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Valve Question


Renthalkx
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So as you guys may know, my cbr1000 is completely disassembled minus the cylinder head. This is my first time ever working on a 4stroke motor so I'm a bit confused about my valves. I understand that you need to shim them when out of spec, but what exactly does cutting the seats do? Does that replace reshimming? I guess what I want to do is since I have it torn apart, restore the head to factory specs so I don't have to worry about something going out of spec anytime soon down the road. Do I buy new seats or just get them cut? I just need somebody to explain how exactly I go about this.

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Ahhh ok thank you. That makes much more sense. I've read that sometimes reshimming is just a temporary fix and then they're out of spec again shortly. Maybe I'm missing something about the shims. Does the head come from the factory with shims or are the valves just naturally within spec and then we reshim as they go out of spec? What happens when we can't shim anymore? 

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 You are a brave man taking on a CBR 1000 as your first four stroke motor to work on. The first four stroke I ever worked on was just a single cylinder. I am no expert but what happens with the valves to my understanding is they wear into the head and that is why you they need re-shimmed.  I know with quads what happens is the quad sucks dirt in there at times through the air filter and it grinds away on the head. Also just wear and tear from the valves beating on the head.  The motor comes stock with shims in it.  As far as it being a temporary fix I believe it depends on how far they are off. If you're just talking a couple thousandths probably not a big deal, reshim it. If it's to the point where the shim you are using is down to next to nothing compared to what the original shim was more than likely that valve has beat the snot out of the head and needs redone.   There are definitely better mechanics than me on this forum so listen to them over me for sure. This is just my elementary understanding of it all. 

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3 minutes ago, durk said:

 You are a brave man taking on a CBR 1000 as your first four stroke motor to work on. The first four stroke I ever worked on was just a single cylinder. I am no expert but what happens with the valves to my understanding is they wear into the head and that is why you they need re-shimmed.  I know with quads what happens is the quad sucks dirt in there at times through the air filter and it grinds away on the head. Also just wear and tear from the valves beating on the head.  The motor comes stock with shims in it.  As far as it being a temporary fix I believe it depends on how far they are off. If you're just talking a couple thousandths probably not a big deal, reshim it. If it's to the point where the shim you are using is down to next to nothing compared to what the original shim was more than likely that valve has beat the snot out of the head and needs redone.   There are definitely better mechanics than me on this forum so listen to them over me for sure. This is just my elementary understanding of it all. 

That actually made it click in my mind. Thank you very much!

I was a little scared to just dive into my bike but I figured it's better to learn myself rather than pay somebody else tl do it. And if something breaks (I already screwed up my crankcase lol), I'd rather me break it than somebody else. I've learned a lot honestly just from taking it apart. I played with the transmission to see how different gears engage, I got to see how the camshafts worked and all that. It's really neat and if I decided to have a shop do this I wouldn't of learned anything. 

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Proper tools and a Honda factory service manual will go a long way to making this task easier. Engine overhauls aren't that difficult, it's mostly knowledge and experience driven. Thing is, in order to check your valve adjustment the motor has to be assembled so you can check the clearances between the cam lobes and the lifter buckets. As previously stated as long as the heqd isn't beat to shit and there isn't a million miles on it, I wouldn't worry about having seats recut. Just get some lapping paste and a lapping tool from AutoZone. Lapping paste is grease that contains abrasive dust, usually diamond, that you put between the valve and the head, then you spin the valve and it polishes it's own perfect seat into the head. Watch a few videos, you basically do it by ear. 

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