2007 yz450f Sand in Motor

Three of us recently got back from St. Anthony Sand Dunes, Id and we had a great trip. The sand is so soft out there we were constantly clutching the bikes really hard and thought our oil was turning black from the abuse we were giving the bikes. We used K&N prefilters over our oiled air filters so sand in the motor wasnt even brought up. But when we got back and went to change the oil we found the oil filter had a lot of grit in it. Turns out under our valve covers there is grit also. The crank breather tube was sucking sand into the motor the whole trip.

Was is our best option to do now? Where is a reputable place to send the motor to to have everything cleaned out? Simple rebuilds we can handle but with sand in the whole motor we would rather have it done right knowing the motor wont lock on us in the air.


I feel your pain, A friend and myself did the same thing 2 years ago, same place, same weekend, damn Yamaha and their breather hoses. We both tore our motors apart and replaced every bearing, main bearings, transmission bearing, etc. The only bearing we didn't touch was the main rod bearing. The only solution for this is to split the cases and replace all of the bearings and inspect to see if anything else is damaged. The bearings in mine would not have held out to much longer. I was able to just clean out the head really good with the valves still in it and had no further problems with them. I got lucky on the cams and only had one journal that got the faints mark on it, so I just ran it never had any problems. It did toast my clutch and basket for some reason.

I have since sold that bike, but my friend still has his with no problems. This was the first time I took apart a 4 stroke, but I have rebuilt multiple 2 stroke transmission and cranks. I actually thought the 4 stroke was not any more difficult, just more time consuming with the timing and everything.

There are a lot of similar posts on this very topic here on TT. Yamaha should take some action to at least prevent this from happening on their new bikes. On my last two YZ 450's I will route the breather hose up into the airbox and put a $12 K&N style filter from Checker on the end of it. It actually works really slick and you don't even have to cut the hose or anything.

All in all I think i was about 350 bucks in parts to rebuild my motor, I did all of the labor myself. You might as well re-ring it and put a new timing chain in it while you are in there. If you are mechanically inclined I would just tell you to get a manual and tear into that thing. If it is your first time, take alot of pictures as you take it apart and label things if needed. I would also order all of your bearings before you take it apart so that you can put it back together before you forget how it goes together. Other than that good luck, It's a bad spot to be in and I spent a few nights in the garage cursing the Yamaha Gods for their stupid design!!!!!

I think you your local shop will be your best option if you don't do the work yourself. But I would be surprised if you can get out of there for under 1500 if they operate like the crooks around here.

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