YZ450F - whistling noise, and general questions


16 replies to this topic
  • ericus

Posted March 15, 2013 - 09:12 AM

#1

Hey! This would be my first post here on this great forum. First of all, expect some grammar and spelling failuers. English is not my native language.

Quick background:

Before this bike, I've been all about 2stroke.
So. I bought a YZ450F 2006, and brought a friend of mine along who knows all about dirtbikes because he's been riding for a long time. He bent and tested most of the bearings that you can check and all of them was OK, and then he did a test run of the bike. Then I did a quick test run. Everything looked fine. It said 57h on the hour counter. sounds like few hours on such an old bike, I'm now the 5th owner.

(Other trivia: my friend knew the third owner, he'd never had any troubles with this machine and when we talked to the fourth owner (the seller) my friend would discover that they had a mutal friend, so he called him up and asked why he was selling the bike, and that wasn't because of troubles with the machine, just lack of interest).

Since the bike has very expensive suspensions (Månsson/Enzo, something Swedish) we'd both assumed it was one of Niklas Granström's old bikes (he always had those suspensions and ended his career back in -06, and always had two bikes). Can't know for sure though. My friend was looking at all parts that wears quickly and he thought that the 57 hours could be correct due to the contidtion it was in.

As soon as I bought it I changed oil, oil filter, air filter and coolant.

Now to the questions that I'd hope someone might be able to answer, since it's my first 4stroke machine:

1: I have a whistling noise that sounds kinda like a turbo charging when I go from low throttle to medium/max throtthle. It sounds like it's coming from the left side, can't tell for sure. It's not as loud as a turbo charged car, but it is kind of how it sounds. Read something about the skid plate making that noise due to the wind? No sound like that on idle and full throttle. I am concerned that it is a bearing in the engine or something.

2. Anything I would take a look at out or replace on this machine before I ride it anymore? Except valve clearance of course, but the valves would be okay since it starts very easily I guess?

3. When I go from almost full or full throttle and then releases the throttle, it goes BANG BANG BANG. Is that backfiring, and if so, is that bad?

Thanks in advance,
Eric

Edited by ericus, March 15, 2013 - 09:23 AM.


  • DGXR

Posted March 15, 2013 - 09:39 AM

#2

Q1 and Q3 - You may have an air intake leak, which could easily make a whistling noise and could also cause a backfire (lean) condition. Yes a backfire condition is bad - not only is it annoying, but also the cause of the backfire (lean fuel mixture) may result in engine damage if it's run this way for a long period. This is my best educated guess and your problem could be something else.

Q2 - Easy starting does not mean the valve clearances are in spec - it's pretty easy to just check the clearances and you may not need to adjust them, so do this first. While the valve cover is off, check the condition of the cam chain and guides, these are wear items. You may need to use a bit of gasket sealer on reassembly to be sure the cover gasket seals up right, get a manual and read it. Otherwise, keep reading online forums and look for any particular items on that year model that may require special attention.

Good luck and have fun! BRAP

Edited by DGXR, March 15, 2013 - 09:41 AM.


  • grayracer513

Posted March 15, 2013 - 09:57 AM

#3

Backfire on deceleration is not an indication of any engine problem you need to seriously worry about. It is almost always the result of one of two things: either the exhaust system is leaking air at one of the joints, or the idle mixture is too lean. Lean idle mixture has never caused any engine damage that I'm aware of in a 4-stroke engine.

Check the exhaust, then adjust your idle trim screw and see what happens:

http://www.thumperfa.../jetting.htm#PJ

http://www.thumperta...ad.php?t=327405

  • ericus

Posted March 15, 2013 - 10:23 AM

#4

Q1 and Q3 - You may have an air intake leak, which could easily make a whistling noise and could also cause a backfire (lean) condition. Yes a backfire condition is bad - not only is it annoying, but also the cause of the backfire (lean fuel mixture) may result in engine damage if it's run this way for a long period. This is my best educated guess and your problem could be something else.

Q2 - Easy starting does not mean the valve clearances are in spec - it's pretty easy to just check the clearances and you may not need to adjust them, so do this first. While the valve cover is off, check the condition of the cam chain and guides, these are wear items. You may need to use a bit of gasket sealer on reassembly to be sure the cover gasket seals up right, get a manual and read it. Otherwise, keep reading online forums and look for any particular items on that year model that may require special attention.

Good luck and have fun! BRAP


About the bold part, it might be a bit to lean fuel mixture due to the cold weather we still have in northern Sweden (around 10-14 below celcius the last time I rode it). Could the temperature be the problem, maybe?

  • ericus

Posted March 15, 2013 - 10:31 AM

#5

Backfire on deceleration is not an indication of any engine problem you need to seriously worry about. It is almost always the result of one of two things: either the exhaust system is leaking air at one of the joints, or the idle mixture is too lean. Lean idle mixture has never caused any engine damage that I'm aware of in a 4-stroke engine.

Check the exhaust, then adjust your idle trim screw and see what happens:

http://www.thumperfa.../jetting.htm#PJ

http://www.thumperta...ad.php?t=327405


Hey grayracer513, the hero of this forum :D
I know for a fact that the exhaust is leaking at least a little from the end pipe (silencer/muffler?). Some strange system named Devil that I've never heard of before. The silencer/muffler (don't know the correct english word for this) needs to be restuffed I think. There's two springs that holds it to the rest of the exhaust, and it does not fit as well as it should do. Might be leaking there. Is that bad?

Any ideas on the whistling noise?

  • grayracer513

Posted March 15, 2013 - 10:33 AM

#6

About the bold part, it might be a bit to lean fuel mixture due to the cold weather we still have in northern Sweden (around 10-14 below celcius the last time I rode it). Could the temperature be the problem, maybe?


Yes, it can, and probably is. A rough rule to follow is that every 6 degrees Celsius that the temperature drops will make the jetting 1% leaner because of the increased air density.

Regarding exhaust leaks that cause backfire on deceleration, it's a bad thing only if it's a fire hazard to the environment, or if it backfires so hard that there is a risk of bursting the muffler/silencer (the two words are fairly interchangeable) or some other part of the system, or if it's just too annoying. You should note that if the bike is perfectly healthy and jetted just right, it should pop off out of the pipe a little bit as it decelerates. Not a lot, not all the time, just "some".

The whistling noise could be an intake air leak, a normal gear whine, any number of things, probably none of them particularly serious except for the potential for an intake leak to cause a jetting problem or allow dirt into the engine.

  • ericus

Posted March 15, 2013 - 10:37 AM

#7

Yes, it can, and probably is. A rough rule to follow is that every 6 degrees Celsius that the temperature drops will make the jetting 1% leaner because of the increased air density.


I remember jetting my 2stroke bikes all the time due to the temperature, but this is years ago. I thought that 4strokes were less sensitive to this, but I've been proven wrong. When my friend did the test run, he said it was probably to lean jetted.

  • grayracer513

Posted March 15, 2013 - 10:44 AM

#8

No, you're not wrong. Four-strokes are a lot less sensitive to temperature and altitude than two-strokes are because they will run acceptably well with a much wider range of rich to lean than a two-stroke. But if the temperature drops enough, eventually, they need an adjustment, too.

Visit the ThumperTalk Store for the lowest prices on motorcycle / ATV parts and accessories - Guaranteed
  • ericus

Posted March 15, 2013 - 11:03 AM

#9

No, you're not wrong. Four-strokes are a lot less sensitive to temperature and altitude than two-strokes are because they will run acceptably well with a much wider range of rich to lean than a two-stroke. But if the temperature drops enough, eventually, they need an adjustment, too.


That sounds legit. But again, anything on the whistling noise? Sounds like zzzzzzZZZZ! Kind of high pitched, like a turbo as said.
EDIT: My bad, didn't see your edit of the post!

Would I be able to test the engine for air leaks with spraying starting gas to find a intake leak as with 2strokes? I would like to know what to begin testing with to see what's making this noise.
Thanks a lot for all the answers! I really, really appreciate it!

Edited by ericus, March 15, 2013 - 11:10 AM.


  • FRANTIK1

Posted March 15, 2013 - 05:34 PM

#10

My 09 yz450 makes the same noise. So does my friends yz 426.It only does it with a load on the engine (riding), mid throttle, right?

Edited by FRANTIK1, March 15, 2013 - 05:37 PM.


  • ericus

Posted March 16, 2013 - 12:04 AM

#11

My 09 yz450 makes the same noise. So does my friends yz 426.It only does it with a load on the engine (riding), mid throttle, right?

Yes, that is correct. I dont recall it making that noise while standing still, but I will look into it again.

So the noise is normal then?

  • ericus

Posted March 20, 2013 - 02:24 AM

#12

Anyone else?

  • Do I Care?

Posted March 20, 2013 - 08:16 AM

#13

My mates 04 has a bit of a whistle when in Neutral but I think it has something to do with how much air is getting pushed through with no load on it. It is not overly loud but still noticeable. If the noise is LOUD you may want to check for intake leaks. Yes you can check for intake leaks by using carb cleaner or similar while the engine is running. The easiest way is checking for cracks in the intake boot, the carb is unlikely to be a problem but check air filter carb boot as well. EDIT: As mentioned check the muffler/silencer/exhaust pipe is not leaking where it joins to the header-pipe or where it bolts to the exhaust port. There is a little gasket in there so check it is working.
Make sure you always have a clean air-filter in this bike or starting & backfire on deceleration will become worst.
The next post will say 03 but it's an 04 LOL.
Happy riding :ride:

Edited by Barra8, March 20, 2013 - 09:32 AM.


  • Do I Care?

Posted March 20, 2013 - 08:40 AM

#14

I might just say that if you ever have to do the timing chain BE CAREFUL not to get it wrong. If you do it will cause HEAPS of backfires on deceleration, over-heating, blown head gasket, loss of performance, header pipe glowing, hard starting etc.. My mate done this once & he had every symptom described & probably more. Also the seals in the water-pump need to be replaced correctly or this can cause issue's.
My mates 03 has the upgraded ECU, with a modified 4-speed gearbox. It hauls ass down low & is a real machine! Beats any of the newer models (even bikes that aren't blue : ) so far! More of a track bike though as top end speed isn't that fast.
If your bike is anything like my mates 03 model it will go like the clappers!

  • ericus

Posted March 20, 2013 - 09:54 AM

#15

My mates 04 has a bit of a whistle when in Neutral but I think it has something to do with how much air is getting pushed through with no load on it. It is not overly loud but still noticeable. If the noise is LOUD you may want to check for intake leaks. Yes you can check for intake leaks by using carb cleaner or similar while the engine is running. The easiest way is checking for cracks in the intake boot, the carb is unlikely to be a problem but check air filter carb boot as well. EDIT: As mentioned check the muffler/silencer/exhaust pipe is not leaking where it joins to the header-pipe or where it bolts to the exhaust port. There is a little gasket in there so check it is working.
Make sure you always have a clean air-filter in this bike or starting & backfire on deceleration will become worst.
The next post will say 03 but it's an 04 LOL.
Happy riding :ride:

I don't know how much they changed the engine from -04 to -06, but from what I can recall the whistling sound is not present without load, only in mid-register during load. It is not super loud like if the engine is going to fall in pieces. I'd say it's about "just under or above noticable" from the noise from the rest of the engine. Also, I bought new air filters, Twin Air, when I bought the bike. Applied air filter oil as I've always done. I don't think the sound would come from the exhaust since I've noticed the sound is coming from the left side? Not sure, just one hour of riding (still snow and cold up here in northern Sweden...).

I might just say that if you ever have to do the timing chain BE CAREFUL not to get it wrong. If you do it will cause HEAPS of backfires on deceleration, over-heating, blown head gasket, loss of performance, header pipe glowing, hard starting etc.. My mate done this once & he had every symptom described & probably more. Also the seals in the water-pump need to be replaced correctly or this can cause issue's.
My mates 03 has the upgraded ECU, with a modified 4-speed gearbox. It hauls ass down low & is a real machine! Beats any of the newer models (even bikes that aren't blue : ) so far! More of a track bike though as top end speed isn't that fast.
If your bike is anything like my mates 03 model it will go like the clappers!


By the timing chain, you mean valve adjustment and/or cam chain change? Again, this is a 2006 with five gears :)
Thanks for your answer!

And let's add another question as well: sometimes the engine would stall (to lean jetted, I hope), and at the first time it did that I thought it'd had seized because the kick starter was VERY hard to kick until I pulled the hot starter, would this be normal?

Edited by ericus, March 20, 2013 - 10:33 AM.


  • Do I Care?

Posted March 20, 2013 - 10:35 AM

#16

I thought you were talking about when the bike is in Neutral lol my bad. On my mate's bike you can hear this when under load but it is more noticeable when in Neutral because you are not moving. This isn't a problem on my mates bike but if your bike is whistling LOUD like a V6 turbo under load then maybe you should check for leaks in the intake. I'm not saying the exhaust is making this, I'm saying that there is a possibility of your intake having cracks in it. This can cause back-fires from a lean condition due to sucking air from the cracks.

On the exhaust side of things, the back fire can be caused from the muffler/silencer/exhaust pipe not sealed where it joins to the header-pipe. Also the gasket mentioned at the exhaust port where the header-pipe bolts on.

All this said... IT POPS A BIT EVEN WHEN TUNED RIGHT!

By timing chain I meant valve timing as in replacing the cam chain.

The 04 has 5 gears as well but my mate's is modified to be a 4-speed.

If you hold the throttle wide open for any longer than a few Klm's though it can stall from the carb bowl not filling up quick enough (does it on the 04 model anyway) I'm not sure what you meant by HARD as it is usually quite hard to kick these bikes, especially after stalling :)

  • ericus

Posted March 23, 2013 - 05:52 AM

#17

I can now happily report that the backfire on deceleration is almost entirely gone, and the annoying whistling sound as well.
This must be due to the temperature, back when I last rode it was around -12, and now around +4c. And it does not stall as eaisly as it would either.

Edited by ericus, March 23, 2013 - 05:53 AM.






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