I've been experimenting for the past two weeks on shortening my warm-up times to the Manufacturer's suggested 30-second full-choke warm-up.  While my bike has 40 non-bleed pilots, it's still a little hesitant after riding away, but slipping, or feathering the clutch is easy to do to compensate.  I have noticed more responsive throttle response and an extra 5mpg added to my fuel mileage.  I'm also hoping to avoid the carbon build-up that I encountered when I did my top-end.

I'm rejetting my bike this weekend and going to be tweaking everything to try to do the same.  What did you play with to get it shorter and better MPG?

I've been wondering about the varying differences of the warm-up time from reading other threads. My bike has a warm-up time of 10-15 minutes for a steady idle. Is that an excessive amount of time? For a water-cooled bike it's like 30 sec to a minute or 2. From reading the other threads, there are people who manage less than half the time of my bike, which is stock. I find the range of times posted by others to be kind of wide. This is the thing that's really bugging me - why the reported warm-up times are so broad.

I'm puzzled. My bike has a long warm-up time even though it easily starts up in 1-2 engine turns.  I have to hold the throttle/revs up while I break for traffic lights when heading out no matter the atmospheric temp.  Bah....

I recently switched from a stage 1 dj kit to richer 145 mains and noticed that my warm up time has increased.  Would leaner jetting make for a shorter warm up time?

My bike is stock (as far as jeets) and my warmup is  about 30sec - 1min  Always have done it that way. I even adjust the choke down a bit so that the fast idle is about 3K, 30sec-1min later... Ready to rock 

I've had my jetting changed out for a while now.  Warm up used to be about 5 minutes, now on a cold morning it's about 30 seconds to 1 minute.  I have 140 mains (I think it's still a little lean), 40 pilots, and DJ needle on clip #2.  Also have a lunchbox filter.  Don't know MPG's yet, but I'm not too worried about where ever that it, cause no matter what it's better than the 13 MPG that I get with my truck.

Quote from: scottpA_GS on December 17, 2007, 07:53:02 AM
My bike is stock (as far as jeets) and my warmup is  about 30sec - 1min  Always have done it that way. I even adjust the choke down a bit so that the fast idle is about 3K, 30sec-1min later... Ready to rock 

I 2nd your experience, stock bike as well. It'll warm up for ~30 sec, maybe with choke half on while I finish putting my gear on, I take off slowly and within another minute or so, I've got the choke off, idle is stable (although a bit low), and it's running good. Another couple minutes and the idle's right where it should be. Unfortunately I can offer no advice as to why it would take 10 minutes!

   I had a 1980 GS450ST that I bought new in 1980. That bike was overly lean also, and in cold temps acted like it just wouldn't warm up fullt. I was able to just shim the needles and that ended the proble, and I didn't even lose any gas mileage (that bike got about 65mpg).
    Jon

My 2001 is stock and in sunny SoCal it takes a minute or so at full choke and another at half before I can move it to 1/4, for another, then take the choke off and let it idle as I finish gearing up. It will NOT let me even touch the throttle or it dies, for at least 5 minutes total I think, I'll have to time it. Then another minute of gentle revs until I can get a consistent throttle response (meaning it doesn't stall with even a gentle rev), then it feels safe to take into traffic, but I rev it up and feather the clutch with care for the first five minutes out. It pops in the exhaust too when cold. On a "cold" day here recently we stopped for about 20 minutes in a coastal park, windy, and the bike cooled down enough that I had to just sit on it and let it run for a couple minutes to get it up to an operable temp again, because when I'd roll on throttle it would die. We're figuring dirty carbs...? And/or a vacuum leak...?
My hubby says it runs like an old two stroke; either nothing or full on, he's never seen a four stroke act like this bike. But he still thinks it's a sweet ride, now that he's had it out himself. But we want to get that low RPM stumble gone.

If warmup times are a problem, check your muffler. The previous owner may have drilled holes into the can (around the exhaust tip) to make the bike louder. Unfortunately, it also increases the airflow, making the already lean carburetor jetting even worse (if I understand things correctly). There are a few recent threads that cover this issue, so check them out.

Yup, have the mufflerectomy mod, but all the drilled holes are plugged with brass hex head screws, only two missing.. should I plug them???

Quote from: scottpA_GS on December 17, 2007, 07:53:02 AM
My bike is stock (as far as jeets) and my warmup is  about 30sec - 1min  Always have done it that way. I even adjust the choke down a bit so that the fast idle is about 3K, 30sec-1min later... Ready to rock 

not me. need a good 5 minutes to get her going

Quote from: Teek on December 31, 2007, 01:53:37 AM
Yup, have the mufflerectomy mod, but all the drilled holes are plugged with brass hex head screws, only two missing.. should I plug them???

Well, they weren't accounted for when the engineers designed the bike, but who knows if just two will make a difference? I plugged mine yesterday (3 unevenly spaced holes remain, as the #14 Robertson metal screw heads interfere with placing more) while adding fuel stabilizer to the tank, just to see what the results might be. That, and I needed to hear the twins again--even a mild winter in Toronto requires you sit out four months of riding every year. The results were inconclusive, partly because the cold start was exactly that, 0 degrees. It took the GS a good 10 minutes, most of it on choke, belching out water vapour, to achieve a stable, off-choke idle.   

Thanks for the feedback, I need to be off to a hardware store anyway, if I find something to plug those with (I want them to match, natch) I'll post back if I notice a difference, but I wouln't think it would be much..?