Bike Stalling During Braking While Cold?
September 1, 2009 at 2:31 pm #3384
My bike is driving me nuts.
When the engine isn’t warmed up yet, it will stall like none other when making a moderate stop. This has been an on-going issue for at least a month. Filling up the tank doesn’t make a difference, nor did changing the oil.
Last night it was in the 40’s and I found it stalling way after choke was turned off and it was warm according to the temperature gauge still. The whole ride, I had to primarily use rear-brake only into a stop, and keep revving the engine to keep the engine speed up.
I noticed when I let it drop off to idle, it’ll hover around 900 RPM. It’s supposed to be idling at ~1300 RPM. I adjusted the idle the other day to 1500 RPM when it was warm, but that didn’t seem to make much difference, now did it?
I just think it’s a disaster waiting to happen. I made a quick stop when a LEO was going the opposite direction with lights and sirens, miles into my ride last night. Engine well warmed up. Only to have it stall when it came to a stop. I’m worried that if I ever needed to do emergency braking then swerve, I’d be out of luck because the engine would be stalled by then.
What’s wrong? The only thing I could think of is maybe I adjusted my clutch cable so it isn’t completely disengaging the clutch when it’s pressed all the way in?September 1, 2009 at 3:48 pm #22129MunchParticipant
“What’s wrong? The only thing I could think of is maybe I adjusted my clutch cable so it isn’t completely disengaging the clutch when it’s pressed all the way in?”
That was my first thought.September 2, 2009 at 12:57 am #22147
OK, I adjusted the clutch again. And it still does it. Stalled out braking on the main drag, when slowing down for traffic light backup, a mile from home tonight. It was being a pain starting, so I moved it to the center turn lane and tried from there. Finally got it started, required mucho choke.
Now I’m wondering… I put very high current bulbs in the lights in the back. I noticed when I brake, it actually causes the headlight to dim. Maybe it’s sucking too much juice, causing too much voltage drop for everything else, and causing the ignition to die? I just got back from a 2 hour trip around town, and once it was warmed up, I could brake without worry. Is it electrical or is it engine? Maybe from the riding it charged up the battery enough so that it wasn’t an issue anymore? Maybe my battery is on the fritz?
I’m chasing my tail. Oil level is right on the high mark when it’s warm. I did notice some very fine metal particles in my oil when I changed it. Is that normal or am I entering in “sell it now” territory?September 2, 2009 at 3:12 am #22155MunchParticipant
“Riddle me this, mechanical guys: can a carb’d motorcycle engine run without a battery or regulator/rectifier power once it’s started?”
The answer is in fact NO. Even though in FI engines you need power to pulse the injectors open, Carb’d engines work on vacuum and gravity. The power source that you do need is for the spark running to the coil and plugs. If the battery is dead or has a dead cell in it then yes you could be losing power via that route. Though the only thing that throws me there is being able to constant crank on the start up re tries.
It’s possible you could have an exposed wire somewhere creating a short with the sudden movement forward on stopping. Maybe causing an unwanted ground. Once the movement or inertia forward is gone the culprit has time to settle back in a neutral position allowing it to become a regular circuit again.September 2, 2009 at 4:25 am #22157
I bet my lighting is the problem.
3 x Sylvania 2357LL dual-filament bulbs. 28.5W brake, 8W run.
Let’s add up the current draw from them all:
6.84 amps for the brake filaments alone plus 1.92 amps for the running light filaments (always on) for a grand total of *drumroll please* 8.76 amps.
Headlight is 60 watts on high-beam, so there’s 4.8 amps. Did I say that right? Yes, I have more current devoted to not getting rear-ended than I do seeing where the hell I’m going at night.
Add in whatever power the spark plugs and all that jazz is using.
Yeah, it makes sense. The main fuse is 30 amps. Usually, it’s typical to fuse things at a slightly higher current than the supply can handle, just so you don’t blow them during equipment startups which have a higher rush current. It’s easy to tell I’m overloading what that regulator/rectifier can output. During breaking, the stator produces less power than when the engine is running (you can try this yourself by watching your lights at night when you rev the engine.) Which is the exact same time almost 9 more amps of current is being used. The battery is probably not as strong as it could be, and because it’s rated at 6 AH, it’s being drained at a quick rate and it can’t keep up with the current, so undervoltage occurs on top of the undervoltage from the regulator/rectifier not producing as much voltage.
There’s still juice for starting the ignition, because when the engine dies, it takes the headlights with it and the cluster backlight and the taillights. I think all the times I got it to start, I was off the brakes, holding in the clutch.The battery has enough juice to start the ignition without the additional load.
That would also explain why the headlight dims when I switch on the brakelights standing still. I’m maxing out what the electrical system can provide.
And why it doesn’t stall when I can slowly get to a stop sign while keeping the hand on the throttle a little to keep the engine speed up and not stall. Add in that last night was in the 40’s, and batteries work less efficiently in the cold.
Holy, shit. Who knew electronics would pay off on a bike.September 2, 2009 at 4:30 pm #22166Moto JParticipant
What kind of bike and year?
Did the problem start right after you installed the new brake light?
My bike stalls (just like yours) if I have the choke all the way off. I’ve got an old 84 with 37,000 miles.
Maybe you need a tune up. idk
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