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Dust inside engine
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Posted by: Boozer---------------------

a freind of mine has a 250F, and he was shocked to find his air filter had let dust into his engine. the foam seal had perished around the bottom of the filter. looking inside the air box boot, there was slight traces of dust, but only around the area of the damaged filter. you could see the dust after a finger was wiped along the surface, but none could be seen where the boot meets the carburettor.
i would like to reassure him that his engine isn't heading for the grave, but i don't know if this is true. does anyone have any experience in this matter? what can be done to check for engine damage? compression test? how many pounds of compression should this engine have? it hasn't done very much work.
thanks for your time my friends.

Posted by: SFO---------------------

I believe the 250f has a pretty intense maintenance schedule.
How long has it been since he checked the airfilter last?
1 ride, or a couple months?
It should last until he sells it, which will probably come before his first tear down. If he feels motivated he could buy the gaskets and do a top end inspection. It is not that difficult, and would create a finite sense of wellbeing.

Posted by: velosapiens---------------------

don't worry about it. a little dust won't kill your engine. if you run it with no filter for a few rides, that might be different.

once i forgot to oil my spare filter and rode 250 miles in VERY dusty conditions. i definitely got some dust through it. far more than your friend got it sounds like. i took the airbox and carb out and dismantled and cleaned it all. 15,000 miles later, the engine still runs great and doesn't consume any oil. eventually, dust might do bad things to the rings, but it'll take a while. witness all those poor farmers in mexico running trucks w/o airfilters.
-mark weaver

Posted by: Boozer---------------------

thanks for the responses. he was thinking back, and the bike must have done one or two rides since the last filter clean/inspection. the poor fella isn't exactly loaded with money, so he was thinking of keeping his bike for a long time. upgrading to a new bike every year or two isn't really an issue for him at the moment, so i'm sure you can understand his concern.
oh, and he did strip the bike of it's air box/carby, and gave them a really good clean.

Posted by: dale williams---------------------

4 strokes aren’t as sensitive to dust as 2 strokes but it will definitely accelerate the wear on the rings and cylinder walls. Dust is a mixture of powdered organic mater and rock. The rock acts like grinding compound. The lower end is fairly well protected because the oil is filtered before it goes to the bearings but running without an air cleaner will fill up the oil filter faster. I'd suggest cleaning the air inlet as much as possible, change the oil and filter, new clean oiled air filter and check it often for leaks and hope for the best.

Posted by: SiCnTwIsTdYz---------------------

well i know dirt sucks when your engine sucks it in! but does he clean the filter after every ride? anyways and does he use any molybendum grease like maxima waterproof grease around the rim where the filter goes on? that can help alot too from water and dirt and dust and any other foreign materials from getting in and it wont wash out

Posted by: Boozer---------------------

the 250F's don't really draw that much air compared to some other bikes, so the filter stays clean for quite a long time. it wasn't really in need of a service when it was removed, but luckly he did. he did not use grease around the filter seal, because the manufacturer said it wasn't needed (aftermarket filter). either way, it was the damaged filter seal that let the dust in. it was damaged quite a bit, and we contacted the manufacturer about it. they sent us a new unit and asked if we could send the filter back for inspection because 'they had never seen this happen before'. the fliter was about 4 months old and cleaned maby three times using their recommended method. i was told they would get back to us once the reason for the failure was found.
thanks for your tips on how to get it running again Dale, i was thinking the same things.
SiCnTwIsTdYz, in the future i think he will use the grease you suggested even though the filter maker doesn't think it is needed. nothing wrong with a bit more protection, i believe.

oh, and once the air box was cleaned, and with the standard filter installed, we took it for a ride. sure enough, the bike still rips! i think it was a close call, because the filter could have gone much, much longer before it was in need of another clean. that's a long time with a leaking seal!

Posted by: DualSportr---------------------

Some of the statements here are a little scary

[

Quote:

don't worry about it. a little dust won't kill your engine. if you run it with no filter for a few rides, that might be different.

A filter or filter seal with a hole in it is basically the same as running without a filter - air will basically travel a path of least resistance - which in this case would be through the gaping hole.

Quote:

4 strokes aren’t as sensitive to dust as 2 strokes

Why not?

Quote:

the 250F's don't really draw that much air compared to some other bikes,

I guess compared to the 426, that would be correct, however, the volume isn't really the question here - unless the thing only cranked a few hundred times (but I'd say if it went a couple of rides, it rotated a few more times than that!).

The thing is, like Dale stated, the grit will wear the cylinder walls. Since this is a coated bore, the CHEAPEST way to fix the problem would be a top end rebuild.

Yes, damage was done (no way around it). If you replace the worn piston and rings, and clean the (possibly) scuffed cylinder, your poor buddy will probably be able to salvage the cylinder. If he waits till it starts to smoke, then he may end up spending a bunch of extra $$ on a new cylinder.

I mean, this is a 250F, with a maintenance schedule similar to a two stroke - if he's been riding for a year, it's time for a new top end anyway.

It's not about wasting money, but about saving big money in the long run.

Posted by: Boozer---------------------

Quote:

Originally posted by DualSportr

Yes, damage was done (no way around it). If you replace the worn piston and rings, and clean the (possibly) scuffed cylinder, your poor buddy will probably be able to salvage the cylinder.

will a compression test reveal the extent of the damage? how many psi of compression should this engine have?

Posted by: DualSportr---------------------

I'd say a leakdown compression test would definitely be a good diagnostic. I don't know what a good compression reading is on this engine (you'll have to check the shop manual), but the leakdown test will be more accurate anyway.

Posted by: Boozer---------------------

okay, we will do the test on the bike, and i guess he will take it from there. this is turning out to be a good thread, because i am sure this would have (or will) happened to someone else here.

Posted by: axo959---------------------

Just curious here, but what type of air fitler was it? Also, what was the preferred cleaning method? (I like to use a solvent to get the oil out, then hot soapy water to wash out dirt and the solvent, then air dry)

I have used stock, uni and twin air. I dont use grease around the lip (I used to). I do apply oil here though. I dont see any dirt getting by using the uni's and honda-line oil. I'm curious as to what made the element break down. Type of solvent? Throw it in the dryer or applied heat? Cause like the manufacturer, I've never seen a filer fail in such a short period of time using recommended methods in 23 years of riding. Its unfortunate if your friend experienced this though.

I also have a YZ250F and I'd suggest to put in a clean/oiled a/f every ride. It's cheap insurance. Same goes for the tranny oil. If your friends only checks the a/f every couple rides, how long does he go between oil changes?

If this is a long term bike for him, he may want to be more particular about his maintenance schedule.

Posted by: velosapiens---------------------

Quote:

Originally posted by DualSportr
Some of the statements here are a little scary

Yes, damage was done (no way around it). If you replace the worn piston and rings, and clean the (possibly) scuffed cylinder, your poor buddy will probably be able to salvage the cylinder.

The sky is falling the sky is falling. This seems a little extreme to me. Despite having an air filter, tiny dust particles always get into your engine. teeny weeny ones get past the filter, plus there's the little bits that drop in there when you're changing filters. then there's carb vents, fuel tank vents, the dust that settles in your gas can when that punk on the atv is doing donuts in the parking lot, etc... You could claim that damage is done EVERY TIME you start your engine, and tho true, this would also be a little extreme. It sounds to me like only a very small quantity of dust got past the filter. When this happened to me (larger quantity tho), i also panicked a bit, but the more i researched, the less it seemed like i should worry. i talked to lots of people who had the same thing happen, and none of them had any significant engine damage from it. i couldn't find a single person who toasted a top end from 1 instance of a leaky filter. as i said previously, i've put another 15,000 miles on that engine with no problems or evidence of excessive wear.

so if you want to be anal about it, or if the bike starts to run poorly, or if the riding weather just sucks and you have tons of extra time, then by all means, worry about it and do a bunch of tests and stuff. i personally would just make sure it was all clean and solid now (which you already did), change the oil and filter and then go ride.

i sure wouldn't be worried about the cost of a cylinder if i were wrong. the cost of me taking the time to screw with the engine for a day or two (instead of riding, or working, or drinking beer and watching hockey, or rolling around with the missus) is MUCH more expensive to me.

-mark weaver

Posted by: SFO---------------------

Is opposites I guess.
You can always find a viewpoint to support yours, or poke fun at someone elses viewpoint.
20 years as a motorcycle mechanic and machinist has shown me many peoples viewpoints.
I was trained never to get into certain conversations with customers, just recommend factory oil and service schedules.
Customers can do whatever they please, and will.
If you want someone to say it is OK to run unfiltered air in your racing engine, then someone will.
If you make your living selling confidence perhaps a different approach would be more apt to be succesful.
I have seen the factory (yamaha, husaberg) authorize complete engine tear downs and inspections when bad intake manifolds were present during the warranty period.
If I had to assume responsibility for this engine I would at least pop the top end off and check it out.
But I have a different sensability than others.
If I feel any doubt about anything I built or ride I have learned that the only way to eliminate the doubt is to double check.
Sure this bike will probably run just fine for boozers friend, but if it poops the bed, someone has to take the blame and I wouldn't want to be the one who said "eh, a lil' dirt and sand or whatnot down the intake manifold don't mean nothin"
The question was asked because there was doubt, and the doubt remains for good reason.
Doubt has made me a better mechanic.
Besides, I like to be anal and work on my bikes.
I also like to drink beer, watch the GIANTS!!! and roll around with the missus.

Posted by: wayneo426---------------------

SFO- Very well said. Better safe than sorry.

On a different note, is Bonds out of control or what?!?!

Posted by: DualSportr---------------------

<<. When this happened to me (larger quantity tho), i also panicked a bit, but the more i researched, the less it seemed like i should worry. i talked to lots of people who had the same thing happen, and none of them had any significant engine damage from it.>>

True. Why not just go back to running without a filter, like they did in the early days of motorbiking? I mean, those board track racers went over a hundred miles an hour, right?

An opposing point of view would say that tolerances on the new stuff make for huge horsepower and very lightweight engines. It also makes for a more rigid maintenance/repair/replacement schedule.

To each his own. But, like Bill sez, there's a question of damage here, and a typical factory mechanic would do a compression test and tear down this engine without a second thought. A shade-tree mechanic might not. If it's your bike, it's your choice.

Posted by: bonzo---------------------

250f not drawing muchair?????

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