Help Sand in Motor!!!! 06YZ450


28 replies to this topic
  • grayracer513

Posted September 25, 2008 - 05:38 AM

#21

If the wear in the cylinder is a polished area running at parallel to the top of the cylinder, just under the top, it's from the compression ring twisting as it changes direction under pressure. There may not be any actual wear, however.

Take the rings off the piston, and put the top ring in the bore near the bottom edge. Put the piston in upside down and use it to square up the ring by pushing the ring against the piston crown. Measure the end gap of the ring with a feeler gauge at with the ring at the bottom, and all the way at the top edge. These areas receive virtually no wear, and the two measurements should be the same. Now, use the piston to push the ring into the area where the wear marks are, and remeasure. Rotate the ring gap to several different positions and remeasure. Since the circumference increases at 3.14 times the increase in diameter, the ring gap will increase by .001 for each .0003 of wear.

You will probably find no wear, and if you are in doubt, have it checked out. If it's good, hone it:

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  • casperkc

Posted September 25, 2008 - 10:32 AM

#22

Since Yamaha has been running that same breather tube the same way since 1998, what makes you think you were, allowing for the sake of the question that it even is a screw up? Frankly, your description sounds more like long term neglect.


Read better next time, I said this happened in 06'. I didnt even have 10 hours on my bike yet. Neglect is not a factor here, as this happened after a stall in a deep unknown puddle. And yes this is a piss poor design on Yamahas part (since 98'). Go look at the others, you wont find crankcase breather hoses routed to the atmosphere. Granted my scenario may have been a little worse than others I still dont understand why would somebody think that that routing is a good idea.

  • grayracer513

Posted September 25, 2008 - 11:35 AM

#23

They are all routed to the atmosphere, one way or other. That is their purpose.

Breathers have been routed that way as long as there have been engines. In virtually all "normal" circumstances, it works. None of the 5 YZF's I own or have owned, nor any of the array of older 4 strokes I've had under me as far back as 1968 have had a problem with it. The YZ series are purpose built MX bikes, not enduro or trail machines. Under all but the most ridiculous conditions encountered in MX, there should not be any reason for the bike to ingest anything through that hose. Note that the WR series, built for off road use, has the breathers routed differently.

  • casperkc

Posted September 26, 2008 - 03:22 AM

#24

They are all routed to the atmosphere, one way or other. That is their purpose.

Breathers have been routed that way as long as there have been engines. In virtually all "normal" circumstances, it works. None of the 5 YZF's I own or have owned, nor any of the array of older 4 strokes I've had under me as far back as 1968 have had a problem with it. The YZ series are purpose built MX bikes, not enduro or trail machines. Under all but the most ridiculous conditions encountered in MX, there should not be any reason for the bike to ingest anything through that hose. Note that the WR series, built for off road use, has the breathers routed differently.


I know that that is there purpose. I meant that they are routed to the atmosphere unfiltered. So if I fall on my left side in a sandy berm on an mx track and that perfectly routed hose is laying in the sand and the bike stalls is "all but rediculous"? Come on Grey:banghead:

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  • grayracer513

Posted September 26, 2008 - 08:02 AM

#25

So if I fall on my left side in a sandy berm ...

Well, that must be it. I never fall in the sand. :lame:

Posted Image

  • Aka.Goose

Posted September 26, 2008 - 09:36 AM

#26

Well, that must be it. I never fall in the sand. :lame:

Posted Image


Hahaha...That guy's definitely getting some dirt in his breather tube!!! lol

  • HONDA NO MORE

Posted September 29, 2008 - 08:34 PM

#27

Once again thanks for all of the replies. My next question is what do I do with the bearings now? I have the cases split and have been spraying brake clearing into the bearings and slowly spinning them, but I can still feel grit in some of them, but the feeling goes away once I add some oil to the bearing. Does anyone have a good method of ensuring that the bearing is clean of grit???

Checked my cylinder, it is still good, getting it honed as we speak. Does anyone know wear to buy a flywheel puller for these bikes? I took it to the local shop to get raaaappppped once again, 25 bucks to do a 2 minute job, I wish I made that kind of money. Is it worth it to through in new rings while I have the motor open?

  • grayracer513

Posted September 29, 2008 - 09:21 PM

#28

The flywheel puller for the '06-'08 YZ450 is the same as for a CRF450R. They are available from the TT Store, and most good sized dealers or parts houses.

Dry bearings will usually feel rough after they have any wear on them. ATF makes an excellent rinse for removing debris from bearings. If you think they are clean, inspect them as thoroughly as possible, and just replace them if there is any doubt. I have reused them successfully on may occasions, but it's always a crap shoot.

  • HONDA NO MORE

Posted September 30, 2008 - 07:17 PM

#29

Okay, I am ordering parts tonight and have one more question for all of you pros.

When disassembling the motor, I pulled the clutch side case off of the crank, just as the manual says. I then expected to have to press the crank out of the main bearing on the flywheel side, well the crank came out by simply a light tap with the end of an old screwdriver. As far as I know this side side is suppost to be press fit between the crank and the main bearing. At present it is a slip fit. So if it comes out this easy does this mean I need a new crank and a new main bearing? :lame: :bonk: I ask this because I think this would allow the crank to spin on the inner race of that main bearing, which will cause a failure pretty quickly last time I checked. Unless the bearing is clamped somehow on that side similar to what is done on the clutch side I think I am SOL. What do you guys think? And how would this have happened? Was the sand to blame once again?





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