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Piston and Valve Life on the YZ250F

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at the non-pro level about 120 hrs or so on the valves.  depends on air filter and fuel quality and rpm's used.

 

same goes for the piston.

 

just change the oil ever 5-10 hrs, when shifting gets notchy and you are golden.

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Totally agree with SUnruh on this. I personally change the oil and oil filter every 3 hours, replace the piston every 40 hours, replace the cylinder every 80 hours, and do a complete rebuild head/valves to crank (top to bottom every 100-120 hours. Yeah I'm a bit anal and overkill w my bikes but they always run really well and I've never had any type of engine failures or issues.

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I think too much emphasis has been put on hours.  There is a huge difference between a rider who rides the mid range power, and short shifts, compared to someone who shifts at the rev limiter.  I have well over a 100 hours on my 08 YZ250F, and my valves are still in spec, with only one needing a very small shim change to put it in spec.  For example, lets say your a trail rider who rides the bottom to mid pretty much all the time, but rides all the time, those hours are not wearing the motor out if your doing the maintenance.  I think 5 hours is a good rule of thumb for oil changes, and keep an eye on the air filter, as soon as it looks a little dirty you change it.  Don't change the air filter just because you went out for a ride.  I have ridden for hours in areas that are pretty desolate, so there wasn't much dust in the air, and the air filter was still clean.  My theory on oil is to use something inexpensive like Rotella so you can afford to change it often.  Same goes with oil though, if you put 2-3 hard hours of motorcross on you bike, then it might be ready for an oil change, and on the other hand if your out on a long trail ride and staying off the rev limiter, then perhaps 10 hours is perfectly fine. Hours don't kill motors, RPM's kill motors. 

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+1 on what mjbd says that it's about how the bike is ridden vs. actual hours.  AND the oil is changed after every harescramble and every couple of rides.  AND I change the air filter constantly; in fact, I rotate 3 air filters so that I always have one ready to go so there's no excuse NOT to change it out.

 

I'm not saying there's necessarily anything wrong with top ends and valve replacements every X hours if it makes you happy (and X isn't too long!).  Better yet, make a maintenance plan that includes some key checks and you will end up replacing things when they are ready to be replaced, probably less frequently than in X hours.

 

My son has passed the 200hr mark on his '11 (purchased in '12) and the original valves are still there.  There's no reason to change them, I check valve clearance every 10-15 hours and they are still in spec.  The bike starts easy, hot or cold. 

 

He races off-road and tends not to run the bike near the rev-limiter and that's a big plus for longevity along with the constant maintenance.

 

I have been through a couple of top ends, though.  I did the first few based on hours but after talking to someone I have complete trust in (Yamaha wrench) I am following his advice.  Which is, pistons/rods don't go like they do in 2-strokes, the bike becomes harder to start and loses power with piston wear (also a sign of valve wear/trouble).  You do a compression check . . . with a new top end, check the compression as a baseline and use that to gauge wear.  I've got 60hrs on the current high-comp piston and have only lost a few psi.

 

To recap:

 

The YZ250F is freakin' awesome when it comes to reliability, do good maintenance and spec checks:

 

  • Change the oil frequently.  Rotella T is very cost effective.  I use Rotella T because the yz250f has a Rekluse clutch and they recommend it but I use it in the rest of the bikes as well because it's just fine like many other quality oils available.  I change the oil every race (2hr) or every couple of rides/practices (~4hrs).  I don't change it often because it's cheap, I change it often because it's the right thing to do.  The fact that it's cheap just helps.  I wouldn't change expensive oil any less frequently.

 

  • Change the air filter every time you wash the bike which should be nearly every time you ride it.  Always keep a clean/oiled one ready to go, store it in one of those 1-gallon zip lock bags.

 

  • Every 10-15 hours, take your gas tank off and do a little extra detailed cleaning around everything you can't reach with the gas tank on.  Then do a valve check per the manual.  You need the eyelash-type feeler gauges to reach that middle intake valve.  Intake should be between .05"-.06" gauges, exhaust .07"-.08" gauges. Check compression, compare to baseline recording. Record date/hours and all results.

 

This isn't an all-inclusive maintenance list by any stretch but does address piston/valve.

 

One more thing, when you do a top end use OEM gaskets and replace the timing chain.

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Just to reiterate, SUnruh and others' suggestions to replace pistons/valves at a given operating hours frequency isn't bad advice at all, but if you are careful with maintenance you can realistically make those dollars stretch.  You have a very reliable bike on your side.

 

I would not be surprised if you got +75 hrs on a piston.

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One more thing, to help ease the somewhat painful process of changing the oil on your '13, consider one of the kits that eliminates the external tank.  Email Jason Raines of Raines Riding University, he has these kits.  After installing the kit he suggests adding the entire amount of oil (1 qt) even without the external tank.  In his experience, the extra oil reduces clutch wear.

 

Some on this site are opposed to this for one reason or another; I value and respect their opinion, but I think it's a good idea and makes one less prone to put off oil changes

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I ran my Wr 250f for 160 racing hours before a change, I am currently on 38 hours on my Athena 290 kit on my 2010 yz 250f and about to do a Wr E start bottom end conversion and im going to change the piston

I am very comfortable with Yamaha pistons lasting a long time but have no idea about the athena

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at the non-pro level about 120 hrs or so on the valves.  depends on air filter and fuel quality and rpm's used.

 

same goes for the piston.

 

just change the oil ever 5-10 hrs, when shifting gets notchy and you are golden.

 

I got 155 on the head / valves.  Pistons for me though...only about 30 hours.  This is based on actual measurements.  I mic the skirt, then check clearance with a bore gauge.  I had to have the cylinder replated at about 130 hours.

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I did an un-scientific test on my second YZ250F, an 03.  I got it used up.  Then I documented another ~125 hard trail hours before it popped.  It was making noises, then jumped time and took out the intakes, no other damages.  When I checked, the small sprocket was worn and thats why it jumped time.  The piston pin bore was worn as was the rod small end.  The 2 loose specs allowed the piston to wobble quite a bit and that was the top end noise it made.  Valves, seats cut, piston, crank, oil pump, and some other misc stuff got it back into shape and its still going strong.  Now I spread my time between several bikes so I don't put so many hours on 1 bike at a time. 

 

Change the oil every 5 hrs or so, oil filter, do maintenace on linkage bearings, and it'll run for a long time... These 250F bikes are some of the best around and have a great following and reputation.

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[*]Every 10-15 hours, take your gas tank off and do a little extra detailed cleaning around everything you can't reach with the gas tank on. Then do a valve check per the manual. You need the eyelash-type feeler gauges to reach that middle intake valve. Intake should be between .05"-.06" gauges, exhaust .07"-.08" gauges. Check compression, compare to baseline recording. Record date/hours and all results.

.

did they change specs? I thought it was .1-.15 for the I take and like .17-.22 for the Exhuast? My exhaust are a little tight at .10 but my intakes are at .15 at about 30 mx hours. Now I'm confused as to how they could be too open according to your numbers?

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This is a little unrelated and I apologise for a partial thread jack...

I've always heard great things about the YZ250 as being very reliable, but does the same ring through to the 450 range?

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I think too much emphasis has been put on hours. There is a huge difference between a rider who rides the mid range power, and short shifts, compared to someone who shifts at the rev limiter. I have well over a 100 hours on my 08 YZ250F, and my valves are still in spec, with only one needing a very small shim change to put it in spec. For example, lets say your a trail rider who rides the bottom to mid pretty much all the time, but rides all the time, those hours are not wearing the motor out if your doing the maintenance. I think 5 hours is a good rule of thumb for oil changes, and keep an eye on the air filter, as soon as it looks a little dirty you change it. Don't change the air filter just because you went out for a ride. I have ridden for hours in areas that are pretty desolate, so there wasn't much dust in the air, and the air filter was still clean. My theory on oil is to use something inexpensive like Rotella so you can afford to change it often. Same goes with oil though, if you put 2-3 hard hours of motorcross on you bike, then it might be ready for an oil change, and on the other hand if your out on a long trail ride and staying off the rev limiter, then perhaps 10 hours is perfectly fine. Hours don't kill motors, RPM's kill motors.

I have to disagree with you on emphasis on hours. There is no other way of really knowing how much time you have put on a bike. When I build engines I always find out what type of riding the customer does and at what level. This helps determine how often the engine needs serviced. I personally have gone easily 100+ hours on a crank and head but a pro level rider will typically need to replace the crank at 50 hours depending on the engine mods. There are lots of variables but tracking hours helps out significantly in determining maintenance requirements for each level and type of riding.

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I've been trail riding a 2007 WR250F with a 262 kit in it and everything else I could put on a VISA and I've never adjusted the valves.

 

Just a piston or 2, a cam chain, 2 clutches and that's it.

 

Good oil changed frequent and always a clean air filter.

 

Never owned a better, more reliable bike.

 

Everyone I know that owns a WR/YZ250 says the same thing.

 

The 450's are just as reliable.

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did they change specs? I thought it was .1-.15 for the I take and like .17-.22 for the Exhuast? My exhaust are a little tight at .10 but my intakes are at .15 at about 30 mx hours. Now I'm confused as to how they could be too open according to your numbers?

He was referring to inches instead of mm.

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He was referring to inches instead of mm.

 

Yes, I was, thanks.  But I did make a mistake and there's a point of clarification needed. 

 

The actual spec range (in inches) is intake valves .0047-.0067, exhaust valves .0067-.0087

 

I left out a zero, I should have listed intake .005" - .006", exhaust .007" - .008".  Another way to state this is intake between 5 and 6 thousands, exhaust between 7 and 8 thousands.

 

But also note that the range I listed corresponds to the thickness of the feeler gauges I use, the actual spec range is a little broader.

 

Is there a way to edit my initial post so that I can correct this to eliminate confusion?

Edited by Yamajeb

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I have to disagree with you on emphasis on hours. There is no other way of really knowing how much time you have put on a bike. When I build engines I always find out what type of riding the customer does and at what level. This helps determine how often the engine needs serviced. I personally have gone easily 100+ hours on a crank and head but a pro level rider will typically need to replace the crank at 50 hours depending on the engine mods. There are lots of variables but tracking hours helps out significantly in determining maintenance requirements for each level and type of riding.

 

 

You misinterpreted what I said, its not that hours aren't a good measurement of when service should be done, its great, but that an hour for one rider can be harder on an engine that 5 hours for another rider.  If a rider is pretty easy on an engine, then they can feel safe in going longer intervals.  My point was there are riders here who have gone 200 hours on a engine before a complete rebuild, and then there are others who grenade their engine after 50 hours.  Hours are not created equal. 

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