Damaged valve seat

[Howie]

Ah, mislead by the photo.  Is the area that is not damaged is greater than 2/32" and you have a seal you should be good.

[stopintime]

I note an 800 here:  http://kaemna.de/cms_en/tu_example.htm?&ct=68 that has 44mm intake (1mm oversize), stock 38mm exhaust, and "fitted camshaft", plus big bore kit etc.  Would they have used 900 cams?

My bike - yes, 900 cams (and much more)

[suzyj]

Oh, I should have made the connection.  Are your intakes 696 ones, or something else?

[stopintime]

The S2R 800 throttle bodies are the same as on the S2R 1000.
As I understand it they are large enough for tuning.

Some spacers/bushings(?) to fit the 900 cams in my heads.
Lots of head work to optimize (port, polish, custom shaped valve seats, valve guides, 4V valve seals, larger intake valves, squish edge work a.s.o.)

[Speeddog]

Just get a light cut on the seat, lap the valve to it a bit, and it'll be good to go.

Really, don't replace the seat.

[ducpainter]

Just get a light cut on the seat, lap the valve to it a bit, and it'll be good to go.

Really, don't replace the seat.

Just because people with over 100 years experience twisting wrenches say it...

doesn't mean an engineer will listen.

[koko64]

 

[suzyj]

Just because people with over 100 years experience twisting wrenches say it...

doesn't mean an engineer will listen.

I'm being quite thick, aren't I?

I'll get it ground, and see how it goes.  That doesn't preclude me from changing it later.  Is there a limit to how far back the seat can be ground?  I presume eventually I'll get to the point where I can't get an opening shim to fit.

The valves also need grinding.  They've got a fair amount of pitting.

Thanks for your help guys!  Once I've had it ground I'll post up a photo of the results.

[ducpainter]

I'm being quite thick, aren't I?

<snip>

Nope...

you're following your training and being an engineer. You can't help it. 

The real world is not that perfect, and doesn't need to be.

Yes there is a limit to how deep the seat can be ground.

Truth is if you get a contact patch of 1/16" or larger it will work just fine.

As Speeddog says, a light cut and a lap will put it right.

[Speeddog]

A *good* performance cylinder head shop can take the minimum cut on the seat to just clean it up.

And if they're quite good, they can do a multi-angle cut that will give you more airflow, and properly shape the ~10mm of the port adjacent to the seat.
It's where the biggest gains or losses are, most of the rest of the port is window dressing.

[koko64]

+1
I'd do that Suzy.
You hankering for more power now? It's a slippery slope.

[suzyj]

The S2R 800 throttle bodies are the same as on the S2R 1000.
As I understand it they are large enough for tuning.

Some spacers/bushings(?) to fit the 900 cams in my heads.
Lots of head work to optimize (port, polish, custom shaped valve seats, valve guides, 4V valve seals, larger intake valves, squish edge work a.s.o.)

Ya - the spacer for the cams is needed because the 800/695 head has only two cam bearings, vs 3 for the 900.  That bit appears quite straightforward.

For your 1mm oversize intake valves, did they fit new seats, or cut your existing seat down to fit the new ones?

The reason I ask is that if I get my intake seats cut down and shaped to suit a 44mm valve, the damaged bit will completely disappear and no longer be an issue.  It's only 20 thou either side, so I can't see that it would affect the integrity of the seat.

Also why the 4v seals?  I presume you mean the seal on top of the guides?  The 695/800 head is already 7mm, so I'd have thought there would be no reason to change this (replace, sure, but with the same part).

[stopintime]

I don't know much about the seat work. They explained the shape and why it was important, but all I can remember is multiple angle changes. Looking at the picture - maybe it looks like it has been widened?

The 4V seals? Probably a "might as well" solution.... or because the new guides require them?
Anyway - my rockers touch the seals and destroy them - we're loking into that soon.
Kämna's race engines are fitted without seals - guides are tight enough and the small amounts of oil burns in a tuned high compression combustion chamber - no worries. (I worry anyway and want it taken care of)

[suzyj]

I don't know much about the seat work. They explained the shape and why it was important, but all I can remember is multiple angle changes. Looking at the picture - maybe it looks like it has been widened?

The 4V seals? Probably a "might as well" solution.... or because the new guides require them?
Anyway - my rockers touch the seals and destroy them - we're loking into that soon.
Kämna's race engines are fitted without seals - guides are tight enough and the small amounts of oil burns in a tuned high compression combustion chamber - no worries. (I worry anyway and want it taken care of)

Good thinking looking at the photo.  The gap between the outside of the exhaust seal and the outside of the intake seal on the photo looks exactly the same as on my head.  If they'd fitted bigger seals, that gap (which is only ~0.8mm on my heads) would be 0.3mm - effectively non-existent.

So that makes me very happy.  I can work on the premise that I'm having the intake seals bored for 44mm valves, and get back to work.

FWIW, I diagnosed what happened with the die grinder - turns out it wasn't the burr that hit the seal at all - it was the collet chuck.  I was busily watching the burr.  I measured its depth today (using a measuring microscope, because I couldn't think of a better way, and I had one in my kitchen   ), and it's less than 0.2mm.  It'll be completely gone once seal work starts.

The 900 cam has like 1mm more lift.  When I was playing with my heads before disassembly I noticed there wasn't a huge amount of clearance between the closing rocker and the seal.  I guess the extra 1mm is a little too much.

Running without seals would be cool for valve and seal life - I imagine the oil would ensure the valves stay nice and cool, but not so good for emissions.

I imagine it would be really easy to fix - you could just turn the nose of some guides down 1mm, then press them through 1mm further.  The guides on the 695/800 head don't have any steps in them, as I found tonight after I pressed mine out.  See photo, including the gorgeous tool that one of my lovely workmates knocked up for me today from silver steel: