Topic: valve seat angle

[kblackburn]

Does anyone know what the seat angle is for the exhaust valve, on a 400 4


thanks


kevin

[bryanj]

Cant remember the exact fogures but it is a two angle job and Hondas prefer to be ground rather than cut

[kblackburn]

The exhaust seats are lightly pitted, and do require some light reworking, before I grind them in. just wanted to check the angles before I cut them.

[bryanj]

Should be in the Honda manual somewhere

[Tracksnblades1]

The attachment is for 1975 cb350f- cb400f.

It's looks like the included angle is included though.😎
I've never had one of these apart. It looks like the manual wants you to do the math.

It's been years since geometry. If this is wrong maybe someone will chime in.

30* + 120* + 30* = 180*   Top stone angle       30*
45* +   90* + 45* = 180*   Seat angle              45*
80* +   20* + 80* = 180*   Bottom stone angle 80*

I'd verify this before you grind. I'll try to look further into these angles. American seat/valve angle aren't usually expressed like this. This may not flow as well as JMR's current work and angle. Some performance Automotive valves had multiple angles ground on their face and top to promote flow.

[thep1pe]

It’s 45 degrees. 99% of gasoline engines prior to emissions regulations were so. Most if not all diesel were 30 degrees.

[kblackburn]

Thank you very much for your Guy's


regards

kevin

[PeWe]

The tools to refresh the valve seats are too expensive. Manuals describe how to do the 3 angle cut with manual tools.
Anyone seen a cheap set? 
China made might work for amateurs that will use them a few times only.

[bryanj]

Cheap sets do not work the seats are hard. Honda recommend, and sold, powered kits with grindstones and jigs for redoing stones. Trigger has a set he spent decades trying to find

[trigger]

It is true, i think i am the only one that has the full Honda tooling. I will post the 3 angles you need for the 400 

First is a blue stone at 37.5
Second is a white stone at 45
Third is a pink stone at 63.5

The seat angle is 45 and the valve needs to be re faced at 44.5, lap in by hand 

[70CB750]

The tools to refresh the valve seats are too expensive. Manuals describe how to do the 3 angle cut with manual tools.
Anyone seen a cheap set? 
China made might work for amateurs that will use them a few times only.

Check out Neway cutters. I use them to cut seats on Red's engine.

[PeWe]

The tools to refresh the valve seats are too expensive. Manuals describe how to do the 3 angle cut with manual tools.
Anyone seen a cheap set? 
China made might work for amateurs that will use them a few times only.

Check out Neway cutters. I use them to cut seats on Red's engine.

Links to the needed cutters?
Is it something like this?
Neway CU128, CU124, cutters and a 120-6.5 mm Pilot.
Mentioned here

Neway info about  fixing seat and valves 

It would be fine if the bigger F2 valves  are covered too.

Mentioned models might not be the correct sizes. Explained here.
https://www.cylinderheadsupply.com/nesmdicubo.html

In 32, EX 28. Oz In valves rather common as 33.5 or 34mm
F2: IN 34, EX 31.

[kblackburn]

That's just the sort of kit I used, when I was working (retired now), I had been to my previous work places, but it seems everyone no longer has the kit's and send
this work out to machine shops, as current technicians do not have the time to do this sort of work.

I managed to get the slight pitting out of the seat by grinding with paste, took nearly all day, but it's done, would have been so much easier with a cutter, but when the kit's here are between £600- £1000 !!!

[PeWe]

I grinded pitted seats by lapping some valves. Used old bad valves for most of the grinding to avoid destroying the valve surface The seat became not good, like a stair of all lapping. Left the head to a shop that fixed the seats. The low lift flow must have been reduced.