HELP! 1980 GS850G Starts, but stumbles-Pops-won't rev??

[Darin Jordan]

Well guys... THANKS to the help I received here, she's no longer a garage queen!

Got everything back together today, and took her for a ride. Felt GREAT!

Still need to officially balance the carbs, and get a few details buttoned up on the fuel system, like adding some quality breathers for the vents and crankcase breather line.

Seems to run pretty good, though it seems to get really lean from around 6500+. Kind of stutters, flutters, pops a bit up there. Pulls nicely to that point, however. Will need to work to figure out what's causing that. Any thoughts or advice on that would be appreciated. Current jetting is per the DJ Stage 3 Jetting kit, 3rd groove on needle with 165 mains. Floats are set right at the recommended 22.4mms. Should I have adjusted that for the larger jets?

Also, I noticed that, when I first set the fuel petcock to prime, I left it on a little too long. Fuel was coming out of the #2 carb's main air jet (2nd carb in on the right side??) If the float needle was working properly, would't the fuel stop filling the float bowl once it's full?

I rode the bike around for about an hour, went up and put fresh fuel in, and didn't notice any more fuel doing this with the petcock on "on", and other than the bike seemingly leaning out above 6500 (just shy of 7000, actually), it seemed to run fine, started right up, idled nicely, etc.

OH, and the front brakes are SOFT! Definitely need to work on that. Feels like the pads are dragging a little, and they may be glazed. They almost feel non-existant at this point.

Here are some pics from today:

[Steve]

Seems to run pretty good, though it seems to get really lean from around 6500+. Kind of stutters, flutters, pops a bit up there. Pulls nicely to that point, however. Will need to work to figure out what's causing that. Any thoughts or advice on that would be appreciated. Current jetting is per the DJ Stage 3 Jetting kit, 3rd groove on needle with 165 mains. Floats are set right at the recommended 22.4mms. Should I have adjusted that for the larger jets?

The float level remains the same, regardless of what else you have done.

Stuttering at 6500 rpm does not mean much unless you also say what the throttle opening was.
- If it was barely open while running in neutral, you were still sort of on the pilot circuit because the throttle wasn't open very much.
- If it was while holding it there in second or third gear, you might have been at half throttle, meaning the needles were in play.
- If it was while acellerating wide open, it would have been the mains that need attention.

Also, I noticed that, when I first set the fuel petcock to prime, I left it on a little too long. Fuel was coming out of the #2 carb's main air jet (2nd carb in on the right side??) If the float needle was working properly, would't the fuel stop filling the float bowl once it's full?

Carbs are numbered from left to right, as you sit on the bike. #1 is under your clutch hand, #4 is under your throttle hand.
ALL references to "left" and "right" are made that way.

And, no, the float does not always stop the flow of fuel. There could have been a little speck of dirt keeping the needle off its seat. It could have been just a little off-center. (The vibrations of a running engine will usually center it.)

OH, and the front brakes are SOFT! Definitely need to work on that. Feels like the pads are dragging a little, and they may be glazed. They almost feel non-existant at this point.

Have you done anything to them yet?

At the very least, you should have cleaned out the master cylinder and the calipers, as well as changed the fluid. Considering that the Suzuki manual suggests changing the rubber brake lines every 2 years, I would guess that they are about 29 years overdue.

Here are some pics from today:

Very interesting color scheme. I like it.

.

[Ranger]

Looks good,

It might have been a stuck float allowing fuel to leak but I don't know. Being lean at those rpms baffle me, it would be lean somewhere else on the power band but I don't remember the jets that are used during different throttle ranges.

Glad the weather held up, not looking good for my drive.

Bleed your front brakes, it'll help. Mine stop with one finger, trick is to feather the brake lever while you're bleeding because air bubbles will stay behind the master cyl.

[Darin Jordan]

Have you done anything to them yet?

At the very least, you should have cleaned out the master cylinder and the calipers, as well as changed the fluid. Considering that the Suzuki manual suggests changing the rubber brake lines every 2 years, I would guess that they are about 29 years overdue.

Nope... not yet, but it's next on my list. I'm planning on new Stainless braided brake lines, and some good brake pads as well. Looking to get a new master cylinder resevoir. Current one isn't leaking or anything, but it looks weathered.

Now that I know it runs, the rest is tinkering and weekend projects I think...

As for the running, the stumbling would occur when cruising along at say 3000, and opening up the throttle to get up and go. Would pull fine through 6500, then start stumbling. Reading through the Dynojet tip sheet now...

[Steve]

Looking to get a new master cylinder resevoir. Current one isn't leaking or anything, but it looks weathered.
...

I just replaced the one on my 850. Best price I found for the reservoir kit was Parts-n-More. I also got the rebuild kit and o-rings for the calipers.

.

[Darin Jordan]

OK guys... You were right...

Woke up this morning to a house full of fuel odor. Fuel petcock rebuild was a failure... Gas was overflowing out of a couple of the carbs. Got a fuel can and disconnected the fuel line, connecting another to drain the tank. Fuel freely flows right on through.

Not sure if I rebuilt it wrong, or if it was just a bad quality rebuild kit. Was a "K&L" kit.

I've read here that this is may be a typical problem and that a new petcock is the only cure. REALLY? What is it about rebuilding one of these that is so touchy? Seems pretty simple inside. Is it just a bad kit? Can a petcock be rebuilt successfully, or should I just pop for a brand new one??

The wife was NOT happy to be awaken at 4:00am to that smell in the house (split level, garage is just below the bedrooms...). SHE wants this fixed right!

[Darin Jordan]

I just replaced the one on my 850. Best price I found for the reservoir kit was Parts-n-More. I also got the rebuild kit and o-rings for the calipers.

.

Thanks... I'll check that out.

[Darin Jordan]

AND... Just so I have this straight... even with perfectly funtioning floats and needle&seats, it would still be "normal" for the float bowls to fill up while not running the bike, and fuel to start coming out of the needle-jet, etc??

That just seems so counter-intuitive to me, since the purpose of the needle&seat and floats is to stop the carb from filling up any further.

I'm asking, because I'm tempted to just put in new needle&seats and floats. However, they all looked and functioned fine on the bench. They are metal tipped needless and looked shiny and new, and the floats, well, floated...

Just double checking so I don't have to spend money on something that isn't broken.

I need to add a "BassCliff" style signature to my profile that says "Thanks for your PATIENCE!"

[Ranger]

AND... Just so I have this straight... even with perfectly funtioning floats and needle&seats, it would still be "normal" for the float bowls to fill up while not running the bike, and fuel to start coming out of the needle-jet, etc??

That just seems so counter-intuitive to me, since the purpose of the needle&seat and floats is to stop the carb from filling up any further.

I'm asking, because I'm tempted to just put in new needle&seats and floats. However, they all looked and functioned fine on the bench. They are metal tipped needless and looked shiny and new, and the floats, well, floated...

Just double checking so I don't have to spend money on something that isn't broken.

I need to add a "BassCliff" style signature to my profile that says "Thanks for your PATIENCE!"

I rebuilt my petcock, mainly I bought a stiff spring from the store and cut it slightly shorter than the original then stretched it and replaced the o ring and no problems. Bike creates enough vacuum to overcome the extra force with the springs I chose.

The bowls will fill up if you're leaking fuel yes because the floats will prevent fuel from flowing into the carbs but for how long is a gamble as you found out.

My temp solution was I put a shut off valve into my fuel line to prevent leaking guaranteed until I got around to fixing my petcock.

[Darin Jordan]

Figured out what was wrong with the petcock rebuild.

Removing the dial, it was apparent that the plunger with o-ring on the diaphram was not extending far enough into the petcock to make a seal. Wasn't even making contact.

I took it apart and looked it over. I suspect that the metal disc on the backside of the diaphram was warped a tad, and was bend slightly backwards (toward the inside of the bike), preventing the plunger from reaching deep enough into the petcock hole. It came this way, so I suspect it happened during packaging or just through the normal production process.

I have fixed it, I believe, by drilling a 1/2" hole in a piece of hard wood, covering the wood with a piece of packaging tape to protect the rubber, and then, with the plunger side down inside the hole, using a small drift to tap on the backside of the plunger and gently bend the disc back into the correct position.

I verified fitmet by removing the dial, and mounting the diaphram, then looking inside the center of the petcock to make sure the plunger was aligning correctly and was centered and seated. It was, so I buttoned everything back up.

I also gave the spring a little stretch to increase it's preload a little. A slightly stiffer spring may ultimately be in order, but it seems to work now. I gave it the "suck test" and it feels like it's now sealing. Will reassemble onto the bike and find out.

I may install a second fuel shutoff, just to have the backup for longer storage, but we'll see how this works.

[Darin Jordan]

Seems I've transitioned my troubleshooting info to this thread...

http://www.thegsresources.com/_forum/showthread.php?p=1369210#post1369210