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hedpi

intake valve super-tight?

23 posts in this topic

Well today i checked the valve clearance on my yzf, which are as follow

left to right exhaust : 035 030

left to right intake: 010 010 000?!

yeah, on the valve more to the right i couldnt even fit a 005!!

is this common? my bike starts, and runs ok, the only problem is a sputter on constant throttle. and (recently) it's too easy to turn over, doesnt need decomp

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Are you talking MM or inches?

I cant tell which you are using.

For an 03 450 it's

.10 - .15 mm ( .004 - .006 ) for intake

.20 - .25 mm ( .008 - .010 ) for exhaust

Are you sure you had the right clearance in the first place?

I would just readjust ride and check again at the regular scheduled time.

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I'll bet that your engine was built in '01 or later, and has titanium valves. Titanium is a fabulous material to use for a valve from a weight and strength standpoint, but it is no where near hard enough for the job. To bypass this, the valve face is coated with an extremely hard compound, Titanium Nitride in the case of Yamaha 's valves, to prevent wear. It works extremely well, but the coating is necessarily also very thin.

The result is that the typical YZF valve will go for years without wearing enough to need as much as a clearance adjustment, but then suddenly, they start wearing very rapidly. This is a clear sign that the coating is worn through, and the valve needs to be immediately replaced.

What happens when the situation is ignored for long enough is that the valve will wear until it has zero clearance, and then begin to vibrate around on the seat, since it no longer has any seat pressure. This actually causes the valve to wear beyond zero clearance, and it's dangerous, because it can also lead to a valve head snapping off, even if you re-shim back to specs.

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it's a 99 yzf400 but with a 426 head (already bought it like that), don't know which year is the 426 head tho, how can i find out?

i've done roughly 25hours with her since i bought her.

i was talking in MM, as in 0.10mm, etc.

i don't know how it was before, as this is the first time i've checked it.

i'm going to get the shims i need installed, when the dealer has them, and after that i'll check it more often, as checking isn't a hard job.

the only weird thing here is the valve that has 0 clearance! could this be the cause of the easy kick-over (i mean easy to kick, but not easy to start, as it's harder to find tdc)?

thanks for the replies

:applause:

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it's a 99 yzf400 but with a 426 head (already bought it like that), don't know which year is the 426 head tho, how can i find out?

i'm going to get the shims i need installed, when the dealer has them, and after that i'll check it more often, as checking isn't a hard job.

the only weird thing here is the valve that has 0 clearance! could this be the cause of the easy kick-over (i mean easy to kick, but not easy to start, as it's harder to find tdc)?

So, it appears you have an '01/'02 head (Ti valves). Yes, the valve will cause the easy kick-over.

You probably have a seriously worn valve Like the Ones in the Lower Picture Here. I advise you to pull the head and take it to a competent local machinist (ask the dealers who they use) for inspection, or remove the valves yourself, if you're able. Failing that, try re-shimming it, but recheck it after each ride; they wear that fast when they're shot.

You DO NOT want to stretch the life of a Ti valve beyond this point very far because it's asking for a catastrophe to do so. Dropping a valve often results in a repair that costs well over what you probably paid for your 400.

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ok so the buckets and shims are off.. bad news (for me)...

the valve with 000 clearance already had the 120 shim :applause: so she's dead...

one other valve was within spec, and i have to get shims for the other 3.

now the bad part is i'll have to get a new valve. what else do i need there?

i know i need the head gasket, the valve, the 2 other things that go with the valve (i don't know their names in english, but where the valve slides into). what else?

i'm going to a shop to take the "dead" valve off and put the new one in, as i don't have the tool to press on the spring/remove the valve.

any comments?

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FIVE valves, not one, unless an inspection shows that there is NO detectable wear on any of the others. Or, replace one and pull the end again in a month or two when the next one sinks.

5 springs (too cheap not to replace)

5 valve seals

Have the machinist inspect the valve guides. They rarely need replacement, but worn guides will shorten valve life.

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ok, so there's no point in ordering the shims right? as i wont know which ones i need until i get the new valves/springs/etc mounted..

thanks for the input

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just to give an update on this subject:

cylinder is 426 but head is with iron valves(400).

almost all the valves were worn, only the center intake valve was ok(the larger one).

4 valves were not leaking, 1 exhaust valve was leaking

the place where the valve touches the head (i dont know the name) needed to be refaced..

valves and seals and gasket and whatever got to the dealer today, head is in the shop to get machined..hope to have it all next week to get it together.

btw, how lame is it that no yamaha dealer has the shims in stock!?

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btw, how lame is it that no yamaha dealer has the shims in stock!?

That would be just a waste of shelf space! :excuseme:

Go to the Honda shop! They have them by the carton load! :bonk:

Seriously, Honda has them in 1/2 sizes!

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cylinder is 426 but head is with iron valves(400).
The '00 426 had Stainless Steel valves. That's more likely what you've got.
the place where the valve touches the head (i dont know the name) needed to be refaced..
Those are the valve seats
btw, how lame is it that no yamaha dealer has the shims in stock!?
Well, it's inconvenient, but they're usually stocked based on how often they get used. :excuseme:

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ok so, after new valve seats being done, 5 new valves, etc etc, i get it all together and the kick lever is stuck after some point...

i removed the decomp so that isnt it, i checked and rechecked and rechecked the valve clearances and they're ok (btw after the new seats i put in 185-190-195 shims to get the correct clearances, if that matters). i don't know what this is about.. can someone tell me more stuff to check!?

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i removed the decomp

You have no decompression device at all? Automatic or manual? I think I know what the problem is....

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i do have it, manual as stock, but i searched this forum for similar problem and someone told them to see if it wasnt caused by the decomp..

i cant kick through with/without decomp. it just stops at one point as it were seized

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well i did... and it seems right, the E is to the left on both cams, the dots on the inside are aligned.. the manual isnt very precise on cam timing..pics?

edit:

ok i found this one http://www.bmnellis.com/images/yz426/camchain5.JPG and mine (at least the intake, which is similar, the exhaust is stock unlike that one) is not like that, i have the E and I paralel, which is 1-2 less than it should.. i'll try again tomorrow like that, with the I dot aligned with the head...

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dont forget, you need to line up the timin mark on the crank first then line up the dots to the head ,make sure your cam chain tensioner is relaxed. put your chain on check timing mark and dots again.. if I remember correctly there should be 12 pins on the chaiin between top dots of the 2 cams .. then put cam caps on gently make sure to put a rag in so you dont drop the half moons into case. at that point get a very good 1/4 !!! IN DRIVE inch pound torque wrench to tighten cam caps.. check manual. i believe it is 80 inch lbs which is 7 foot pounds of torque. this is critical so check manual and go half that first and then go again to full spec then drown everythin in oil and release the cam chain tensioner

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yeah it's 1kg torque i think on other topics i read they said 14 pins though..

my only problem is i didn't know how to lign up the dots, but as i understand form that picture, i have to line the dot on the "I" side with the head, right?

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