GS1000G 1980 no midrange after about 15 minutes running

[Guest]

Last week my GS1000G would not take throttle while on a long ride. The next day I started it up and found #1 and #4 header pipes cold at startup. I rebuilt #1 and #4 carburetor. I found the #4 float to be stuck (no gas in bowl) and the #1 to have a clogged secondary. I road around the neighborhood about 15 minutes and it lost mid range again. The bike would idle fine and if I could get and keep it over about 5K RPM I managed to get back home. Next day it started fine again. It appeared all 4 header pipes were warming up nicely. Again after about a 15 minute ride I was scrambling to get home. The bike would idle fine. Bogged in the mid range but would clear up at about 6K RPM. Are there know issues with this bike that could be causing these symptoms? Could it be a coil getting hot? Diagram looks like #1 and #4 are same coil.


Valves have been adjusted. Carbs have been synced. Bike does have the 12V wiring fix to the coils.

[Nessism]

Maybe the fuel cap isn't venting like it's supposed to? Crud in the tank clogging up the carbs?
Did you do a proper full carb rebuild per the tutorial on Basscliff's site (and linked in my signature?)

PS: coils get a lot of false blame for running problems. If both 1-4 go out regularly it could be the case though.

[Steve]

If you bothered to take the carbs apart enough to "rebuild" #1 and #4, why did you not also do the other two?

On the other hand, that leads me to the assumption that they were not properly rebuilt, they only had some parts changed. Any shortcuts taken (in ANY project) are simply another opportunity to do it over and do it RIGHT.

.

[TowPilot]

No just cleaned #1 and #4 to fix the current issue. Been 256 miles since the rebuild of all four. No shortcuts taken. I am guessing you response is suggesting it sounds like a carb issue to you? Photo so you can see the carbs were taken to the bones. The 4th carb was spending the night in the can! CarbBath.jpg

Sorry the only photo I could find also showed the engine (which will probably result in more questions). And yes the boots where changed, o-rings replaced. How about those burnt wiring harness? also repaired and upgraded to the Polaris RR while replacing all of the crispy pieces.

[Big T]

Ignition ignitor may be going out
Test it

[TowPilot]

Geez found the issue!! Evidently not getting enough gas when the petcock is in the ON position. I switched over to PRI and no problems. I could kick myself for overlooking the easy stuff! It all makes sense now, drive around for a few minutes starts to sputter (burned the reserve in the carb bowls) would get enough gas to idle but not enough to accelerate. Let it cool off (actually allowing time for the carbs bowls to fill back up due to the restriction) would run fine for a while. rinse-and-repeat.