Topic: Performance valve grind angles, cb650

[1981cb650c]

Found out somebody I work with has valve grinding equipment and will do my cyl head AND I have a spare head I'm not using, so....

What angles need to be cut for a street grind and what about polishing?

[crazypj]

Don't use the Honda 46 degree angle, use a 45. They usually use around 30~32 degree top cut and a 60degree throat cut into the port.
 Personally, I do 30, 45, 60 and 45/30 on valve.
Make sure its someone who knows how to do motorcycles or valve may end up too deep in head
PJ

[CBJoe]

Canuck... Next time I come to Canada, I might sneak my 650 head through customs and drop it off to you (after you experiment of course  ) 

[kayaker43]

What's the logic for avoiding the 46 degree cut? Is it just a matter of finding the odd cutter? I don't think its a flow thing, just heard it speeds initial break in when the seat and valve mismatch one degree. In a very short time they wear to match anyway.

Also I'm fairly certain its a bad idea to do any grinding on the valve to clean it up, they are just surface hardened. I've even read that lapping too much is a bad idea and some say its completely unneccessary? Just throwing some ideas out there, surely someone will disagree?

[kayaker43]

More thoughts,.. I always hand cut the seats with Neway cutters so I could obsess over them and get them perfect. They never needed lapping for a solvent tight seal.

I've seen some done by automotive equipment using grinding stones that looked absolutely horrible. I even saw one guy do a valve job in 5 minutes with a cordless drill and some kind of stone that cut a radius seat, then he lapped it aggressively with the drill to sort of make a seat,.. says he's been doing it that way for 25 yrs!!

Apparently any old thing will make a valve seat well enough to start and run OK.... That's why no one else works on my bikes 

[crazypj]

Kayaker43, you answered your own question, they wear in pretty quick.
 I much prefer to use Neway cutters as they not only give a better surface you can also position seat where you want it.
 I don't think is been possible to lap any Japanese motor valves to head since about 1977 as the surface coating on intakes is real thin and the stelite on exhausts not much thicker. Using a power drill is not only lazy, it puts radial grooves into valve and sea which really screws things up.
 I've been doing engine re-builds since about 1969~70, made a few mistakes in early years but learned quickly from them.
The 'old school' methods of 1960's just don't work on Japanese bikes.
 (and I have been Honda trained, we went through this a couple of years ago when I re-joined SOHC)
PJ

[goon 1492]

I did a set of corvette 327 heads once back in votec, and these were the old soft seats made for leaded gas, had to replace two of the valve seats and three guides and did a 3 angle jobby on the vlaves and seats. It was 15-30-45 for the angles= better flow. I'm no pro though and that was almost 10 years ago i did that job.

[MRieck]

 How about the Serdi or Sunnen that can cut 5 angles at once or a full radius with no run out. Now there are CNC valve machines that can create just about any seat shape you want

[crazypj]

Serdi and Sunnen are great machines for repeatability.
You are limited with the cutters though.
Seat width and position is fixed, if you want to change it for different applications you need a new cutter (about $90.00 each last time I priced them for Serdi)
PJ

[goon 1492]

How about the Serdi or Sunnen that can cut 5 angles at once or a full radius with no run out. Now there are CNC valve machines that can create just about any seat shape you want

Hell yeah that sound like it would be fun just to watch, kinda like a 5axis router, its just fun to watch em go

[MRieck]

How about the Serdi or Sunnen that can cut 5 angles at once or a full radius with no run out. Now there are CNC valve machines that can create just about any seat shape you want

Hell yeah that sound like it would be fun just to watch, kinda like a 5axis router, its just fun to watch em go

Yeah it would be fun. I've never seen a CNC seat cut but I've seen CNC work a million times. The Serdi isn't that exciting though it is a neat machine in its own right.