IGNITION LIGHT

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mcmarvelous

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Here's another one for you technical wallahs.

My mk3 850 is running ok, but the ignition light flickers and comes on when the revs drop below 2000-1500. On a 50 mile run yesterday, with the lights on, the bike ran a bit rough, could have been missing, at lower speeds so I turned the lights off and it 'cured ' this.

the bike has a new loom, Pazon and I charge the the battery when I leave the bike (usually, although I didn't plug it in last week).

What is the ignition (red) light telling me? On an old FIAT I had years ago, it was the alternator not charging that was the problem, is it the same? I have the bike plugged in and will run it Sunday to see if it is the battery/ charge affecting the running.

Also, my alternater has a 'crinkle finish' to the outside of the it, noticed when I had the oil seal and clustch pushrod seal fitted etc, the alternater was also hot, but I had been riding for an hour to get tot he engine shop. My mechanic had not seen this before.


Any ideas?
 
I would start by putting a voltmeter across the battery terminals while stopped to get a baseline. This should be at least 12 Volts. If not, you need to replace the battery. Then running at about 1800 rpm check the voltage again. If your alternator is putting out you should have at least the same as you measured at rest. Revving past 2000 should show 13-14 volts.
The half wave rectified Mk3 alternator develops about 180 watts, but does not make appreciably more current at low rpm. The 3-phase alternator will make more power at the lower rpm.
 
As long as we are on the subject, my ignition light flickers a bit at idle. I just took that for low output at idle. Last week I rode the bike in the dark so the ignition light really showed up. I found that the light went out as I came off idle, and then came back on as I approached 2800 rpm. As I was pulling to a stop, the light would go out between about 2800 rpm, and idle. Any ideas on where to look? I figure I have a short or something in the wiring. I think it just started this after I had some work done, but I am not really sure.
 
It could just be a faulty assimilator unit or a loose connection?
 
Speaking of loose connections....

The rusty steed broke down twice on Friday morning, once in my road when I discovered I had not turned on the fuel . I traced that to a faulty nut sitting on the seat.
Then 20 miles in, the right coil made a break for freedom, pulling the spark lead out. Soon tightened up at the roadside. This is the second time this has happened so the loctite will be out now
 
calbigbird said:
As long as we are on the subject, my ignition light flickers a bit at idle. I just took that for low output at idle. Last week I rode the bike in the dark so the ignition light really showed up. I found that the light went out as I came off idle, and then came back on as I approached 2800 rpm. As I was pulling to a stop, the light would go out between about 2800 rpm, and idle. Any ideas on where to look? I figure I have a short or something in the wiring. I think it just started this after I had some work done, but I am not really sure.
Click to expand...

If you are using one of the new fangled solid state warning light assimilators, they go on dimly at idle and it's normal. It's also normal for some brands of electronic rectifier/regulator devices to flicker the warning light at idle even with the stock electro-mechanical assimilator. If your alternator, assimilator & rectifier are all stock it's not normal to flicker and I would suspect the assimilator first.
 
assimilator? Is that on the end of the giggle sprocket, next to the laughter shaft?

Seriously guys, enlighten this electrical numpty and tell what this is ...
 
The assimilator senses AC output from the stator, and switches the charge warning light off an on as necessary.

It is normally in the form of a small silver can, somewhat similar in appearance to a flasher unit, having White/Brown, Green/Yellow and Red wires connected to it, although the 850 MkIII assimilator is a black plastic encapsulated five terminal unit.
 
L.A.B. said:
It is normally in the form of a small silver can, somewhat similar in appearance to a flasher unit, having White/Brown, Green/Yellow and Red wires connected to it, although the 850 MkIII assimilator is a black plastic encapsulated five terminal unit.
Click to expand...


Thanks LAB, It sounds like something I haven't changed yet! What with the new loom, ignition, leads and all sorts I wouldn't want the bike failin for an happenth of tar.
 
mcmarvelous said:
assimilator? Is that on the end of the giggle sprocket, next to the laughter shaft?

Seriously guys, enlighten this electrical numpty and tell what this is ...
Click to expand...

No, it's near the muffler bearing :lol:

The "warning light assimilator" is just a relay inside a round tin can. It usually mounts in a coiled spring under the tank, secured by the rear left ignition coil mounting bolt. The normally closed contacts power the charge warning lamp. When the alternator gets to about 6 volts the relay pulls in and the light goes out.

Current path for the relay coil is from one alternator wire, through the rectifier to ground. That's why they flicker sometimes with aftermarket rectifier/regulator units - no direct path to ground.

Apparently the Lucas assimilator was also used on British cars - here's a link to a solid state replacement from a Jag:

http://coolcatcorp.com/Merchant2/mercha ... ry_Code=EL
 
Just got back from vacation, so I haven't been able to check this thread. When I rewired my MK III, I purchased a new assimilator from a reliable source. I aslo replaced the rectifier and diodes with a regulator/rectifier. Assuming the assimilator may have gone south, what method should I use to trouble shoot it? The bike ran fine at night with the lights on, and I did not see the headlight going dim at idle.
 
calbigbird said:
Just got back from vacation, so I haven't been able to check this thread. When I rewired my MK III, I purchased a new assimilator from a reliable source. I aslo replaced the rectifier and diodes with a regulator/rectifier. Assuming the assimilator may have gone south, what method should I use to trouble shoot it? The bike ran fine at night with the lights on, and I did not see the headlight going dim at idle.
Click to expand...

Is this the square black encapsulated one (p/n 066393) or the "can in a spring" electro-mechanical one? I would start by checking the voltages across the battery at the rpm at which it goes out and then comes back on. Are the voltages continuously rising? I.E., does it start at 11.5, go out at 12.5 then come back on at 14.5 volts? or do the voltages go from 11.5 to 12.5 then drop back to 11.5?
 
Thanks, I'll try to check that sometime today. I think I will run all the wires to and from the assimilator first.
 
My mk3 850 is running ok, but the ignition light flickers and comes on when the revs drop below 2000-1500. On a 50 mile run yesterday, with the lights on, the bike ran a bit rough, could have been missing, at lower speeds so I turned the lights off and it 'cured ' this.

Thanks for all this, i'll get a new assimilator.
It was pouring with rain yesterday on a rare day off, so I thought i'd kick it over to save wet sumping and the carb just flooded. Fearing some form of blockage as I have recently put a new tank on it, I stripped it down to find a float full of petrol! might explain the rough low speed running and richness! All changed and the bike is running much better.
I have only done 2000 miles on the new carb, or around that and no visible damage to the float, can they go porous that quickly or is it the vibes that kill them off so quickly.
I have a spare in case anyway (had it all the time but only remembered on the way back from buying another some 20 miles away).
:oops:
 
mcmarvelous said:
I have only done 2000 miles on the new carb, or around that and no visible damage to the float, can they go porous that quickly or is it the vibes that kill them off so quickly.
Click to expand...

The floats generally tend to fail along the 'welded' seam between the upper plastic 'plate' part of the float and the hollow lower section, which I believe is probably due to either vibration or expansion and contraction of the air within the float overstressing a weak area of the joint?

In an emergency, if the crack can be located and sprung open with a thin sharp knife blade, the fuel can be drained out and an attempt can be made to re-seal it with a soldering iron or similar tool, or even by touching the float seam against a hot exhaust pipe.


IGNITION LIGHT
 
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