do valve seats always need to be recut?

[04scrf250]

Getting ready to rebuild to pend on 04crf250r. Valves (per prev. owner) have never been shimmed or replaced and are still within spec. Obviously I will check the head or have it checked once I tear it down, but just curious if they should be re cut anytime you replace the valves. I have ordered new valves x4 and springs. Plan to replace all as it is a used bike and I am unsure of hours. Just curious about the valve seats on my 1st rebuild. Thanks, Steve

[Throttlejockey]

I would check them and if they aren't seating correctly have them recut.

The manual covers the procedure for checking them.

But, it I were you I would plan on having them recut.

[jrcgaf364]

i usualy set the head upside down and pour some mineralspirits in there...if it leaks out thats a good indication theyre leaking. and need to be re done

[sealusion]

If the seats need to be cut, have someone with pin guages check the valve guides for wear. If they are out of spec, have them replaced and then the seats cut to match the guides.

[MXER43]

If the valves are worn at all, then the seats need to be re-cut for sure. If the guides are worn, you will want to replace them before installing your new valves or else the new valves will wear out fast.

[Crazyced]

i usualy set the head upside down and pour some mineralspirits in there...if it leaks out thats a good indication theyre leaking. and need to be re done

What do you mean upside down? Aren't you putting the mineral spirits in the intake/exhaust ports? ?

[copsey]

It serves the same purpose as long as the spark plug is left in the head. Although it may be a little bit harder to decipher which valve is leaking, though if one is leaking it would be wise to replace them all.

[cjlan66]

? My 04 rt intake went to 0 so it was time for rebuild at 50hrs. After having seats cut and installing new valves i used parts cleaner instead of mineral spirits and all 4 leaked!!! ? My brothers 05 with all four valves still in spec with 52hrs also (hr meter).We performed the same test and 3 were leaking with old valves.Waiting on new valves to try again.The pistons looked worn on the skirts could used rings at 35-40 hrs.Not sure what to do about the 04?