3 days in sand, now I need a full rebuild


117 replies to this topic
  • albertaguy

Posted January 07, 2008 - 12:53 PM

#81

That would be the wrong thing to do, since, as you say, when they are dry, nothing sticks to them.


My thought was it's not actively sucking all the time like your air filter is, except in the times when you stall and its sucks back for a second (according to Yamaha it doesn't suck at all) in which case it would just be there to stop debrie from mechanically bouncing around and falling into the hose. Just curious what other people are doing. At the moment probably 99.9% of them out there have the breather hose totally open and exposed as they come stock with surprisingly few issues. According to yamaha to get the amount of sand in there that I had I would have had to pull the hose up and pour sand down it with the engine off. They're not oiled when used in a car but I don't really know what they do there either and it's a much cleaner environment. It's not really a foam material in mine, more of a cotton batting and thought oil might gum it up to the point of no air going either way. Probably cut up an older air filter into the same shape and have a zip lock baggy full of oiled foam pieces and change with airfilter changes. Thanks.

  • grayracer513

Posted January 07, 2008 - 01:07 PM

#82

Many of the filters from these applications are a fairly loose fiber mat material which won't filter dust well without oil. There are two things to bear in mind about terminating the hose in the air box:

1) There is a LOT of fine, easily airborne dust in the airbox.

2) The hose, and therefore the path to the engine, is shorter in this layout than in the stock setup, and and is mostly horizontal with a net downhill path, rather than mostly vertical, with a net uphill path. Without filtration, it's conceivable that an engine could pull dust in at an idle.

  • albertaguy

Posted January 07, 2008 - 01:11 PM

#83

Oiled it is. Thanks

  • Team_Oatmeal_Pie

Posted January 07, 2008 - 04:01 PM

#84

I run a small K&N 1" clamp on style filter over the end of the breather hose, people always ask what it is. At the very least it stops the occasional drip of oil from landing on the garage floor. While the hope was it would prevent anything going up the breather hose.

  • bnyfe

Posted January 07, 2008 - 08:23 PM

#85

I am speechless! I have never heard of such a thing as the motor filling with sand via the breather tube.

I feel terrible for anyone who has ever lost a motor because of this. I pray it never happens to me. I really think that Yamaha should go good on this one. I would press them to no end until they paid for it~

  • BergArabia

Posted January 08, 2008 - 08:45 AM

#86

Many of the filters from these applications are a fairly loose fiber mat material which won't filter dust well without oil. There are two things to bear in mind about terminating the hose in the air box:

1) There is a LOT of fine, easily airborne dust in the airbox.

2) The hose, and therefore the path to the engine, is shorter in this layout than in the stock setup, and and is mostly horizontal with a net downhill path, rather than mostly vertical, with a net uphill path. Without filtration, it's conceivable that an engine could pull dust in at an idle.

Never thought of that..
Thanks for the heads up Gray.. Will get some filter oil on there..:busted: :banghead:

  • MotoXT

Posted January 08, 2008 - 09:10 AM

#87

Maybe this is too basic, or shot down earlier in the thread, but why not just shorten the breather tube and have it terminate high enough to prevent ever being stuck in the sand? Aside from that, Grey's idea about a second tube inserted in the breather closer to the top that would break any vacuum is the way to go IMO.

  • TommyBoyee

Posted January 08, 2008 - 02:45 PM

#88

Putting a small check valve in the breather line that only allows flow out of the engine would serve the purpose no?

I would think something similar to the vacuum booster check valve that holds vacuum when the engine stalls or is shut down.

I find it very strange that anything is getting through the breather hose at all. After all this is a vent for blowby gases. There is no vacuum in the crankcase when the engine is running.

It could be that these engines are so well sealed(rings) that there is intermittent pumping and vacuum on the breather. Strange indeed.

  • grayracer513

Posted January 08, 2008 - 03:39 PM

#89

I find it very strange that anything is getting through the breather hose at all. After all this is a vent for blowby gases. There is no vacuum in the crankcase when the engine is running.

You are comparing a single cylinder engine to a multi cylinder car engine. In almost all engines with more than 3 cylinders, there is a piston moving down the bore for every one that goes up. Not so with a single, or most twins.

A piston displaces the same volume of air on both sides of the piston, so as a thumper piston moves down it forces 450cc of air out the vent. The trouble starts when it moves back up and draws 450cc of air back in. At idle speeds or higher, the piston changes direction so quickly that there normally isn't enough time to move that much air through a half inch hose before the pressure reverses, so only a small part of the total displacement volume actually moves in or out, and while running, there is little danger of drawing anything into the engine. The risk is only at cranking speeds, or just as the engine stalls. Under those conditions, it is theoretically possible to lift unwanted stuff up through the hose.

But air does have to be able to move in both in both directions through the breather, so your check valve idea won't work unless there is a second air path into the engine. Without that, the first upstroke would try to suck the whole hose assembly into the cam box. You wouldn't want that.

  • albertaguy

Posted January 08, 2008 - 04:29 PM

#90

On the ktm 450/505 forum a guy that goes by travisD37 (I think) was posting a one way checkvalve he invented and had a video showing the breather hose sucking up water w.o. the valve then no problems with the valve, even went as far as drilling pressure guages into the head and such. Seemed like alot of work and you would think air needs to be able to move both ways. Anyway I'm sure you could search it out and watch it. I want to see what happens to the water in the glass when the bike stalls - does it suck back a rapid gulp? In my mind I think the most probable time I could have taken in sand is when I was going to crest over a razor back but got cut off by a guy comming from my right cresting at a different angle, I went left and fell short of the crest, down hill on my left side very possibly burrying the hose in the sand as the bike was laying downhill and stalled. So gravity would be in favor of running down the hose while it was burried and stalled. Seems a bit like all the stars and moons had to line up just right to wreck my engine on that one but for anyone who rides in the dunes you know you can crash in just about any configuration in that stuff.

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  • TommyBoyee

Posted January 08, 2008 - 04:31 PM

#91

Ah, I hadn't thought of that.

So if the newer bikes have the breather line running into the intake wouldn't that create a pulse in the air flowing into the carb. As in vacuum during piston movement up and pressure during piston moving down?

When I get my 426 put back together I'm going to put my thumb over the breather and see what the hose does. It should build pressure due to blow by gases me thinks.

  • KJ790

Posted January 08, 2008 - 04:35 PM

#92

Ah, I hadn't thought of that.

So if the newer bikes have the breather line running into the intake wouldn't that create a pulse in the air flowing into the carb. As in vacuum during piston movement up and pressure during piston moving down?

When I get my 426 put back together I'm going to put my thumb over the breather and see what the hose does. It should build pressure due to blow by gases me thinks.


The breather doesn't run into the intake, it runs to the valve cover, thus dumping sand on the cams in the cases when it sucked sand.

  • tnl

Posted January 08, 2008 - 07:34 PM

#93

I have about 10 hours of run time at the dunes with my 05 with a skid plate on it. I have crashed often in the sand and had my bike roll end over end (sideways) once along with the typical dune spills and can say that at no time has my breather tube been fully submerged at idle or at start up. Every time I've start my bike in the sand even after crashes I always inspect the breather hose location to make sure there is no sand accumulating down there. When I tore my bike down recently to do some major work there was sand at the breather tube at the cam cover inlet? I change my oil every 5 hours, filter skins on air filter, air filter cleaned after every ride (except for the 3 day weekends at the dunes) and I clean my s.s. oil filter (Scott's) with the oil change. My air box has never been flooded with sand either? It can happen and did in my case?

  • albertaguy

Posted January 08, 2008 - 10:59 PM

#94

I have about 10 hours of run time at the dunes with my 05 with a skid plate on it. I have crashed often in the sand and had my bike roll end over end (sideways) once along with the typical dune spills and can say that at no time has my breather tube been fully submerged at idle or at start up. Every time I've start my bike in the sand even after crashes I always inspect the breather hose location to make sure there is no sand accumulating down there. When I tore my bike down recently to do some major work there was sand at the breather tube at the cam cover inlet? I change my oil every 5 hours, filter skins on air filter, air filter cleaned after every ride (except for the 3 day weekends at the dunes) and I clean my s.s. oil filter (Scott's) with the oil change. My air box has never been flooded with sand either? It can happen and did in my case?


Exactly, my air box and carb were clean as new, even verified by a yamaha tech just incase yamaha might have covered it somehow (fat chance). Can't say exactly when it happened but over a three day ride in the dunes with air filter and oil changes plus running outerwears prefilter. Breather hose was lined with sand as was my engine. Reroute it and filter the end or be at risk.

  • crf450xracer

Posted January 08, 2008 - 11:25 PM

#95

I LOVE THE SAND !!!LONG LIVE GLAMIS!!! The honda breather tube has a cap on it so sometimes you need to let a little bit of foamy fluid out and recap.

  • grayracer513

Posted January 09, 2008 - 07:07 AM

#96

The Honda breather routes to the clean side of the air filter, and the cap you mention is on a T off that line. You can do the same thing with a YZ if you want:

http://www.thumperta...573#post4956573
http://www.thumperta...637#post5188637

  • MotoGoalie

Posted January 09, 2008 - 01:51 PM

#97

I've been told the new WR's have theres into a nipple in the air boot (between air filter and carb). That eliminates the need for a second filter but I would be very cautious about rigging something up like this incase your seal ever weakens. I like the pictures of the one in the air box with the orange filter. My air boot and carb are crystal clean, it got in through the breather hose for sure.



I'll tell you directly, that I've experienced NO problems rerouting my breather tube up to plug directly into what WAS part of the AIS system on my 06 WR. The 'nipple' is about an inch in front of the air filter, on the clean side of the carb to air box boot. It's a perfect, tight fit that you usualy shove a plastic plug into when using the AIS removal kit. The difference of the WR breather tube is that it has more pronounced bends in it and seems to be more pliable. I dont know why that is.



When I had my 03 YZ450 I used a PVC air breather filter found at any car parts store that fit directly onto the breather line and I routed that into the air box just like what has been shown in this thread. You can see the breather tube snaking along above the carb and into the air box.

Posted Image


I've heard various explanations about vacuum and pressure on this breather hose and I'm of the opinion that it is not only possible but probable that the breather tube both purges air and experiences vacuum at times depending on what you are doing with you engine.

WE have the proof right here in this thread.

Unless you are doing pure MX on a groomed track you're best bet is to fix this breather tube up correctly.

Similarly you need to mind your T-vents on you carburator. Especially if you do stream crossings. Submerged vents will ruin your day.:banghead:

  • TommyBoyee

Posted January 10, 2008 - 03:03 PM

#98

I checked mine(00 426) out tonight and sure enough there are small bits of grit in the tube on the end that enters the valve cover. I think I will take sage advice and route it to the above mentioned nipple on the airbox.

Any closer pics of how you routed it?

  • MotoGoalie

Posted January 11, 2008 - 08:15 AM

#99

I checked mine(00 426) out tonight and sure enough there are small bits of grit in the tube on the end that enters the valve cover. I think I will take sage advice and route it to the above mentioned nipple on the airbox.

Any closer pics of how you routed it?



Nope, sorry, I sold that 03. IT doesnt have the same boot nipple that the WR has. Just go to the auto store with your CLEANed hose and find a PVC breather that fits, then oil the element and shove it however you can into your airbox.

  • grayracer513

Posted January 11, 2008 - 09:15 AM


The nipple/airboot pics are in post 96, above MG's.





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