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04 Yz250f

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Feb 1, 2003
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#1
Hey guys, I got a new 04 yz250f and was jus wondering about how long (or hrs) it should be before i do a valve adjustment?....some have been telling me i should do it right after break-in (first few rides), and others say u can leave it for a whole year?...any suggestions???

By the way all i do is trail ride..well maybe the odd track but not very often.
 

nikki

Moto Junkie
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Apr 21, 2000
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#2
You should check your valve clearances after break-in (1-2 hrs on the bike) but 90% of the time, everything will probably still be in spec. After that, you might want to check the valve clearances every 10-15 rides, or if the bike ever becomes hard to start. My '03 has about 15 races and 20-25 play rides and, last time I checked, the valves were still in clearance, so no adjustments needed.

Checking the valves takes about 20-30 minutes and consists of pulling the valve cover, getting the piston at TDC, and sliding a feeler guage between the valve pullers and valve caps to see if the clearance for the exhaust and intake valves falls in the ranges listed in the manual. If they aren't, then you'll need to reshim to get them in clearance.
 
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#3
ok ,thanks...but when i re-install the valve cover, do i need to use a new gasket or torque it?
 

Imho

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Mar 6, 2002
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#4
As long as you don't stretch it you can re-use the old gasket.
 

Fark

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Aug 12, 2002
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#5
My bike is used, an 02. I asked the guy if he ever adjusted the valves and he said no. I just checked mine and they are still on the tight side (i can't get to the center intake valve though... any tips)?
 

Imho

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#6
I don't have any tips on the centre valve but I believe that it is better to have clearances on the loose side rather than the tight side. As the valve seat wears the valve seats deeper in to the head, therefore reducing the bucket/lobe clearance. The worst scenario is the valve eventually closes the gap and doesn't seat properly. Burnt/damaged valves and head are the result. If the clearance is loose it may well detract from the performance but it just means the valve will open later and close earlier. Even slightly reduced clearance (below min. spec) can open the valve too early/close it too late and accelerate wear.
 

Imho

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#7
I should also clarify the above and say that cam lobe/bucket wear also affects clearance in that as they wear the clearance increases. Cam lobe/bucket wear is more pronounced when an engine is new or has just been rebuilt (or is poorly maintained) and is part of the bedding in process. Generally, if an engine has been run-in then valve seat wear and reducing clearances will be the major factor. All of the above is most prevalent on the exhaust side where temperatures are higher and the valve cooling happens when the valve is sitting in the valve seat.