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Stalling after downhill

3K views 22 replies 6 participants last post by  flitecontrol 
#1 ·
After a 2-3 minute run of mostly downhill, partly using the throttle, I am finding the bike has a tendency to stall when I come to a stop.


Yesterday I chem-dip/sonic/air clean and boy it runs so much nicer, no dead spots, except when still cold, which is to be expected.


Now it stalls after 10-20 seconds of downhill.


Anybody have an idea what is going on?
 
#2 ·
Is it being choked at that time? It is super rich when choked. I had forgot to unchoke one time, ran fine until I stop, and dead it went. I quickly realized it was choked. Pushed it off and it fired right back up.
 
#5 ·
I read idle was 1,400 rpm. But without a tach...

I think (and I'll double check when I can) that during the long off-throttle decent, your engine is likely running rich (normal). The throttle is closed cutting off air, largely. Maybe during that extended time the spark plugs are slightly fouling. When's the last time you put fresh spark plugs in it?
 
#7 ·
Fist time I had it set to 1200, it ran for 3 months before the stalling occured. This time around I set it to 1300. I guess next time I adjust it, I'll just try for 1400, LOL. The manual I have says 1400 in one place and 1300 +/- 100 in another place.



Plugs were reset gapped about 1000mi ago, were a nice tan. I checked the colour only a few days ago, still a nice tan, but didn't gap them.
 
#9 ·
You may be onto something there. The last section is (guessing) 45 degrees straight, tight right, tight left, short straight leveling out to about 5 degrees. So I'm definitely off the gas for the end of that.


Thanks, I'll check the odometer next time that happens.
 
#11 ·
You are right, it's definitely not 45 (but it does look a bit like a wall coming up, 2nd, 3rd take a long time to wind up). It's hard to gauge 'cos I think the sign at the top says 18%, but it's got 2 long flat spots so it's not really indicative.


I'll try to stop next time and measure it.
 
#12 ·
An 18% grade would be a roughly 9 degree incline. That is quite steep.

On one occasion I ran my tank low enough that I needed to switch to reserve. About 5 minutes before that happened, I had been going down a moderate sloped hill that was about 1/2 mile long. While going down that hill the engine was surging a bit, and I was worried something was wrong. It smoothed out again at the bottom of the hill, until it sputtered and nearly died a few miles farther down the road.

So I can easily see how a long and VERY steep hill like the one you encountered, could mimic low fuel in the tank.

Maybe try switching to Reserve next time it happens, just to test the theory?

.
 
#13 ·
Well I now think the downhill part is a red-herring.



Yesterday I turned the idle up just a little.


Then I took it down the hill, no issues at the bottom, turned around came back home. While I was duck-walking backwards into the parking spot, idle was nice and steady then cut out like it lost spark. This reminded me it did something similar when I was doing a U turn several days ago.


Today I come into work, let the bike idle as I coast the last few seconds and come to a stop. I sit there for 10-20 seconds it's idling like a champ. On impulse I turn the handlebars all the way to the left, great, all the way to the right and it cuts out like it lost spark.


Not really sure how/if there's a relationship, but it's feeling more like electrical than fuel at this point.
 
#18 ·
On impulse I turn the handlebars all the way to the left, great, all the way to the right and it cuts out like it lost spark.

And again last night at home, this morning at work. My guess is the Run switch wiring is getting pinched and shorting. I'll be looking into that today.



I was looking at the wiring diagram last night and isn't that RUN/OFF switch wired the wrong way? I thought B/W on the CDI was grounded to kill i and that's doing it in the RUN position, just like the ignition does in Off and Park.
 
#14 ·
Telemetry

Here's the screens from the run downhill (9 degree slope) and uphill (16 degree slope!). I'm not sure why they differ so much, but I'll do it a few more times.
 

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#15 ·
Here's the screens from the run downhill (9 degree slope) and uphill (16 degree slope!). I'm not sure why they differ so much, but I'll do it a few more times.
As I read that - - unless I am misunderstanding - - the average slope for the hill was 2 degrees (in both directions, ie up and down.) That would work out to a grade of about 4-5%, which is still a fairly substantial grade.

(There can be quick blips of much steeper maximum grade that get recorded. But the average over the entire distance of the hill is really the important figure.)

Interesting about the possible electrical gremlins.
 
#19 · (Edited)
Yes the Black/White circuit when grounded will stop CDI from firing coils..

The ignition switch shows the correct internal connection, the Engine Stop Switch is Bass Ackwards

Link to 85-87 wire diagram I scanned from oem shop manual, feel free to download..
 

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#20 ·
I much prefer that wiring diagram, thank you.


I disconnected/taped the B/W wire from the stop switch inside the junction box and that seems to have fixed the cut-out on full right lock ..
 
#21 ·
Nope. Last night it was more like fuel, engine spluttering at right lock.


This morning I took a closer look and it appears the choke cable is getting pinched against the frame, so after brunch I'll investigate that.
 
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