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Search the Dirt Rider Forums:Checking Bottom End for Wear on a 4 Stroke??
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Hey there. Im just wondering if there is any way to test a dirt bike for bottom end wear without actually splitting the case??I know the best way to find out is by splitting the case but I mean is there any tests I can run on the bottom end to get a general idea? Or are all the tests like leak and compression tests mainly just for checking top end wear?
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Which is it top or bottom?
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bottom. i want to know if i can check the bottom end for wear using some sort of test or something without having to split the case.
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change your oil regularly and make sure you take a good look at the drained oil. this is one of the best ways that i'm aware of to look for bottom end wear, other than listening to the motor, or the dreaded splitting of the cases.
As far as I know there isn't many if any other ways but someone else might chime in with an idea.
-1999 RM250
-2001 CR250R
-2005 RM250
-2007 KTM450 SX-F -
cool. thanks mate :)with exactly in the oil am i meant to look for? dust, change of color, etc?
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Yeah, mainly for metal shavings in the oil. If the bike is new, or if you have any fresh internal engine components there will be clearly visible metal shavings, but other than that there should be little to none at all. The color of the oil itself will tell you if there is water or coolant finding its way into places that it should not be.-1999 RM250
-2001 CR250R
-2005 RM250
-2007 KTM450 SX-F -
ok thanks so much :) ill go and check it out later on. im asking because the bike is used and just bought it. it's a 4 stroke KTM 450 EXC with 7000k's on it but seems to run fine...but will go check the oil.
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To check crank bearings pull head and cylinder off. Push an pull on connecting rod. There should be zero up and down wiggle. If there is main bearings going bad.
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magnetic drain plug bolt
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what about the magnetic drain bolt??
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Thats what I said. aluminum will not stick to them.but they help they have a magnetic oil filter cover to..why are you doing this?? I had a old head tell me to plug exhaust and give few kicks,if its leaking I will hear it or no pressure will come out of the exhaust when I unplug it.mite be redneck way but I left my plug in my exhaust forgot about it tryed to start it the compression was crazy and when I pulled plug I felt the pressure release,
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inspect the oil filters for metal shavings. have seen brass flakes caught in the oil filters just as the side shims were coming apart on a big end bearing before but you're lucky if you find it really. usually bottom end bearings will be fine right up untill they seize up. it all happens very quickly once the bearing starts to fail. its better to just replace the rod bearing based on a time interval. 100 hours max if you want a reliable bike.
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Winning is 90% rider and only 5% bike, the rest is luck -
NZ by that estimation your talking complete rebuild once a year..... what makes these parts so fragile people think they need replaced constantly? Crank bearing on a car last the life of the vehicle, why is the time difference so extreme?
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You know I always see paint in mine, because it's new??
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See paint In what?
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My oil,it looks like the stuff the aluminum is finished with
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if you're doing 100 hours a year then yes that'd be a new conrod kit once a year. but it also means a reliable bike. i've seen crank bearings crap out well before 100 hours when abused.
the difference between car and bike cranks is that nearly all MX bikes have a needle roller big end bearing which is constantly wearing away on its supporting cage even when properly lubed. a car big end has a oil fed plain bearing which when properly lubed never has metal to metal contact and therefore never wears out.
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Winning is 90% rider and only 5% bike, the rest is luck -
@NZ well that blows. I don't know why they would make them so different. Is this only a mx bike thing? I only say that BC my quad an street bikes all share basically the same motor with subtle differences. But the quad is a Ltz quadsport which I would assume is a racing quad. Also shares same motor as a dz400 dual sport bike. Anyway the point is there's guys that have ridden a sv650s or 1000 to 100000 miles or more without a rebuild. I'm not arguing I'm just saying. The svs are v twin but it just 2x325cc cylinders or 2x500cc. (I have both). I'm gona see what manual says in all cases including my yz250f. I just don't see why they'd build them to fail if it could easily be avoided with a few small changes.
@Sean... that can't be good. Id think ur bike would be broke in by now. -
I know,so what's causeing this
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a plain bearing requires a super consistent oil feed to be reliable. a roller bearing can get away with intermitent oil pressure loses with no negative effects. if you lay your bike on its side and its still running the plain bearing crank may get damaged while the roller bearing crank will be fine.
they dont build mx bikes to fail. they build them for performance so as light as possible even if that requires higher maintenance. trail bikes have bigger heavier cranks which last much longer. most road bikes have plain bearing cranks. new KTMs have plain bearings too.
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Winning is 90% rider and only 5% bike, the rest is luck
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