White/Blue Smoke on throttle - 07 450fw

Yamaha YZ450F 2007

43 replies to this topic
  • fldrifter

Posted November 04, 2013 - 09:23 AM

#1

Firstly, I know it is oil burning.  There is a small bit of oil sludge in the exhaust tip as well. 

 

I bought the bike a few weeks ago, only had a couple hours on a new top end.  Bike has been running strong without any issues but was very loud. 

 

Last week:

1)I repacked the muffler, the packing that was in the exhaust was 2/3s gone, and I mean nonexistent/burnt out.  

2) Changed the oil with Valvoline 10-40 four stroke oil (what prior owner was using) and new yamaha oil filter. I put in 1L as per the manual. (Put in quart, started bike/shut off, checked level, added splash to top off.) (1 quart container plus a splash from a second one)

 

Started bike, let it warm up and rode it down the street with out issues. 

 

Yesterday, went trail riding, I was the back man, bike sounded great, pulled hard like usual.  Once I passed my buddy, he made a comment my bike looked like a two stroke from behind. That's when I realized that when reving the bike I was making a smoke screen.  After the hour drive home, pulled the bike off the truck and started it up to clear the carb, rode it down the street with no smoke issues. 

 

Bike only smoked when on the throttle, idle there was nothing, and no smoke on start up (cold or hot) and she fires up on 1 kick every time (cold or hot).

 

I have not checked my oil level to see how much was burned, I will do that tonight or tomorrow. I have seen smoke issues like this with cars, when to much oil is in the system and it burns it out, (lots of smoke until it returns to normal levels).

 

So, should I try riding again and see what happens?  If there is to much oil in the system, I can drain some out and lower the level before I go riding again. 

Take the top end off and put a new head gasket/ oil seal on it? 

 

Thanks Fellas!



  • grayracer513

Posted November 04, 2013 - 09:38 AM

#2

Sounds like rings and possible bore damage.  Time to have a look.

 

However, I have to ask; you refilled with the right amount of oil (1L with a filter service, 1Qt with just an oil change), but when you drained it, did you drain from both the left side plug under the flywheel cover AND the sump plug at the right rear of the trans?



  • fldrifter

Posted November 04, 2013 - 09:57 AM

#3

Sounds like rings and possible bore damage.  Time to have a look.

 

However, I have to ask; you refilled with the right amount of oil (1L with a filter service, 1Qt with just an oil change), but when you drained it, did you drain from both the left side plug under the flywheel cover AND the sump plug at the right rear of the trans?

 

 

I drained from front left and back right plugs, and swapped out the oil filter.  

My process was:  unscrew fill port & level check port.  Unscrew and drain front left side plug, then unscrew lower oil filter bolt, then bottom plug. Changed filter, replace bolts in reverse order. I tipped the bike towards the filter side some as well to drain from the bottom oil filter bolt hole.   When I filled the system, the oil level showed full after running it at idle for a couple minutes.  When I drained the system, I only filled an old quart container 3/4s of the way.  Which not knowing 4 strokes very well and oil consumption, did not send any alarms off in my head that I am burning oil. 

 

If it is the rings, can I get away with just ring swap on the piston or do I need a whole top end kit?  Keeping in mind, say the top end is only 8 hours old and looks fine when I open it up.


Edited by fldrifter, November 04, 2013 - 09:59 AM.


  • grayracer513

Posted November 04, 2013 - 09:59 AM

#4

Did you just re-do the top end?



  • fldrifter

Posted November 04, 2013 - 10:05 AM

#5

Did you just re-do the top end?

 

No, the guy I bought it from did.  However, I do not have any way to verify it was done, outside of him saying he put 1.5 hours on the bike after the new top end.  It was his race bike/back up, everything else was well maintained, besides the exhaust, I have found. 

 

 

The bike did not smoke at all before this weekend, which is after I repacked the exhaust with Lexx premium 4 stroke packing and the oil change. 


Edited by fldrifter, November 04, 2013 - 10:11 AM.


  • grayracer513

Posted November 04, 2013 - 11:48 AM

#6

And you say it "looks fine when I open it up".  Have you had it apart?



  • fldrifter

Posted November 04, 2013 - 12:07 PM

#7

And you say it "looks fine when I open it up".  Have you had it apart?

Sorry, miscommunication-

I have not taken it apart. 

When you said rings probably need to be replaced, I was asking if I could get away with just doing rings and not a whole top end kit "if, everything looks good when I open it up"



  • grayracer513

Posted November 04, 2013 - 01:02 PM

#8

I see.  OK, well, given all of that, it's possible that the smoke you saw was related somehow to the new packing, but I haven't run into that sort of problem before.  At this point, with all the variables involved, I don't think I'd do anything but keep an eye on it and see if it continues to smoke under a load. 

 

In the event that it does need work, and the bore looks good, mics out OK, and the piston looks new, then just rings and a quick refinish of the bore with a ball hone (use the right size, 95mm, and nothing more aggressive than aluminum oxide at 240 grit) should do it.



  • fldrifter

Posted November 04, 2013 - 01:12 PM

#9

I see.  OK, well, given all of that, it's possible that the smoke you saw was related somehow to the new packing, but I haven't run into that sort of problem before.  At this point, with all the variables involved, I don't think I'd do anything but keep an eye on it and see if it continues to smoke under a load. 

 

In the event that it does need work, and the bore looks good, mics out OK, and the piston looks new, then just rings and a quick refinish of the bore with a ball hone (use the right size, 95mm, and nothing more aggressive than aluminum oxide at 240 grit) should do it.

 

 

I can definitely do that!  I will check my oil level when I get home and see where it sits.  If it still shows full then I may syringe a tad bit out to bring it just under the line. Will keep an eye on everything and give it another ride maybe next week.  

 

Thanks for the help!



  • i want to ride

Posted November 04, 2013 - 01:54 PM

#10

go back to Yama lube oil

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  • grayracer513

Posted November 04, 2013 - 02:06 PM

#11

go back to Yama lube oil

 

And just exactly what, pray tell, would that accomplish in the context of this thread?

 

I can definitely do that!  I will check my oil level when I get home and see where it sits.  If it still shows full then I may syringe a tad bit out to bring it just under the line. Will keep an eye on everything and give it another ride maybe next week.  

 

Thanks for the help!

 

Run the engine briefly before checking the oil level (about one minute).  Wait 30 seconds before opening the dip stick to let the bubbles stop rumbling up the return passage.  Reason being that the oil level in the oil reservoir is higher than the exit of the return or scavenging oil passage where the oil comes back from the sump to the "tank".  There is a low pressure check valve to resist oil migration back to the sump while the engine sits, but not on the return side.  Left alone, oil will slowly work its way back past the return pump rotors until it's about half way down the stick.



  • fldrifter

Posted November 04, 2013 - 02:14 PM

#12

Run the engine briefly before checking the oil level (about one minute).  Wait 30 seconds before opening the dip stick to let the bubbles stop rumbling up the return passage.  Reason being that the oil level in the oil reservoir is higher than the exit of the return or scavenging oil passage where the oil comes back from the sump to the "tank".  There is a low pressure check valve to resist oil migration back to the sump while the engine sits, but not on the return side.  Left alone, oil will slowly work its way back past the return pump rotors until it's about half way down the stick.

 

 

I will report back tomorrow or tuesday what my oil level is at now.  The bike has been running on Valvoline 10-40 for quite some time, changing the oil brand, doubtfully would fix my issue. 

 

I know as well, the bike has good compression when you kick it over.  If the rings were weak, would that not make kicking that much easier but be slower to start the bike?

 

I will do what you said the post prior Grey, and check it over and go ride it again and see what happens.  Thanks again for your help today!


Edited by fldrifter, November 04, 2013 - 02:15 PM.


  • i want to ride

Posted November 04, 2013 - 02:16 PM

#13

if your buddies are making a comment about it looking like a 2 stroke there is a problem so look into it. it could be a number of things.

  • motoxvet

Posted November 04, 2013 - 02:28 PM

#14

What color was the smoke?  Blue is oil burning - WHITE is coolant being burned.  That white smoke from coolant burning also seems to hang in the air a long time and not dissipate very fast....and it's white SMOKE, not steam.



  • i want to ride

Posted November 04, 2013 - 02:31 PM

#15

sounds to me like when they put the new top end on the cylinder wasn't bored and the ring gap is too wide. blow by pressure. are you seen any oil around cam /rocker arm covers

  • i want to ride

Posted November 04, 2013 - 02:34 PM

#16

did this all start after packing the exhaust pipe this could add more back pressure on engine

  • grayracer513

Posted November 04, 2013 - 02:53 PM

#17

1) YZ cylinders can't be bored.  They need to be either replaced with new parts, or honed and replated.

 

2) "Blow-by" doesn't ever end up in the exhaust, it goes into the crankcase.

 

3) "Back Pressure" does not cause exhaust smoke.

 

4) The engine did not originally smoke with its current brand of oil and its current top end.  As stated in the original post, it was only after the repack and oil change that it started, so it's either overfilled or the packing is "burning off".



  • i want to ride

Posted November 04, 2013 - 02:58 PM

#18

You are so right.

  • fldrifter

Posted November 04, 2013 - 03:02 PM

#19

did this all start after packing the exhaust pipe this could add more back pressure on engine

see below

 

1) YZ cylinders can't be bored.  They need to be either replaced with new parts, or honed and replated.

 

2) "Blow-by" doesn't ever end up in the exhaust, it goes into the crankcase.

 

3) "Back Pressure" does not cause exhaust smoke.

 

4) The engine did not originally smoke with its current brand of oil and its current top end.  As stated in the original post, it was only after the repack and oil change that it started, so it's either overfilled or the packing is "burning off".

 

Grey summed it perfectly with number 4, and what I hope is either to much oil or the packing burning off. 

 

No oil leak anywhere on the outside of the motor.  My first thought when out riding was the new packing causing more back pressure, but I couldn't find any way that would cause an oil burning issue.  

 

Definitely not coolant, smelled like oil and was confirmed by the guys riding behind me that it was not coolant.  Again, only under throttle does it smoke, at idle or start up, there was nothing.  

 

Could there be any drain lines which could be clogged up with mud that would play into this?


Edited by fldrifter, November 04, 2013 - 03:03 PM.


  • grayracer513

Posted November 04, 2013 - 03:17 PM

#20

No.  The breather can become pinched or obstructed, but then there will be a build up of pressure in the crankcase which will typically cause one of the "half moons" at the cam cover to pop out. 

 

With an overfill, the pressure balancing tube that connects the oil reservoir to the crankcase (the hose running from the front of the engine to the right side cover) carries the excess oil being returned right back to the sump again, since there is no room for it in the tank. 







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