07 YZ450 Engine Noise?

I'm new to the 450 motors as well. I've been riding and building atv engines for years and years. I swore my 06 450 i bought this january was on the verge of blowing up from all the rattles and knocking noises it was making. I tore it apart to rebuild it and everything looked like new still. Since it was apart i obviously couldn't put it back together stock, so i ported the head, did a valve job, bored the cylinder to a cp piston, balanced the crank etc... to tighten everything up.

I got the engine running on sunday and the damn thing still sounds like it has piston slap and is knocking. I guess i learned the hard way these motors are noisy no matter what! My quesiton is if it sounds like it is knocking when everything is fine, how do you know it is about to blow up? Does it get quite???

Normaly the blue ones dont blow unless its operator/mechanic error. But if they do, you normally don't know until.....................Bang! These motors are damn near perfect. They aren't over engineered and are easy to work on, best yet they are reliable.

Too funny. I just bought an 05 YZ450F yesterday. (Previously an RM250) Never owned a 4 stroke. First question I asked when he started it was "How much is that top end rebuild going to cost me?" He looked at me like I just slapped him or something. :excuseme:

ha, glad im not the only one that was starting to think my bike was making noises.

I do hear a little bit of chatter, but its been there since day 1 and it runs like the day i bought it, so i never let it bother me.

07' YZ450F

My 07 has maybe 12 hours on it and it does have a hashy type sound when your rise the RPMs up some off an idle but its done it for a long time. would like to know how to make it sound umm tighter but i dont think anyone has an answer to that. valves are withen spec, never adjusted just checked.

Mine did get louder and louder...turned out to be piston slap from the rings going bad...When rebuilding I stripped the bike to the frame, carried the frame outside to wash it, and noticed I had a rattle going on inside it...A loud rattle...It was hard as hell to figure out even where it was coming from because it resonated throughout the entire frame! Turned out it was a weld piece inside the crossbar where the seat goes...Literally sounded like a 12mm bolt was in there...When you shook the frame it sounded like it was coming from everywhere...I was able to spray foam into a little hole in the crossbeam and seal it...No more rattle...

If I didn't strip it down to the frame I would've never known and probably always would've had an unusual rattle that couldn't be pinpointed...

Can you take a picture of where you spray foamed it?

and post it?

thanks

Yeah, I had taken pictures during the rebuild process...The rattle inside went all the way from one side of that crossbeam to the other...I used the tip from a ball inflate needle to put into the hole...

DSC04394small.jpg

DSC04409small.jpg

DSC04408small.jpg

Yeah, I had taken pictures during the rebuild process...The rattle inside went all the way from one side of that crossbeam to the other...I used the tip from a ball inflate needle to put into the hole...

DSC04394small.jpg

DSC04409small.jpg

DSC04408small.jpg

Hate to rain on your parade, but I have been there and done that with great stuff foam and I bet you 10$ that stuff didn't harden in there. It needs air to harden and it will stay goopey in the middle of the frame tube. You really need to use a catalyzed foam such as urethane pillar foam to do something like that.

No, I thought of that...I sprayed a just a little in, shook the rattle til it got stuck in it, then let it dry...Then did it 3 more times with dry times between, the last time it squirted back out the hole...It's all good now...And if it is a little gooey in the middle, so what? It stopped the rattle for good I'm sure...

Except when you suck sand up your breather hose; true story.

i hear that! i did a race at the cost and in practice i had to stop at the top of a hill because someone had just crashed infront of me. flamed out and pumped a large amount of sand into the valve cover.... burned a nice hole in my pocket

my 06 stock make more noise from the top, compare to the 08-09 i seen, but maybe its beacuse all of them had a loud drd pipe.

It is worth checking your cam chain and tensioner when you start to hear noise. I replace mine once a year now. I bought an 06 toward the end of 06 and by the end of 07 my timing chain had stretched beyond what the tensioner could tighten and jumped 3 teeth on the exhaust cam 3 was lucky cause 4 would have been kaboom. Just check the two once a year to make sure things are tight and you should be fine.

Glad this is normal. I've just got me an 08 and riding it for the first time today realised this noise. I'm going to get some foam inbetween the skid plate and bottom of engine see if it gets any quieter.

Grey, I have an 08' 450 that has developed a pretty good rattle at idle. Pulled it down and found it to be the balancer. Seems to slap at the gears and harmonic over to the left side. Now I did do this, I have only run Belray thumper oil 20w50, changed every three rides, I'm a woods / Hare Scramble rider. I had to use 10w40 because my local shop is out of 20w50, and the bike has about 45 hours total on it. No loss of power or any other problems, just the rattle. I have searched TT and seems no one has spoke of this, any idea's?

is this engine sound normal?

sounds ok... doesnt sound lke its knocking.. when is the last time you put a cam chain in it and checked the valves?

Grey, I have an 08' 450 that has developed a pretty good rattle at idle. Pulled it down and found it to be the balancer. Seems to slap at the gears and harmonic over to the left side. Now I did do this, I have only run Belray thumper oil 20w50, changed every three rides, I'm a woods / Hare Scramble rider. I had to use 10w40 because my local shop is out of 20w50, and the bike has about 45 hours total on it. No loss of power or any other problems, just the rattle. I have searched TT and seems no one has spoke of this, any idea's?

Lighter oils will allow gear rattling to sound louder, yes. Remember that your engine does not turn at anything like a steady speed at an idle. If you could watch a tach in slow motion you would see it accelerate abruptly as it fires, slow just a little as it opens the valves, then decelerate abruptly as it hits the next compression stroke.

Connected to the crank, you have the big heavy clutch assembly, and the gears in the transmission, and the balancer, all coupled by gears with some clearance in them, and this constant change in crank speed causes them to thrash back and forth kind of like your dad did in the passenger seat when you were learning to drive a stick shift. This produces a lot of racket at idle, most of which is pretty normal.

There should be a growling/rattling noise at idle that will go away when you pull the clutch in. That's the trans rattling, and it's normal. If most of the rest of it disappears as you raise the engine speed to around 3-4000, you're probably hearing normal gear lash and nothing more.

But the balancer can produce an abnormal noise if the bearings fail, or if the primary drive gear nut loosens on the crank. Check the nut, and check the balancer shaft for excessive up/down play in the bearing (more than about .004-5").

Also, see if the clutch basket has any free rotational movement within the driven gear assembly that would indicate beat up drive cushions.

OK so every noise everyone talked about I have and like the rest i'm glad to here its normal. One noise I haven't seen anyone talk about one other noise I have. I have a 09 yz450f. Ride heavy woods. Tight trails and unexpected hill climbs. And that is where the noise comes in. On a unexpected instant hill climb when I have to gas it. If i don't have the speed its almost sounds like the chain slapping. Almost has a jerking feeling to it. Like i'm in to high of a gear. I change the rear sprocket and the chain is alittle bit more tighter than usual. Both of these mods helped but didn't solve the problem. Specially when it comes to a rooted climb witch. The bike come more easy to stall out. Please does anyone have any info. I'm sending my bike to the shop this week to get the valves check.

Lighter oils will allow gear rattling to sound louder, yes. Remember that your engine does not turn at anything like a steady speed at an idle. If you could watch a tach in slow motion you would see it accelerate abruptly as it fires, slow just a little as it opens the valves, then decelerate abruptly as it hits the next compression stroke.

Connected to the crank, you have the big heavy clutch assembly, and the gears in the transmission, and the balancer, all coupled by gears with some clearance in them, and this constant change in crank speed causes them to thrash back and forth kind of like your dad did in the passenger seat when you were learning to drive a stick shift. This produces a lot of racket at idle, most of which is pretty normal.

There should be a growling/rattling noise at idle that will go away when you pull the clutch in. That's the trans rattling, and it's normal. If most of the rest of it disappears as you raise the engine speed to around 3-4000, you're probably hearing normal gear lash and nothing more.

But the balancer can produce an abnormal noise if the bearings fail, or if the primary drive gear nut loosens on the crank. Check the nut, and check the balancer shaft for excessive up/down play in the bearing (more than about .004-5").

Also, see if the clutch basket has any free rotational movement within the driven gear assembly that would indicate beat up drive cushions.

 

First post on this forum…

 

Due to a loud crankcase rattle at idle, I’m looking at a friends recently acquired YZ400F. I’ve read forum posts confirming how noisy they are. The crankcase covers are now off. The lock nuts on the gears are tight and there is no rotational play with the clutch basket or between the clutch and the  driven gear.

 

The rattle appears to be the slight play between the driven gear and the balancer gear.  There is no horizontal or longitudinal play in the balancer shaft  just rotational play. The gears don’t look worn. 

 

Is this slight play normal ? Would using 20/50 rather 10/40 oil help quieten it ? 

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now