How long does the valves on a 250 fourstroke motocross bike last and how much does it cost to replase?

Answer 1

There are issues with the titanium valves and seats used on the 250F's. In an effort to keep valve train weight down they had to sacrifice a little longevity. Lifespan depends upon how judicious you are about staying on top of adjustments and clearances. From what I've seen the average is about two piston/ring replacements.

The hot ticket seems to be replacing them with stainless steel valves from Kibblewhite. But even then staying on top of adjustments is the key.

Answer 2

Depends on how often you ride and how hard you ride. The new 4-stroke MX bikes run at significantly higher RPM's than 4-strokes made just 10 years ago. A couple problems with the valves/valve train are associated with these increased stresses. One is valve seat wear and the other is valve stretch or elongation. This problem can be identifed by regularly check the clearance between the end of the valve stem and the rocker arm. I'd recommend purchasing a service manual for your bike and making valve clearance inspection part of your routine maintenance practice. Of course you won't know if the valve seats are excessively worn or the valves are stretching until you disassemble and inspect the components.

As far as replacement cost goes, I have no idea. Then again I'm a 2-stroke guy.

Answer 3

The crankshaft has a design life of about 25 HOURS on all the new fourstroke MX bikes and valves, springs and any other wear items should be changed at the same time. The new racing engines need much more maintainance than the older twostrokes (but you dont find that out until AFTER you buy one)
Most people get a lot more than 25 hrs on cranks but they are not racing or using max rpm all the time. If you drop a valve (you dont 'throw' them) its going to trash your engine, if you get really 'lucky' broken bits will take out rod and can get into transmission and wreck that as well
Ignore the rubbish about it lasting for thousands of miles, it wont

Answer 4

Oil changes are crucial to the valve life.
If you only play around and don't race, you can go a long time without problems,
Do a bunch of flat track racing like we do, and you can get a good 30 to 40 hours before adjustments need to be made.

Plan on paying at least $400 for valve job. More if you want good parts.

Answer 5

They should last as long as the bike, or at least they shouldn't be the first thing to go if you keep the oil clean and full. How much it costs to replace depends on how much damage is done if one is "thrown". It is probably easier and cheaper to find a used engine from a wrecked bike, and just change the whole unit. Wrecked bikes are dirt cheap.

Answer 6

if they are new or reground they should last a long time. They dont cost much if you do it yourself. Its more the labor to take it apart and put it togehter.