WR450F Bad Oil Leak


13 replies to this topic
  • YamahaWR450FMike

Posted April 08, 2012 - 10:04 PM

#1

A buddy of mine has a 2004 WR450F. We went riding today and just a few miles into our ride he had smoke and oil leaking everywhere. I towed the bike back to our home and couldn't find anything that could be leaking. But today I noticed up on the front of the cylinder head a little round hole near the exhaust. It looks like a cap of some sort has came out of this hole. Is that normal? Any ideas?

  • zibbit u2

Posted April 08, 2012 - 11:45 PM

#2

the manual decomp plug fell out. Fairly common issue.

  • travertt

Posted April 09, 2012 - 05:57 AM

#3

the manual[color=#282828] decomp plug fell out. Fairly common issue.[/color]



I own an 04 ...as far as I know...there isn't any manual de-comp on this model year

  • mikewrf18

Posted April 09, 2012 - 06:17 AM

#4

Not really familier with the 04' models, but on my 07', that would be where my AIS block off plate is.
Could that AIS block off plate came off?

  • mikewrf18

Posted April 09, 2012 - 06:24 AM

#5

I own an 04 ...as far as I know...there isn't any manual de-comp on this model year

It may not have a decomp lever, but i think there weren't many changes between the 04' engine and older models and the decomp hole may have been blocked off from the factory on the 04's. Not 100% sure though.
On my 07' that location would also be near where my AIS block off plate is, but I did a search, and it looks like the 04' models didn't have AIS?

Edited by mikewrf18, April 09, 2012 - 06:25 AM.


  • woods-rider

Posted April 09, 2012 - 06:25 AM

#6

I also think it sounds like the place where the AIS block off plate goes. Got any pics?

  • travertt

Posted April 09, 2012 - 06:36 AM

#7

It may not have a decomp lever, but i think there weren't many changes between the 04' engine and older models and the decomp hole may have been blocked off from the factory on the 04's. Not 100% sure though


My 04 does not have a decomp lever or AIS fittings. Now mine is a Canadian model...but I believe the AIS did not appear until the '05 model year.

However mikewrf18 could be spot on with the idea that in the '04 model year, the factory just plugged the hole in the cylinder head for where the decomp lever used to be in earlier model years.... and that this "plug" may have been whats fallen out.

Definitly a picture is the way to figure this out.

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  • grayracer513

Posted April 09, 2012 - 06:50 AM

#8

None of the 450's had manual decompression, but all the Gen1 engines ('03-'06 WR's) have the machine work in place to install one, and it's listed as available in the parts books. The plug that blocks that off is a wimpy little plastic thing that will pop right out if the breather line gets pinched or if the weather's wrong. Replace it with something better.

Read:

http://www.thumperta...419#post1522419

http://www.thumperta...mpression-plug/

  • zibbit u2

Posted April 09, 2012 - 07:40 PM

#9

Sorry, maybe I should've been more specific.. yes, yamaha had a manual decomp lever already machined into the head from the previous generation WR's, unfortunately they never changed the casting for the head when they went to a Auto Decomp system, instead, they installed a "wimpy plastic plug" to block off the hole. If the main breather hose gets restricted and/or plugged, it creates too much pressure in the cylinder head, thus blowing out that wimpy plug and unleashing a whole lot of oil just above the exhaust header.

There is aftermarket alternatives for that plug on Ebay.

  • grayracer513

Posted April 10, 2012 - 05:58 AM

#10

There is aftermarket alternatives for that plug on Ebay.


There are aftermarket alternatives right here at the TT Store (see the second link I posted). You can also use an 18mm "freeze plug" from an auto parts store, but they can be a challenge to install with everything assembled. Some have just used the OEM plug and glued it in place, but I wouldn't trust it.

  • miweber929

Posted April 11, 2012 - 08:39 AM

#11

There are aftermarket alternatives right here at the TT Store (see the second link I posted).


I tried the link earlier this season and just now and get nothing.

Haven't found any in quite a while not OEM.

Mike

  • zibbit u2

Posted April 11, 2012 - 10:00 AM

#12

Just search "Decompression Plug" on ebay, you'll get like 17 hits in various colour options

  • SPLATT

Posted April 11, 2012 - 04:54 PM

#13

I used an 18mm freeze plug on my 04 WR450. 6 years later no issues with leaking or coming out.

  • Rocky739

Posted April 16, 2012 - 07:51 PM

#14

http://motors.shop.e...ompression plug

Just ordered one tonight for my 03, cheap fix compaired to dumping all the oil and trashing my engine...




 
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