Ripped head off, and cylinder (03 450) and...

So i've never quite worked on a four stroke before.    But with some advice from Grayracer....i tackled it myself due to my cooling system getting pressurized and likely needing a head gasket (it was overflowing and spewing out rad cap (i got a new rad cap too)..    I took his advice and bought some feeler gauges and measured the clearance of valves before removal. 



-I dont see any obvious spots where the headgasket is blown, unlike when i worked on two strokes, it was pretty evident.


-Upon putting the piston top dead center (according to flywheel i'm guessing its the middle line on it as i see three lines). i looked at the cams, and the dots on cams gears, weren't even remotely close to the edge of the head.  When i lined the dots on the cam gears with the flywheel is almost on the 3rd line...but a little past?     The bike ran really strong and pulled really hard. (two pics included to show you)












-Another thing that kinda freaked me out, but my buddy said its normal (its from heat treatments?).....the crank, near the main rod bearing, was discolored....i always remember this being a very bad sign on my old kx125. lol. 

  Is this in fact normal discoloration?   I have some slight twisting motion on the Rod, near main crank bearing, but no up and down....wristpin has no up and down either.  If i remember right, you can have some twist, just no up and   down motion







I took the cylinder off as well, and i see and feel no ridge in the cylinder.....and i can see some crosshatch still inside cylinder.

Head looks pretty clean, no dings, etc in it. 




First off head gaskets can be pooched and look like they are fine. Second, the third line is your tdc mark the first two with a dash between is for ignition timing. By the pucture shown your timing is bang on.Also the discoloration on the crankshaft is normal.

Put a new gasket set in and ride her

Timing is correct. 


The heat color on the crank was done at the factory during assembly and is normal.


The correct way to measure rod bearing clearance is to use a dial and see how much the rod can rock side-to-side without the big end moving left to right on the crank pin.  Picture from the manual below (measurement "F"):




Thanks always ... your the best! Grayracer for President!

2-3 years is all I would need. :devil:

So my mechanic got to my head. Hes pretty busy. Cylinder surfaces were good. He found the head wasnt flat in one he sanded it down a bit and thinks it will be good now. i had them put new valve seals in.

One thing left. They found some scoring where the cams the little channels between valves. if memory serves they are called cam journals?).

Anyways im bringing cams in and they are gonna check clearances.

He said he couldnt get the buckets out at first because a small ridfe of metal was pushed over from where cam rides over into where valve buckets ride

in truth am i likely looking at a new head here? If metal was pushed over enough to make it so buckets would not come right out? He mentioned smoothing out the scores but wanted the cams first for clearances.

Edited by soulsedg3

in truth am i likely looking at a new head here? If metal was pushed over enough to make it so buckets would not come right out? He mentioned smoothing out the scores but wanted the cams first for clearances.


No.  In the worst case, the head, cams and cam caps can be sent off to a company such as Engine Dynamics, or Millennium Technologies and have the cam bores rebored.  This is done by first taking a very thin cut off the mating surfaces of both the head and the caps, then torquing them in place and running a boring tool through them on a mill.  It's called "line boring".  The process normally runs to roughly $250 USD. 


Your mechanic, if he's a good one, can see if he can torque the caps down and polish out the scoring to a workable degree by using a split rod and some emery cloth on a low/mid speed drill, etc.  If he succeeds, and the clearance checks out OK with Plasi-Gage, you can run it like that.


"Journals" are the portion of a shaft supported by plain bearings that sit in and rotate against the bearings.  In an engine that uses plain insert bearings that sit in a split bore like this, the half round portions of the engine that carry the shaft are called "saddles".  The parts that hold the bearings and shafts down (or up, or whatever) are the caps.  Those are the terms that commonly get used.  Journals may even be more technically accurate in a case like this where the saddles and caps are in fact the actual bearing surface, but you don't generally hear it that way very often.

fantastic. Mechanic has the cams and caps now. See if he can work some magic. Other then what looks like a small metal wear mark. I only felt one little score that caught my fingernail a little.

Hopefully he can work it out. :)

I think im going to sell this bike and upgrade to the 2016 yz250x 2stroke next summer. Not liking four stroke maintenance thus far.

Im in canada guessing 2200 would be an ok price for 2003 yz450? (Carb rebuilt. Wire mod on carb. Completely new water pump system...bearings seals shafts impeller...everything. New rings. New oem yamaha gaskets. New valve seals. Cylinder checked and good. New plastics)

Think thats an ok rate gray or am i aiming too high? If i were to sell.

Edited by soulsedg3

Here in ontario an 03 goes for 2500-3000 still

You best estimate of your bike's worth is local sales.  I don't follow stuff like that much.

Here in ontario an 03 goes for 2500-3000 still

Excellent. Thnx buddy :) if head needs line bored at least i have some room to up the price to compensate.

Well thats here in ontario. Best thing to do is go on kijiji and see what they go for in your area

If you want to use Millennium for head work in Canada, call up Fast Enterprises in Manitoba, fast is their Canadian rep. I used them last winter for plating and am extremely happy with their work. Plus it's easier than having to send it to the us with customs and taxes...

Thanks for the heads up(no pun intended lol).

I live next to the u.s. border and i have a po box over in maine... so cheaper to ship and get back without hassle. :) i send most all my u.s. ordered stuff there.

but im curious about the plating you had done. I have a ducati 996 also and they have a flaw in the motor with the rockers in the engine flaking the plating off and valves lose clearance. Was wondering if there was anyone here that could resurface them properly if i were to find any bad ones. Its pointless to put oem ones back in as it just happens again. I might call.for that :)

Edited by soulsedg3

The only "plating" that can be done and/or restored in your YZF is the cylinder.  They are plated with Nikasil, and it can be cheaper to have the cylinder bored over, replated, and finished back to size than to replace the cylinder with a new one.  During this process, even very deep damage can often be repaired by welding before finishing to size for the plating.


Worn valves cannot be retreated and used over.

They can probably re cut the seats on the Ducati, but the valves sound like they need to be replaced... Wonder if kibble white make stainless valves for that bike...

Its the surface on the rockers that causr the ducati to lose clearances i guess. The plating flakes and things go outta spec.

Heard of people rebuilding the surface on rockers back up. Grinding back down to spec and that solves the problem.

Probably can be done, i would call millennium up and see if they can do it. Welding the rocker up and than grinding it back down might work, but it would probably take some kind of heat treatment to harden the surface... I would check with them, maybe the same coating that is used on cylinders could be used on the rocker... The rockers and the cylinder bore seem like they would both be under the same type of conditions (load and heat) so it might work...

Good. Back on topic. Got head back and all. Going to start reassemble tonight. Manual says apply molybdenum disulfide oil to cams. I am in a small town....cant find any engine assembly lube. Im assuming good old engine oil will do. I found the grease version for the head bolts though like recommended. I was always yold to put anti seize on those in rebuilds....not grease.

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