Valve seat cutting

[loxley007]

Hi all, I was hoping to do some light cutting (at home) of the valve seats on my 1979 head.

I’ve now purchase and returned two lots of cutting tools as they are too wide to use with a pilot guide. With the Sealey kit (expensive set) the tools kept getting caught even when I adjusted them. With the cheap ones they were just too wide.

Has anyone found a set of valve seat cutting tools that work with the shape of the 1979 CB750 head?

I really don’t want to send this off to a machine shop as I’d rather buy the tools to enable me to do this work again with another head for my next build.

Any ideas?

 

[madmtnmotors]

I have a set of the Neway seat cutters and was very happy with the results. Determining the correct components can be a little maddening...

 

[loxley007]

I have a set of the Neway seat cutters and was very happy with the results. Determining the correct components can be a little maddening...

Hi, can you link me the ones you have?

 

[madmtnmotors]

This is the set I used:

https://www.newaymfg.com/parts/KM2650
I'm not sure how the DOHC valves compare to the SOHC valves (mine are all SOHC, pre '78), but I imagine they are pretty close.

 

[loxley007]

T

This is the set I used:

https://www.newaymfg.com/parts/KM2650
I'm not sure how the DOHC valves compare to the SOHC valves (mine are all SOHC, pre '78), but I imagine they are pretty close.

Thanks, I think the small series ones will be best for the DOHC as there is not a lot of room to play with as the photo shows.

 

[dirtdigger]

I also use Neway cutters for my sohc stuff

 

[brettp]

I had no idea valves could be cut. The '81 750 is the oldest bike I've owned. Is this something particular to older bikes?

 

[loxley007]

I also use Neway cutters for my sohc stuff

I had no idea valves could be cut. The '81 750 is the oldest bike I've owned. Is this something particular to older bikes?

Valve seats rather than valves.

Most valve seats (to my knowledge) can be cut. Many can be replaced entirely if you are doing a full valve job. I think the best way is on a milling machine which is expensive.

I’m just hoping to get the seats a little less pitted and then lap the valves themselves.

 

[brettp]

I watched a couple videos on this toool. Looks easy enough. Yeah, I did see it was for the seat and not the valve itself. Hope it works out for you!

 

[madmtnmotors]

Yep, I have only used the seat cutter to clean up any pitting on the seat surface and then lap the valves to clean up the valves and mate them to the new surface on the valve seat. I will likely try my hand at new valve guides at some point and will need to recut the seats to align with the new guides.

 

[loxley007]

I watched a couple videos on this toool. Looks easy enough. Yeah, I did see it was for the seat and not the valve itself. Hope it works out for you!

Cheers, I’m hoping it works out. I’ve asked the Neway supplier (Fondera) in the UK to quote me for the 45, 60 and 30 degree small cutters (the bigger ones don’t fit in the 1979 DOHC head).

 

[loxley007]

Yep, I have only used the seat cutter to clean up any pitting on the seat surface and then lap the valves to clean up the valves and mate them to the new surface on the valve seat. I will likely try my hand at new valve guides at some point and will need to recut the seats to align with the new guides.

Nice one. Was it successful?

 

[madmtnmotors]

Nice one. Was it successful?

I was happy with the results.

 

[dirtdigger]

Yep, I have only used the seat cutter to clean up any pitting on the seat surface and then lap the valves to clean up the valves and mate them to the new surface on the valve seat. I will likely try my hand at new valve guides at some point and will need to recut the seats to align with the new guides.

They do work. you have to go slow cutting till you get the seats to start cutting concentric with the guides...if you push too hard you can make the pilot deflect and you wont get a good concentric seat with the new guide. I find the cyclex iron guides seam to be closer than the bronze guides after install. I use a tool to pull the guides in as well instead of driving them in....they seem to come back in more accurate this way. I have used them to open up for bigger valves...just takes a while

 

[loxley007]

They do work. you have to go slow cutting till you get the seats to start cutting concentric with the guides...if you push too hard you can make the pilot deflect and you wont get a good concentric seat with the new guide. I find the cyclex iron guides seam to be closer than the bronze guides after install. I use a tool to pull the guides in as well instead of driving them in....they seem to come back in more accurate this way. I have used them to open up for bigger valves...just takes a while

Thanks, some good tips in there.

 

[loxley007]

Cheers, I’m hoping it works out. I’ve asked the Neway supplier (Fondera) in the UK to quote me for the 45, 60 and 30 degree small cutters (the bigger ones don’t fit in the 1979 DOHC head).

For anyone UK based, the guys at Fondera were very helpful. I have spoken with Richard who has suggested the following cutters (prices include VAT).

Cutter 122 , 45 degree, body dia 24.8 range 22.5-29mm £104,08
Cutter 143, 45 degree body dia 23.5 range 21-23.5 mm £117.32
Cutter 123 31 degree body dia 24.8 range 22.5-28 mm £104.08
Cutter 133 60 degree body dia 22.2 range 18-22 22 mm £117.32

I’m going with cutter 122, 123 and 133 to see if that will work on both intake and exhaust. If needed I’ll pick up the cutter 143 as well.

Going to have to get them ordered from the US which means a bit of a wait but it’s such a bit/important job to do.