Exhaust valves EATEN?!

[sharky]

Hi everyone!!  I'm new to this site...  ive got an odd question about the gs500.  i ride a 99 model, i've got about 17,5xx mi on the bike, and i just melted down an exhaust valve.  one of the locals here in the bay area says it happens from time to time on these bikes.  i'll be rebuilding this head shorty, but in the mean time, i was interested to see if anybody has run into this problem before?  My bike ate the right cylinder exhaust valve...wasted.  anyone see this before?
-jack

[pantablo]

these bikes dont "just do that". no bike does. there was a lack of maintenance that lead to that.

[JamesG]

Yep, poor maintenance.  I can even tell you exactly how it happened. No valve clearance checks and the vavle clearance dropped to < 0 and was being held open thru the entire cycle. High temperature gases streaming past the valve act like a blow torch.

The GS is forgiving, but not THAT forgiving.

[The Buddha]

OK When you price the valves check into the costs of intake vs exhaust ... you'd find exhaust is more $$$ ... why ... cos its made of better - harder and more heat resistant material ... yea they try to save 20 cents worth by putting cheaper sheite in intakes ... But I digress ... most air cooled bikes the manufacturers made the intake valves also hard enough and suzuki has been great about putting in decent stuff even in the intake (Kawi watercooleds are horrible - old ninja 6's, 900, concourses, eli's and EX500's especially) ... but exhaust is harder than intake ... burning an exhaust is definetly maintenance related, or at the very least some oil supply or detonation related. Somehting has to have been wrong with it in the past or right now ... Find it and fix it before you slap it back on and then have it die (albeit slowly ... )
Cool.
Srinath.

[werase643]

I bought a nissan truck...yrs ago
pulled the head....3 valves fried
looked like someone took a torch to the edge and blasted them

[sharky]

i posted a month or so ago about a burnt exhaust valve in a 99 gs 500.  so i tore the head off, and pulled out the wasted valve.
for starters, the margin was nominal, it looked as thought the valve had litterally receded into the head.  no space left to adjust this valve cause all sorts of wierd driveablity concerns.  so the head is off, the valve is out, and its not terribly burned (not like a 98 crv), but it is completely worn out.  the other three valves look good, and after lappin a new valve, i dont think this head is going to the machine shop.
the concensus seems to be lack of maintenacen caused the problem.  could be so.  i meticulously (and i mean extremely picky) maintained this bike (lof's to the 0.5 mi, chain lube every 300, valve adjust/check every 4000mi on the dot, etc...) however, i bought the bike with 10,5xx mi on it from a kid who seemed not to know much of anything about bikes/machines.  i noted the front fender had a burn mark on it right infront of the header (leads me to believe this bike spent some time idling.), so maintenance could be the culprit for this failure.  talking with a few people locally, this seems to be a fairly common fault for this bike.  i saw another 99 for sale (only $1000!) with the same problem.  allegedly shitty valves encourage it.
i should also note, i ride this bike HARD.  my shift point is usually about 10500rpm, right when the top end makes a strange clacking noise ( i think its the valves floating), and the tach never falls below 7000.  i'm convinced this type of riding, incorporation with a neglected motor to begin with caused the fault.  i'll post again once the head is back on and let everyone know how the project turned out.
for all the people out there with the same problem:  this is an easy job.  parts cost about $120 for me from eastbay motorsports, (1 valve, all valve seals, head gasket, top end gasket).  probably about 6 hours total time.
ps.  i dont have a manual...does anyone know how tight the head nuts should be?

[The Buddha]

I's have done all valves at the same time with valves from kibblewhite ... available as a Kit as well I believe ...
Cool.
Srinath.

[makenzie71]

I doubt it was lack of maintanance.  I've seen lots of 20 and 30k bikes that have never had the covers off to check clearances.

The majoraty of the time when I see a burned valve, it's due to poor tune.  There's usually an oversized exhaust, a k&n and stock jets to blame.

[GeeP]

Nearly every time I've seen burned valves in service the valve clearances were tight.  

"Hard" riding certainly doesn't help things.

[dgyver]

ps.  i dont have a manual...does anyone know how tight the head nuts should be?

Cylinder head nuts: 25.5-29 lb-ft, 35-40 Nm

Make sure you follow the tightening sequence on the head.

Here it is if you cannot see the marks:

5 1 3 7
6 4 2 8

[sharky]

OKAY!  so the motor is finished.  i replace the right side exhaust valve, lapped the other three, replaced all valve seals, cleaned the damned hell of the head (its shinnier than a brand new quarter in there!), and re-assembled.  i'll tell you.  i dont like working on dohc motors.  i dont like doing t-belts on crvs.  this was alot like a crv, except no manual to reference.  after about 1 1/2 hours of screwing around with the timing chain, i finally figured out how to assemble the motor wiith the chain set on right.  okay, adjusted the valves: beautiful.  the downside:?
the motor wouldnt start.  i killed the battery cranking it (okay, it was weak from sitting for 3 weeks).  so i bought a battery charger and a gallon of fresh gas.  next day: drained the carbs, shook up the fuel tank and VVVVRRRRRRRRMMMMMMM!  that baby purrs.
i wish i had rebuilt this motor when i bought the bike.  it runs GREAT!!! one crank and it fires!  flawless performance.  i dont think this gs500 has EVER run like this before!  so, i put it up for sale on craigslist, and sold it to a nice lady as her first bike.  she's lucky.  thats a nice gs500.
all said and done:  the project went highly successfully.
NOTE:  i do not recommend this repair for the average do-it-yourselfer, but if you've ever done a timing belt, or head repairs, dude:  THIS IS GRAVY!  total time: approx 14hrs.  next time: 6hrs.

[makenzie71]

EXCELLENT news man!  I wouldn't have been able to sell it, though...I have a problem parting with things I've performed surgury on.

Doing head jobs and rebuils and stuff...it's really nowhere as difficult as people imagine at first glance.

[pantablo]

sweet! glad it all worked out. did you happen to direct the new owner here?

[sharky]

yeah mang!  she is happy as hell!  i told her about this site...thank you to whoever had the info on cylinder head nut torque.  you guys kick ass!
i rode it over to herin mill valley, that thing was pulling like it never had before!!  man!  pickup until about 9000 is 6th!  pretty good.  skatin thru traffic!!  she was terribly excited.  i alread miss that bike.  it is a really nice one--and it runs like fun bags too!
yall kick ass!