Stalling issue when coming to a stop

cmills83

cmills83

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I just replaced the head and triple checked the timing, valve clearance and cam chain tension. Also, just synced the carbs. I noticed I was running a little bit rich so I adjusted the mixture screws 1/2 turn in. Not sure where else to go from here.

While riding the bike runs fine, I can ride on the hwy 10 min at 75mph no issues but when coming to a stop even from a ride up the block there is an intermittent stalling issue. I turned the idle up a bit to compensate but any suggestions are welcome.

In the video I am holding it between 3 - 4k rpms for about 10 seconds then returning to idle.

 
I think the tach is ok, I’ll put up a better video. Went through and adjusted the cam chain tensioner, valve adjustment both looked close and I got them to spec. Timing was ok. I noticed the battery was at 11.5v, I had left the lights on and don’t think it fully charged on the charger and noticed the plugs were slightly fouled.

Hopefully it’s as simple as charging the battery and putting in new plugs which I had to order
 
So you let go of the throttle and it's like turning off the key. Hummm. What happens if you say hold the idle at 1200 with the throttle, then screw in the idle screw until it holds the lever in that exact same position and you can let go of the throttle? That's a start.
 
Nah in the video I’m not holding the throttle, just letting the bike idle on its own.

If I hold it I can usually catch it before it stalls
 
Ok, it idles fine for a bit on its own and then quits. Maybe an air leak that isn't showing symptoms when riding but is too big to let it idle. You could check that the carbs are all the way into the boots and there's no leaking around there.
 
Thanks for the reply, yeah they are in there tight and the intake manifolds are new. If you think of anything else to check let me know. Aside from the plugs and charging the battery I’m out of ideas
 
Have you checked the carburetor fuel levels? Perhaps one is just slightly high and causing flooding at idle, kind of like switching the choke on when the bike is warmed up, or is the choke sticking.
 
it doesn't sound like a typical mixture problem . The engine cuts out too cleanly and suddenly. There is no cough or splutter that you might associate with an over rich idle mixture or a fuel supply issue .

Maybe the carbs are out of sync and the engine is struggling to idle on one pot ?
Perhaps one of the pilot jets are blocked ?
Also check the tiny idle mixture supply holes are clear in the roof of the venturi ..and the idle air jets are clear .
 
Last edited:
Check your idle screw, note distance, end of screw to the bracket, this distance is about the same on all years, models, WHEN THE CARBS ARE SET CORRECTLY and everything is working well. If this distance is not allowing a smooth even idle. or the screw is tightened much further to make the engine idle without stalling, it is a sure sign you are not done cleaning, adjusting, synching your carbs.
idle stop screw.jpg
 
See Paul's suggestion. When braking to a stop, weight transfer depresses the front end and fuel sloshes forward in the float bowl, richening the mixture. If fuel level is too high, the motor stalls quickly, with no sputtering. Here's a quick check: bring the motor to cruising speed, disengage the clutch with no engine braking, and let the motor settle to idle. Then brake. If engine speed drops or the motor stalls, check the fuel level with a sight tube.
 
From your last video, it appears to me to be electrical in nature, like you're losing electrical power and/or spark, at least momentarily. I assume it starts right back up? It does appear and sound like it is running on both cylinders, although your idle speed is kinda high.
 
Thanks for the feedback. I turned the idle speed up a bit since that seems to help the stalling issue. I just cleaned and reinstalled the carbs and had run them through an ultrasonic not too long ago. Could always give it another try.

The stalling seems to mostly happen after coming to a stop for 10+ seconds or even just revving the bike and letting it return to idle without even riding.
 
Interesting, I'll have to take a look. The stator is new but the rotor is original. Possible I damaged it running an antigravity 4 cell battery for 500 miles.

Wouldn't a failing rotor also effect spark at higher rpms too though?
 
A simple test, to help determine whether to pursue carburetion or ignition. But, requires astute, rapid, observational skills.

Hook up a timing light, and just watch it pulse during idle. The moment that the engine dies, it'll still rotate a couple more turns, within a fraction of a second, before it fully stops.

If the timing light stops pulsing precisely at the same time the engine quits, consider an ignition failure.

If the timing light puts out an additional pulse or 2, then consider carburetion...
 
I’m thinking weak charging system or battery. What type of ignition system have got? TCI, points or other? At idle the charger doesn’t put out too much and if you have a marginal battery, that makes it worse. A struggling 12 volt bus will ultimately affect the igniter and less power to the coil result in weaker or missing sparking. I had similar problems with mine. Try running it without the headlamp for a bit by pulling the fuse. The headlamp is a significant load. If it is suddenly idling better, it could be an indicator of charging/battery issues. There are some charging checks you can do as well.
 
Ok so changed out the plugs and charged up the battery and still having the issue. I am going to replace the rotor, that's really the only thing I haven't replaced in the charging system so far.

Right now I'm running an Antigravity 8 cell battery, Ricks Electric stator and Regulator/Rectifier all about 6 months/500 miles old. I redid all the wiring about 800 miles ago. Stock electronic ignition off a 1980. Ill check the wiring, replace the with the rotor, then maybe the ignition black box. Unless there are some more ideas
 

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