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LEMMON1

Omg!

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so i was at the track today thinkin of riding or not considering it was 43 degrees and windy. but anyway, there was a younger kid who is supposedly is sponsered and was doin decently well. a bunch of us were watching him and saw him whip it over a jump that goes down past where no one can see into hte lower section of the track. we heard the biek go over and as we were waitin for the sound of the motor to rev up and haul butt...we heard nothing. so we all ran down to him and he was fun...didnt see any signs of a wreck and asked what happend as his mechanic was loookin at the bike.

found out hte motor blew...at first i was like hes probably a honda since i couldnt see that well and as i came down to help push it up the hill i noticed it was a yammie. i was like no way this cant be. a few of us started askin the simple things like what year blah blah blah...found out it was an 08 they had recently purchased and had less then 30 hours on it. then we were all def like ***? the mech takes off the seat cover and the rest of us looked and sw the filter and was like holy bleep blep bleeepe!!!! the filter was soooo nasty it literally doesnt look like its been cleaned in its entire 30 hours of life. u could scrap it with ur finger and there was still massive amounts of dirt on it.

the mechanic tried sayin that it was from the track and his rider is justhard on his bikes and really hard on his filter..but i kow hes full of it as ive been ridin the track for a lil over 6 months now and never ever gotten to lookin like that...

the mechanic came to say at least 1 possbily 2 valves look like they dropped. i believe hte motor is actually not gona be that bad but the top end is gona need rebuilt. luckily the motor still could spin smoothly when movin the kick starter but def a large notice loss of compression...

so the lesson here learned is...clan yo damned air filter, cause ouch, it could be a hurtfl expensive one!

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i always have a fresh filter ready to go everytime i head to the track.. and sounds like lack of maint.. but if hes like most other "a" riders.. they are hard on their equipment.. wonder if it was stock motor or not..

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motor was bone stock minus he had the FMF full exhaust. ..he did say he was an A class guy but even still, when he was riding he wasnt exactly hammerin the dog crap outta it to where i would think i would blow like that

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the mechanic tried sayin that it was from the track and his rider is justhard on his bikes and really hard on his filter..but i kow hes full of it as ive been ridin the track for a lil over 6 months now and never ever gotten to lookin like that...

Usually a dirty air filter won't cause a motor to implode. As dirty as you make it sound, I would think the thing wouldn't even run because it can't get any air into it.

MX motors can blow up. Especially when ridden hard.

The mechanic could be absolutely correct. You say you've been riding for 6-months? I'm willing to bet he's been wrenching for a lot longer than that. He probably has a better idea what happened. He's prolly seen it before. Several times...

A lot of guys keep the thing reving when they land, which can easily blow the motor. Fast guys are always told to either be on the gas or on the brakes. The quicker they're on the gas, the faster their lap times. That, and having the thing going for the landing takes some of the force off the suspension.

It happens... Even to blue bikes:eek:

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:thumbsup:

Usually a dirty air filter won't cause a motor to implode. As dirty as you make it sound, I would think the thing wouldn't even run because it can't get any air into it.

MX motors can blow up. Especially when ridden hard.

The mechanic could be absolutely correct. You say you've been riding for 6-months? I'm willing to bet he's been wrenching for a lot longer than that. He probably has a better idea what happened. He's prolly seen it before. Several times...

A lot of guys keep the thing reving when they land, which can easily blow the motor. Fast guys are always told to either be on the gas or on the brakes. The quicker they're on the gas, the faster their lap times. That, and having the thing going for the landing takes some of the force off the suspension.

It happens... Even to blue bikes:eek:

Im not trying to argue because you very well may be right, but with such a dirty air filter even the slightest hint of dirt particles could have caused the valves to go since they are so sensitive. After all the mechanic is human and he could have made a mistake.

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"The mechanic could be absolutely correct. You say you've been riding for 6-months? I'm willing to bet he's been wrenching for a lot longer than that."

negative ghost rider...ive been riding at that track for bout 6 months...and as a mechanic myself, i look at the filter as a tell tell sign that he or hte mechanic are not taking care of the bikes properly...if they cant take care of a simple thing like a air filter that was effin disgustin that in itself can cause enuff problems in itself < just ask honda owners> then that tells me they are not takin good care of the rest of the bike.

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Whether or not it had something to do with the air filter or not I find it very sad that the mechanic didn't keep up on the maintenance of the bike... I ride in CA and I have never herd of someones air filter getting that dirty that quick on a track ...

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Could someone explain why would the valves drop from some dirt??? Where do you take these ideas from? If SOME dirt would get sucked in (though the airfilter is mounted), it would been blown out on the exhaust. After a while, it would scratch the cylinder, probably scratch the bottom of the valves. And? Don't tell me, sand would build up in the intake (or exhaust) ports, and block the valves from closing and the piston would hit them.... Did you ever hold some valve springs in your hand, just to see how strong they are? You are not running a shit-pump, that pushes dirt through the engine. Even if the airfilter is dirty like hell, more plausible is that won't get enough air and the engine won't run as well as it should, but that's it.

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Rufuz - when sand/fine dirt goes in through the intake, it has to travel past the valve stem to get into the cylinder, the slightest amount of oil (and there will be some) will attract the dirt and make it stick to the stem, the stem moves up when the valve closes, the seal pushes the dirt along the stem (like sandpaper), likely, the dirt will now stick at the seal edge and the continuous movement of the stem along this area will continue to score the stem, this will score the stem really quick (RPMs) and next thing you know - BAM! we didn't even address the seat or piston yet.

ANY dirt getting into the intake is a BAD thing.

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Could someone explain why would the valves drop from some dirt???
Sure, if you calm down a little.

Foam air filters work by capturing dirt in the coating of oil on the foam membrane. The oil can only hold so much dirt, and once the filter reaches its capacity, it's far more likely that it will allow dust to pass through the filter unmolested that it is for the filter to choke off the engine. They do get to that point, but by the time there's enough crud built up on the outside to affect performance, the filter will have passed a considerable amount of dirt right on into the engine.

The effect of this on the valves is that it wears at the valve face and the seat, and because the wear seldom occurs in a precisely circumferential pattern at a uniform angle, the valve begins to "scrub" to one side as it seats, rather than dropping into the seat squarely. This repeated scrubbing flexes the stem, and over time, can fatigue it to the point that it breaks.

This is not the only cause of valve stem failure, but it is one of the big ones. But it's also unlikely that it was the cause of this particular failure. The failure cycle above is usually predicated by at least one significant valve adjustment, and I don't think that 30 hours would have been enough time for it to run its course.

Still, an air cleaner in that condition probably did not happen in a single day's work, and it's not really excusable except under the worst dust conditions. My son and I ride desert races and run in a constant dust cloud for two plus hours at a time. His filter especially looks pretty scary at the end of the day, but not caked with stuff as described here. You should start EVERY ride day with a clean filter unless you ride by yourself in a very low dust environment.

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Sure, if you calm down a little.

Sry for that, was little drunk when I've read the post :banana:

Anyway, the process that the sucked in sand would grind the valves face, back, or valve seat to a level that it twists or flexes the whole valve to a point that it breaks should take a long(er) time in my opinion. Even in dusty environment there would be no constant flow of sand, like in a sand-blaster, and the flow of air combined with *some* sand would not be concentrated to the stem of the valve. I can imagine that a loose valve guide, or not proper shimming could result in a dropped valve (like mine which dropped last summer :lol:) much faster than using your bike as a vacuum cleaner on track :lol:

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