83gs750e dies at 3500rpm every gear

[Nessism]

No.
The bike used to work fine, then towards the end of last it year started doing this out of the blue.

We figured the carbs were just dirty so we pulled them apart and cleaned them and fixed a small issue with the petcock.

Unfortunately none of that made any difference at all.

Did you rejet the carbs to run without the airbox?

[rABIDwOLF]

What issue with the petcock? And what happened to your airbox? You have pods now? Jet kit? Did you replace the petcock? its possible your fix didnt really fix it, and now you're starving the carbs.. that's probably right about where you'd notice it too... Just bouncing other, simpler to fix possibilities out there..

The diaphram in the petcock was shot to hell.. it was all crunchy. ordered a replacement and replaced it.

like i said the issue was before we did that. bikes essentially the same as last year when the issue cropped up on a trip from michigan to illinois

[rABIDwOLF]

You should be able to see the advance kick in with a timing light. There's no gradual curve, above 3,500 rpm you'll see the timing jump as you give it gas.

so...anything special on how to use a timing light?
never used one before

[TheCafeKid]

The diaphram in the petcock was shot to hell.. it was all crunchy. ordered a replacement and replaced it.

like i said the issue was before we did that. bikes essentially the same as last year when the issue cropped up on a trip from michigan to illinois

Well, not to sound like a jerk, but GENERALLY, the petcock rebuild kits that are sold either dont work, or only work for a while. Rebuilding them, as most have found, is at best a temporary fix. Id start by assuring that your petcock is functioning properly. Remove the line from the tank, and using a secondary piece of fuel line, set the petcock to prime and see if fuel flows freely. If so, THAT part of the petcock is good. Then, you could either reinstall your fuel line, leave the petcock in the prime position and take the bike out and see if the bike still has your problem. If not, you know that the ON or Reserve position in the petcock is NOT working properly. If it DOESNT solve your problem, we'll move on to the next possible issues...

[rABIDwOLF]

Well, not to sound like a jerk, but GENERALLY, the petcock rebuild kits that are sold either dont work, or only work for a while. Rebuilding them, as most have found, is at best a temporary fix. Id start by assuring that your petcock is functioning properly. Remove the line from the tank, and using a secondary piece of fuel line, set the petcock to prime and see if fuel flows freely. If so, THAT part of the petcock is good. Then, you could either reinstall your fuel line, leave the petcock in the prime position and take the bike out and see if the bike still has your problem. If not, you know that the ON or Reserve position in the petcock is NOT working properly. If it DOESNT solve your problem, we'll move on to the next possible issues...

The only thing that was replaced on the petcock is the diaphragm that limits the gas...the previous one had giant holes in it and was passing gas through to the vacuum line.

So we replaced it. The gas is flowing beautifully on Prime, On, and Reserve. I tested all there settings to make sure it was getting good flow through going on. So it has seemed to work fine since our replacement.

And like I said the problem existed before the part was replaced.

[TheCafeKid]

The only thing that was replaced on the petcock is the diaphragm that limits the gas...the previous one had giant holes in it and was passing gas through to the vacuum line.

So we replaced it. The gas is flowing beautifully on Prime, On, and Reserve. I tested all there settings to make sure it was getting good flow through going on. So it has seemed to work fine since our replacement.

And like I said the problem existed before the part was replaced.

Ahh ok, missed that part. Ok so, you have no airbox. Do you have pod filters? And if so, did you install a jet kit?

[blowerbike]

GS vaccum carbs shut off around 4k when the air box is removed and the carbs are not rejetted/jet kitted.
they will free rev but bog badly when under a load.

[rABIDwOLF]

Ahh ok, missed that part. Ok so, you have no airbox. Do you have pod filters? And if so, did you install a jet kit?

He bought the bike from a mechanic guy about 4-5 years ago and the guy had rejetted the whole thing and it ran pretty good.

I'm not sure the exact size of the jets in there its been awhile since I looked I know they are not stock however.

The issue didn't crop up until the end of last season so he got a good 3+ years out of it and a good amount of miles before this popped up out of the blue.

[TheCafeKid]

He bought the bike from a mechanic guy about 4-5 years ago and the guy had rejetted the whole thing and it ran pretty good.

I'm not sure the exact size of the jets in there its been awhile since I looked I know they are not stock however.

The issue didn't crop up until the end of last season so he got a good 3+ years out of it and a good amount of miles before this popped up out of the blue.

Hrmm If its jetted, and ran well and now all of the sudden it doesnt, I'd start looking at your electronic advance like was suggested in the first place. Im no expert by any means, but I just cant think of what else would cause the bike to fall on its face like that if everything else was running fine before..

[blowerbike]

stop by and i'll plug a known good ignitor box in and see if that fixes it
i'm waiting

[rABIDwOLF]

Hrmm If its jetted, and ran well and now all of the sudden it doesnt, I'd start looking at your electronic advance like was suggested in the first place. Im no expert by any means, but I just cant think of what else would cause the bike to fall on its face like that if everything else was running fine before..

That's what had me massively confused. Ran good then one day just started having issues.

Figured it was just dirty carbs (that's the usual suspect) and when that wasn't it got really confused.

Then the whole it working fine in neutral but having issues under load just confused me more.

I've never worked on one with an electronic advance so once we get our hands on a timing light it sounds like we should be able to tell easily if thats the issue.

If that is the issue do we just replace the whole igniter unit or is there something we can tweak?

Also I could really use some tips on how to use a timing light, never used one before and advice would be appreciated.

[TheCafeKid]

stop by and i'll plug a known good ignitor box in and see if that fixes it
i'm waiting

Well if his ignitor was bad, would it run at all? I had always read that the ignitors were pretty much a work dont work proposition??

[rABIDwOLF]

stop by and i'll plug a known good ignitor box in and see if that fixes it
i'm waiting

HA! I wish I was a little closer and I would do just that

[TheCafeKid]

That's what had me massively confused. Ran good then one day just started having issues.

Figured it was just dirty carbs (that's the usual suspect) and when that wasn't it got really confused.

Then the whole it working fine in neutral but having issues under load just confused me more.

I've never worked on one with an electronic advance so once we get our hands on a timing light it sounds like we should be able to tell easily if thats the issue.

If that is the issue do we just replace the whole igniter unit or is there something we can tweak?

Also I could really use some tips on how to use a timing light, never used one before and advice would be appreciated.

And you're ABSOLUTELY SURE you put the carbs back together EXACTLY the way they came apart. I am not trying to insult your intelligence, just making sure. One small mistake like the needle clip being in the wrong slot could cause a major difference like this..

[blowerbike]

oooooops..lol