How do you know if your valves are bad?

[redskinman]

What do your valves look like when their bad? What are the symptoms of bad valves? Im guessing low compression,anything else?
Heres a pic of a head I just got off ebay,what do I look for on the valves to see if theyre good or bad? The carbon buildup left on these does not want to come off,can I use a flexshaft with a soft wire brush to get it off or is that a nono?
thanks

[atc500x]

easy test,install a spark plug and fill the combustion chamber with brake cleaner or gas,check for leaking in intake and exhaust port

[Dirtcrasher]

And when the seats and valve contact area look hammered...... they'll have raised edges rather than being perfectly flat and angular.

The wire wheelin all over the perimeter kinda says "I just got brushed!! I need a rebuild......" :lol:

[portland250r]

doesnt it blow up if you put too much gas into the cylinder at once? i was always told if you fill the cyclinder with gas and try to start it the whole thing will catch on fire.

[tri again]

x2 on what dc said

Valves are cut at a degree or 2 off from the seats so there should be a perfect line where they contact. Specs are in the book, no doubt.

If it was mine? x2 on atc500x too.
if it won't leak a small molecular weight solvent, it will prob run with no more concern.

If you are comfortable removing the valve springs, there is a blue dye you can use to see where the valves touch the seats and hopefully see a perfect sealing line. but again, if it doesn't leak, it'll prob run.

If the seats are hammered or buried, almost any machine shop can dress them up. If the guides are a little sloppy, they can be knurled instead or replaced sometimes. With the springs off, you can check for an axial side wobble.

If the carbon esthetics bother you, maybe some oven cleaner as long as it doesn't touch any rubber valve stem seals, if it has them.

ok, now why do you have a new head in the first place?

[1984 honda 200s]

doesnt it blow up if you put too much gas into the cylinder at once? i was always told if you fill the cyclinder with gas and try to start it the whole thing will catch on fire.

no if you put to much it wont start because it would be flooded then lol, if you put a little gas the bike will kick right away and run...

[tri again]

doesnt it blow up if you put too much gas into the cylinder at once? i was always told if you fill the cyclinder with gas and try to start it the whole thing will catch on fire.

I think atc500x meant to fill the head only with solvent, like just the way we see them.
spark plug in, prop them level, fill with solvent and see if it leaks past the valves beFORE he puts the head back on.

[redskinman]

x2 on what dc said

Valves are cut at a degree or 2 off from the seats so there should be a perfect line where they contact. Specs are in the book, no doubt.

If it was mine? x2 on atc500x too.
if it won't leak a small molecular weight solvent, it will prob run with no more concern.

If you are comfortable removing the valve springs, there is a blue dye you can use to see where the valves touch the seats and hopefully see a perfect sealing line. but again, if it doesn't leak, it'll prob run.

If the seats are hammered or buried, almost any machine shop can dress them up. If the guides are a little sloppy, they can be knurled instead or replaced sometimes. With the springs off, you can check for an axial side wobble.

If the carbon esthetics bother you, maybe some oven cleaner as long as it doesn't touch any rubber valve stem seals, if it has them.

ok, now why do you have a new head in the first place?

I bought an engine that both the cylinder head exhaust mounting bolts were thouroghly screwed up.Got a good price on this head,at least i thought it was a good price,30 bucks shipped.
I dont see how anybody makes money parting out a 200x,there are way too many pages of parts for them on ebay.

[atc500x]

Yes dont fill the cylinder!!!!
Fill only the head before installing on the motor

[Dirtcrasher]

I always trusted the gas method until one KX 250F didn't leak yet had low compression after I rebuilt it. I sent the head/valves out and they were hammered; Now I remove them and check them out.......

[Billyboy34]

In regards to cleaning the carbon deposits, I just cleaned mine the other day using mineral spirits and a piece of fine steel wool. It worked great. I just soaked the head in my parts washer first. It will take a little muscle to remove it all. For the tough to reach areas, you can purchase a siphon-type sandblaster (~$25 on Amazon) and use baking soda for the abrasive. Water will dissolve any baking soda left in the head (a little tip I got from ametzker).

[WilliamJ]

What do your valves look like when their bad? What are the symptoms of bad valves? Im guessing low compression,anything else?
Heres a pic of a head I just got off ebay,what do I look for on the valves to see if theyre good or bad? The carbon buildup left on these does not want to come off,can I use a flexshaft with a soft wire brush to get it off or is that a nono?
thanks

Someone has been a bit aggressive with a sander or rotary wire brush there! That head may need refacing to make sure the head gasket seals properly.

You really have to take the valves out and inspect them. Should be a clean line about 2mm wide on the valve and on the seat.

To clean the valves once they are out, put them in a drill with the drill in a vise, spin them up but not too fast and use fine emery tape on the face and under the head to remove the carbon. If the seats are okay don't touch them. DO NOT TOUCH THE STEMS WITH THE EMERY (the bit that goes into the valve guide). And be careful not to damage the stems in the drill chuck.