Picked up an '03 YZ450F

Pretty excited. Traded my YZ125 for it. So my out of pocket was around $1k. 

 

Oil looks like chocolate milk, carb leaks, but it has pretty much every major aftermarket thing on it you can imagine, and runs quite well. At least till the gas drains out of the bowl. Rebuild time.... Lets play spot the aftermarket parts.. What do you see...

 

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I see lots of stickers!

Day 1:

-ordered all the wp parts

-rebuilt the carb - clogged pilot jet and general crud

-rebuilt petcock - now the tank will actually hold gas. 

 

Pics of stuff:

 
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my helper goofing around later:

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Got some more work done today. 

 

Mostly just the waterpump. Damn that old one was nasty. The impellar shaft was all chewed up. So hopefully should get the carb and stuff back together tomorrow and fire her up. 

 

The mystery oil was Valvoline VR-1 from another thread.

 

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Clutch was in immaculate condition, as were all the gaskets 

 

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yuk

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Well day 3 is a mix of good and bad...

 

Good:

got the carb working properly

got everything reassembled

found out I have stage 1 Hot Cams

found out I have a HotRods rotating assembly

found out I have a vertex piston (high comp?)

 

Bad:

blown headgasket. 

had to tear it all down again

stripped screw in head. 

 

Hopefully get an extractor set this week to remove the screw, and order some new gaskets. 

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You guys think the piston is good to reuse?

You guys think the piston is good to reuse?

yes but after being apart why not hone the cylinder and go for piston and rings your already there.

I don't care what people say if it's nicaseal just run a ball hone through it real quick.

I used to race boats two stroke engine I ran ball hone through a lot.

When I was young I did it on my mx bikes to take the lip off the top of the cylinder if it has one

oil the shit out of it and

hone it it will be fine.

while your in there you should debur the cylinder don't open the ports just smooth them out.

Nothing that shows in your pictures gives any information about the condition of the piston or bore walls, so there's no way to tell.  The crank was replaced at least once; that one's from Hot Rods.

 

Judging by the look of the cam journals, the previous owner wasn't a big fan of frequent oil changes. 

yes but after being apart why not hone the cylinder and go for piston and rings your already there.

I don't care what people say if it's nicaseal just run a ball hone through it real quick.

I used to race boats two stroke engine I ran ball hone through a lot.

When I was young I did it on my mx bikes to take the lip off the top of the cylinder if it has one

oil the shit out of it and

hone it it will be fine.

while your in there you should debur the cylinder don't open the ports just smooth them out.

 

I will absolutely hone the cylinder. But on a bike I am not sure if I will keep I do not want to spend $200 on a new piston kit. Especially considering the old one is in good shape. 

 

 

Nothing that shows in your pictures gives any information about the condition of the piston or bore walls, so there's no way to tell.  The crank was replaced at least once; that one's from Hot Rods.

 

Judging by the look of the cam journals, the previous owner wasn't a big fan of frequent oil changes. 

 

Ya. They are not perfect, but judging from the amount of water in the oil, and general shittyness I will be doing several oil changes to get everything out. Hard to take proper pics of bore.

 

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I'm more concerned about the piston.

I'm more concerned about the piston.

based on what?

Based on the fact that there aren't any pictures of the skirts.  You'll also need to carefully gauge the wear in the ring grooves to see if they are tapered open from inside to out.  Too much clearance allows the rings to twist at the top and bottom of the stroke, accelerating wear on both rings and bore.

I will use a feeler gauge on the rings tonight. 

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Piston is confirmed by vertex as a 13.5:1 high comp unit. You can tell by the bump in the middle. 

 

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What are you waiting for put that bad boy back together.

Head gasket and jug gasket shipped out today. Didnt know I needed it till yesterday.

Head gasket and jug gasket shipped out today. Didnt know I needed it till yesterday.

Okay take your time doing it follow the manual to the t any questions call or jump on tt and ask don't rush it let me know how you make out lol.

My biggest concern is hoe to set proper timing without the stock case cover..

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