Valve Seat Angles

Hi

I'm hoping to draw on some of the vast engine building experience that exists at this form.

For my 78 KZ650sr the The Kaw manual gives the 30,45,60 deg valve seat angles as their spec. I've had some people recommend cutting interference angles in the seats at 31 and 46 deg. The interference angles are supposed to give you a better valve seal and therefore higher compression. As I see it though it would give you less contact area and less heat transfer from the valve. I would love to hear some opinions on this.

As always thanks for your time.

One degree is not that much, you do that so the valve and the seat have a " sharp " edge to seat on at first, within a few miles you will have the full contact patch on the valve and the seat.
This was done to eliminate the lapping in of the valves.

Thanks for the reply BSKZ650.

So the valve basically seats it's self into 1 degree difference after a few miles. Makes sense i guess. Are there any negative effects in terms of valve life? Has any one run this for a few thousand miles?

How much Valve clearance can I expect to loose once the valves settle in to the interference angles? I'm trying to figure out how I'd have to shim the valves to account for the settling?

Thanks

I have done a ton of valve jobs using this method, never saw any decrease in life over doing it the equal angle method.
as far as change in clearance, its about the same as normal valve wear, you will see some change in the first few thousand miles, but thats normal, after that routine mait, will keep things in check.

One note, when you install any head make DAMN SURE you oil the valves and guides, prior to start up, they get the most heat and are the last to get oil to them

Thanks BSKZ65o I really appreciate the help and advice. I'm looking at getting a set of Neway cutters and trying to cut the seats myself. Do you have any experience with the Neway sets. Is there anything I should watch out for.

In my opinion, the neuway cutters are junk, I would not use them, but thats just me.
I do have a few questions,
is this your first try at a valve job?
are you replacing the valves or are you going to grind yours?
make sure you check the valves and guides for wear and replace if needed, this may need to be done by a shop with the right equipment

While I'm familiar machine shop work (Dad was a machinist and I spent many hours helping him rebuild stuff). Yes This is my first try at performing a valve job. I know I should probably take it to a shop to have it done but I'd really like to have a go at doing it my self. I do also have a spare junked head that I can practice and experiment on b4 I try my good one.

I have checked all of the guides and all are within the service limit stated in my Kaw service manual. Checked by using the small bore gauge(at 3 or 4 places down each guide) and the valve tilt method (using a dial indicator). I have a new set of valves that I'll be using that I have also measured to be in spec. The Intake seats don't look to bad at all it's the exhaust side that is pitted.

What method do you use to restore the seats.

well here is the good news bad news,,
You should still grind the new valves, cant tell you how many times a new valve was not 100% true, it wont take much but its worth the time and effort to make sure they run true.
thats the bad news

I like either to grind the seats with a sioux stone set, or better off use a serdi machine to grind the seats. either way works well.

the ex seats are going to be pitted, normal, when you grind the 45 seat it gets wider and deeper, the 30 on top brings it back down to the seat area of the valve, the 60 under cut gets you the proper width of the seat,
just remember every time you grind the 30 you are lowering the seat, which will make the valve taller on the other end, thus the need for adj the stem height to maitain shim range.

also dont forget to check the valve sring height, they may need shims there also

Once again Thanks for the help. It's really nice of you to share your experience.

unfortunately I don't have access to either of those machines. Do you feel that the neway cutters leave the seats to rough or they are not accurate enough to do a good job?

Sorry but I don't understand the last bit of you're response: "also don't forget to check the valve sring height, they may need shims there also."

Do you mean valve spring height? I didn't find anything about shimming valve springs in the Kaw manual I didn't know they made shims for the valve springs. All the manual says is to check the height, tilt, and tension of the springs and if it is out to replace them.

As set from z1 is only about $65.00

I never liked the accuracy of the nueway system, the seats never seem to be concentric.

let me explain the spring shims,, if you gring the valve seat "down" into the head by .030 the valve will then become taller by the same amount on the other end, thus cutting the valve tip so you will be able to shim the valves, at the same time the spring is also going to be .030 longer, this reduces the seat pressure and reduces the open pressure of the spring, you need to be able to compensate for that distance change.

I am not wanting to discourage you from doing the work yourself, but.... the right tools and experiance in working on motorcycle heads goes a long way.
I dont have all the tools needed to do a complete valve job,and I done more heads than I care to admit, I will send mine out to a shop for the needed repairs.

I have read both the clymer and the kaw manual and neither of them mention anything about spring shims. Doing a quick google search I can't find any one who seles them for my bike. I under stand that as you remove seat material the spring exerts less tension to close the valve.

The valves stems in the 650 engines can't be ground. At least not according to the KAW service manual. There is not enough clearance between the top of the valve and the top of the keepers. If you do grind them there is a chance the keepers will hit the shims and get knocked loose and the valve will drop.

When I took the head apart the the shims under the buckets were 2.50mm to 2.65mm. The smallest shim that I can find at Z1 is 2.05mm. Assuming that the clearance on the valve with the 2.50mm shim was right gives me a max of .45mm .018" to remove and not run into trouble. This is actually one reason I want to do the work my self. I'm afraid of some one else removing too much material from the seat. Suddenly I have to get custom valves( If I even can) or I have to find a new head and start over. I figure if I do it my self I can first try it on my junk head to get a feel for it and then move to my good head and take it slow. Any way will a maximum of .018" make that much difference to the spring tension?



I agree with you that having the right tool for job is very important. They can make the job a lot easier. As far as experience goes the only way to get that is by doing it. It all depends on how much risk you want to or can take.

Even if I get some one else to do it I have to trust that they know what they are doing and will take their time and do it right. The more I know about the job the easier it will be to hire the right person if I decide to go that way. I would really rather spend my money even if it costs me more,to buy the tools and experience do it myself.

It should be possible to rework the head my self. I know that others have done it. You your self said that you've done more heads than you care to admit to and didn't always have all of the latest tools. I realize that you have learned a lot along the way and I really appreciate that you are willing to share that knowledge with me and the rest of us here at KZrider. The only advice I won't take is "you can't do it don't even try get some one else to do it". I have at least try that's just how I am wired.

Thanks