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silentZ

Question on recently adjusted valves

8 posts in this topic

08 450 with 126 hours

During valve inspection here is what was found:

LI=.008

RI=.011

MI=.005

LE=.010

RE=.010

After adjustment

LI=.005

RI=.005

MI.005

LE=.010

RE=.010

I bought this bike used and it looks like the RI was extremely out of spec.

Any idea what kind of engine difference I should expect to see since the adjustment?

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I believe you adjusted your valves to the incorrect clearance. I think the clearances are .10mm - .15mm for the intake valves, and .20mm - .25mm for the exhaust. That is just remembering off the top of my head. Check the manual to be sure.

I wouldn't ride your bike until you are POSITIVE of the correct clearance, because the clearances you mentioned seem very tight

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I just rebuilt my 06 450 and all the valves were in spec except the right intake, it was .007. I adjusted it to .005, I haven't ridden it yet so I don't if it has moved.

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I believe you adjusted your valves to the incorrect clearance. I think the clearances are .10mm - .15mm for the intake valves, and .20mm - .25mm for the exhaust. That is just remembering off the top of my head. Check the manual to be sure.

I wouldn't ride your bike until you are POSITIVE of the correct clearance, because the clearances you mentioned seem very tight

The clearances he gave are obviously in inches, which would mean they are correctly set.

However, I am somewhat suspicious of the clearances given for the outer intakes, as they were, according to this, both loose, which is NOT a normal wear condition. There are three things that could account for this: Bent valves, carbon preventing the valves from closing entirely when cold, or a serious and abnormal wear condition at the lifter face or cam cap. If it has compression, you can rule out bent valves, but I'd recommend revisiting the clearance of your intakes, gently bouncing the valves down on the seat by tapping the lifters gently with a punch. When the valves tighten, it's normal. Not welcome, but normal. When they get loose, something's not right.

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The original findings where very strange according to the guy I take my bike to. He thought that the person that previously inspected the valves had no idea what he was doing. I TOTALLY trust the guy I take my bike to, as he is the expert regarding 4 strokes in these parts. He services 90% of the guys bikes I see on the tracks areound here and is a retired engineer that knows the YZ450s inside and out.

What I was wondering, was if everything is good to go with the current clearances, should I expect to see improvement in power, etc.

Thanks for the replies.

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The original findings where very strange according to the guy I take my bike to.
That makes me feel a little less apprehensive.
He thought that the person that previously inspected the valves had no idea what he was doing.
...And that's a possibility.
What I was wondering, was if everything is good to go with the current clearances, should I expect to see improvement in power, etc.

No. But it should be a little quieter.

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Thanks so much. I have been a 2 stroke guy in the past and I have not ventured into the inner workings of the 4 stroke engine. I really appreciate your expertise!!!

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