Auto Advance Unit

Gamecio

Member
Riding for 2 Years
Local time
Today, 08:27
Joined
Sep 2, 2019
Messages
25
Points
7
Age
51
Location
illinois
My Ride
1968 Triumph Bonneville T120R
I think that I may have a problem with the auto advance on my 68 Bonneville.
I've only had the bike for 3 weeks and only started it once for about 30 seconds. It didn't sound or feel right so I have been tinkering with it when I get the time. I just manually advanced the auto advance mech. (timing plate still installed) with a small screwdriver but the mechanism did not return to the unadvanced position without assistance. The question is: should the mechanism snap back into the unadvanced position as soon as you let go of it, or does the engine have to be running for it to function properly? I'm trying to determine if there is a problem before I tear into it. It seems like something is too tight or is not lubricated properly. Any insight would be very much appreciated.
 

Rudie

Member
Local time
Today, 14:27
Joined
Jun 25, 2017
Messages
75
Points
17
Location
GB
My Ride
Several
should the mechanism snap back into the unadvanced position as soon as you let go of it,
Yes.

As its name suggests, it "advances" the timing as the engine rpm increases - although it's hard to see, the spark does take a finite time to travel from the coil to the plug while each cylinder goes from around eight sparks a second at tickover to 25 sparks a second just at 3,000 rpm.

The AAU 'advances' the timing - starts it more degrees BTDC (Before (the piston reaches) Top Dead Centre) - by turning the whole points plate mounted on it, so the points cam (being turned by the exhaust cam on '62-on Triumphs) opens the points earlier in its rotation.

The AAU turns the points plate with two bobweights; as the AAU spins, centripetal force pushes the bobweights outwards. Pulling the bobweights back in - to turn the points plate the other way to retard the timing when engine rpm falls - each has a spring.

trying to determine if there is a problem
If the engine isn't running, you push the AAU into its advanced position and it doesn't return when you let go, yes, there's a problem. It might be nothing more than wear causing extra friction while the springs are shagged, which might be 'fixed' by a clean, lube and new springs.

But, if the AAU on your bike is original, it's over fifty years old, Triumph only fitted them because they were cheap, new AAU haven't been made for nearly forty years, there isn't a huge market for AAU spares because most owners fit an electronic ignition ... so it's pot luck whether any AAU spares you buy (e.g. springs or bushes) are any better than the bits you take out.

Otoh, before deciding to replace AAU and points with EI, note EI isn't a silver bullet for crap or 51-year-old electrics - alternator, battery, wiring, switches, etc. must be in tip-top condition - EI are 12V and they mean it, 11V or 10V when the headlamp's on doesn't cut it; don't believe the maker(s) who say the existing '12V' coils are ok, EI with '12V' coils on a twin is far more likely to come back and bite you on the ass than not.

only had the bike for 3 weeks and only started it once for about 30 seconds. It didn't sound or feel right
If the AAU bobweights are tucked away, the timing is retarded for starting, any starting problem isn't the AAU.

If you've only had the bike three weeks, did it run before you bought it? Will the seller come over, check it and show you how to start it? If you haven't had an old Triumph before, the starting 'ritual' is pretty weird to someone only used to fool-injected or modern carburetted vehicles.
 

Rocky

Still Rocking
Riding for 27 Years
Administrator
Staff
Local time
Today, 10:27
Joined
Jan 28, 2006
Messages
17,672
Points
893
Age
82
Location
Halifax
First Name
Rocky
My Ride
2006 T100 Bonneville
Good reply Rudie TUP

I agree that almost every like his has a starting technique and you have to be shown or learn to get it right.
 

Gamecio

Member
Riding for 2 Years
Local time
Today, 08:27
Joined
Sep 2, 2019
Messages
25
Points
7
Age
51
Location
illinois
My Ride
1968 Triumph Bonneville T120R
Supposedly, the bike ran great before I bought it but I don't see how that could be correct after what I've seen while checking things over, valve gaps, point gaps, and even plug gaps needed correcting. The air screws also needed correcting as they were both completely screwed into the carbs.
I do not have an issue with the starting procedure as I have had it started as previously stated but it didn't feel right so I shut it down until further investigation. I now think that the sluggishness of the engine when revving may have been due to this AAU issue. I didn't try to let it idle but don't see how it could have with the air screws turned all the way in.
As far as the seller helping out, that is not possible. The seller characterized himself as "not a motorcycle person". He really didn't know how to maintain the bike and only bought it because he thought that it was beautiful. This may be why he thought that it was running great when it really was not.
The bike was restored 7 years ago and barely run since. The restorer did a great job getting the correct parts and making the bike look nice but his attention to detail was lacking. Points cam and associated felt pads were dry among a multitude of other details left unattended. So, I can see how it is very possible that the AAU was simply not lubricated 7 years ago and with the added lack of maintenance from the previous owner it has become an issue.
I have not checked into this but I do have an old AAU unit off of a 1975 Norton on which I installed an EI unit. If new parts for the Triumph unit are not available, would you have any idea if the Norton unit would be the same as the unit fitted on the Triumph? Thanks for the previous reply and the very useful information, Rudy.
 

grandpaul

Old Bike Lover
Riding for 50 Years
Staff
Local time
Today, 08:27
Joined
Apr 14, 2006
Messages
3,008
Points
272
Age
62
Location
Laredo
My Ride
Legend 900 Triple
No, Nortons spin CCW at the cam/points, Triumphs spin CW.

So, the bobweights will never open to advance position.
 

Gamecio

Member
Riding for 2 Years
Local time
Today, 08:27
Joined
Sep 2, 2019
Messages
25
Points
7
Age
51
Location
illinois
My Ride
1968 Triumph Bonneville T120R
Very good point GP. Thanks much for the reply, I will keep my old Norton unit for an old Norton.
 

Gamecio

Member
Riding for 2 Years
Local time
Today, 08:27
Joined
Sep 2, 2019
Messages
25
Points
7
Age
51
Location
illinois
My Ride
1968 Triumph Bonneville T120R
I believe that I need to go to EI. When I removed the timing plate, the springs were not hooked up to the weights. It seemed as though that was the answer to my problem but after removing the AAU, I found quite a bit of wear on the inside of the weights where the pins ride. I tried to sand it out with some sandpaper with moderate success. After lubing and reassembly, I still have a stickiness to the weight movement. I think that rather than continue to try to make the original system work that I would be better off just junking the old system and going to EI. I would like to stay with the original coils etc. I did this on a 1975 Norton with a Boyer system and it worked perfectly with no issues for 11 years now.
Any suggestions about repairing the old systems or the best EI system to use would be appreciated. Thanks.
 

Rocky

Still Rocking
Riding for 27 Years
Administrator
Staff
Local time
Today, 10:27
Joined
Jan 28, 2006
Messages
17,672
Points
893
Age
82
Location
Halifax
First Name
Rocky
My Ride
2006 T100 Bonneville
FWIW, I've been using Boyers in my vintage bikes for 20 years with not one glitch.
There are other systems on the market now so you have a choice.
 

grandpaul

Old Bike Lover
Riding for 50 Years
Staff
Local time
Today, 08:27
Joined
Apr 14, 2006
Messages
3,008
Points
272
Age
62
Location
Laredo
My Ride
Legend 900 Triple
If the AAU works reasonably well, you could at least re-install the points and attempt a test-fire and see how the engine does.
 

Gamecio

Member
Riding for 2 Years
Local time
Today, 08:27
Joined
Sep 2, 2019
Messages
25
Points
7
Age
51
Location
illinois
My Ride
1968 Triumph Bonneville T120R
FWIW, I've been using Boyers in my vintage bikes for 20 years with not one glitch.
There are other systems on the market now so you have a choice.
Rocky,
Did you keep the old 12 volt coils or go to 6 V as recommended?
 

Gamecio

Member
Riding for 2 Years
Local time
Today, 08:27
Joined
Sep 2, 2019
Messages
25
Points
7
Age
51
Location
illinois
My Ride
1968 Triumph Bonneville T120R
If the AAU works reasonably well, you could at least re-install the points and attempt a test-fire and see how the engine does.
Thanks GP, I will probably try smoothing the inner weight surface some more and try it out. I would like to get the bike running properly with the old system before attempting to change to EI since if there is an issue after installing the EI, I won't know if it was a pre-existing problem.
 

Rocky

Still Rocking
Riding for 27 Years
Administrator
Staff
Local time
Today, 10:27
Joined
Jan 28, 2006
Messages
17,672
Points
893
Age
82
Location
Halifax
First Name
Rocky
My Ride
2006 T100 Bonneville
Rocky,
Did you keep the old 12 volt coils or go to 6 V as recommended?
6v on the twin and a single 12 on the single cylinder. I figured Boyer knows best so did exactly what they said.
 

Gamecio

Member
Riding for 2 Years
Local time
Today, 08:27
Joined
Sep 2, 2019
Messages
25
Points
7
Age
51
Location
illinois
My Ride
1968 Triumph Bonneville T120R
6v on the twin and a single 12 on the single cylinder. I figured Boyer knows best so did exactly what they said.
I just went to Boyer's website and the unit would be an MK-IV. In their description it states that it is designed to run on original or replacement coils, so it doesn't appear that 6V replacements are required but would they work better? The Bonneville Shop recommends 6V replacements, but Boyer does not. Did you see somewhere that Boyer does recommend replacements?
 

Rocky

Still Rocking
Riding for 27 Years
Administrator
Staff
Local time
Today, 10:27
Joined
Jan 28, 2006
Messages
17,672
Points
893
Age
82
Location
Halifax
First Name
Rocky
My Ride
2006 T100 Bonneville
My units were fitted about 20 years ago so the latest instructions and units could have easily improved/changed over the years.
I would do whatever the latest instructions are.
 

Rudie

Member
Local time
Today, 14:27
Joined
Jun 25, 2017
Messages
75
Points
17
Location
GB
My Ride
Several
I just went to Boyer's website and the unit would be an MK-IV. In their description it states that it is designed to run on original or replacement coils, so it doesn't appear that 6V replacements are required
There isn't anything "designed" about it, Bransden Electronics (the maker, not "Boyer") have been claiming that (and that the triples' version will run with three 6V coils) to my certain knowledge for over forty years; when Ernie (Bransden) first claimed it, the only competition was the Lucas Rita EI, Lucas supplied either two 6V coils for a twin or three 4V coils for a triple, Ernie made that claim and didn't supply coils so it made his systems look cheaper.

If you understand basic electrics - the relationship between Volts, Amps and Ohms - I'll be happy to run through the reasons why you should use two 6V coils on your bike with any EI; if you don't understand electrics, just take Rocky's and my recommendation?

would they work better?
No question, absolutely.

The Bonneville Shop recommends 6V replacements,
Did you see somewhere that Boyer does recommend replacements?
When I started fixing old Britbikes with electronic ignitions - most often Boyer-Bransden - the "Technical Help" was a 'phone number answered between 4pm and 5pm every day ... When you 'phoned up, one of the first questions would be, "What coils does the bike have?" If you answered, "12V" (on a twin) or "6V" (on a triple), the advice was always to change 'em for 6V and 4V respectively ...

the best EI
The isn't really a "best", they all have their strengths, you just have to decide what appeals most to you - back-up I've listed by each one; digital electronics (Pazon Altair, Tri-Spark) have things like idle stabilisation (essentially speeds up the idle a little if it detects the engine's about to stop) but must have resistive spark plugs (preferable) or plug caps.

Boyer-Bransden Mk.4 you've found; it's cheap and, if anything goes wrong (or you even suspect it and want it tested), Coventry Spares is authorised by Bransden to test and replace as required.

Pazon Sure-Fire; note the "Recommended Ignition Coils" on page 10. Has a 7-1/2-year guarantee. However, any warranty problems, it has to be returned to New Zealand ...

Pazon Altair

Tri-Spark Classic Twin; the only one that doesn't have separate 'box' and trigger unit, everything's in the unit that replaces points and AAU. Again, note the coils shown in the wiring diagrams on pages 6/7. Any warranty problems, it has to be returned to Australia.

Wassell; not sure what the back-up is although, despite Wassell's normally dismal quality rep., the EI are put together by Vape, a widely-respected automotive electronic components maker. Once again, note the"RECOMMENDED IGNITION COILS" ...
 

Gamecio

Member
Riding for 2 Years
Local time
Today, 08:27
Joined
Sep 2, 2019
Messages
25
Points
7
Age
51
Location
illinois
My Ride
1968 Triumph Bonneville T120R
There isn't anything "designed" about it, Bransden Electronics (the maker, not "Boyer") have been claiming that (and that the triples' version will run with three 6V coils) to my certain knowledge for over forty years; when Ernie (Bransden) first claimed it, the only competition was the Lucas Rita EI, Lucas supplied either two 6V coils for a twin or three 4V coils for a triple, Ernie made that claim and didn't supply coils so it made his systems look cheaper.

If you understand basic electrics - the relationship between Volts, Amps and Ohms - I'll be happy to run through the reasons why you should use two 6V coils on your bike with any EI; if you don't understand electrics, just take Rocky's and my recommendation?


No question, absolutely.


When I started fixing old Britbikes with electronic ignitions - most often Boyer-Bransden - the "Technical Help" was a 'phone number answered between 4pm and 5pm every day ... When you 'phoned up, one of the first questions would be, "What coils does the bike have?" If you answered, "12V" (on a twin) or "6V" (on a triple), the advice was always to change 'em for 6V and 4V respectively ...


The isn't really a "best", they all have their strengths, you just have to decide what appeals most to you - back-up I've listed by each one; digital electronics (Pazon Altair, Tri-Spark) have things like idle stabilisation (essentially speeds up the idle a little if it detects the engine's about to stop) but must have resistive spark plugs (preferable) or plug caps.

Boyer-Bransden Mk.4 you've found; it's cheap and, if anything goes wrong (or you even suspect it and want it tested), Coventry Spares is authorised by Bransden to test and replace as required.

Pazon Sure-Fire; note the "Recommended Ignition Coils" on page 10. Has a 7-1/2-year guarantee. However, any warranty problems, it has to be returned to New Zealand ...

Pazon Altair

Tri-Spark Classic Twin; the only one that doesn't have separate 'box' and trigger unit, everything's in the unit that replaces points and AAU. Again, note the coils shown in the wiring diagrams on pages 6/7. Any warranty problems, it has to be returned to Australia.

Wassell; not sure what the back-up is although, despite Wassell's normally dismal quality rep., the EI are put together by Vape, a widely-respected automotive electronic components maker. Once again, note the"RECOMMENDED IGNITION COILS" ...
Rudie,
Thanks again for your replies and yes I do understand basic electricity and would be very interested in your explanation of why 6V coils will absolutely work better than 12V coils.
When I stated previously that Boyer had stated in their description that the original coils could be used, they may have meant that if you currently have 6V coils they could be used, it was not explicit.
 

Rudie

Member
Local time
Today, 14:27
Joined
Jun 25, 2017
Messages
75
Points
17
Location
GB
My Ride
Several
The 'Volts' of an ignition coil are only an indication of its primary resistance. All coils intended to be switched by points usually draw between 3A and 4A when the rated Volts are applied across them. So a '12V' coil generally has a primary resistance between 4 Ohms and 3 Ohms respectively, a '6V' coil between 2 Ohms and 1.5 Ohms, a '4V' coil between 1.3 Ohms and 1 Ohm, etc. (ime, most original Lucas coils are in the middle of those ranges).

Multiple coils switched by points are connected 'in parallel' - on your bike, like most British bikes, each coil has its own supply from battery -ve through the ignition switch; the corresponding points have their own return to battery +ve (through their attachment to the points backplate, that mounted on the engine, the engine having a wire from it to the battery).

Otoh, except for the Tri-Spark and Sachse e.i. for triples, all e.i. for old Britbikes have only a single switched coil(s) output, so multiple coils must be connected to it 'in series' - the switched output is connected to just one coil's "-" terminal, that coil's "+" terminal is connected to a second coil's "-" terminal, etc.

In the case of a twin like yours, the 'series' is only two coils, it ends with the second coil's "+" terminal being connected to battery +ve. As you've looked at the Boyer-Bransden Mk.4, if you look at its Fitting Instructions, the last page shows the wiring diagrams with two coils connected as described.

Digressing briefly, the reason for the single switched output is historical; when Lucas and Bransden were developing their e.i. for bikes in the late 1960's/early 1970's, unit costs were cheaper if the same basic electronics box could work on all engine configurations from single cylinder/coil upwards.

The main difference between connecting electrical components in series and in parallel is, in series, individual components' resistances are cumulative - two '6V' coils connected in series have the same total 3-Ohm-to-4-Ohm resistance as either original '12V' coil connected in parallel; otoh, if your bike's original '12V' coils are connected in series, their total resistance is between 6 Ohms and 8 Ohms.

This increased resistance depresses the current draw - given a nominal 12V, an original Lucas '12V' coil having a 3.5-Ohm primary resistance draws about 3.5 Amps; otoh, both original Lucas '12V' coils connected in series, the cumulative primary resistance is 7 Ohms and the current draw becomes a little under 2A.

Cutting coil Amps draw can be good or bad, depending how it's done:-

. A coil primary takes a finite time to charge; ime, original Lucas coils given the correct charge will charge up fast enough to be quite happily still firing a spark plug at ~18K rpm.

. So, triggered by points/mechanically, the lower the engine rpm, the longer the coil primary is connected between sparks, the more current drawn by the coil is simply turned into heat after the coil has charged fully.

. The "good" way to cut coil primary current consumption is to stop charging it after it's fully-charged - Tri-Spark for triples does this. Regrettably, afaik none of the e.i. listed in my earlier post do it, not even the Tri-Spark for twins.

. The "bad" way to cut coil primary current consumption is simply to increase the resistance ... say by connecting two '12V' coils in series ... The consequent cutting of the current drawn increases the coils' charge time; because the coils are triggered every engine rpm (rather than every two rpm by points, when a given cylinder is on the compression stroke), there is a real risk coils won't charge fully at even the higher rpm old Britbikes can manage without the engine turning itself into a 3D version of the parts book drawings ...

When I stated previously that Boyer had stated in their description that the original coils could be used, they may have meant that if you currently have 6V coils they could be used, it was not explicit.
The only Triumphs with 12V electrics and 6V coils are the electric-start T160 and '79-on twins:-

. On the T160, the Volts across the coils are reduced by connecting them through what's known as a "ballast resistor"; the b.r. has a similar resistance to a '6V' coil's primary, so the system normally works similarly to two '6V' coils connected in series as described above. Digressing, the reason for this was reliable electric-starting - the starter could depress the Volts to the coils, so the coils have a separate supply that bypasses the b.r. only when the starter's in use; battery Volts between 6V and 12V would more-likely still fire '6V' coils (happy owner), when they might not fire '12V' coils (unhappy owner).

. '79-on twins have '6V' coils because they have oe Lucas Rita e.i.

. '71-on Norton Commandos have the same system as T160's, although they didn't actually get the electric starter 'til '75, same as the T160.

Risking labouring the point about '6V' coils with e.i. on a twin, despite what Bransden might claim about '12V' coils elsewhere, note all the wiring diagrams in the Fitting Instructions label all the coils as "6V" ...

I'm not saying two '12V' coils in series on an old Brit twin definitely won't work - if nothing else, Bransden can't have been making the claim for at least forty years and still be in business if no-one could get it to work. Also, you'll find many posts on other forums by people who've even raced with the set-up. The final thing I'd say here is: the spark is only one part of a successful "bang" in suck-squeeze-bang-blow; particularly racers tend to obsess over every little detail; lower HT Volts combined with spot-on carburation might be reliable enough ... do you want to spend that much time fiddling with the carburation before every ride to save the cost to two '6V' coils? I've always used '6V' coils on a twin just to remove one opportunity for Murphy's Law ... :)
 

Gamecio

Member
Riding for 2 Years
Local time
Today, 08:27
Joined
Sep 2, 2019
Messages
25
Points
7
Age
51
Location
illinois
My Ride
1968 Triumph Bonneville T120R
Thanks Rudie for the primer on 6V vs. 12V coils. I very much appreciate the time and effort that it took to convey your explanation. I have already ordered a Pazon EI kit along with two 6V coils. I also try to do everything I can to cut down on the number of possible problems that could occur in the future, which is why I ask a lot of questions gathering as much information as I can before I making a final determination. When I think that I have gathered enough information to make a reasonable decision, I do so.
I agree that saving 50 bucks on 6V coils is not worth the added risk of problems down the line but I also like to know why I'm doing something and not just doing something because someone told me to. Many have gotten themselves into much trouble doing just that and I have learned over the years that that is not a viable Mode of Operation.
Thanks again, very much for your help/advice.
 

grandpaul

Old Bike Lover
Riding for 50 Years
Staff
Local time
Today, 08:27
Joined
Apr 14, 2006
Messages
3,008
Points
272
Age
62
Location
Laredo
My Ride
Legend 900 Triple
Having a decent understanding of electricity (NAVY Basic Electricity & Electronics class and Aviation Ground Support Electrician training), it still AMAZES me to think of what electrons are doing at 5,000 RPM in a classic motorcycle engine, and how the 2-stroke, and especially the 4-stroke cycle can do what it does! Those spark plugs are REALLY busy!
 

Gamecio

Member
Riding for 2 Years
Local time
Today, 08:27
Joined
Sep 2, 2019
Messages
25
Points
7
Age
51
Location
illinois
My Ride
1968 Triumph Bonneville T120R
Yes it certainly does boggle one's mind, it is amazing and hard to fathom.
 
Premium

Support TriumphTalk by becoming a Premium Member.

 What You Get

Donate

 

 

Top Bottom