Why do Suzuki say not to use valve grinding paste

[pad]

Why do Suzuki say not to use valve grinding paste in the manual.
Am I old fashioned and missing something
Or is Suzuki just being strange.

[Sam]

I think the stock valves have a hardened surface that the paste will remove.

If the valves leak then chances are the coating is long gone or pitted, so no further harm to be done

Never stopped me doing it and my clearances remain stable for many miles

[tl1000lasse]

Originally Posted by Sam

Never stopped me doing it and my clearances remain stable for many miles

depends on what END you measure yours

[6cuda6]

Originally Posted by pad

Why do Suzuki say not to use valve grinding paste in the manual.
Am I old fashioned and missing something
Or is Suzuki just being strange.

The modern thinking is that you will actually HARM the surface the has just been made....so if you use a cutter [not a grinder] to do the seats the surface is perfect, by using a compound you grind in a rough surface therefore creating the potential for leaking.

I still like to lap the valves in by hand, this way i know they are matched/sealed.....

[The Ring-In]

Got to throw my 2c in here.
If you cut the seat you create a flat surface at the angle of your cutter (45 or 46 degress) then you grind the valve to suit .
both should be perfectly (?) flat.
If you grind the valve onto the seat sure you ensure they are matched but you actually grind a small groove the size of the seat in the valve face.
When the valve and head are cold these align, when the engine is at running temp the valve grows slightly in size and then they don't.
If you take a worn valve and seat and grind the two together you get a round seat and a round groove in the valve and when that gets hot it will seat worse than when you started.
I have seen people use a dummy valve to "polish" the seats with paste. and then use fresh ground valves to match .
test your valve job three ways.( I use all three every time)

1. with a vacuum tester.

2. push on the stem and lift the valve slightly off its seat, push the valve sideways in each of four directions (front back and sideways) while lowering onto the seat. This is called sliding. the valve should slide equally back onto the seat in all directions. If the seat is not quite concentricc to the guide . it will slide further from one side than another and needs to be recut with a more rigid tool.

3 blue it. put a light coat of blue on the valve and almost wipe it off. drop the valve onto the seat a couple of times and pull the valve out . chech the valve it should be getting clean evenly all round . check the seat it should be blue evenly all round. wipe the valve clean and drop it in again. pull it and see how the blue has transferred back from the seat. same deal. if it is thin one side thick the other . cut the seats again .
Don't rotate the valve when bluing just drop it on the seat.

[pad]

Cool that makes sence

[bdejong]

It's also strange there are no replacement valve seats on the microfiche. Just get a new head is the message.

Had my valve seats freshened up (recut) once. There's not much room for that in the valve clearance range, I ended up with the thinnes shimms.

Dunno if there are aftermarket valve seats available.

[The Ring-In]

you need to take it to a specialist (auto engine reconditioner) . seats require specialised equipment to fit and are usually machined from a range of presized inserts which are very close in dimensions.
If a seat is worn out then removing it usually requires fitting a slightly larger item (OD). not something for the home mechanic.

[Sam]

Originally Posted by The Ring-In

you need to take it to a specialist (auto engine reconditioner) . seats require specialised equipment to fit and are usually machined from a range of presized inserts which are very close in dimensions.
If a seat is worn out then removing it usually requires fitting a slightly larger item (OD). not something for the home mechanic.

TL heads are available in abundance, no need to pay for specialist re-seating just yet

[brent_b]

I just thought I would throw my two cents in. When I had a gsx250 (1994 model) I managed to get carbon stuck between the valves and seats after a slide down the road. Though the manual said not to use valve grinding paste I did, just enough to get rid of minor inperfections. These engines rev to about 13.5k and to this date the engine is still going well, with over 60,000km on it. I just did it because I had nothing to loose..