Topic: What happened to this valve?

[Blasbo]

Is it usable or do I need to replace it? 750 K7 #1 intake. The bike has not run since I've owned it (ran when parked  ) and I don't know the history. None of the others are buggered up like this.

[TwoTired]

Looks like it lost its adjuster screw at some point and was run that way for a while.  If the stem isn't bent, the guide still within tolerance, and the adjuster tip doesn't interface with the worn bits, it can be used.

If you want to remove the valve from the head, do grind/file off the bits that make the stem diameter larger, so it won't score the guide during removal.

If you find anything wrong with the other end of it, then replace it with new.

Cheers,

[754]

 Check that rocker..

[Blasbo]

Thanks TT. I did file the burrs off before I removed it.
Don't know if it's bent but I will check. I don't see anything else wrong except a lot of carbon build up.

[Blasbo]

754, I took a quick look at the rocker and it looked similar to the others, i.e. no big scrapes or scratches. I will double check before I make a final decision.

[cougar]

Ouch ! Personally I'ld replace it. Since you already have the head off you're only out the cost off the new valve. If you reuse it and it starts deteriorating down the road (Oh say on a long ride) and you don't catch it you're gonna be doing quite a bit more damage. Replacing the valve now will cost a lot less !! Plus the piece of mind that nothing "might be going wrong" ! Just my opinion.   ...cougar...

[Blasbo]

I thought about replacing it, but I didn't know if I could replace just one, or if I would need to replace them as a set.

[MoMo]

I would replace it, follow the post about removing it.  You may or may not need a machine shop to recut the seat when a new valve is installed. You will only need to replace the one.  Have fun with the build...Larry

[crazypj]

You need to re-check the rocker, remove adjuster and check the threads

[Blasbo]

I looked at CB750Supply.com and an intake valve is only $10 so replacing it seems like the prudent thing to do. I will also check the threads on the rocker adjuster.

MoMo - how do I tell if the seats need to be recut?

[MoMo]

I looked at CB750Supply.com and an intake valve is only $10 so replacing it seems like the prudent thing to do. I will also check the threads on the rocker adjuster.

MoMo - how do I tell if the seats need to be recut?

You can using blueing compound to see if the new valve seat seals uniformly around the perimeter or you can install the new valve, fill the chamber with fluid and see if it seeps out around the seat. 10 for a valve seems more than reasonable...Larry


Two ways work to check if it seals.  Install the

[crazypj]

 Filling combustion chamber is pointless, you can't see leaks unless they are so bad you could see gap 
Stand head on exhaust ports and fill up intakes, wait at least 5 mins
Then stand head on intakes and check exhaust side

[MoMo]

Filling combustion chamber is pointless, you can't see leaks unless they are so bad you could see gap 
Stand head on exhaust ports and fill up intakes, wait at least 5 mins
Then stand head on intakes and check exhaust side

 I did not mean combustion chamber even tho that is how it sounded. Misplaced the word chamber for ports.  As you said filling the combustion chamber would do nothing....Larry