Oil Consumption/Oily Spark-Plug

[blueberg17]

I recently switched to putting full synthetic 10w-40 into my 'o8 450. I've heard oil consumption will increase a bit the first time running full-synth. After a couple 3hr rides I noticed I had to add oil; about 200ml. After another 2hr ride i had to add another 200~250ml... I think this is a little excessive, but I could be wrong?

So I was changing oil/filter today and decided to change the spark plug, and doing so I noticed the plug was very black and wet, almost dripping. I know how to read spark plugs on 2strokes; not so much on the 4ts. I'm guessing its rich or burning oil?... Didn't smell like oil or anything for that matter. This bike runs great and pulls strong, so I wouldn't think oil is getting past the rings yet. I haven't noticed any smoke at all. No leaks.

I maybe over analyzing this. Would you guys have some input on what I've got going on here?

Thanks,

LM

[grayracer513]

I recently switched to putting full synthetic 10w-40 into my 'o8 450. I've heard oil consumption will increase a bit the first time running full-synth.

According to some people, synthetic oil will cause oil consumption, make your clutch slip, your rings to fail, your seals to leak, cause speed wobbles, turn your lawn brown, erase your credit cards, leave the toilet seat up, and turn your KY into super glue.

All of it is BS, and is rooted in a complete lack of understanding of what a synthetic oil is. Forget you ever heard it.

After a couple 3hr rides I noticed I had to add oil; about 200ml. After another 2hr ride i had to add another 200~250ml... I think this is a little excessive, but I could be wrong?

That's excessive. A healthy YZ450 should use virtually no oil at all. You have a problem that needs to be found out. The most likely cause is damage to the cylinder/piston/rings as a result of some foreign material scoring the walls.

Time for a tear down.

[blueberg17]

Thanks for your input Grey.

Looks like I'm going to have a fun weekend!?

[jasen 2007]

"According to some people, synthetic oil will cause oil consumption, make your clutch slip, your rings to fail, your seals to leak, cause speed wobbles, turn your lawn brown, erase your credit cards, leave the toilet seat up, and turn your KY into super glue.

All of it is BS, and is rooted in a complete lack of understanding of what a synthetic oil is. Forget you ever heard it."

A+++ Grayracer, I can't even tell you how many times I have heard that over the years...

[blueberg17]

That's excessive. A healthy YZ450 should use virtually no oil at all. You have a problem that needs to be found out. The most likely cause is damage to the cylinder/piston/rings as a result of some foreign material scoring the walls.

Time for a tear down.

Grey, if there was damage to the cyl./piston/rings wouldn't I notice a loss in power or smoking out the exhaust?

I took off the top end this weekend. With no more than 15~20hrs on this bike everything appears to look perfect, except for some carbon build-up on top the piston. I didn't notice any varnishing on the cylinder wall. Valves were in spec, and the head looked great as well.

[grayracer513]

If you average only 5000 rpm on your rides, burning 100cc per hour requires no more than 0.00067cc in the combustion chamber each time it fires. That might make a noticeable amount of smoke, or it might not. A two-stroke running 32:1 and burning a gallon an hour would be running 20% more than that through the engine.

A 10-15% loss in compression ring efficiency would go mostly unnoticed by a lot of people, and the compression rings can be working much better than that while the oil rings are leaking. Then there are valve seals....

Hone it, re-ring it, and drop a new set of seals in.

[yz450fcranker]

yes it needs some rebuilding for sure

[Octanee]

heres what happend to my bike, i always run synthetic, but, i had redid my piston, new rings, and put in 3 kibblewhite stainless steel valves with there springs, and valve seals, well it started to eat up that oil, and it got worse, and worse... some times you could see the smoke a bit, any how, turns out it was the kibblewhite valve seals, i tore down the engine, replaced piston and rings again, got rid of the kibblewhite valve springs, (you dont need to run the stiffer springs, its bs) so wasted 250$ into springs, and used stock yami valve springs, and she's running strong,

now incase you dont know, you ahve to run kibblewhite seals with their springs, stock yami's wont fit, but yeah, kibble wanted me to pay them, and i would not see my seals from them for a while, so yeah i said screw it aint taking a chance there, although i took a chance not running their valve springs, but the bike works well!

[grayracer513]

It's off the main topic, but Kibblewhite valves are stainless steel, and weigh almost twice what a Ti valve weighs. For this reason, they do in fact require heavier than OEM springs, and/or some weight reduction elsewhere in the valve train. Part of what makes KW spring sets so expensive is that they use titanium to make the spring retainers, so they lose some weight there instead, and they don't have to make the springs as heavy as the stock '98-'2000 model springs for the OEM SS valves are. But they still need to be heavier than stock to be safe.

If you have a 2000 or earlier model, you didn't need KW springs because your bike came with SS valves in the first place, and the stock springs were already made for that. If you reused the KW retainers, you lost some weight that way.

Either way, you got away with doing something that shouldn't be done, so far. Just say that and let's not recommend it to anyone else, shall we?

[FLFX4]

Check your cylinder head really good, I had carbon build up on my piston as well and turned out the vavle seals had cracked. If you have to order a new cylinder head, buy it here:

http://www.babbittsonline.com/yamaha-motorcycle-parts#/Yamaha/YZ450F_-_YZ450FX_-_2008/CYLINDER

even with shipping its cheaper than any place else. thats where I bought mine.

[blueberg17]

Check your cylinder head really good, I had carbon build up on my piston as well and turned out the vavle seals had cracked. If you have to order a new cylinder head, buy it here:

http://www.babbittsonline.com/yamaha-motorcycle-parts#/Yamaha/YZ450F_-_YZ450FX_-_2008/CYLINDER

even with shipping its cheaper than any place else. thats where I bought mine.

Thanks I'll keep that in-mind, although my head checks out great. Just like gray mentioned, I plan on throwing a set of rings in it, hone the cylinder, and a new set of valve seals while I'm at it.

My local yama dealer went out of business, so i get to wait on part orders from the internets.?

[twomancrew]

Grab a timing chain also, $16. Getting ready to do my top end too.

[blueberg17]

Grab a timing chain also, $16. Getting ready to do my top end too.

why would i need a timing chain. nothing wrong with the one thats in there now.

[grayracer513]

why would i need a timing chain. nothing wrong with the one thats in there now.

OK, fine. Run that one. ?

[blueberg17]

OK, fine. Run that one. ?

I've always stood by: 'don't fix it unless it's broke.'

[grayracer513]

I've always stood by: 'don't fix it unless it's broke.' ?

Then maybe you can tell me how much longer until it does? (and you might want to think about what happens when it does, too).

And since you can get a whole set of valve springs for $50, I'd change them, too, as long as the head is apart.

You do buy insurance, don't you?

[blueberg17]

Seriously? Are these parts really susceptible to wear which would need to be replaced every time I do rings? I don't even have to adjust my valves yet! I am capable of replacing what is needed, but when does it end? Should I replace the valves while it's apart?

[grayracer513]

Valves are rather more expensive, and will generally give an indication as to when they need to go by wearing rather than breaking, and when they wear, nothing explodes. When a timing chain decides to start binding at the links or crawls of a guide because it got too loose laterally, it will do so suddenly, and may take out the aforementioned valves in the process, along with the head, piston, etc.

Valve springs are subject to fatigue, and you'll have them out anyway to do the seals. They're about $8-9 each, and if one breaks, well, spectacular is one word...

Probably not the word you will say, though.

[blueberg17]

So, I found the root of my oil burning... no cross hatching on the cylinder and some slight vertical scarring. Also found a few extra goodies [sarcasm] that the previous owner left me with; a Hot-Rods piston rod, and scarred cam journals:banghead: Take a look:

Exhaust:

Intake:

I plan to hone the cylinder and hopefully remove the vertical lines.... but can the cyl. head be fixed/machined to be reused? or is there no other option but to replace?

[grayracer513]

Contact Engine Dynamics about the head. It's fixable. ?