Bike won't start when it's cold - too rich?

[sultan]

'83 GS650, 23K miles. This past spring I:
-replaced the piston rings
-honed the cylinders
-replaced all gaskets
-adjusted the valve clearances
-disassembled, dipped, and rebuilt the carbs, replacing o-rings
-balanced the carbs
-cleaned and oiled the air filter
-replace the spark plug caps

All summer the thing has been running great! With the choke half-on, I'd just have to tap the starter once and it would fire right up. Compression is 175 (or better) on all 4 cylinders.

As the temperature has dropped though, it's become harder and harder to start. Today, for the second time this fall, I cranked (and paused) and cranked (and paused) until the battery went dead. (Interestingly, it did the exact same thing with the same symptoms *last* fall when the temperature dropped, which prompted all the work in the spring. In a pinch a couple of times I used starting fluid in the air filter, and doing that caused the bike to fire right up.)

With the choke off, it will sputter a bit like it wants to start. With the choke all the way on, the starter bogs down and turns slower and never sputters. I tried holding the throttle wide open while hitting the starter for about 10 seconds (did this a couple times), and that had no effect.

Taking out the spark plugs, #1 and #4 were wet with gas. Someone had suggested that I change the spark plugs anyway to fix this problem, so I had some on-hand and went ahead changed all 4 of them. So, now all 4 are definitely dry, but still the bike wouldn't start.

I'm confident that I have good spark (though, I guess I could/should check just to be sure) because once the thing starts it runs well and smooth.

So, the bike will start when it's 80 degrees, but not when it's 50. I checked the valve clearances and balanced the carbs less than 100 miles ago. Obviously it's running too rich, but I'm not sure how to fix that. After rebuilding the carbs I had the fuel screws 2 turns out, and in response to this problem I took them in another half-turn and turned the idle down a bit. Still no difference.

So, anyone have any advice as to what to try next? How else can you adjust the fuel mixture other than the choke, idle screw, and fuel screws?
What am I missing?

Ideally, I'd like to ride the bike until the roads get bad, but I can't do that if it won't start. Any advice is appreciated.

Thank you.

[rustybronco]

I'm confident that I have good spark (though, I guess I could/should check just to be sure) because once the thing starts it runs well and smooth.

Better yet, do you have proper voltage at the coils when cranking?

[GQROD]

Did you check the color of your plugs to see how good the mixture is?

Often the biggest problem once ignition is ruled out is proper mixture, this goes for adjusting the choke cable and ensuring your mix is correct.

Hope this helps.

[waterman]

My 650g is in your same state of tune, freshly rebuilt within last 1300 miles. I too have noticed a change in the cold start up recently now that the weather has begun to cool. I would try to keep the same choke position as you had during the warmer weather, again no throttle. Mine doesn't like full choke, usually 1/2 at most.

I can think of several weather related issues affecting starting. First batteries will develop less power at cooler temperatures, thus lowering cranking rpms and potentially robbing the spark. Oil is thicker, gasoline doesn't evaporate as well.

My advice is to make sure battery is well charged and then try to find the magic choke position to have it fire immediately. Mine will instantly fire a couple of cylinders and then stall out. Usually I can quickly hit the starter again and get it to fire and stay running until it warms enough to accept throttle without bogging. If it dies and will not fire, I assume it is flooded and go with no choke until it will sputter and then reset choke again. Hope this helps, I am going to ride until snow flies. If I encounter more trouble, I will probably break out the colortune plug to see how rich I am at idle.

[simon kuether]

My 'S did the same.Got me one of those gel batteries and no problems since.Cheers,Simon.

[almarconi]

Try blowing into the carb breather hose..one or two quick puffs. Apply choke and hit the start button. When my bike is cold this is the only method I found will get it started. I may have some carb issues but at least I am able to get the bike started. Once the bike is running it seems to run fine.

[skidMarkNZ]

mine had exact same issue, replaced battery. problem went away.

[skidMarkNZ]

Try blowing into the carb breather hose..one or two quick puffs. Apply choke and hit the start button. When my bike is cold this is the only method I found will get it started. I may have some carb issues but at least I am able to get the bike started. Once the bike is running it seems to run fine.

dont see what the hell this would do but err okay.

[BassCliff]

Random suggestions...

Hi,

If I may, I have a few thoughts. How many miles since your valve check? Are you due for another? Tight valves contribute to cold starting issues. How is your charging system doing? Have you checked voltages as per The Stator Papers? I love my AGM battery too, but test everything before you spend the money. Perhaps the coil relay mod is in your future? Please keep us informed.


Thank you for your indulgence,

BassCliff

[Steve]

Try blowing into the carb breather hose..one or two quick puffs. Apply choke and hit the start button. When my bike is cold this is the only method I found will get it started. I may have some carb issues but at least I am able to get the bike started. Once the bike is running it seems to run fine.

dont see what the hell this would do but err okay.

What this does, is to pressurize the float bowl and send some extra gas up through the jets into the throats. Essentially, it is like an accelerator pump, it puts some extra raw gas in the air flow. Awkward to use, but it is effective.

.

[sultan]

Hi,

If I may, I have a few thoughts. How many miles since your valve check? Are you due for another? Tight valves contribute to cold starting issues. How is your charging system doing? Have you checked voltages as per The Stator Papers? I love my AGM battery too, but test everything before you spend the money. Perhaps the coil relay mod is in your future? Please keep us informed.

Thank you for your indulgence,

BassCliff

Thanks for the follow-up.

I've done so much to the bike it's hard to mention it all. This past spring I did a whole valve job, resurfacing the valve seats, etc. I checked the valve clearance less than 100 miles ago when I balanced the carbs. Only 2 valves were out of spec, and those by only a tiny margin.

I've also replaced the stator and rectifier (last fall) with the better after-market items as recommended by this forum. I also replaced the battery last fall. It was on a low trickle charge indoors all winter. After the first no-start problem when I drained the battery, I hooked the charger back up and got a good charge on it, and the no-start problem continued to happen. The water levels in the battery are fine. A few days later when the temperature warmed up, the bike started without too much problem.

I took a look a the manual last night in regards to testing the coils. Something about using a 1.5 volt battery to trigger the coils discharging (?) and watching the spark. I hope to at least try that this weekend, but other than a visual inspection, is there any way to tell if I'm getting *good* spark? Blue is good, yellow is bad, and that's it? Can you safely measure the voltage coming out of the coils? And if so, how? (I have a electronic volt/ohm meter.) How about using an in-line spark testers? Is that a decent $5 investment?

I'll also double-check the stator voltages, but I have a feeling those OK. You guys know more than I do, but I still feel that either I'm running too rich, or yeah, I'm not getting enough spark somehow, even though the electrical & charging system should be fine.

Thanks for the advice.

[sultan]

What this does, is to pressurize the float bowl and send some extra gas up through the jets into the throats. Essentially, it is like an accelerator pump, it puts some extra raw gas in the air flow. Awkward to use, but it is effective.
.

As mentioned, 2 of the spark plugs were wet with gas. #1 and #4. I don't think that giving it *more* gas is going to fix the problem. Now that I'm starting to suspect the ignition system, it would sound like I could be having a problem with one of the coils, no? The same coil fires cylinders #1 and #4, right?

It's definitely not a scientific test, but could I swap the coils (input and output, of course) and crank-crank-crank, then if plugs on #2 and #3 are wet with gas (and not firing) then that would point to a bad coil, right?

If the wet-plug problem stayed with #1 and #4, then that would mean that there's a problem upstream in the signal generator or something, right? Or am I just shooting in the dark here?

Thanks.

[rustybronco]

I took a look a the manual last night in regards to testing the coils. Something about using a 1.5 volt battery to trigger the coils discharging (?) and watching the spark. I hope to at least try that this weekend, but other than a visual inspection, is there any way to tell if I'm getting *good* spark? Blue is good, yellow is bad, and that's it? Can you safely measure the voltage coming out of the coils? And if so, how?

That would be voltage to the coils...

about the 1.5v battery, this should be of help.

http://www.thegsresources.com/_forum/showpost.php?p=902587&postcount=1

I'm not getting enough spark somehow, even though the electrical & charging system should be fine.

Thanks for the advice.

Who said, to measure is to know? Nesissm...
measure my friend.

[82Shafty]

Your first step is this:


1) Check your voltage at the coils. I found out that mine was 1.5 volts short of battery voltage. Measure your battery voltage, then keep your negative cable connected and check the hot wire at each coil. Remember that only 1.5V is multiplied by the secondary side so if only 14 volts can equal 30G volts, what is the missing volts Roughly 3200 volts then you factor in your resister boots: oh boy.

Search Coil Relay Mod.... you will find lots of info.

Next, how old are your spark plug boots. Unscrew them and check resistance ... they are supposed to be around 5K ohms. I found out that two of mine were infinite. They are 3 bucks a piece, more resistance is less spark to the plug. I replaced all four.

While your at it measure primary and secondary resistance at your coils.

http://www.thegsresources.com/_forum/showthread.php?t=130409&highlight=coil+relay+mod&page=2

With schematic

http://www.thegsresources.com/_forum/showthread.php?t=127900&highlight=coil+relay+mod

[sultan]

Next, how old are your spark plug boots. Unscrew them and check resistance ... they are supposed to be around 5K ohms. I found out that two of mine were infinite. They are 3 bucks a piece, more resistance is less spark to the plug. I replaced all four.

Spark plugs are *brand new*. The engine has never been started with these plugs in them.

Thanks for the advice! I'll check voltages & resistance all around this weekend and go from there.