08' WR 450 problems


I am obviously new here, I read the FAQ and did a search but could not find any answers. If there is another thread or threads you know of that answer my questions please point me to it and accept my apologies in advance. Second sorry for the novel but much of the story has to be told.

Here is what I have going, I purchase a new 2008 Yamaha WR 450, I immediately modified it with a GYTR AIS kit, air box, grey wire etc., put on a new IMS tank, and rode it 5-6 times, 30-50 mile each ride. The bike ran great no problems and no issues. That was my break in and shake down for a 10 day Baja trip.

Once in Baja, the second day of riding, my bike starts to dump oil in the air box and starts to cut out. The cutting out is like hitting the off switch quickly and letting go again repeatedly and is mostly half to full throttle 3-5 gear. It first appeared doing about 60 mph on the highway. That night I added about a 1/4 quart back in.

Next day I ride again and the same thing happens oil in the air box 1/4 quart dump but this time the cutting out is more pronounced meaning it last longer and is more frequent. I had a buddy ride the bike who is on his 6th WR 4xx and he said he thought it felt like a transmission issue (he blew up the dogs on a 450 9k miles) because when it cuts out you can pull the clutch and it immediately revs up with no cut out, no delay, all very clean.

Anyway, long story short, my buddy blew up his top end on his bike that day and we had no support vehicle and since my bike was running like crap and nothing to clearly identity the problem too, I thumbed a ride 400 miles back state side with my buddy and called the rest of the trip done.

Once I got back, I went through the bike trying to find issues with no luck. I started the bike and rode it a short distance and there was no oil blowing out but I had the cutting out issue? So I took it to Sierra Yamaha an Out The Door Motorsports shop where I bought it from and the mechanic discovered that the breather tube on the head was pinched under another hose. They called, said it was fixed.

I picked up the bike and took it for a spin, warmed the bike up first then took it on the highway at 55 mpg 5th gear held steady, the bike did not blowing oil (so far) but it still cuts out within 5-10 second of holding steady at speed.

I took it back to the mechanic and he took it out for a ride and came back with a huge attitude and told me "there was nothing wrong with the bike". I disagreed, and the mechanic started arguing with me saying "there was nothing wrong with the bike". Soon he was yelling at me :applause: and telling me "he was not a good enough mechanic to work on my bike" and that I needed to leave. This was unbelievable since I was level headed, cool and calm the whole time, after all, I just wanted my bike fixed.

Then the manager and my sales guy came out because of the mechanic yelling at me so loud and he road the bike and agreed that the bike was not running smooth (claimed jetting). I then asked him if the mechanic was certified he said he was. He then talked with me over his shoulder and the mechanic told him "we were both wrong and there was nothing he could do".

The manager then turned to me and said if the mechanic says "there is nothing wrong with the bike, there is nothing we can do to help, we can not fix a problem that we can not identify". :p

I really do not like the shop or the mechanic :eek: anymore, since the mechanic is the boss and the manager doesn't know customer service. The mechanic thinks I am basically an idiot and the bike did not have a problem even though the manager and three of my friend who have road it say there is something wrong with it.

I do not think it is a jetting issue because it ran fine prior to going to Baja at 4-5000 feet and ran fine at Baja as well. If it was a jetting issue I would expect that it would have ran rough at one of the two elevations?

So my questions are:

1. Anyone ever have their WR dump oil in the air box or know why that would happen if the breather tube from the head is pinched?

2. What is you opinion of my cut out problem is it related to the oil dumping, transmission or jetting ?

3. Am I the idiot on his second WR (2000 WR 400) which ran smooth and lasted 10k miles and was sold still running strong as day one just expecting to much from my new bike?

Lastly, should I being making a stink about the way the shop has handled the situation and if so, what should I do?

Thanks in advance a frustrated new WR owner in Reno, Nevada

I don't have anything to say about the oil in the airbox, mine has never done that, however the steady throttle stutter is an issue on my bike. Search the forums for "stutter" "misfire" or "TPS" and you will find a lot of info. I have not been able to fix this issue completely on my bike yet, buit I am close. This is a jetting problem which is exagerated by the TPS mapping of the ignition timing. A lot of people disconnect TPS and the problem goes away, or is minimized. That is not good enough for me, I want to get the problem solved and have my TPS to trim the ignition advance for best power.

On the topic of jetting, here is my experience with the 07-08 WR 450 at sea level. The pilot circuit is very rich, but just off idle the needle takes over and goes lean, then main circuit takes over and runs correctly. You cannot go down to the proper sized pilot without changing the needle. The stock needle and the DTR needle in the GYTR AIS kit have a very lean straight diameter, and with the proper pilot, you get a very bad leanout at light throttle. It will turn your pipe cherry red when riding!!! To minimize the issue of stuttering at steady throttle in the 1/4 to 1/2 throttle range, you will have to change the needle. JD kits will definately help, or you can go the Sudco route. There is also a Dr D article from Dirt Bike a few months back that had some jetting specs for your bike that may help. Search for Dr D or Dirt Bike here or in the jetting forum for the complete details.

Hope this helps.

Oil in the air box.

I’ve read a few post on this…most peoples advice was that “the bike was over filled with oil”. I do not know if this is fact or fiction, But I did read one post where the guy said that he had solved his oil in the air box issue by changing the breather tube to the YZ style system. I think his conclusion was that the air box was so restrictive that the vacuum developed was enough to suck oil thru the breather tube while flat out riding in the desert.

sorry to hear about your problems

i have a 08 WR450

no oil have ever been detected in the oil box

not the tranny; jetting/TPS problem i would go after.

did you have to pay for the suspect repair ??? if so by all means complain.

NOTE mine is not perfectly smooth at a steady clip 50/60mph... i just thought it was the throttle is so responsive tho.. i still have the off idle bog a little bit... Also mine is a stock 08 WR450 with AIS removal, snokel removed, grey wire mod...little restrictor taken out.. thats about it.

cheers & good luck


I agree overfilled with oil...for environmental reasons they put it in the box instead of letting it fall to the ground

Oil in the air box.

I’ve read a few post on this…most peoples advice was that “the bike was over filled with oil”. I do not know if this is fact or fiction, But I did read one post where the guy said that he had solved his oil in the air box issue by changing the breather tube to the YZ style system. I think his conclusion was that the air box was so restrictive that the vacuum developed was enough to suck oil thru the breather tube while flat out riding in the desert.

I would venture to guess that it is possible for the airbox at high RPM to help a little in sucking out the oil. I have taken both breathers on my '08 and routed them upwards and capped the ends with Uni crankcase breathers. The one from the lower case (starter area) ended up just about where the AIS used to be and the one from the head snaked through the hole in the frame up by the front tank mount and the filter zip tied to the top of the radiator louver. I've done this with bikes in the past. The idea was to keep the end of the breather tube high so that the oil does not escape and the air is cleaner than what it gets from the dirty side of the airbox. Stock, it's just a downhill run from the top of the head to the airbox and any oil that goes in the tube is gone.

The one thing I would like to know is about the bottom breather. Most engines just have one breather so my guess was that this may not be for breathing as much as a return for the oil from the top breather (as they are connected at a "Y" fitting). But if people are finding oil in the airbox than it either does not work or was not designed for that and actually just needs to breathe like the breather off the head.

When Yamaha routed the crank case vent into the airbox (07'?) I thought it was because all of us were already doing that mod to prevent water being sucked in.... but it could have been for enviro issues too?

Anyway, I had my 07' for 4 months when the airbox filled with oil. I had not been draining the resevoir infront of the crank case properly and found that I had eventually over-filled the motor with oil. You must drain from the left side drain plug everytime, with the dip stick pulled out so as not to create a vaccum:prof:

The cutting out sounds like TPS :thumbsup:

the only thing I've found in the bottom of my air box is water and some drip from an over oiled air filter.

but, I've followed the oil chage procedure correctly and I never really open her up for long periods.

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