Topic: Valve Grinding

[nashvegas]

Hey folks, I have read in other forums and here where people will suggest a valve grind and I am wondering what a valve grind is and why would you have it done.  Also, how is it done exactly?

[MRieck]

The 45 degree face of the valve is ground slightly to clean up surface pitting which occurs after use. This allows for a good seal against the seat(as long as a fresh valve job is done). It is done in a special machine which turns the valve as it is ground on a stone wheel. Lightly scored tips can be ground as well. Modern OEM valves shouldn't be ground as they are surface hardened.

[Bodi]

Grinding a valve means using a special machine to make a new sealing face on the valve head. You do this to valves when the sealing face gets worn or burnt and has pits or grooves that prevent a good seal with the valve seat in the cylinder head.
Honda valves are hardened with a process known as Stellite coating. This coating or hardened surface is quite thin - grinding the valve will remove it. Honda says "do not grind these valves, period" and some people who have reground them have had them wear out quickly. I know of several engines with reground valves that have gone a LOT of miles without trouble, and a few reputable machine shop operators have told me that regrinding is fine. Honda wants to sell spare parts, machine shop guys want to do machine shop work. Who to believe?
Reseating the valves, using "valve grinding" compound between the valve and the seat and then rotating the valve to mate the two surfaces and polish them together for a good seal is different, and this process is always done when a valve is ground or replaced, the valveseat reground, or the valve guide replaced.
Honda uses cast-in valve seats that are not replaceable. Although they can be ground - and getting a multi-angle seat profile ground is common - each grinding removes some metal and after a few times the head will be junk.

[SteveD CB500F]

As Bodi says, valve grinding is different to valve lapping which most of us have done at one time or other.

[MRieck]

Grinding a valve means using a special machine to make a new sealing face on the valve head. You do this to valves when the sealing face gets worn or burnt and has pits or grooves that prevent a good seal with the valve seat in the cylinder head.
Honda valves are hardened with a process known as Stellite coating. This coating or hardened surface is quite thin - grinding the valve will remove it. Honda says "do not grind these valves, period" and some people who have reground them have had them wear out quickly. I know of several engines with reground valves that have gone a LOT of miles without trouble, and a few reputable machine shop operators have told me that regrinding is fine. Honda wants to sell spare parts, machine shop guys want to do machine shop work. Who to believe?
Reseating the valves, using "valve grinding" compound between the valve and the seat and then rotating the valve to mate the two surfaces and polish them together for a good seal is different, and this process is always done when a valve is ground or replaced, the valveseat reground, or the valve guide replaced.
Honda uses cast-in valve seats that are not replaceable. Although they can be ground - and getting a multi-angle seat profile ground is common - each grinding removes some metal and after a few times the head will be junk.

The tips of the OEM valves are stellite as are many aftermarket stainless valves that are used with screw type lash adjusters. The faces of these old OEM valves can be ground. New OEM valves, like the ones on my busa are surfaced hardened and it is stated that these valves should not even be lapped. After porting I lap them and and haven't had any problems. If something was wrong it would reveal itself in the form of disappearing valve lash. I've had seats replaced especially when using oversize valves larger than 2mm or 2.5 mm over stock and or using titanium valves. It is not that difficult to do on a Serdi.

[nashvegas]

Thanks Guys!  That's exactly what I wanted to know.

[maksuttt]

Hi!
I checked shop manual for CB 750 about valves seats cutting.
This process required special cutters 26 degrees (IN) cutter head and 40 degrees (EX). Plus 2 cutters 15-60 degrees (or somthing like this).
Usually on other bikes used 45 degrees cutter...

The problem is: i couldn't find good cutters with those angles.

Does anyone know, were to buy them?
Thanks!

[bwaller]

maksuttt, I'm not sure if you're talking about those old manual valve seat cutters, but I'd ask your local bike shop where they get their machining work done and take your cylinder head to them. The new equipment these shops use will do a far better job.

[maksuttt]

Yes, i told about old manual.
I checked local machinshop, they will do it for 400$. It's not too bad, but i want to do it by myself. I also checked Neway cutting tools, some other manufactures. They have standart 10-15-30-45-60 angles cutters... May be aftemarket CB 750 valves have different working angle? gonna check...

[lefty]

did you try searching the flanders catalog?  they have a set up that you can get various cutters and guides for hondas and a bunch of other stuff it's a neway i think. i read in the how to restore your motorcycle book that a serdi tool that cuts all the angles at once was good.  some use grinding stones too i think.  i've rescued several old hondas from a local junkyard and have considered investing myself.-lefty oh yeah,i also read somewhere that sometimes the seal is cut at a little smaller angle so it wears in better.

[Lumbee]

Reseating the valves, using "valve grinding" compound between the valve and the seat and then rotating the valve to mate the two surfaces and polish them together for a good seal...

...I've had a couple of bikes where I just "cleaned up" the head, but no machine work, as the valves seemed fine.  Could I buy some of this compound and when I disassemble a head for tune up use this pocedure to improve the seal between the valve and head?  Seems like a nice do-it-yourself way of improving head performance...

[maksuttt]

did you try searching the flanders catalog? 

  Thank you!
Checked, http://www.flanderscompany.com/Images/PDF/180-Valve%20Seat%20Cutters.pdf, nothing for Honda:(
And nothing close to 26 and 40...

[Big Jay]

In this day and age, valve seats are machined using very sophisticated machines that cut all or the angles and radiuses at the same time, and do it concentric to the valve guide. The machine head floats on air to line up perfectly with the valve guide centerline.  No one grinds seats anymore or uses the hand cutters.

Check it out;
http://aperaceparts.com/headwork.html

Jay

[MRieck]

In this day and age, valve seats are machined using very sophisticated machines that cut all or the angles and radiuses at the same time, and do it concentric to the valve guide. The machine head floats on air to line up perfectly with the valve guide centerline.  No one grinds seats anymore or uses the hand cutters.

Check it out;
http://aperaceparts.com/headwork.html

Jay

I agree with that. The Serdi can bore the throat for the optimum size....and alot more.

[cd811]

$400 wow..I paid $80 for my heads on my v-8 360 to be reworked...on my sohc, I had one valve that I could not get to seal, so I took it to him...he fixed it for $10...sounds like I was lucky

[Big Jay]

$400 wow..I paid $80 for my heads on my v-8 360 to be reworked...on my sohc, I had one valve that I could not get to seal, so I took it to him...he fixed it for $10...sounds like I was lucky

I think you are confusing a performance valve job which will increase flow and power, with getting a valve to seal.

Jay

[cd811]

performance valve job ???increase flow and power ???I think you may be confused with a valve job and porting...now porting and polishing a head will give ya flow and power,,,no dought

[Big Jay]

The valve seat is the steel area that the valve closes on to seal. All the flow in and out has to go past the seats. The area above the seats is the ports. Porting and modifying the valve seats are two different things.

I have to assume you are new to the performance scene and don't know about performance valve jobs. Do a Google on it, you will find a lot of info that can enlighten you.

Jay

[MRieck]

performance valve job ???increase flow and power ???I think you may be confused with a valve job and porting...now porting and polishing a head will give ya flow and power,,,no dought

cd....Jay is not new to anything concerning the CB engine. While he and I disagree on some of his "stuff" I will say he offers excellent service on crank work etc and parts. A "Serdi" valve job will increase flow across the seat be approximately 10%...period. Jay is a knowledgable man with alot to offer. He is not the end all say all BUT he knows what he is talking about.

[cd811]

hey wait a minute...I'm not stepping on toes or doughting anybody...no i'm not new to to performance...not by a long shot...I'm not going to pay $400 for hi tec valve seats on a 4 cylinder...I think your going to get more flow and power from polished and ported heads....ya rarely see drag blike without nice head work...I did all my porting on my shovelheads and I feel i gained much improvement there...I did not rework my sohc heads because there just to small for me to work

definitely did not mean to upset nobody...I'm 48 and still learning...have a nice day

[MRieck]

hey wait a minute...I'm not stepping on toes or doughting anybody...no i'm not new to to performance...not by a long shot...I'm not going to pay $400 for hi tec valve seats on a 4 cylinder...I think your going to get more flow and power from polished and ported heads....ya rarely see drag blike without nice head work...I did all my porting on my shovelheads and I feel i gained much improvement there...I did not rework my sohc heads because there just to small for me to work

definitely did not mean to upset nobody...I'm 48 and still learning...have a nice day

cd, you're not stepping on any toes. A port job will definitely increase CFM. A good port job and a good valve job will really increase flow. Add oversize valves and you get even more. Here is a pic of a CB head i just got back. It has a full radius seat (and some port work). The great thing about the Serdi is you get each seat the same quickly and easily. The value of a good valve job really came to light when people began supersport roadracing where there wasn't much you could change according to the rules. People went as far as replacing the valve seats and putting in new seats that were slightly higher to increase the compression ratio a tiny bit. That stuff gets expensive but every little bit helps. I'm 48 too and still learning....the day I stop learning is the day I stop breathing.

[maksuttt]

Nice job:)
Thank you guys for info!

[Big Jay]

I'm not going to pay $400 for hi tec valve seats on a 4 cylinder...

Yeah, don't even know anyone who charges that kind of money for a valve job.

Jay

[cd811]

I believe and really I'm not surprised at how much one can spend on a sohc motor...carbs,head,rods,crank and so on...but why?...in my opinion, if you want to max out on speed why not get something modern...they come stock and fast...if ya want more, put money in one of those...for ex.,I can buy some smoothbores for my sohc for around$400 then boots for $200 to adapt...that kind of money and thinking is just out of my league...I just like the thinking they had in the early 70's with a few modern(and cheap) ideas here and there

[cd811]

big ray...I would really like your opnion on my "bad head gasket" thread

thanks