Need help with '75 Commando Mark III Electric Start

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MexicoMike said:
As noted, there is plenty of help available here. Is there a specific electrical issue that you are trying to sort out or are you just wanting to generally "go through" the system to ensure everything is working correctly? If the bike has been essentially untouched for years, some elec maintenance will probably be necessary. That would include cleaning all the bullet connectors to ensure good electrical contact and adding a ground wire from where the battery cable connects to the frame to a point on the engine itself. Sketchy ground connections on the Norton are often a source of odd electrical issues so they are a critical item to check. It is possible that a new wiring harness may be necessary if the original has been chewed up by creatures over years of storage! ;) Some folks make up there own harness; the OEM harness contains a lot of wires you won't use because it was designed to work with all Commandos, including police models which had a lot of accessories that are not used/need on a "normal" bike.

Welcome!
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[just wanting to generally "go through" the system to ensure everything is working correctly?] YES!

See my post at 12:04 CDT
 
concours said:
Before you attempt to start it... STOP.
Read.
There is significant wisdom to recommend pulling the exhaust rocker covers, and put a few ounces of engine oil in there to drain down on the lifters & cam after a long dry spell. Quick, easy insurance.
Welcome to the most in depth Cdo resource available.
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Taking the advice of one of the professional British bike restorers here in Minneapolis, I put about 1/2 oz. of Seafoam in each spark plug hole and let it soak for a couple days to free up any possible sticky rings. Once that was through I put in some 20w50 engine oil to re-lube the cylinders. I'll take your advice and lube the top end as well. Thanks!
 
concours said:
Before you attempt to start it... STOP.
Read.
There is significant wisdom to recommend pulling the exhaust rocker covers, and put a few ounces of engine oil in there to drain down on the lifters & cam after a long dry spell. Quick, easy insurance.
Welcome to the most in depth Cdo resource available.
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Will do. Thanks!
 
84ok said:
sounds like you may have tried starts & not have much luck with the electric starter (maybe seems weak?) then the same no start results with kickstarting? I haven't tried starting it. I want to make sure all the electrics are hooked up correctly and function properly.

did you check for spark? No

what carb(s?) are on the bike? Amal

how long has the bike not started?
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It's been idle and stored in unheated space, inside, for at least 2 1/2 years.
 
L.A.B. said:
As it is an electric start 850 Mk3 then it should already have a heavy-gauge battery (positive) cable connected to the engine.
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The red cable is there and hooked up to the engine, but the battery end is taped off. The system is now a Boyer electronic system.

L.A.B. said:
The fitting of any secondary "battery ground wiring" should be avoided on an electric start model (unless the wire is fused) due to the potential for the starter motor current to use the light-gauge wire as the return to the battery.
What the Mk3 needs and should already have is a harness return connection to the engine (head steady, so the complete electrical system must use the heavy positive cable for the final battery 'return' stage.
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I know what you're saying here is important, but I don't quite understand the correct wiring hookups. Could you be more specific about which wire goes where?


L.A.B. said:
The factory made the mistake of including a secondary light-gauge positive (red) battery connection (ring terminal) in the harness and this is also shown on the wiring diagram but it should not be connected if the starter motor is operational.
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Is the potential problem mentioned in your previous paragraph resolved by doing this?
 
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grandpaul said:
Sorry to hear of your wife's loss, I'm sure the bike will serve as a happy memory in that respect.

Looks like you've got a good start to go on, a decent shop manual is a big part of the puzzle.

I bought a copy of the original factory manual and will check out the weak links, cautions and recommendations. Thanks!

Several POTENTIAL weak links in a MkIII e-start system are dirty/loose cables, dodgy starter button, sprague clutch in the primary drive whose teeth can fail, and incorrect tension on the anti-backfire clutch. All are detailed in the shop manual. Original Lucas starter solenoids have a finite life, also.

Let us know how you get on...
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You'll see me responding to each of you until I'm spending more time doing that than working on the bike! Then I'll have to be more selective.
 
Arlen Johnson said:
Turns out it has an updated electronic ignition system. That's good.
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It is the older Micro MkIII system that is more sensitive to low voltage than the later MkIV version so make sure the battery is fully charged or the system can cause kick-backs that could damage the starter motor drive sprag clutch (and be painful if kickstarting).


Arlen Johnson said:
The Boyer box wires are hooked up as follows: The red wire splits, one goes to frame ground, the other goes to the + terminal on the left spark coil.
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Ideally, the original ignition condenser pack earth/ground (red) wire should also be connected to the LH coil positive terminal. The standard coils should be 6V.

Boyer instructions (MkIII/MkIV):
http://www.boyerbransden.com/pdf/KIT00053.pdf
"13) Remove the red wire from its earthing point on the end of the condensor pack. Reconnect this to the + marked terminal on the left-hand ignition coil."


Arlen Johnson said:
The black wire goes to the + terminal on the right spark coil.
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See Boyer diagram in link above.


Arlen Johnson said:
The white wire goes to terminal 3 on the indicator light panel.
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White is the switched 'feed'.
If you mean terminal 3 of the ignition switch then that does not sound correct as white should connect to terminal 2. Brown/green should connect to Ign. Sw. terminal 3.
The feed to the Boyer box white would normally be white/yellow 'WU' (from the handlebar kill switch) unless the handlebar kill switch has been bypassed.


Arlen Johnson said:
The yellow on black and white on black wires go to the old points/condenser area. Is this all correct?
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Yes.


Arlen Johnson said:
Do I understand correctly that with this newer system the ground is now negative (-) as opposed to the original positive (+) ground from the factory?
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Unless there is evidence that the electrical system has been converted to negative ground then do not assume it has.
 
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It looks like I should copy sentences and sentence segments in the member's replies, and then paste them into my reply to answer them. Otherwise, I see that my responses get hidden and possibly missed by the person I reply to. Poor wording, I know, but hopefully I'm understood here.
 
The Boyer you have is a MK3, the issue here is the battery and the starter. A low voltage gets the Boyer to over advance the spark at low revs, a marginal battery and a cold start using the electric starter will drop the voltage enough to over advance the spark at exactly the same time you do not need it, the bike backfires and the sprag loses another of its limited lives. Best to to go Pazon or Boyer MK4. Until then make sure the battery is in good condition, fully charged and all the connections are good before trying a cold start.
 
Arlen Johnson said:
It turns out the bike has an updated electronic system; that’s good! The Boyer box connections are as follows: The red wire splits, one goes to frame ground, and the other goes to the plus (+) terminal of the left side spark coil. The black wire goes to the plus (+) terminal of the right side spark coil. The white wire goes to terminal three (3) on the indicator light panel at the handlebar. The white on black and yellow on black wires both go to the old points/condenser area. Does this all seem correct?

Did the original factory setup have a positive ground, but the new electronic system has a negative (-) ground?


Need help with '75 Commando Mark III Electric Start


Need help with '75 Commando Mark III Electric Start


Need help with '75 Commando Mark III Electric Start
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As far as I know Boyer electronic ignition is not good for a MK3 commando if you are going to use the electric start
If the volts drop down the ignition goes to full advance it kicks back and destroys your starter sprag
Maybe with an absolute tip top battery it might be ok!
Others with more knowledge than me will chime in
 
Only try starting this bike on the kickstart would be my advice
 
L.A.L. - Give me awhile to absorb all the info in your posts. Based on what you and "baz" just posted, it sounds like I should get the newer Boyer system.
 
kommando said:
The Boyer you have is a MK3, the issue here is the battery and the starter. A low voltage gets the Boyer to over advance the spark at low revs, a marginal battery and a cold start using the electric starter will drop the voltage enough to over advance the spark at exactly the same time you do not need it, the bike backfires and the sprag loses another of its limited lives. Best to to go Pazon or Boyer MK4. Until then make sure the battery is in good condition, fully charged and all the connections are good before trying a cold start.
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Good advice...essentially the same thing "baz" and L.A.L. are telling me.
 
The Boyer is a good update and much easier to deal with than two semi-independent sets of breaker points.

The best pre-emptive strike on an old Lucas electrical system is to replace all the rubber-covered connectors with new. No EE degree required, just count the ones and types you have and replace them. The metal part on the originals is crap and disintegrates inside the rubber over time. New ones are made of a different metal. This will preclude nickle-and-dime electrical problems in the future.
 
Arlen Johnson said:
The red cable is there and hooked up to the engine, but the battery end is taped off. The system is now a Boyer electronic system.


I know what you're saying here is important, but I don't quite understand the correct wiring hookups. Could you be more specific about which wire goes where?


Is the potential problem mentioned in your previous paragraph resolved by doing this?
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Put simply, only the heavy-gauge starter cable should be connected to the battery positive terminal if there is an operational electric starter.

(Edit: One exception to this would be when a reg/rec box has replaced the original rectifier and Zener diodes (Mk3 has two Zeners). The positive reg/rec wire can be connected to Edit: the bat+ terminal, if required)
 
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Arlen Johnson said:
It looks like I should copy sentences and sentence segments in the member's replies, and then paste them into my reply to answer them. Otherwise, I see that my responses get hidden and possibly missed by the person I reply to. Poor wording, I know, but hopefully I'm understood here.
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You can freely trim between the QUOTE and /QUOTE marks to shorten the citation you are replying to, which should help with the hidden text.
 
Arlen Johnson said:
I'm going to take a lunch break. Whew! Lots to absorb. Thanks to all of you I'm learning fast.
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take your time & enjoy, everyone here started from scratch,

best to start specific issues one at a time with fresh threads,

the more info u provide, the easier the fix
 
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