What are symptoms that indicate to check valve clearances

[popnlock]

I recently started riding this spring and purchased a 90 gs500e. I don't know if the valve clearances were ever checked or re shimmed.

On a possibly related note, I took a long ride about 3 hours a few weeks ago when i went on vacation and it seemed on the highway when i would travel about 50 miles or so the bike would bog down similar to it being out of gas and then shut down. I would have to pull over and if i just waited a few minutes (less than 5 min) and started the bike up again it would be fine for another 50 miles. I don't know if this is a new issue or not because before this i never rode more than 50 miles at a time. Since then i have not gone further than 50 miles at a time and it has been fine.

Could this be because my valves aren't opening and closing properly and what are good symptoms that indicate this. I have read on this site people generally check clearances about once a year.

PS: I have check the spark plugs they are new and they look fine. fresh gas in the bike, relatively full tank, air filter recently cleaned, carbs recently cleaned and rebuilt. No inline fuel filter and the lines are free of kinks. Gas filter inside the fuel tank attached to the petcock is clean as well.

[007brendan]

Sounds like fuel starvation caused by the gs fuel petcock.  I  had the same issue. Switch it to prime and your problem will likely go away.

[BockinBboy]

I'd say the 50mile problem is fuel related.  Likely candidates causing the issue would be vapour lock or crosswinds on your carb vent hose. 

Vapor lock is typically cause by a clogged tank vent or pinched tank vent hose... This doesn't allow air into the tank as it drains from fuel consumption, and slows fuel flow sometimes caused by tank bags, especially when the bags get wet.  This is similar to a water jug that doesn't allow air in, or your disposable coffee cup with a vent hole that didn't get punched all the way through.

Crosswind stumble is caused by the carb vent hose being routed so that wind catches it.  At higher speeds, or winds, gas flow is limited or even stopped due to pressures caused by the airflow.  The carb vent hose should be routed between the airbox and the battery box out of the wind.  Many folks see this issue when they install a lunchbox air filter or misdirect the hose routing after working on the carbs (carbs recently cleaned/rebuilt?!) or working on anything under the tank.  Also ensure that this hose doesn't get pinched/kinked.



- Bboy

[adidasguy]

You can run with the gas cap open to see if it the gas cap vent.

The fuel petcock can be cleaned. Remove the retainer clip and remove the lever then the conical valve part. Often there is crud in there. Cleaning it makes all the difference.

Note the position of the lever and the cone when you remove them. The lever is supposed to go on only one way, though it kind of looks like it can go 180* rotated. The fit of lever to valve cone is critical so ON and RESERVE are in the right place. It can be put back together 180* backwards!

[fetor56]

Valve Clearances:
In general if valves don't seat properly then there can be a loss of compression,power,backfiring,noisy tappets.This does not sound like your problem,but when u get more comfortable with your bike it would be a handy idea to check(recommended every 12 mths)

[twinrat]

if you have a tank vent problem stop and open the tank cap ,bike should start when u put the key back in the ignition as the carbs have time to refill . sometimes you can hear the air rush into the tank when you lift the cap these are signs of a blocked vent or the hose from it is trapped not letting air into the tank in the normal manner

[burning1]

With the GS500, assume that a valve adjustment is due if you don't know the last time it was done. Unfortunately, the bike doesn't hold clearance very well when using factory spec clearances.

Time to do a valve adjustment.

[SuperFish]

Dont know if this is your issue, but this has been my experience:

Ive had a long running problem with the valve clearances on my bike (2 adj done the last year, currently pulling the bike apart myself to see if I can find what is causing it). The shop initially thought it might have been a vacuum problem, so perhaps everyone here is on to something. My bike would definitely bog down, then die, almost like it had just run out of fuel. If it rested, it would usually start a few minutes later, but quickly die again. Definitely wasn't able to run another 50 miles if it had just died on me.

Good luck

[Bluesmudge]

Yeah, the problems of the OP and Superfish sound fuel or vacuum related. On my GS I know the valves are getting tight when the bike takes a long time to warm up or if it dies when I pull in the clutch coming up to stop lights or stop signs. Once the bike warms up there are absolutely no symptoms that the valves are out of spec, that's why you have to open her up and check.

When you adjust your valves you should then sync your carbs.