Valve seating

[wesleyweazel]

I need to replace an exhaust valve. Could someone please explain how to seat a new valve properly. All I know is that it involves grinding paste, but I don't know what the procedure is. I also need to know how to remove and succesfully fit valve stem seals. Obviously without damaging them.

Is there any easy way to release the valve springs and remove the collets or is it just easier to get a valve spring compressor.

[Billy Ricks]

The way it's actually supposed to be done is to clean up the seat and let the valve seat itself. You're going to get arguments on this but that's what Suzuki calls for.

[Doctor Shifty]

The Suzuki manual will tell you NOT to seat the valve with grinding paste. The proper surface is the velvet look of a cleanly tooled seat, for which you need the proper facing tool - it's a thing with lots of angled blades around it.

My own cheapster way out of this was to carefully scrape any carbon from the seat with a plastic tool, you don't want to score the surface. Then get some wet&dry sanding paper, about 600 grit, form it into a cone with the sanding edge against the seat, insert the valve to hold the paper against the seat, and slowly turn the valve and paper together a few turns with lightish pressure. (Nice a vague directions, eh?) I gripped the valve end with pliers, pulled the valve against the seat, and turned the pliers while holding the paper and valve together with the other hand. This cleans up the seat without damaging it.

Then just set up the valve. It will seat itself in the first few seconds after the motor is started.

Remove the valve seals by pulling them directly off the metal with long nose pliers. They will probably crush as you do so.

To install, dip them in some oil, hold them carefully with the long nose pliers, push them directly over the metal post. Don't let them crush or turn off sideways. They are a clean fit when they go on properly, and with care you will get it OK first time.

Kim

[wesleyweazel]

Engineering

Some real advice for a change. Thanks a lot to both of you. Who taught you these tricks or did you have to learn them the hard way (the expensive way)

[Nessism]

Lapping paste is fine to use to check for the proper seating pattern but it should not be used to try to take irregularities out of the fit of the parts. As for the seals, it's best to just get new ones since they are fairly cheap. I say take the entire head apart (using a spring compressor), clean, lightly lap the valves to check for proper valve seating, and reassemble with new seals.

Good luck.

Ed

[83'GK]

Also, wouldnt hurt, since you already have the head off, to go ahead and replace the other exhaust valves, as they probably are not too far behind the one your replacing....

[Nessism]

Many times the exhaust valve burns because it doesn't have enough lash. You might get lucky and only have to replace the one. Of course, you are going to have to take every thing apart to check.

[Suzuki mad]

All very good suggestions and advice. I don't know any way of getting a valve guide seal off of a valve guide without damaging it. There are very reasonable in the UK, cheap in US, so I suggest that you get yourself new ones. It's going to save you money in the long run with the cost of head gaskets. Any seal that's been in heated up and cooled down in oil will go hard. Its false economy not to change them when you have the chance.

Grinding/lapping issue.
The Suzuki manual states not to grind(lap) but re cut the valve seat with the official Suzuki tool. when the engine fires up and the valves touch the seats then the engine sorts out the rest.
I'm having to do this on my GS(X)1100 here in the UK. I was told by Suzuki mechanic's to change all 8 exhaust valves as it would take about 2 hours per valve to grind/lap them in. As my engine are still used on drag bike there must be some scope for reworking valves and seats.

You do not say what bike you have.
If you have the bucket and shim type valve adjustment be very carefull of how much you do in the way of lapping in valves, as the shims may have to be changed for the bike to run right. Change of clearance's!
If you have the cam follower and the nut with tappett adjuster version, then you have more room to play with in lapping or recutting the seats.

When these bikes were first made nobody gave them a service life of more than 20,000 miles or 5 years!

Suzuki mad
1981 GS1000E 250 miles in the last 3 days
1983 GSSX1100ESD Still in a lot of bits

[wesleyweazel]

Lapping?

It's a GSX400F 1981. Inline 4 cylinder with a 16 valve head. I think it has cam followers.

Thanks for the advice. It might sound stupid to you, but what is the difference between lapping and grinding? I am not a mechanic and these terms are new to me.

You said your from the UK. I'm in South Africa.

[Billy Ricks]

It's a GSX400F 1981. Inline 4 cylinder with a 16 valve head. I think it has cam followers.

Thanks for the advice. It might sound stupid to you, but what is the difference between lapping and grinding? I am not a mechanic and these terms are new to me.

You said your from the UK. I'm in South Africa.

Lapping involves using an abrasive paste and a suction cup like device to spin the valve. The paste is applied and the valve is inserted into the head to clean up the seating area. Grinding involves using a tool, a rotary file if you will, to clean up the seat and the seat area of the valve.