Second most common cause of cold starting issues

[Guest]

So it's gotten slightly chilly here in Arizona, and my '81 GS850G takes a fair amount of coaxing to start on cold (37°) mornings. I'm from New England, so say what you want, but my bike thinks 37° is cold, K? :-D

I tried it yesterday after it sat for about 24hrs. The temp outside was probably around 65° and she fired right up.

Anyway, I did my search and the threads I found all stopped with checking the valve clearances. I did that a couple of weeks ago, swapped one shim and everything seemed to be in order. At that same time I also replaced my fuel petcock and sealed up the airbox and replaced the airbox boots, which were all shrunken and leaky. My intake boot o-rings are also new.

I'm open to the possibility that I made a mistake on the valves, but assuming I did that correctly, what's the next thing I could try to help my cold starts?

[bwringer]

Where are your bike's idle mixture screws set?

I usually end up at about 2.5 - 3 turns out on an 80+ GS850, which makes the idle a bit richer than stock. This helps ease cold starting, and in hard riding in any weather, this smoothes out the off-idle transition quite a bit.

The bike should pretty much fire instantly in any weather, assuming reasonably fresh gas and all engine/intake/airbox issues have been addressed as you noted. I regularly ride in temps 25 degrees or so, and I've ridden in single digit temps several times.

[Roostabunny]

Hmmm, I'm not sure where they're set. My mechanic friend (with a sync tool) helped me with that, and it was the one of the first things he helped me with, so I didn't pick up as much as I would now. I wonder if he remembers...

Meanwhile, safe to say that we set them (back in October or so) with my old, shrunken airbox boots and leaky airbox seals. With my sketchy understanding of carbs, it seems that would lead to extra fuel once I sealed up the airflow, but maybe it's just the opposite?

Either way, I'll ask my friend. I'm planning a carb rebuild for Feb so I guess I'll be scheduling some time with him anyway for a set-up session.

In the meantime, would setting the petcock to prime help? I tried it the other day for a crank or two, but it didn't seem to help and made me nervous (was I going to flood the thing?), so I switched it back.

[Steve]

Priming it for 30 seconds or so certainly would not hurt, but be sure to turn it back to RUN before you forget. :shock:

The idle mixture screws that Brian mentioned are independent of the sync screws that are adjusted during a carb sync. You can check the idle mixture adjustment without affecting the sync. Remove the fuel tank, turn each idle mixture screw in, slowly and gently, counting the number of turns until it seats lightly. Record that number for each carb as it may be different. If your screws were less than 2 turns out, start with them at 2 turns. As Brian suggested, you might end up at 2.5 or more. Start the bike, warm it up thoroughly (go for a 5-mile ride), then pull the tank and find a way to get gas to the carbs with the tank off the bike. Set the idle with the master idle screw to about 1200 rpm. Turn the mixture screw on #1 slowly, each direction, until you find the highest speed. Reset the idle to 1200, repeat with the other carbs. Now go back and count the turns on the screws again, record those numbers and keep them for future reference.


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[rkubik]

sparklers, filter

It may sound boring, but new spark plugs (or cleaned and gapped) may help a lot. And sometimes it's also an air filter that wants cleaning.

Could also be crappy gas - try changing to a good brand from a station that looks like it has clean tanks, may make a difference.

[Roostabunny]

Gotcha, Steve - I keep forgetting that mixture and sync are separate. Just both require a long screwdriver and some kind of trick gas tank. And a fan, right?

That reminds me, newb question, but don't I want the bike warmed up when I make this adjustment? And an 8" flat-head driver with a narrow blade should do the trick?

Edit - Duh, not a newb mechanic, mind you. I meant a newb READER. 5-mile warm-up. Gotcha.

And just for future reference, I'll redo the whole process (and sync again, of course) after I rebuild the carbs next month?

[Steve]

And just for future reference, I'll redo the whole process (and sync again, of course) after I rebuild the carbs next month?

That would be correct. :shock:


One other thing you might want to check: battery. Even though it may sound like it's turning the engine over well enough, you might check the voltage while it's cranking the starter. If it's less than 10 volts, it's time for a new battery. The engine might be turning over, but, with less than 10 volts available to the coils, they just don't have enough to fire the plugs.

If you don't have a voltmeter handy, try this...get your car close enough to use jumper cables to connect the bike and the car. Leave the car turned OFF. The point of this is to just use battery power to turn the bike over. The larger battery in the car will not be affected as much by the load of the bike's starter, so you will easily see if it starts better with a known good battery.


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[Roostabunny]

That would be correct. :shock:


One other thing you might want to check: battery. Even though it may sound like it's turning the engine over well enough, you might check the voltage while it's cranking the starter. If it's less than 10 volts, it's time for a new battery. The engine might be turning over, but, with less than 10 volts available to the coils, they just don't have enough to fire the plugs.

If you don't have a voltmeter handy, try this...get your car close enough to use jumper cables to connect the bike and the car. Leave the car turned OFF. The point of this is to just use battery power to turn the bike over. The larger battery in the car will not be affected as much by the load of the bike's starter, so you will easily see if it starts better with a known good battery.


.

That's a good call - I had that problem a couple of months back. Replaced the battery. If it didn't crank like gangbusters and start up real easy in anything above 45° I'd suspect the battery as well. Throwing the voltmeter on there is easy enough, though. I'll double-check tomorrow.