2010 YZ450f tear down, valves look odd? Expert opinion?


24 replies to this topic
  • Davey762

Posted April 25, 2011 - 11:59 AM

#1

Hey guys,

Have 50 hours on my 2010 YZ450 and decided to do a piston change over the weekend. I thought the bike would be a little harder to work on than the conventional design but it turned maybe easier than my old honda, just a bunch more electrical connectors with the efi system.

Anyway, taking a look at my head/valves... one of my exhaust valves is very white, I'm assuming this is a hot/lean valve, but odd that only one of them is white and not both. Any experts have some advice? Maybe the fuel map I'm using is too lean? The bike runs amazing so maybe it's a little lean.

Posted Image

Thanks, Dave.

  • grayracer513

Posted April 25, 2011 - 01:58 PM

#2

... one of my exhaust valves is very white, I'm assuming this is a hot/lean valve, ...

You are assuming incorrectly. They look fine to me.

  • crf450319

Posted April 25, 2011 - 03:08 PM

#3

I'm curious as to why you changed the top end after 50 hours ? And wondering what your old piston looks like, any chance we can see some pics of it ?

  • Davey762

Posted April 25, 2011 - 08:05 PM

#4

You are assuming incorrectly. They look fine to me.


That's good to hear gray, bike ran fine just looked abnormal but thanks for the reply.

However, do you have an explanation to the difference between the two exhaust valves? Not that I have a lot of 4 stroke rebuild experience (around 5x) I have never ran across this before.

  • Davey762

Posted April 25, 2011 - 08:11 PM

#5

I'm curious as to why you changed the top end after 50 hours ? And wondering what your old piston looks like, any chance we can see some pics of it ?


I'll get a pic of the piston for ya tmrw.

I just did it as a peace of mind thing, preventative maintenance. My bro got bit on his 07 running his piston too long and it cost a bunch more money to fix it when it broke than beforehand, thinking he had about 80-85 hours on it.

The manual states the replacement should happen much earlier than 50 hours, but then again... I think they tell you to replace the engine oil at 15 hours and the piston/rings at the same time lol.

Not saying it HAD to be done, but I feel better knowing it has been done... and I'm still waiting for the snow/water to go away so I have some time to kill.

  • grayracer513

Posted April 25, 2011 - 08:38 PM

#6

do you have an explanation to the difference between the two exhaust valves?

Not for sure, no, but it would have to be something about the way the flame spreads and the gas flow in the combustion chamber. Doesn't look unusual, though.

  • Davey762

Posted April 25, 2011 - 09:15 PM

#7

Ok, thanks gray.

  • yz450fcranker

Posted April 26, 2011 - 01:04 AM

#8

If you can see there is an extra water jacket next to the white valve which is keeping it "NEW" according to what i see

  • grayracer513

Posted April 26, 2011 - 06:51 AM

#9

If you can see there is an extra water jacket next to the white valve which is keeping it "NEW" according to what i see

The one valve is whiter because it was hotter. Now if you can explain how an "extra water jacket" accomplished that,....

Besides, the "extra" is just a port through which the coolant passes from the cylinder to the head. The entire combustion dome is in the same water jacket inside the head.

  • crf450319

Posted April 26, 2011 - 10:12 AM

#10

I'll get a pic of the piston for ya tmrw.

I just did it as a peace of mind thing, preventative maintenance. My bro got bit on his 07 running his piston too long and it cost a bunch more money to fix it when it broke than beforehand, thinking he had about 80-85 hours on it.

The manual states the replacement should happen much earlier than 50 hours, but then again... I think they tell you to replace the engine oil at 15 hours and the piston/rings at the same time lol.

Not saying it HAD to be done, but I feel better knowing it has been done... and I'm still waiting for the snow/water to go away so I have some time to kill.


Gotcha, I've normally run mine for 90 to 100 hours and they've all looked pretty good. Not a whole lot of wear on the skirt, not a lot of wear on the cylinder etc. I like to hear about how/why guys perform maint. at different intervals than I do, gives me something to think about.

On my '05 Honda I had some wear on the small end of the connecting rod at 65 (ish) hours that worsened by 150 hours (no surprise there). At 150 hours on that bike I replaced the crank/conn. rod/piston/rings etc. etc.

Visit the ThumperTalk Store for the lowest prices on motorcycle / ATV parts and accessories - Guaranteed
  • Davey762

Posted April 27, 2011 - 10:58 PM

#11

Gotcha, I've normally run mine for 90 to 100 hours and they've all looked pretty good. Not a whole lot of wear on the skirt, not a lot of wear on the cylinder etc. I like to hear about how/why guys perform maint. at different intervals than I do, gives me something to think about.

On my '05 Honda I had some wear on the small end of the connecting rod at 65 (ish) hours that worsened by 150 hours (no surprise there). At 150 hours on that bike I replaced the crank/conn. rod/piston/rings etc. etc.


Glad to hear your stuff has lasted longer... makes me feel better for sure. Here is a pic of the piston as requested, sorry about the delay had a busy couple days and also was feeling a little under the weather. FYI the very center of the piston was just tapped on which is why there is carbon missing there.
Posted Image

  • crf450319

Posted April 28, 2011 - 06:16 AM

#12

I also replaced the piston & rings on my '05 crf at the 65 hour mark on my hour meter, I had bought that bike used and I'm guessing there was about 20 hours on it when I bought it which would have put me at the 85 hour mark (for those poor at math !). The previous owner didn't have the hour meter on it, I put it on before I'd ridden it. I re-read my post and I didn't think it was very clear as to when I'd replaced the top end.

I've got 75 hours on my '09 yz450f now, but was planning on running it for 100 to 110 hours before I replace the top end. I ride MX only, in "B" - depending on what area I'm riding in..

Thanks for the pic, I hate to bug you anymore.. but I was more interested in what the skirt on the intake/exhaust side looks like ? Any chance we can see a pic of that ?

You give an inch right ? :thumbsup:

  • harrperf

Posted April 28, 2011 - 06:21 AM

#13

Just me - but for an efi bike it looks really rich....

I have not spent much time testing maps with this bike - so I can't say for sure either way - but almost all the plugs that come out of efi bikes look darn near brand new.

Typically it would only be rich lower throttle openings for something like what you see there...

All that said - considering the big surge in power the yamaha has at low throttle openings - and the fact a lot or people are making it even richer to combat this - could meean yamaha knew it too and has it a little fat.

Edit: I will also add most bikes have TWO ex valves that look that whiter color too...as grey says from heat. Having only one valve that color further suggests it's rich...

  • grayracer513

Posted April 28, 2011 - 07:28 AM

#14

But richer always makes it go faster, doesn't it?? :thumbsup: [/sarcasm]

(general editorial comment not directed at anyone in particular) :thumbsup:

I agree that normally both exhaust valves would be more like the whiter one here, but it's really not that odd to see one darker. I do disagree with the notion that very much can be determined about the bike's jetting/mixture mapping from "reading" the carbon deposits in the head, though. I've torn down lots of engines with perfectly beautiful looking spark plugs that I know were jetting right or very close to it that had combustion chambers a lot like that one. I think it depends a lot on what the engine did during the last 3-5 minutes of run time prior to being shut down. Any extended idling or cruising through the pits can darken it quite a bit.

Davey, the picture of the piston that would be most useful would be one of the intake side skirt, not the crown.

  • crf450319

Posted April 28, 2011 - 08:57 AM

#15

but I was more interested in what the skirt on the intake/exhaust side looks like ?


Davey, the picture of the piston that would be most useful would be one of the intake side skirt, not the crown.


:thumbsup:

  • Davey762

Posted April 28, 2011 - 09:02 AM

#16

Thanks for the insight guys... I'll get another pic of the intake skirt side today.

The weird thing is that the map I'm running is cutting fuel and advancing the ignition so shouldn't that make it less rich?

But like gray mentioned, extended idle times could darken it and this makes sense. I have not ridden the bike since november and it's been stored in a heated garage over the winter and I did start it every couple weeks until the head got warm so it was just sitting there idling.


Here is the exact map (from yamaha) also running a yoshimura exhaust.... stock otherwise, no air box mods.

GYTR or Stock Exhaust
Sharp throttle response; more overall power
Fuel
-2 -4 -4
-2 -4 -4
-2 -2 -2
Ignition
+3 +2 +2
+3 +3 +2
+3 +3 +3

  • harrperf

Posted April 28, 2011 - 05:15 PM

#17

I based my comments on the spark plug - the insulator is dead black...

But now he has said he not ridden it and it's just been started up on the stand...makes perfect sense.

  • Davey762

Posted April 28, 2011 - 09:04 PM

#18

Intake side pic. At 50 hours do you guys recommend changing the spark plug? I was planing on it but just curious to see what you guys thought. Thanks again for the opinions.

Posted Image

  • grayracer513

Posted April 29, 2011 - 08:38 AM

#19

At 50 hours do you guys recommend changing the spark plug?

OK, no offense, but how funny is that, when we have arrived at a situation where someone can even wonder if a spark plug might outlast a piston? We used to go through plugs like pretzels until precious metal electrodes and CDI ignitions came out, and now with four-strokes...

I think I change my plugs every year,but I don't remember exactly when I did the last one. :thumbsup:

The piston does show a little scuffing. It's not perfect, but it's not bad. I asked for the intake side because it gets the highest thrust load on a conventional engine.** On yours, I should have asked for the exhaust side because your cams are in a reversed location. The other side look like that too? Are there any scoring marks in the bore that don't hone out completely in 2-3 quick passes with a ball hone?

** In a forward rotating engine, the connecting rod angles back toward the rear of the cylinder as the piston is pushed down under power. This means that the back side of the piston bears the angular thrust of the power stroke.

  • Davey762

Posted April 29, 2011 - 10:22 AM

#20

OK, no offense, but how funny is that, when we have arrived at a situation where someone can even wonder if a spark plug might outlast a piston? We used to go through plugs like pretzels until precious metal electrodes and CDI ignitions came out, and now with four-strokes...

I think I change my plugs every year,but I don't remember exactly when I did the last one. :thumbsup:

The piston does show a little scuffing. It's not perfect, but it's not bad. I asked for the intake side because it gets the highest thrust load on a conventional engine.** On yours, I should have asked for the exhaust side because your cams are in a reversed location. The other side look like that too? Are there any scoring marks in the bore that don't hone out completely in 2-3 quick passes with a ball hone?

** In a forward rotating engine, the connecting rod angles back toward the rear of the cylinder as the piston is pushed down under power. This means that the back side of the piston bears the angular thrust of the power stroke.


Exhaust side is in better condition. Cylinder was ok, nothing you could feel. No pics of that though.

No offence taken to the spark plug response, but on my bros last bike the plug outlasted the piston gray :confused:
Posted Image





Related Content

Forums
Photo

Is it worth it? (Cam and High compression piston) by macgi77


Dirt Bike   Make / Model Specific   Honda   CRF 150/230 F/L
  • Hot  36 replies
Reviews

Yamaha YZ450F 2017 by Chris.GVS


Yamaha YZ450F 2017
  • - - - - -
  • 0 reviews
Forums
Photo

yz250x vs 450 4t comparisons (preferably desert riding) needed by JakeNorthrupYZ450F


Dirt Bike   Make / Model Specific   Yamaha   Yamaha 2-Stroke
  • 9 replies
Forums
Photo

First Hare scramble tips by dhend8


Dirt Bike   General Dirt Bike Forums   General Dirt Bike Discussion
  • Hot  33 replies
Forums
Photo

Megabomb Fitment by 288yz450


Dirt Bike   Make / Model Specific   Yamaha   YZ 400/426/450
  • 1 reply
 
x

Join Our Community!

Even if you don't want to post, registered members get access to tools that make finding & following the good stuff easier.

If you enjoyed reading about "" here in the ThumperTalk archive, you'll LOVE our community. Come join ThumperTalk today!

The views and opinions expressed on this page are strictly those of the author, and have not been reviewed or approved by ThumperTalk.