Quote from: adidasguy on March 01, 2012, 02:19:36 AM
OK. So before you go ripping things out and changing things, why not ask a parts whore if you could try a new petcock or two then see if it works? Then  return it or pay for it? A couple petcocks is $5 postage in a flat rate box.

Unless there us a design improvement, I feel we should replace parts and make things work as designed.

We have a few parts whores here. Not always necessary to deal with ebay or BikeBandit.

There are ways to test a petcock. maybe I should do  a video this weekend? Need to re-shoot some scenes for the electrical system. Could shoot petcock testing.

We should be working together in swapping parts to get bikes working with OEM parts  rather than having parts sit on the shelf or hack things into something of a completely different, untested design.

BTdubs-

I never replaced my petcock because I thought that every one would fail, though I was under the impression that the GS500 line was wanton in its rate of flow as whole.

I replaced it because I wanted manual control of my fuel flow, and fewer rubber things moving vacuum around the bike, that when they fail, and rubber does, it will wreak sudden havoc. I live in florida, land of the sun, heat, 130% humidity, salt, and pretty much everything that can kill an automobile. The more I fool proof the thing, the better I feel.

And yeah, because I'm that guy.

Quote from: adidasguy on March 01, 2012, 02:19:36 AM
OK. So before you go ripping things out and changing things, why not ask a parts whore if you could try a new petcock or two then see if it works? Then  return it or pay for it? A couple petcocks is $5 postage in a flat rate box.

Unless there us a design improvement, I feel we should replace parts and make things work as designed.

We have a few parts whores here. Not always necessary to deal with ebay or BikeBandit.

There are ways to test a petcock. maybe I should do  a video this weekend? Need to re-shoot some scenes for the electrical system. Could shoot petcock testing.

We should be working together in swapping parts to get bikes working with OEM parts  rather than having parts sit on the shelf or hack things into something of a completely different, untested design.

Doing this will also be a valuable learning process for all of us regarding the parts in out GS500's. I have a few bikes to look at and a lot of spare parts. We parts whores would serve the community by loaning pout extra parts to see if that fixes their bike. If it does, then they can pay for the parts. If it doesn't fix it, return the parts. Documenting what happened will add to the loads of knowledge for the WIKI.

Well, sorry Adidas, I just really didn't think to ask. I feel like you've already been very generous to me and I guess I felt like I might be taking advantage of you.

I guess it also really didn't even occur to me that you would have an extra one. 

I wasn't able to test my theory by running it on reserve (rain). I'm still out of town, but I've got my bike with me, so on my way home I'll see if it'll run fine on reserve. If it does...then I will again check other things. Then, if it doesn't work, I can safely say it is the petcock and I'll buy one from you.

Thank you Adidas, once again, for your generosity.

Time to revisit this.

I rode home today. On the highway in 6th gear with the motor steady at 6k RPM +/- 100 RPM, it took almost exactly 20 miles before the issue arose this time. The difference was I had it on "RES" instead of "ON" and it seemed less severe. I switched to "PRI" while riding and it immediately stopped acting up. I rode another 60 or so miles and then stopped for lunch. Upon dismounting the bike I switched it to "RES" so it wasn't sitting on "PRI". After lunch I put it on "ON" instead of "PRI" by mistake and I didn't make it half a mile down the highway before it really started acting up. It was bucking and acting like it was running out of gas. I thought 'Oh, great...now it's f%$king up on PRI TOO??'. I stopped, looked down at the petcock and realized my previous error and switched it to "PRI" and all was well from there on out.

I guess I'll be replacing the petcock, or at least opening it up to inspect it. Considering there isn't a spec of anything in the tank, my guess is the diaphragm has bit the dust. I also triple checked the vacuum line and it's producing a very strong vacuum and it's completely on the carb and petcock.

Guess it's time to call on Adidasguy once again!

Quote from: Funderb on February 28, 2012, 11:53:49 AM
since burning1 is on top of the breather,

Remember, every time you open the throttle, you will cause a drop in manifold pressure proportionate to the throttle opening.

Not that it adds anything to the discussion, but...when  you open the throttle, the manifold pressure goes up not down...

In theory, if the throttle is wide open and no restrictions, the manifold pressure would be 29.92 in hg (ambient... if weather is "standard")

as you close the throttle, (when bike is moving) the manifold pressure would be less...less than ambient...the throttle "throttles" the air by restricting the flow of air...the iston is sucking, but the throttle is holding back the air..hence less pressure....if throttle is wide open, piston sucks and get lots of air...almost ambient pressure....

some call this vacuum.....really it is simply lower than ambient pressure....(manifold pressure cannot be negative)......

running at low speeds in high gear at wide open throttle will cause high manifold pressure.

Going down hill with throttle closed, in lower gear but high speed will cause low manifold pressure.

A good example (but most on this group are  probably not old enough to remember) is the car from the '60's which had vacuum operated windshield wipers......in the rain, if you floored the car, the wipers would just about stop wiping.... If you were going down hill with no throttle, the wipers would go like crazy!


Cookie

Had this issue once.  EVERY symptom pointed to fuel starvation.  Over the next month, I replaced the following in this order:  Started with the gas tank vent...no change.  Then the carb the vacuum line...no change.  Then went to the fuel line...no change.  Then replaced the Petcock...no change.

At this point, I was FED UP!  I was ready to take off the plate, scratch off the VIN, and deep-6 the bike into the Ohio river when it happened...The RH cylinder suddenly quit firing.  A quick diagnostics told me that the CDI-Igniter box went bad.  My symptoms all along were because the electronics were failing.  Only when it completely failed did it make total sense.

Wasted over $150 in NOS parts figuring it out.

Try a different petcock from Mr. Adidas.  Cheaper in the long run.

My 2 cents