Almost There! Running great, but 1 carb ques.

[Surly]

The 78 GS1000 is running well once again. Pulls frighteningly strong. Revs up with nary a hiccup. But I wanted to get some opinions on a carb issue.

When idling in the garage, if I "blip" the throttle, you know, just snap it open real fast, the bike tries to die. But, if I roll the throttle on quickly, it revs up real strong. So, it isn't what I'd necessarily call a problem I can't live with as performance is plenty good, but if I can improve the performance I am going to.

The airbox is on. Air flliter in place (K&N type cotton filter). Carbs are clean and bench synced only. New petcock. Jetting specs are all stock, except I have turned the air screws on the side of the carbs in a quarter turn. I thought this might be an air rich/fuel lean scenario and this seemed to improve the condition a small amount. However, I live at 4500 feet so jetting may be a little rich. The plugs are dark, but should be replaced.

Thoughts? Thanks in advance.

[grips11]

not to sure about your question there but when I try starting my bike after its been sitting for a couple of days and its cold and I snap the throttle really quick, it will try and die as well. More often then not it does die. However I let the bike warm up in Neutral for about 3 to 5 mins, let the bike get hot and snap the trottle then I get nice engine response. I tend to think its because the engine is cold and the fluids inside are still working there way around the engine. That might be way the engine stalls on a cold bike. Maybe that helped...maybe it didn't. \\/

[renobruce]

Set each air screw at highest RPM. Vacuum synch your carbs. A quick blip will cause a hesitation, even on well-tuned VM carbs. Get the carbs adjusted and synched and do some chop tests at minimum, 1/3, and full throttle to see if you are running rich.
I'm at 5,200 ft., and both my bikes run a tad rich by choice. I can then drive at lower altitudes and not worry about running too lean, which is not good for your engine.

[Surly]

So that's where the Reno in RenoBruce comes in.

Set each air screw at highest RPM. Vacuum synch your carbs. A quick blip will cause a hesitation, even on well-tuned VM carbs. Get the carbs adjusted and synched and do some chop tests at minimum, 1/3, and full throttle to see if you are running rich.
I'm at 5,200 ft., and both my bikes run a tad rich by choice. I can then drive at lower altitudes and not worry about running too lean, which is not good for your engine.

I'm just southeast of you in Ogden, UT. Thanks for the info, I'd forgotten about the air screw/RPM adjustment from the carb repair series. I'll need to locate a sync'er.

Have you changed your stock jetting for the altitude? Sea level jetting should have us both pretty rich, but like you say, not a bad thing if you ride at a lower elevation.

[renobruce]

Have you changed your stock jetting for the altitude? Sea level jetting should have us both pretty rich, but like you say, not a bad thing if you ride at a lower elevation.

My 1150 is all stock, no jetting changes. My 1000 has K&N individual filters and a V&H 4 into 1 pipe. I re-jetted using a dynojet kit and some help from Keith Krause with setting them up for altitude.

In my opinion, if your bike is stock with a stock airbox, you shouldn't need to re-jet. You should be able to dial your carbs in using the stock parts. It may run a tad rich, but that's OK.