Valve adjustment?

[tykho]

So yea I know, another damn valve adjustment post, but anyway...
I'm at about 6,200 miles and haven't checked my shims yet, should I do it asap or am I okay for another few hundred while I order the correct shims so I don't have to buy an entire kit?

On a side note, I was coming home from my parents house last week, which is about 200 miles away, and I was doing 85 on the interstate @ ~7k RPMs in 6th, when the engine sound changed and sounded much deeper, and I began losing power. I downshifted by the engine would not rev above 7k for about 3 minutes, it then cleared up and I was fine for about 45 minutes, at which time it happened again. I ended up stopping for gas, and listened for a gasp when I opened the cap thinking maybe the vent was clogged, but I heard nothing. I've been riding it back and forth to work, which is about 5 miles away every day since then, and I haven't had any problems. I'm not particularly experianced with engines so I'm more curious than worried, especially since it hasn't happened again, but what could it have been? I was thinking bad fuel or something, I always buy 91 octane and I didn't really think about people not buying premium fuel, so it was probably sitting in the res for a while before I pumped it, lol.

[burning1]

At 6200 miles, you're well overdue for a valve adjustment. You probably aren't going to ruin anything by going another 200 miles, but I'd do it ASAP. It's possible that your exhaust valves are already down to 0 clearance.

[tt_four]

I've heard people say you should always try to fill up at pumps that have separate hoses for the different types of gas. If it's just one hose, and you pick the best gas, you're really just paying the higher price for the last gallon or so of cheap gas in the hose. Not as bad if you're filling up 4 gallons, but I always fill at 100 miles, so I'm only getting 2 gallons to begin with.

Not sure about the bike problem though.

[burning1]

On a GS500, you should run 87 octane fuel. The 91 octane fuel burns slower and produces less energy by mass than the 87 octane stuff. The only time it's really beneficial is when you have an engine for it, where lower octane stuff causes knocking, or causes the ECU to retard ignition timing.

[Electrojake]

I was coming home from my parents house last week, which is about 200 miles away, and I was doing 85 on the interstate @ ~7k RPMs in 6th, when the engine sound changed and sounded much deeper, and I began losing power. I downshifted by the engine would not rev above 7k for about 3 minutes, it then cleared up and I was fine for about 45 minutes, at which time it happened again.

For what its worth. . .
See the 14th post down on page one of this thread. It was posted by gsJack.
http://gstwins.com/gsboard/index.php?topic=52255.0

He poses a fascinating concept on loss of power at high speed.
I have had similar issues at sustained high speeds (80+ indicated) in windy conditions on my 07 GS500F.
It has never happen on a burst of high speed, just sustained high speed.
-Ej-

[kylegod]

On a GS500, you should run 87 octane fuel. The 91 octane fuel burns slower and produces less energy by mass than the 87 octane stuff. The only time it's really beneficial is when you have an engine for it, where lower octane stuff causes knocking, or causes the ECU to retard ignition timing.

under my seat, on my 98 gs, on the fender, it says run 91 minimum. dunno what year you have, but you might wanna check.
 

My 98 runs perfect, no flat spots no fuel starvation, runs so good while riding. when coming to a stop, the engine bogs and wants to die. at every stop or light i have to hold my throttle slightly to keep it at 1200+ rpm. From what Ive read on here and elsewhere, this could be a valve problem? specifically a tight exhaust valve?

Carbs are fine, new jet kit, good float level, clean, etc etc. Not carb issue. I have Yet to do a leak down test, but a compression test showed 110psi and 117psi. bike has 21K on it and really doubt that its had a valve check. I bought it used, and from what i know about its history, its been bought and sold quite a bit.

So after that info, my main questions is:  Could the low compression and lack of idling be due to valves, and more specifically a tight exhaust valve?

Didnt mean to overtake this thread with my situation but didnt want to start another valve thread... thanks in advance

[burning1]

I'll check, but to be honest, where I ride, 91 is the lowest octane rating you can buy.

[007brendan]

I'll check, but to be honest, where I ride, 91 is the lowest octane rating you can buy.

Do you live in America?  Cause '87 is basically available everywhere here.  Pretty standard octane for low-test.  I remember back in the 90's some places even sold 85; and 93 was popular, too.  But anymore it's basically 87, 89, and 91.

[Toledo Jim]

He's in California, they do everything the most difficult and expensive way possible. 

[the mole]

So yea I know, another damn valve adjustment post, but anyway...
I'm at about 6,200 miles and haven't checked my shims yet, should I do it asap or am I okay for another few hundred while I order the correct shims so I don't have to buy an entire kit?

You can answer this one yourself, because before you can order the correct ones, you have to pull the cover and measure the clearances. If they're not too tight, you're OK for a few more miles. If you can't get your thinnest feeler gauge in there, and the bucket doesn't want to rotate, its too tight and you shouldn't ride it if you want your valves and seats to last.

[kylegod]

Would tight valves cause the bike to not hold and idle and cause poor compresion?

[pandymai]

Would tight valves cause the bike to not hold and idle and cause poor compresion?

yes it can.

[kylegod]

Thanks. Just so I understand...is the low compression and poor idling due to air/exhaust leaking from the slightly open valves since they're too tight? Does this make sense?

[pandymai]

that could very well be it. the valves arent seating properly and completely between cycles.

[burning1]

Do you live in America?  Cause '87 is basically available everywhere here.  Pretty standard octane for low-test.  I remember back in the 90's some places even sold 85; and 93 was popular, too.  But anymore it's basically 87, 89, and 91.

Race bike. At the track, pump gas starts at 91 unleaded, and goes up to 116 octane.

[Electrojake]

Just so I understand...is the low compression and poor idling due to air/exhaust leaking from the slightly open valves since they're too tight? Does this make sense?

Just check the lash and be done with it, no?

[burning1]

Hint: Your valves will go out of adjustment long before you notice anything wrong with the engine. Don't put off the adjustment, do it according to schedule. It's a fairly simple procedure on this bike, and could be finished in an evening if you've done it before.

[kylegod]

...done in an evening if you have a pile of shims laying around...otherwise expect a week or so out of commission to measure what you need and order them.

[burning1]

...done in an evening if you have a pile of shims laying around...otherwise expect a week or so out of commission to measure what you need and order them.

And if you're smart... When you're done, order the next size down for every shim on the bike, so that the next time around, you can do it in an evening the next time around...