dabalot Posted March 13, 2006 Report Share Posted March 13, 2006 (edited) I picked up a new 2006 4rt a few weeks ago. If you have recently purchased one, you should check that the engine breather is venting properly. The hose comes out of the top left of the valve cover and goes up to a small catchment tank up underneath the steering head. From the tank, a second hose runs to the top left front side of the air box. This routing recycles any excess air out of the engine back into the intake via the air box. From the factory, my breather hose was doubled back on itself just before the air box, effectively sealing it. It wasn't that obvious as the pinched part was tucked up behind the frame, just above the rear brake reservoir. The quick way to check if it is plugged is to remove the breather hose from the valve cover and breath into it. If you get dizzy trying, you need to check the hose. What happens if you ride it with the breather blocked? Mine created enough pressure inside the engine to dislodge the right side crank seal. This seal separates the engine compartment from the transmission compartment. It sounds drastic, but it was a fairly simple fix. How do you know that the seal is damaged? (1) Engine oil level seems low after running the engine for a few minutes, even after waiting the manual-recommended 3 minutes since shutoff. (2) You get black rubbery plastic bits and metal flakes in the transmission oil (3) During constant running, oil comes out of the transmission breather hose. If you have any of these things happening, you should take off the right crankcase cover and check the crank seal. The engine oil presumably gets low because the engine forces some engine oil past the bad seal into the transmission when it's running. After waiting 15-20 minutes or so the engine oil level goes back up as some of the oil leaks back from the transmission into the engine through the faulty seal. The black bits in the transmission are caused by the cranks seal pushing out of the crankcase into the transmission compartment. As it moves out, it rubs against the gear on the back of the clutch hub. This disintegrates the seal and accounts for the bits in the transmission oil. The transmission breather hose runs from the top rear part of the cases up to, and is clipped onto, the engine breather hose just before the engine hose enters the air box. However, unlike the engine breather, the transmission hose doesn't enter the air box. When the engine is running at a constant RPM, there is enough engine pressure venting past the bad crank seal to send some of the transmission oil out of the transmission breather hose onto the front left side of the air box. It then runs down and conveniently oils your chain. Although I didn't check it on my bike, I would assume that with the engine running at mid-RPM you would be able to feel air coming out of the transmission breather hose if the crank seal is leaking. The good news is that was easy to fix, and both the engine and the transmission seemed to retained sufficient oil while I was riding it. To fix the seal, you will need to drain the radiator and remove the hose connected to the water pump. Then remove the right crankcase cover, the clutch hub and the idler gear. You don't need to disconnect the clutch oil-line. You should be able to pull the damaged crank seal out and replace with a new one from there. The seal is the same as in a Honda CRF450, so your friendly local Honda dealer might even have one in stock (mine did). Be careful putting the crankcase cover back on. You will probably need to remove the water pump cover and turn the impeller in order to align the water pump / idler / oil-pump gears before fully installing the cover. After putting it back together, I changed the transmission oil a few times after riding it for a few minutes between changes to get any reaming bits of seal out of the transmission. Despite the above human-error-assembly glitch, it Edited March 14, 2006 by Dabalot Quote Link to comment Share on other sites More sharing options...
oz thumper Posted March 14, 2006 Report Share Posted March 14, 2006 Thanks for warning, not something I would have been looking for when working on the bike. Quote Link to comment Share on other sites More sharing options...
munch Posted March 14, 2006 Report Share Posted March 14, 2006 surely all 06s are still under warranty? so why not get your dealer to look at it and do the fix foc Quote Link to comment Share on other sites More sharing options...
rapid roy Posted March 14, 2006 Report Share Posted March 14, 2006 I AGREE WITH THE LAST COMMENT DID THE DEALER DO THE WORK I WOULD HATE TO SPEND THAT TYPE OF MONEY ON A NEW BIKE WITHOUT BACKUP Quote Link to comment Share on other sites More sharing options...
dabalot Posted March 14, 2006 Author Report Share Posted March 14, 2006 Yes, the dealer did the work. Quote Link to comment Share on other sites More sharing options...
hopkins92 Posted March 15, 2006 Report Share Posted March 15, 2006 Well, my breather must be clear because there was about 100 cc of oil in the airbox after the first time I changed oil. Getting the oil level right is tricky business. Quote Link to comment Share on other sites More sharing options...
hopkins92 Posted March 15, 2006 Report Share Posted March 15, 2006 I did a filter change and then used the "more is better" method. I'll bring it up slower next time. Quote Link to comment Share on other sites More sharing options...
dixie Posted March 24, 2006 Report Share Posted March 24, 2006 more is better, not in fourstrokes,be carefull my sherco 4t looked like a clowns bike at the circus when it dumped oil all over a hot pipe Quote Link to comment Share on other sites More sharing options...
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