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"08 kx450f" General Valve Shimming Question

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I have one intake valve with 0 clearance. I have not checked to see how many shims are there already or begun the process. Just wondering if there are a maximum number of allowed shims to be installed as the service manaul only states that if clearance is 0 to start with extra thicknessness shims. For reasons of extra wear unaccounted for yet im sure. Not sure really why all other valves are at the loose end of spec technically good and just the one intake is like it is. Open to comments, advice, and conversation.... oh and im doing this because the bike has become hard to start, last two rides out and the last time has given me a backfire on startup. I do run it a bit hot down here in the woods but i shut it off at idle and minimal overrevving compared to mx use.

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There is only 1 shim above each valve spring not multiples. The shims are just different thicknesses depending on what clearance you need between the cam and valve.

 

If you have a 0 clearance under one cam lobe you will have to pull the cam out and check the size of shim with calipers or a micrometer. You will need to get a shim kit or order multiple sizes because having a 0 clearance under one doesn't really help you know what size you need, it will only help you get in the ball park.

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Thank you sir, i was confused from the manuals plural use of shims that there may have been more than one for some reason lol.

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If you have zero clearance, you should consider sending the head off for a full rebuild.  Once a valve begins to sink into the head, trouble is usually right around the next corner.  It also beats the hell out of the valve head and weakens it.  If it were me, I wouldn't shim it, I'd pull the head and get it freshened up.

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Yeah i did a bit more research and makes sense i could have a problem with that valve and or seat. Being that this engine was previously built i want to make sure there wasnt an error shimming in the build so ill go the route above and see what happens.

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If it shims out and starts good ill do a couple clearance checks after the next few rides to see what that valve is doing

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9 minutes ago, Dubbyueffohh said:

Yeah i did a bit more research and makes sense i could have a problem with that valve and or seat. Being that this engine was previously built i want to make sure there wasnt an error shimming in the build so ill go the route above and see what happens.

If someone made that large of an error, I would pull it apart just to check the rest of their work.  In other words, it's not likely that it started out that way.  When a valve lets go, it usually makes a window in the motor somewhere and causes a couple thousand dollars in damage.  If it were me, I would never run a valve that was previously at "zero".  That valve is now compromised.  It's not worth the risk.

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