When to change plug??

If your Yz 450f is running great....(i.e. no problems, spark plug color is good), do you still change the plug out every x number of hours, or should I leave the plug in ??? I've put about 20 or 25 hours on this plug and I'm wondering if I should change it anyway. I primarily woods ride, with an occassional slow run on the local MX track. I never race.... let me know whether to change or just leave it in till I develop a problem. Thanx.

when the bike dont run or it fouls

just leave it in till I develop a problem.
:D If you're not racing, pull it out the first time it misses on top. Carry a spare, though.

these bikes can go a very long time without changing the spark plug.

Thanx for the responses....

Check the plug, blue spark is good, yellow is bad.

I went a whole year before replacing the plug and when I did the spark was still blue. Spending $3 a year on spark plugs isn't going to break the bank. Go the extra mile and get a Platinum or Iridium plug for $7 and it'll probably last you close to two years. I've seen it happen.

I replace my Iridium twice a year. I don't know why, I just do. Cheap insurance I suppose.

I changed regular plug at 1870 miles, but it was working awful at that time

bike got harder to start when cold or flipped over

book says to change every 620 miles

now I went for iridium and at 1250 miles still like new

You could always take a look at the strap of the plug. Rounded edges means time for a change.

Also, if you have it out to look at it, change it anyway.

The strap breaking can cause catastrophic engine damage. Changing a couple of times a year could possibly avoid trouble due to a broken strap.

Yeah that's not a bad idea. regarding the strap...I'll check it out.

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