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Pancho_Jsy

The dreaded 'Oil in the airbox' on my WR450F-SM

17 posts in this topic

Hi all,

 

I recently bought an '07 WR450F from a friend. It had been parked up under a cover for at least three years and was looking a bit rough. I gave the carb a full rebuild, set the valve clearances, put a set of Continental SMs on the 17'' wheels and started using it for blasting around the back lanes. The bike runs absolutely spot on, starts first kick, never stalls, never smokes. It's a stock UK bike except for AIS removal and an FMF silencer.

 

My problem is that despite having the oil level correct it spits oil into the airbox every time I ride it 'enthusiastically' Now the previous owner says he never had this problem so I'm assuming I've routed the breather hose wrong somehow. It all appears correct to me and I cant see any way to route the stock breather pipe higher.

 

Could anyone share a photo of the CORRECT breather hose routing to make sure I've done it right?

 

I'm an experienced motorcycle technician and usually I would make notes of this kind of thing but in my excitement to get the bike on the road I forgot. Your help would be massively appreciated

 

Cheers,

 

Pancho  

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You more than likely have your bike slightly overfilled. They only hold a quart.

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You more than likely have your bike slightly overfilled. They only hold a quart.

 

Nope, definitely have it bang on the line, after a ride the airbox is full and the oil level is below the low mark. The longer i ride the lower it goes...

Edited by Pancho_Jsy

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You got something funky going on there. Graves racing makes a air oil separator.

But I dare say no one else's bike does what yours is doing unless it has excessive blow by?

Get or download a shop manual.

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Is the airboot between the air filter and carburator oily inside as well or just the airbox around the filter ?

 

By the enthusiastic Supermoto type of riding, I'm guessing it implies quite a lot of compression braking

so a lot more chance of creating blowby and perhaps some reversion into the carb/airbox.

 

Is the crankcase breather routed in the airbox ?

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Is the airboot between the air filter and carburator oily inside as well or just the airbox around the filter ?

 

By the enthusiastic Supermoto type of riding, I'm guessing it implies quite a lot of compression braking

so a lot more chance of creating blowby and perhaps some reversion into the carb/airbox.

 

Is the crankcase breather routed in the airbox ?

The breather exits into the airbox, not between the airfilter and carb. I don't see how hard braking would create more blowby, I was thinking more that wheelies and hard acceleration might encourage the oil up the starter gear breather.

 

A new workshop manual is over $150 here and there's none on Ebay currently. If anyone has one it would be really helpful if they could share the relevant pages on routing. A photo of a healthy example would be even better. TIA

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You can download the owners/service manual here: http://www.yamahaownershandbook.com.au

Unfortunately the link just takes you to the Yamaha AUS main page. Scoured the website but couldn't find any owners/workshop manuals.

 

UPDATE:

Found a workshop manual on the website via the link below. The pictures in the manual were useless so I'm still hunting for a photo of the breather routing. If anyone has their tank off over the weekend please take a quick photo to help me out.

 

The sun's shining and I'm desperate to go thrash!

 

http://www.yamaha-motor.eu/eu/services/owner-manuals/index.aspx

Edited by Pancho_Jsy

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On the excessive blow-by and reversion theory,

noticed I wrote 'compression braking ' as done with the engine, not only braking.

 

Since you are a motorcycle technician you likely have easy access to testing equipment,

run a leakdown test on the engine, may give you a better indication of it's internal condition.

(valve seals, piston rings etc.)

 

If that engine is run as hard as suggested, it may be in need of a refurb.

 

Also, did you check if there was any oil in the airbox (filter to carb boot).

Edited by mlatour

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 Basically the top of the valve cover breather goes into a three way tee next to the carb. The starter breather also goes in there. The third one wraps around and goes into the air box. I put an extender in mine and routed up under the seat.

 

If that doesn't do it post a couple of pics of yours and we can go from there.

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 Basically the top of the valve cover breather goes into a three way tee next to the carb. The starter breather also goes in there. The third one wraps around and goes into the air box. I put an extender in mine and routed up under the seat.

 

If that doesn't do it post a couple of pics of yours and we can go from there.

 

Yep that's how mine's plumbed but i think it must be routed wrong. I'll get the tank off and take some photos over the weekend.

 

@Steve I'm pretty confident its not blow by because the previous owner never found oil in the airbox. The rings wouldn't have worn while it was parked up (although i guess the bore could have corroded) and it runs perfectly with no smoke or noise. We do have a leak down kit at work but there's no space or time to get in there

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*UPDATE*

 

Checked the breather routing twice more to be 100% I hadn't cocked something up but it was definitely bang on. Rode it to work, puked about 500ml of oil into the airbox and the oil level was on the low mark. I though hmm well maybe the oil's degraded after sitting in the bike for so long. So I pulled the drain bungs out, and at least 3 litres of oil poured out! So you were all right, it had been waaaay overfilled at some point. What I cant work out is when, the previous owner had plenty of experience with MX bikes and never had this issue. It's also weird how it never looked overfilled on the dipstick and the oil level would go down after a ride?

 

Anyways, it's sorted, runs better than ever and we're off on our first track day tomorrow :D

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Even with the electronic manual I'd suggest picking up a paper copy, I'd rather get that greasy than the laptop. http://www.ebay.com/itm/2007-YAMAHA-WR-450-FW-DIRTBIKE-MOTOCROSS-CYCLE-SERVICE-REPAIR-SHOP-BOOK-MANUAL-/301735206509?hash=item4640d1de6d:g:OWUAAOSwQPlV7xDZ&vxp=mtr is one example, $30, I imagine you can find them in the UK for a reasonable price as well. 

 

How gassy is the oil? At one point mine ended up with way too much "oil" in it thanks to the float bowl getting dumped into the oil on short trips, so I drained a huge amount... but it was obvious it was a lot of gas, not just oil. 

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@toten The images in the workshop manual were no help at all but as I said in my previous reply, it's fixed. There was over 3 litres of oil in the motor! And it was oil, not a mix of oil and fuel.

 

The bike performed flawlessly at a local Go Kart track on Friday. Got the pegs down and I went off the edge of the tyres. The stock suspension handled it better than expected but the stock front brake faded badly after a few laps. Even hassled an old geezer on a '16 FS450. I cant praise the Continental ContiAttack SM tyres enough, the perfect tyre for fast road and the occasional track day :D

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@toten There was over 3 litres of oil in the motor! And it was oil, not a mix of oil and fuel.

Just a thought... I wonder if he was checking the oil level without first running the motor?

The first time I changed the oil on this bike I put in the requisite liter of oil, checked it immediately, and added more oil because it was low. It took well over 2-1/2 liters before it showed full on the dipstick.

After re-reading the manual and threads on TT, I realized the oil level needs to be checked shortly after running the motor. I drained the excess oil, ran the engine, checked the level again - Bingo!

I would expect that running the engine would distribute the oil throughout the motor, leaving the reservoir under the dipstick low. I was certainly wrong, although I don't know why. I'm sure someone much smarter will followup and explain the missing details.

Anyway, glad you figured it out!

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