Checked my 2010 YZ450f valves today with only 47 hours

I thought the bike seems to take a kick or two more last weekend to start when she was hot so I decided to check the valves today for the first time as I am the second owner I do not know what they were at before. I do know this is the first time they have ever been checked and there is 47 hours on the meter that is true to the bike.

Intake 0.05-0.05

Ex 0.09-0.12

As you can see they are too tight but I am unsure if this was tight enough to affect start up?

Anyhow on Hondas we tend to run them tighter then OEM specs so my question to you guy is what do you set your valves at with these 2010-2010 yz450f?

Should I aim tighter then specs or right on?

Also do you think these valves are walking at this low of hours? I don’t see that it ever sucked in dirt or anything by checking the intake boot.

I think the gaps are there to cover thermal expansion so that they still seal when the bike heats up, otherwise you could just run them at .0000001. So, I think it's less critical if they're a little tight when the bike is cold, meaning that I don't think the numbers you've presented should affect how it starts when cold. Valves often go out of spec once when they're new, then hold for a long time, then starting moving. If they've never been checked, my guess is that they've just a been a little tight since new. How often do you clean your filter? On a dusty day, the filter will be dirty after just one ride and a clean filter makes valves happy.

Edited by corndog

The valves need to be adjusted to fall within specifications, simple as that. No fudging. Ideally, they should be as near to the tight limit of specifications as they can be set, but before you get too caught up in that, remember that the whole range of allowable clearance is only .002" from tight to loose, so it really doesn't matter that much.

In a YZF, the valves are actually tighter when cold than when hot, so typically, tight valves first start having a negative impact on compression and starting with a cold engine.

Thanks for the replies.

I know Grayracer I plan on adjusting them this week I have 3 bikes so I am in no hurry. I do plan on going on the tight side of the specs aiming for 0.10 intake and 0.20 exhaust if I remember correctly.

I have only put 5 hours on this bike since I bought it and I absolutely love it I just hope that they have not moved far enough that they will need to be replaced soon. It seems that if they were shimmed correctly by Yamaha that they have moved 0.10 on the exhaust and 0.05 on the intake during the break in or during its life span. I hope that’s not deeper than the coating put on titanium valves to keep them from wearing.

Corndog I clean and well oil my filters after every day of riding and I always make sure dust and dirt is not making it past the filter. I had a 2006 crf450 that I got well over 100 hours on the stock valves and only adjusted one valve one time.

If the valves move again shortly after I adjust them I will replace them but does anyone know how tough the valve seats are on these Yamaha’s? Will I most likely need a new head too or just simply new valves?

Thanks again.

Edited by Modmotoman

No need to replace a head unless you damage it, everything in the head is rebuildable. If you haven't replaced the valves in the head yet then the valve seats can just be recut and new valves can be put in (make sure to check the valve guides for wear as well). Once the seats have been cut a few times (after you have gone through about 3 sets of valves) then the seats themselves would need to be replaced. I don't know anyone that has put enough time on one of these engines to reach that point though.

One of the keys to determining what's going on with the valves when they need adjustment is to follow up with a recheck of the clearance after you've corrected it. Get them set right, then come back and check again in 5 hours or so. If they have already closed up, the coating on the valves is shot, and you're going to have to replace them. If, on the other hand, they're stil right about where you put them, the original problem was probably wear at the seat, and the valves themselves are OK.

Since your clearance numbers were fairly uniform at all four valves, I'm guessing that the wear was at the seats, and was reasonably normal.

Do valves start getting noisy when their is too much clearance or not enough? My 2011 has 7 hours on it and the valves seem a little noisy (light rapid ticking). I checked them at about 2 hours and they were dead on. Do i need to check them again?

More clearance makes more noise, but the bike will have all kinds of normal noises.

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