Head Work - Valve Seats

Cutting off center is nearly impossible because the Neway seat cutters are guided by a pilot shaft
that is centered in the valve guide.
He must be a total idiot to mess up such an easy valve job..





Michael

Scirocco, that’s exactly what I thought, and that’s exactly what the tech at the automobile engine machinist said.
“How the hell did he do that?!?” Were his exact words.
But I guess that even having machine work done at a motorcycle shop is not a guarantee of success.
Food for thought.

Daftrusty wrote: I have a zr550 head that had exhaust seats so pitted that they needed recut. So I took it to the local independent motorcycle shop (support local businesses and all) and he used a Nu-Way hand cutter to do them. And he cut them so off center that when I lapped the valves and did a gasoline leak test, none of the combustion chambers could hold gas for 30 seconds. The gas literally poured out of the valves in seconds.
So I took it to a automotive shop and he recut the seats on a Serdi (really deep to get past the off center portion) and then after careful measuring, I had him tip the valves and cut down the valve retainers. Not one issue since.

A Serdi machine is the only way to go as far as doing perfect valve seats. Not a cheap machine to buy, but the best always costs the most!!!! Most motorcycle shops farm out their valve work. And if they do it in house, its a butcher job at best. Since I have been playing with 4 strokes, the best people I have found to do my valve work were some guy buried away in a 2 or 3 car garage filed to the rafters with equipment!!! None of them would even think of using a Neway cutter. They cut too much too quick. Before Serdi came along, they all used KwikWay stones to cut valve seats. Instead of that over-used phrase "three angle valve job" What you want is a radiused valve seat. With a three angle cut you end up with a sharp edges between the 15,30, and the 45 degree cuts. I used to see stones shaped to a 16, and a 17, a 29, 31, and 44 and a 46 degree angles. They would remove those sharp edges between each cut on the seat. Now if you look at a big buck cylinder head under a magnifying glass you will see what I mean!!!

Since I have been running four strokes, there has been only THREE people that have done my valve work. Ones dead, ones retired, and that last one is the only one left that I let touch any of my cylinder heads!!! OH by the way, all three of them used to do most of the cylinder head work for all the surrounding cycle shops.

The old way of doing valve seats!!!


The new way of doing valve seats.

Dr. Gamma wrote: .......... Instead of that over-used phrase "three angle valve job" What you want is a radiused valve seat. With a three angle cut you end up with a sharp edges between the 15,30, and the 45 degree cuts. I used to see stones shaped to a 16, and a 17, a 29, 31, and 44 and a 46 degree angles. They would remove those sharp edges between each cut on the seat. Now if you look at a big buck cylinder head under a magnifying glass you will see what I mean!!!

No doubt you have far more experience and expertise than I do in valve jobs, so please don't take this as criticism; it's just a question to clear up my confusion. The Kawasaki Service Manual states that it's important to have a valve/valve seat contact area that is between 0.5 and 1.0 mm wide (see images below). Does using the radiused valve job rather than the 3 angle valve job described in the manual still give one that contact area width? Thanks, Ed

My valve seat widths were about .030 to .040 thousands. Closer to .030 on the intakes, and closer to .040 on the exhaust valves. The seat area on the intake valves were moved more towards the outer edge of valve.

I never noticed that Kawasaki wanted you to run as little as .020 (.05 mm) valve seats!!!! Thats a little too narrow in my book. I know my drag race buddy used to like those tiny little seats. But they pulled their heads after about 10 runs or so.

When I used to pick up my cylinder heads from my machinist, it would turn into a 2 or 3 hour lesson in cylinder head preparation!!!! I learned a lot just listening to him. Thats where I picked up on all the stones that were cut to those funny angles.

I replace the valve guides before cutting the seats. Might as well just lap the valves unless that is done first.
Steve

SWest wrote: I replace the valve guides before cutting the seats. Might as well just lap the valves unless that is done first.
Steve

Thats the first thing that gets checked before anything else is done to my cylinders heads. All of my heads never had valve guide seals on the exhaust guides. That helped the guides on the exhaust side last a little longer.

Road race motors are run mostly between 6,000RPM to 10,500RPM at wide open throttle most of the time. I might run like 150 to 175 miles on a race weekend. I would get 2 to 3 race weekends before I would pull the top end. 5% leakdown was tear down time. If I missed a gear, I pulled it apart even after 1 weekend.

I used to laugh when a drag racer would say he got 100 runs out of his motor. Thats what 25 MILES!!!

When using Neeway cutters it's critical to apply pressure in an axial direction otherwise it is possible to cut the seats unevenly. And when the cutter blades are new they cut really beautifully with light pressure but that edge goes away pretty quickly and then you have to pressure harder, which brings in more risk. I've done several heads with my set of cutters now and they all turned out beautifully. Make no mistake though, hand held tools are no Serdi.