insurance in my opinion.

If you are of a mindset like mine I tend to try and keep a hold of things as long as possible. If I find out that I am spending too much money not finding a problem I lengthen my service intervals. I guess I am just repeating myself in that.."When Yamaha recommends its 30 hour rebuild ( which is in my mind conservative meant for the protection of Yamaha at national level racing)"..

Yamaha does not know the usage of the vehicle but it is giving a basic idea of not to have any problems for its intended use. A weak valve spring while running against the rev limiter doing donuts in the snow can make you feel like this guy:mad:

[jmics19067]

ok than what mods would you do ive just got the gytr pipe know and we ride mostly dunes and trails here in michigan i was goin to do the cams before summer

I would open up the exhaust and get the exhaust cam timed right(new cam) so the engine would atleast run as it is intended too.keep it fresh and see what you think you need from there. HIgh compresion sounds like it might be quite a bit of fun in the dunes but your maintenance schedules,fuel allowance and wallet should decide that not me.Personally I think the stock compression is more than enough for trail riding and I am actually thinking of cutting mine down a smidgen for a little bit smoother part throttle fighting thru the nasty stuff.

[firedowg]

when you say new cam do you mean like a set of HOT CAMS

[2fun]

when you say new cam do you mean like a set of HOT CAMS

You should check out the reviews on the Crower intake cams over at www.yfztech.com Sounds like they are gonna be hard to beat!

[toofa]

when you say new cam do you mean like a set of HOT CAMS

Good question firedawg, I was about to ask the same thing except gytr cam.

[jmics19067]

If I am not mistaken the YFZ exhaust cam is like the WR cam in that it is the same profile as a YZf cam but advanced to far to be taken seriously.

A yz or any of the aftermarket EXHAUST cams is going to be the real deal. An aftermarket intake cam after the fact might be icing on the cake especially if you can adjust the timing of it to suit your needs better.

since I work at a dealership I bought the yz cam because it was cheaper for me than any of the others. if you shop around you just might be able to pick up a low hour YZ cam from someone who just installed an aftermarket set