78GS1000 won't idle after running on highway a long distance

[Anonymous]

OK my friends,

Here's a good one for the collective...

I have a pretty much stock 78 GS1000 that I've been occasionally commuting with to work for the past year (about 5 miles one way). The engine runs great at this time. Acceleration/idling is fine.
However, I took the bike for a +/- 250 mile roadtrip last Saturday and after each leg of about 60 miles long doing 60-70 MPH the engine would not idle (stalled). So, adjusted idler screw. The idle needed adjusted higher evrytime I stopped.
The condition of the bike is still all original - even the exhaust - and has 23,000 miles.
I cleaned the whole bike up last year including coating the inside of the tank and adding a fuel filter. I also had the carbs sync'd and checked all the valve clearances. The carb boots and air box are in good condition, no dry rot or cracking.
The only reason I can think of this happening is the float level might be too low. However this was also checked and set last year using a Chilton's shop manual.
If anyone has any ideas or past experiences with this, I would sure like to hear from you.

Thanks, 3catfamily

[KEITH KRAUSE]

Hi. I think it's running rich. A lean condition usually makes the idle higher.
Make sure the air filter is clean. Then try adjusting the side air-screws out 2 1/2 turns. If they have never been touched,be carefull of stripping the head. Use a good fitting screwdriver and seat them lightly and then adjust out. I have heard of this problem before on longer trips,especially in higher elevations. The bikes would sometimes start if the throttle was opened more than usual(which is the same as adjusting the idle screw).
Also,spray some carb cleaner in the gas cap vent,just to be sure there is no vacuum problem. These are the easiest things to do. If you still have a problem,try a plug read when it is doing this. You may have to have carbs cleaned. If it is running lean as you think, and everything is stock,and considering the things you have checked, then a cleaning might help.
PS: An easy test if problem is lean related. If you take the bike on another long ride,see if giving it just a bit of choke stops the stalling. If it does it's obviously lean. But like I said,I still think it's rich. Keep us posted. KK.

[Anonymous]

I'm having a very similar experience with a 400 Bandit. I suspect it's running very rich because it'll start without choke (that's saying something in the middle of an Irish winter) and the exhaust stinks of petrol. It runs fine but cuts out on a closed throttle. I'll be taking the carbs off to check and clean up - they're leaking anyway. I'll keep you posted in case it helps.

[Anonymous]

Thanks for all the input.

I checked the settings on the carb. The air-screws are turned out 3/4 turn for the outside cylinders and the inside screws have about 1 1/4 turns on them.
I will be taking the bike in for carb-sync/smog tune-up (yes, here in Phoenix this bike needs a smog check every year!) this Saturday and talk about these settings in more detail with the Motorcycle Tech. I had the same shop sync. the carbs last year and have not touched them since.
I also will look at the O-rings in the cylinder head intakes that was mentioned in another post here on the forum.

Cheers, 3catfamily

[crag antler]

(that's saying something in the middle of an Irish winter)

So what does a Irish winter feel like?
I know here in Vermont on the Green Mountains,winters are cold,cold cold..., Snowy,windy and grey.About 6 months total NO riding. 8O
I know for some of you die hards/Canadians, that's nothing. 8)

But little ol me, being nothing but a Florida boy. I don't ride below 40 8O

[redliner1973]

my Carb boots looked pretty good too, until I removed them and replaced what was left of those O - Rings. you would be suprised what probs they will cause, and what they look like after 20 years! :twisted:

[KEITH KRAUSE]

Thanks for all the input.

I checked the settings on the carb. The air-screws are turned out 3/4 turn for the outside cylinders and the inside screws have about 1 1/4 turns on them.
I will be taking the bike in for carb-sync/smog tune-up (yes, here in Phoenix this bike needs a smog check every year!) this Saturday and talk about these settings in more detail with the Motorcycle Tech. I had the same shop sync. the carbs last year and have not touched them since.
I also will look at the O-rings in the cylinder head intakes that was mentioned in another post here on the forum.

Cheers, 3catfamily

As a rule of thumb,the side air-screws should be adjusted to achieve the highest idle and if it's a bit high you adjust the idle screw for final setting.
It's easier to hear the idle pick up or level off if you adjust 2 at a time at 1/2 turn increments. I don't think your settings are correct,they're too rich
and they should not have to be 1/2 turn apart(2@3/4 and 2@1 1/4). Even on old Chevy's,etc,you always adjusted the air-screw for highest rpm. The only times you should have to make temporary changes
(maybe a 1/2 turn in or out)is if you're riding in the desert or high elevations. You can't always trust a mechanic's opinion. Keep us posted. KK.