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2012 WR450F Head Rebuild

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My bike started blowing oil into the air box and I was always pulling up the rear and no one noticed any smoke / I didn't notice any.  I have about 400 hours on the engine (and Head parts), and 200 hours on a piston / rings and timing chain).  I pulled the piston and cylinder and both look great.  The head looks good too, but obviously there must be an issue with either one of them and I currently do not have the tools to disassemble the head.  I already plan to change piston / rings / wrist-pin, timing chain, and timing chain tensioner.

This bike is my 1st 4 stroke and haven't dealt with a head rebuild before.  Just looking for some experienced people to give me their 2 cents.  I was planning on OEM Titanium valves, and getting new valve springs.  Do I need to also by the valve stem seals?  Are valves something I can drop new ones in and be good, or do I need to send the head and parts to a reputable head shop?  What about the valve seats (didn't think you could cut titanium seats), and valve stem guides?  I know I have read stuff about pouring water and seeing if the valves leak, but at 400 hrs, why even try to trouble shoot (Unless I'm way off on replacement hours).

I'm kind of broke at the moment, so trying to cut as much cost as possible.. but things like this, you can't really cut that much other than finding OEM parts from online dealers and comparing prices.

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You need to have it done professionally, as it is cheaper that way, unless you wan't to buy the machines and tools to do the job as needed.

At 400 hours, you need all new parts. The valves will show some level of mushrooming, and that means the seats are shot, and the stem seals are ovaled.  New valves requires new springs, keepers, etc. The seats must be at least 3-angle cut (5-angle for better flow). They are not Titanium, they are a steel/copper alloy.

Lot's of 'head service' companies out there.

You are VERY VERY lucky that you did not break/drop a valve for going so long on the stock head....

https://www.google.com/search?rlz=1C1CHMO_enUS529US530&q=dirt+bike+head+service+nevada&oq=dirt+bike+head+service+nevada&gs_l=psy-ab.12...17046.17932.0.20196.9.9.0.0.0.0.117.737.6j3.9.0....0...1.1.64.psy-ab..1.0.0.wnBD4AobLV0

 

https://www.google.com/search?rlz=1C1CHMO_enUS529US530&q=yz450f+head+service&oq=yz450f+head+service&gs_l=psy-ab.3..33i160k1.18483.22346.0.22465.19.19.0.0.0.0.118.1491.16j3.19.0....0...1.1.64.psy-ab..0.19.1485...0j35i39k1j0i131k1j0i20k1j0i46i67k1j46i67k1j0i67k1j0i22i30k1j33i21k1.-yTEipGTLJA

 

IMHO, avoid the company specializing in head work, that rhymes with 'rape'.....

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I'm in Las Vegas, but I was thinking about fast Heads in St. George.  Looks like $699 for full rebuild.  Think that is the ticket.

Edited by mch
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How often are you guys servicing your heads?  I got about 5 years and 400hrs on it, but it sounds like that is too many hours to go without a head rebuild.  Factoring in all the tires, etc., it might not seem like a lot.. but $1,000 for head work, new piston, cam chain, etc. is kind of a lot to do all at once.

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9 hours ago, mch said:

How often are you guys servicing your heads?  I got about 5 years and 400hrs on it, but it sounds like that is too many hours to go without a head rebuild.  Factoring in all the tires, etc., it might not seem like a lot.. but $1,000 for head work, new piston, cam chain, etc. is kind of a lot to do all at once.

That is the price to play. .....and yes make SURE you replace the cam chain and tensioner.

Race bikes can need the same level of service in as little as 50 hours.

Pro SX racers only go 3 hours....

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