Bike Dies while crusing, then eventually runs again

[JerbGas]

So I've been having an off and on issue with my bike.

When I first start her up for the day's ride, it turns over fine and warms up just like i'd expect. Then, sometime in the day I stop for one reason or another for about 10 minutes and then she doesn't want to start at all. Eventually does with some fiddling with the choke.

Then occasionally will slowly loose power and die while cruising at 65-70mph. Wait several minutes, barely starts and doesn't want to idle. After riding a bit more after this, come to a light and notice it wants to idle at 3000rpm. I then adjust the mix screw until its at about 1700. Then after a bit, now it seems like it wants to bog out at the light and i have to turn it back to keep it from dying.

Fuel filter is clear, although petcock MAY be going bad. I know it doesnt prime when set to prime, but once i manually prime the carbs and set it to run, i havent had to mess with it. Other than that I'm pretty sure its not an electrical issue since most of the electrical system has been replaced extremely recently. Carb boots are new, airbox is seated tight, air filter could probably use a cleaning though.

Anyone have this happen before? What did you do to solve it?

 

[Nessism]

That's the leverless petcock right? To get the prime to work you need a pulse of vacuum to open the diaphragm. The check valve in the back cover often fails though so I'd just replace it.

Tight valves are a common condition that can cause the issue you describe. How long since you last checked/adjusted the valves?

 

[tom203]

Get a new petcock for $50 and rule it out as a problem. Plus you don't need additional fuel filtering gizmos

http://www.georgefixs.com/1980-gs550-gs750-gs850-gs1000-gs1100-petcock/

 

[JerbGas]

That's the leverless petcock right? To get the prime to work you need a pulse of vacuum to open the diaphragm. The check valve in the back cover often fails though so I'd just replace it.

Tight valves are a common condition that can cause the issue you describe. How long since you last checked/adjusted the valves?

I actually havent checked the valves yet as I bought it recently. I guess its time to rule that out.

 

[Nessism]

I actually havent checked the valves yet as I bought it recently. I guess its time to rule that out.

Incorrect. It's time to do maintenance. Once the valves hang open and cause running problems they are likely to be damaged. Hopefully not seriously so.

 

[JerbGas]

Incorrect. It's time to do maintenance. Once the valves hang open and cause running problems they are likely to be damaged. Hopefully not seriously so.

no yeah i meant time to check them and such haha

 

[Nessism]

Get a new petcock for $50 and rule it out as a problem. Plus you don't need additional fuel filtering gizmos

http://www.georgefixs.com/1980-gs550-gs750-gs850-gs1000-gs1100-petcock/

I bought one of those petcocks off ebay and the check valve crapped out right away. Maybe it never worked, not sure. It looked almost identical to the OEM Suzuki petcock so I was surprised. Anyway, I ponied up an extra $25 for the Suzuki part the second time around and the petcock works like it should.

 

[JerbGas]

Anyone know if my bike is the 16v that I DONT need shims for?! Would be an early Christmas if so lol.

 

[JerbGas]

Nevermind, that was easy to google.

 

[chuck hahn]

Here. Now you wont need to google or guess.

http://zeus.mtsac.edu/~cliff/storage/gs/GS550_77-82_all.pdf

 

[JerbGas]

Here. Now you wont need to google or guess.

http://zeus.mtsac.edu/~cliff/storage/gs/GS550_77-82_all.pdf

I have a clymers manual but this will be a GREAT cross reference. THANKS!!!

Also - are shims something that my local bike shop would have on hand? Not exactly up for waiting 1-2 weeks for them to ship.

 

[Guest]

You may be lucky - why not ask them? If they don't, I believe Z1 are popular suppliers in your part of the world. Whichever way, if the clearances need doing, they need attending to quickly, or run the risk of doing serious damage to the engine.

Did you ask 'Steve' for a copy of his valve clearance spreadsheet yet?

 

[JerbGas]

You may be lucky - why not ask them? If they don't, I believe Z1 are popular suppliers in your part of the world. Whichever way, if the clearances need doing, they need attending to quickly, or run the risk of doing serious damage to the engine.

Did you ask 'Steve' for a copy of his valve clearance spreadsheet yet?

I have not, and with only a few days left to ride this year, the temptation to ride anyway is strong...but alas i wont...sigh.

 

[Nessism]

Download the factory manual for your bike from Basscliff's website and throw that Clymers manual in the trash. They site the incorrect valve adjustment instructions for one thing so do the job right and get a proper manual.

 

[JerbGas]

Okay so I started the bike up again today and did some troubleshooting to rule out any other possible causes other than the valves.

So...now it sputters and bucks in 1st and 2nd gear, not so much in 3rd and 4th,
and
Getting an RPM flutter regardless of RPM

I tried idling with the gas cap off, no change
I sprayed WD40 all around all the intake manifolds from the carbs to the engine, and on the connections from the carbs to the airbox....no change
Checked the plugs, not fouled but show a lean condition as they were a little white.
Checked to make sure the tank vent line wasn't blocked.

However, I assume the lean condition could be caused by the mix screw being set wrong to account for the bike wanting to ever so slowly bog out at idle on the "correct" setting.

I rode around the neighborhood and took it easy on her...Id come to a stop, adjust the air screw to get the rpms lower, then ride a few blocks and stop again, the RPM was back up around 2200....would adjust it down again...keep going....back up at 2200....adjust down...same result.

Still sound like tight valves?

 

[jsandidge]

What you've been adjusting is the idle adjustment screw, not a mix screw. There is only 1 idle adjustment screw, while there are mix screws on each carb. You should also get rid of an in-line fuel filter if you have one. These bikes didn't come with them from the factory, as they have a screen in the petcock and individual screens in the fuel inlet of each carb. Generally, those in-line filters are too restrictive and cause fuel delivery issues.

 

[Nessism]

Still sound like tight valves?

Not really. More like a bike that needs maintenance. Check my signature for the Newbie Mistakes thread. It will help guide you.

 

[JerbGas]

What you've been adjusting is the idle adjustment screw, not a mix screw. There is only 1 idle adjustment screw, while there are mix screws on each carb. You should also get rid of an in-line fuel filter if you have one. These bikes didn't come with them from the factory, as they have a screen in the petcock and individual screens in the fuel inlet of each carb. Generally, those in-line filters are too restrictive and cause fuel delivery issues.

dont have a in line filter like that. and okay, i thought i was adjusting the mix...what does the idle adjustment change then?

I guess I should take a look at the actual mix screws

 

[JerbGas]

Not really. More like a bike that needs maintenance. Check my signature for the Newbie Mistakes thread. It will help guide you.

I've read it...many times hahaha. And I've already done a lot to the bike. AND it WAS running fine before...the issue just gets gradually worse. Well, back to the drawing board hahaha.

 

[jsandidge]

i thought i was adjusting the mix...what does the idle adjustment change then?

It opens or closes the butterflies on all 4 carbs at the same time. They are all linked together. This will let more or less fuel and air into the cylinders. This has the same effect as twisting the throttle. Doesn't affect the ratio of air to fuel at all.