stalls when braking hard

hey y'all --
'82 XJ750 23k miles. I have not owned the bike long, and have done nothing to the engine other than valve clearance adjustment. Last week I cleaned and flushed the brake lines, and I noticed the bike stalled when braking very hard during a test ride. Today it did it while riding, but I was braking *way* harder than I needed too, again just stressing the recent repair. All the times it stalled in this situation it was reasonably cold, and the choke was still on. Today it took a few cranks to start up.
ideas? normal? learn to freakin' ride?

 

Let the bike warm before riding.
This way if it does it again you can eliminate the choke as a cause.
My guess would be a loose connection that only loses contact under hard breaking.

 

Well, I could have tested it after an hour long ride tonight, but I was lost in the moment hehe. I will see if I can duplicate it cold, then ride until its hot and try the same braking.

 

what gear are you in when braking hard? (not jeans & leather jacket) is your clutch fully disengaging?

 

I say this because when I put my carbs back on after the cleaning, I reattatched the choke cable wrong allowing the handle bar end not to seat.
It caused no problem unless you moved the sheath toward the carbs, then it would die pretty quickly.

 

I'm thinkin' your clutch isn't adjusted correctly and you are not getting full disengagement, thus stalling the bike. Rick-o-Matic has written a wonderful how-to, look it up and give it a shot.

 

Did you update your fuse box?

 

Spot on robert, hound, and wizard. You are stalling the engine with the rear brake.
Pull clutch and if it still stalls you have a clutch issue, NOT disengaging 100%
I powerbrake around corners and sometimes forget the clutch
Did I mention I am crazy!@!!!

 

Thanks all -- clutch is dialed in. I had a ton of problems until I replaced the cable last month. I adjusted it until the clutch arm where the cable attaches has no more room to twist when the clutch is pulled in, then backed it out slightly when the clutch slipped under heavy load.

When I was testing it was 1st gear at maybe 10 MPH, when I was riding 4th at 40 or so. When I was testing I heard it sputter and die, once it sputtered and caught with a little throttle; when I was riding I felt it, but didn't hear it. In neither case did I feel it buck, so I really don't think clutch.

Upgraded fuse box.

Hound, I don't quite understand what you said about moving the sheath on the choke. Are you saying moving the sheath caused the 'enrichment circuit' to engage even when the choke lever was pushed in? That makes sense.

I will post again if I can confirm some symptoms

Thanks all!

 

Yes, on the carb end of the cable there is a silver knob that should mount inside the hold down.
I mounted it behind the hold down, so it did not sit in the seat at the handle bar end.
When I noticed it was loose, in the seat, I touched the sheath it killed the bike instantly.
Also caused a rich condition.

 

I had a similar problem. From day one of owning the bike the choke never seemed to do much, and it would bog down at low RPMs. Last week I bent the holding clamp at the carbs to hold the sheath of the cable. I never realized how the choke was supposed to work. It makes it quite easy to start now. Not only that, but it doesn't bog down at low RPMs.

 

Is there anything else that could cause this? I tried adjusting my clutch with no success. Today I did notice that it stalls easier when stopping on a downhill slope.

 

Are you low on fuel? Buddy of mine recently had a similar issue, died on deceleration, especially downhill. He knew he needed to fill up soon, but otherwise the bike would start right back up and ride off. Could just be fuel sloshing away from the petcock.

If your bike tries to pull when the clutch is in, then you likely need to adjust it, or replace the cable.

 

For the sake of my mental sanity, does it bobbbobblebobbDIE or does it just cut off instantly in a split second?

 

from my past experiences either 1 of 2 things. 1st you said you flushed the lines. In the past i have had problems with stalling from floats that are set a little to high or needles not seating properly as the needles and seats wear the float level rises also the little pin on the needle start sagging and get weaker with age. 2nd There is a possibility your tci has a bad solder joint or connection or wire loose. Usually if it is electrical it wont crank back up right away. But it could be something else but i would check these first

 

It dies instantly. Fuel was below half, but not too low.

The carbs need work (winter project). I should probabley just stop asking any more engine related question until I rebuild them, as it seems all problems can be tied to filthy carbs.

 

It could be as simple as a flaky sidestand switch. If the bike suddenly thinks the sidestand is down, it will shut off RIGHT NOW.

 

Fitz, I didn't think the 81 maxim had one.

 

Sorry, I thought they all did. I knew some didn't use a separate relay, but I thought they all had switches. My error.

The suddenness of the cutting out still smells electrical to me though.

 

Yes very well could be electrical. First thing to check on this front is your battery. Don't just check the voltage, do an actual load test. Some auto parts places can do this, some can't. Make sure they have a tester than can test for the proper rating of current for your battery (CCA-cold cranking amps).

I had a problem like that that was due to low battery voltage. When you suddenly slow down, your alternator (perhaps generator on that bike?) suddenly makes a LOT less current, and this can "cut off" your electrical system.

If that's the case, the next step is to figure out WHY your battery is low, but that's a different post.

 

The battery is new this season, and it has done this right off the get go. Could it be the alternator?

 

It could be. That was the source of my battery issues. Actually, my alternator was fine, but there was a badly corroded connector that was sucking up all the juice and making the overall system voltage drop.

This is my favorite electrical troubleshooting chart (someone else may have posted it on this site at one time, I don't remember how I found it): www.electrosport.com/media/pdf/fault-fi ... iagram.pdf

Check your voltages under the different conditions they list. I think the most telling thing is the voltage at idle and at 2500 rpm. If there is something wrong, it's hard for these readings to come out right.

 

I avoid electrical whenever possible. It may as well be rocket science to me....

 

Rocket Science is methodical, most would compare electrical to black magic. But you're working on a 30 y/o bike...you're going to have to suck it up and dig in if in fact your problem is electrical.

Arm yourself with a multimeter, and start testing. The most important test you can do is voltage drop testing, like pygmy_goat said. Test your battery voltage at idle and 2500 rpm. If it doesn't go from about 12.7V to 14.5 V in that rpm range, then you have charging system issues and should start on that flow chart. Voltage drop testing is also a great way to test for bad grounds, corroded connectors, and shorts.

If your battery and alternator check out, the next place to look is your ignition system. You could have coil issues that is preventing spark.

Does it start easily after it dies? Does it turn over but not fire? I'm still not 100% convinced that it isn't fuel related. The pilot jet is in the front of the carb bowls. If the float levels are off and the jet is too rich, it would be possible to throw in too rich of a mixture and cause the bike to die right away when braking after chopping the throttle.

 

The bike starts badly - but consistently. When cold, choke out and crank until it starts and dies. Repeat until it stays running (usualy 2 or 3 times).

It starts easily after it dies (as easy as my bike ever does).

Got a guy here at work who knows electrical, and we've got a meter here, maybe I can get him to help me out.

 

Hard starting, if not carbs, usually means you need to attend to your VALVE CLEARANCES. It's the one thing I don't see mentioned in your list of things you've completed.

While not related to this specific issue, it will affect the "hard to start" syndrome.

 

You likely have a few thing to deal with that could be causing you to shut down.

The Fuse Panel.
If it's Original; can fail in a number of ways causing an Open Circuit.
It might TEST OK.
But, a Fuse Panel going on 30 years old is cooked and should be replaced.

Your Carbs.
Hard Starts indicate that the Enrichment Circuit isn't functioning well.
In decent weather; the Bike should fire right up without a lot of cranking.
You must be long overdue for a Carb Cleaning.
A proper one; where everything gets the white glove treatment.