Checked valves, again

My buddy jokes me with this bike. I have had it for three months, put 4.2 hours on it, and checked the valves 4 times. LOL! They are at-intake .110mm all three,  exhaust is at .208 across both. That is what it was when I got it and they haven't changed. I know it's not required to check them that often but I wanted to make sure they were not needing replaced. I bought the bike very slightly used but it is an 03. The original owner had service paperwork with oil and air filter service and I could tell the valves had been checked at least once, but the cam bolts did not look like they had been removed, so it is doubtful they have ever been shimmed. This is my first motocross 4 stroke and I actually prefer the two stroke 250, but man those are hard to find. As I ride this 450, I get more and more comfortable on it. It's just the thought of dropping a valve and busting everything up that makes me cringe. I do my own engine and maintenance work and have a shop here that I can do it all in, so that is not the problem. It's just that thought hanging in the back of my head every time I start this thing. 

Cool story bro

My buddy jokes me with this bike. I have had it for three months, put 4.2 hours on it, and checked the valves 4 times. LOL! They are at-intake .110mm all three, exhaust is at .208 across both. That is what it was when I got it and they haven't changed. I know it's not required to check them that often but I wanted to make sure they were not needing replaced. I bought the bike very slightly used but it is an 03. The original owner had service paperwork with oil and air filter service and I could tell the valves had been checked at least once, but the cam bolts did not look like they had been removed, so it is doubtful they have ever been shimmed. This is my first motocross 4 stroke and I actually prefer the two stroke 250, but man those are hard to find. As I ride this 450, I get more and more comfortable on it. It's just the thought of dropping a valve and busting everything up that makes me cringe. I do my own engine and maintenance work and have a shop here that I can do it all in, so that is not the problem. It's just that thought hanging in the back of my head every time I start this thing.

Son in law is still riding an 09 with over 300 hrs without a single valve check or shim.

So, you're worried.  There is some foundation for that, I suppose, but not a lot with a YZ450.  I had an '03 that logged over 350 hours after I bought it used in '04.  Never needed the valves adjusted. 

 

But you were right to check fairly frequently at first, because it told you something important.  That is that the valves in their current condition are holding their adjustment in a stable manner, and that means that the hard coat on the valves is still in good condition.  It's quite likely that yours has also never once been adjusted.  So relax a little. 

 

Check them again after 10-15 more hours of actual engine run time.  The only concern you have is whether they remain at their new settings whenever they actually need to be adjusted.  If they do, fine.  Things are still good.  If they close up again in 5 hours or less, they need replacing, and you should do it then, not later.

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