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MkIII Commando running rough, then worse

Submitted by michael_wallace on Tue, 02/01/2018
Forums
Commando

Hello Gents,I would appreciate any help you could give me with my ES MkIII. Owned for about 14 years and had given running trouble for the last several.Anyway, coils,plugs, carb all sorted and I did a hundred miles in Wales, perfect. Started to deteriorate after return home and could only get home using choke (week spark?) and sooted plugs.Decided to diagnose ignition direction. Now here's mistake No1. I red on a forum connect Boyer (MkIII) direct to battery. I used the battery charger lead and it almost melted after 3 secs! This action must have connected batt. direct to earth, anyway it knackered my new batt. which will only hold 10.5V now- bin.I'm now using my old batt. 12.6V and suspect other damage. When I switch ignition on the neutral and ign. lights come on as expected and then immediately go out, every time as if discharging a capacitor.Do you think I've written off the Boyer? Maybe I'm due a MKIV anyway.I did find during analysis that the supply to the Boyer box had a very corroded spade connector and I suspect this was the original problem.

This message also sent to Al Osborne.

Mike

Submitted by david_evans on Tue, 02/01/2018

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Which wire from the Boyer did you connect to the battery charger lead? white is the normal power feed for +ve earth boyer.

If you could only get home using the choke and had sooted plugs sounds like a carb issue to me. You say carb, singular. is it a single carb conversion? tell us more.

Submitted by robert_wright on Tue, 02/01/2018

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Hi

first the ign lamp and neutral lamp are separate the only common conection is on the ign switch (white wire) check for 12 volts there..

do your frount and back brake lights work ....

if not look at the ign switch as this could also effect the boyer if you have a high resistance contact..

Submitted by andrew_windsor on Tue, 02/01/2018

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Hi,

I will follow this thread closely , i run a MK111 commando also with a miss fire. Mk111 boyer single mikuni.

Submitted by michael_wallace on Fri, 05/01/2018

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Previously andrew_windsor wrote:

Hi,

I will follow this thread closely , i run a MK111 commando also with a miss fire. Mk111 boyer single mikuni.

Thanks Gents,

I feel I'm "not alone". To Dave, Boyer white cable was connected to battery. I run a single Amal MK2 and MKIII Boyer. I've had a reply from AO and the first thing to do as advised is find where the battery is draining to by disconnection starting with Boyer. I understand everyone is pointing to the Amal, I have done so much work, stay up float, seals and checking jet blockage. After all this as said I did 100 miles. Anyway, I will work on this ign.elec. problem first. I will update on this messages but it may be a while.

If anyone is bored and has a magic wand....I live near Buckingham.

Mike

Submitted by michael_wallace on Sat, 06/01/2018

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Previously michael_wallace wrote:

Previously andrew_windsor wrote:

Hi,

I will follow this thread closely , i run a MK111 commando also with a miss fire. Mk111 boyer single mikuni.

Thanks Gents,

I feel I'm "not alone". To Dave, Boyer white cable was connected to battery. I run a single Amal MK2 and MKIII Boyer. I've had a reply from AO and the first thing to do as advised is find where the battery is draining to by disconnection starting with Boyer. I understand everyone is pointing to the Amal, I have done so much work, stay up float, seals and checking jet blockage. After all this as said I did 100 miles. Anyway, I will work on this ign.elec. problem first. I will update on this messages but it may be a while.

If anyone is bored and has a magic wand....I live near Buckingham.

Mike

Next day:

I connected my multimeter on 200mA range and registered 0.2 falling to 0.1 that seems like enough to light my dash bulbs, so possibly no drain to earth otherwise. Then with Volts across battery 12.5V fell to 3V and lower. After ign. on of course. This is my old battery and I think it's done!

Will order new battery and continue.Mike

Submitted by michael_wallace on Thu, 18/01/2018

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Previously christopher_winsby wrote:

Have you still got the 2MC capacitor?

Yes I still have zener and capacitor. Will be fitting battery soon. I am optimistic the bad connector to boyer caused the fault.

Submitted by christopher_winsby on Thu, 18/01/2018

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Previously michael_wallace wrote:

Previously christopher_winsby wrote:

Have you still got the 2MC capacitor?

Yes I still have zener and capacitor. Will be fitting battery soon. I am optimistic the bad connector to boyer caused the fault.

I would remove it and check it out as instructed in the manual and carry out checks for shorts and high resistance joints etc.

Submitted by michael_wallace on Fri, 09/02/2018

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I've now fitted a new battery and carefully monitored the discharge to circuit as I connected. Ignition on,0.39 Amps then connected Boyer 0.42 A with 11.93Volts at Boyer; that seemed normal to me. Plugs out and kicked over, no spark either left or right. This was not the case before I started my destructive diagnosis, new Boyer I think. Any comments gents?

Submitted by maurice_cloud on Fri, 09/02/2018

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Hi Mike

Not against Boyer but if I was you I would fit Pazon as it takes less volts to run somewhere around as low as 7.5 Volts where as Boyer needs really all of the 12 volts.

anyway I have had Pazon on both my Mk3 commando and my Bonneville for years and never let me done...Now I have said that I am keeping my fingers crossed :)

Also I use a motobatt AMA pro racing MBTX20UHD Battery 20% more cranking power and that is very good amp`s

Mo

Submitted by ian_soady on Sat, 10/02/2018

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I don't think it has been mentioned but a Boyer should spark when the power supply is removed eg when the ignition is switched off. If it doesn't it would indicate a problem with the control unit.

Submitted by michael_wallace on Sun, 11/02/2018

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Thanks gents for all your comments.I,ve bench checked the mc2 and zener, both conform to manual figures.I think it was Ian who commented ign. on and the boyer should spark plugs, it doesn,t. So I think now it,s got to be a new ign. system. Pazon is recommended, any more experiences?

Mike

Submitted by david_evans on Sun, 11/02/2018

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Trispark but fitted with a matching trispark coil makes it a bit pricey. I have a old Boyer Mk 3 sitting on the for sale board if you want to give it a whirl to prove your diagnosis ( if you promise not to fry itWink) You fry it you buy it.

Submitted by michael_wallace on Mon, 12/02/2018

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Yes sorry Ian typing error. Anyway, success! I reinstalled the zener and Mc2 reconnected the Boyer ign and bingo ign on/off and plugs sparked. So I hadn't cooked the Boyer (thanks for the loan offer David) only the battery. Plugs back in, tank on and started straight away.

In conclusion I found several spade connectors quite badly corroded and I,m fairly sure this caused the problem. I,m not sure how but I can,t come to any other conclusion. The next step will be a road test in a couple of weeks.

MIKE

Submitted by ian_soady on Mon, 12/02/2018

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Boyers are very susceptible to poor connections.

On one trip to France I was plagued with misfiring which I thought was muck in the carb. After stripping it a couple of times (fortunately I had a single fitted to my 828) I was sitting beside it while the engine was running and just touched the black & yellow leads from the points. This stopped the engine immediately.

I discovered that the problem was those horrible crimped connectors that Boyer supplied for the coil plate. A temporary repair of twisted wire got me home with no more misfiring.

Submitted by michael_wallace on Tue, 01/05/2018

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Well I thought my troubles were over, WRONG it appears I'm pretty much back to square one. No start, poor sparks both pots. Contacted Boyer and went through all checks now seem to have good sparks and fired, promising, then nothing. Choke off and attempt to vent cylinders, a couple of kicks and a backfire like a rifle shot.

That repeats itself. Plug inspection shows the lefthand plug wet but right dry. How can that happen if flooded? The RH pot is not firing and burning off.

Secondly, what does a backfire mean technically is happening.Previous texts from me detail all the bits replaced.

Any help appreciated. Mike

Submitted by ian_soady on Tue, 01/05/2018

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Backfires are often caused by the timing being off. If your battery is even slightly below full charge the Boyer may be defaulting to full advance which may be at least part of the problem.

Do you have twin or single carb(s)?

Submitted by michael_wallace on Wed, 02/05/2018

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Previously ian_soady wrote:

Backfires are often caused by the timing being off. If your battery is even slightly below full charge the Boyer may be defaulting to full advance which may be at least part of the problem.

Do you have twin or single carb(s)?

Thanks Ian, single MK2 Amal. Which I have also reconditioned along the way. The battery is brand new and is regularly on charge. I've checked 12V at supply to Boyer so no high resistance up to ign. unit. I'm beginning to think maybe a valve is sticking, next thing to check. I've been in touch with Boyer and maybe even though the unit is sparking I didn't think it could be advancing the much, I'll put that to them.

Submitted by ian_soady on Wed, 02/05/2018

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Odd that one plug's wet and the other dry with a single carb as you say, although you can have a bias to one side I wouldn't expect it to be that much.

You can quickly check the valves for sticking by just popping the tappet covers off and checking there is clearance.

Submitted by michael_wallace on Fri, 04/05/2018

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Yep, done that ian no problem with valves. Checked the wires on stator plate are connected correctly (from Boyer). I think my next step must be to get the Boyer off for checking.

Submitted by gordon_robertson on Fri, 04/05/2018

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Sounds like an intermittent power supply to the Boyer.

I had a similar problem with poor starting and backfiring which turned out to be worn contacts in the ignition switch.

Good luck with your diagnosis!

Submitted by mike_sullivan on Tue, 08/05/2018

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How about the wires at the stator plate, classic place for breakage on the early Boyer & easily repairable (sorry not familiar with the later Boyers).

Submitted by colin_cheney on Tue, 08/05/2018

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Dear Michael,

I had similar problems with my Boyer in 2012 after riding for three hours in torrential rain on the previous day. The rain didn't stop overnight and I should have left the key in the ignition. Water must have got into the ignition switch and, added to the wear and corrosion inside the switch, it produced similar symptoms to those you have described. I had well over 12 volts going into the switch but fewer than 10 volts on the side that supplies the coils. I had sparks at both plugs when removed from the engine but kicking back when trying to start. I by-passed the switch completely with some spare wire and the machine was fine for the way home. By this time it had become dark so I noticed an additional benefit was that the lights were much brighter.

Your switch, if original, will be around 40 years old and it may be worn out. I bought a replacement from Andover Norton who kindly supplied a small rubber boot (not shown on my parts list) that can fit over the bottom of the switch to keep dirt and water from reaching the switch from underneath. At rallies, or whenever the machine is parked up outside, I cover the top of the switch with a small polythene cover secured by the rubber grommet which surrounds the key insertion point.

I hope this may be of some help to you,

Best wishes, Colin Cheney, Leicestershire.

Submitted by michael_wallace on Sat, 16/06/2018

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Previously michael_wallace wrote:

Hello Gents,I would appreciate any help you could give me with my ES MkIII. Owned for about 14 years and had given running trouble for the last several.Anyway, coils,plugs, carb all sorted and I did a hundred miles in Wales, perfect. Started to deteriorate after return home and could only get home using choke (week spark?) and sooted plugs.Decided to diagnose ignition direction. Now here's mistake No1. I red on a forum connect Boyer (MkIII) direct to battery. I used the battery charger lead and it almost melted after 3 secs! This action must have connected batt. direct to earth, anyway it knackered my new batt. which will only hold 10.5V now- bin.I'm now using my old batt. 12.6V and suspect other damage. When I switch ignition on the neutral and ign. lights come on as expected and then immediately go out, every time as if discharging a capacitor.Do you think I've written off the Boyer? Maybe I'm due a MKIV anyway.I did find during analysis that the supply to the Boyer box had a very corroded spade connector and I suspect this was the original problem.

This message also sent to Al Osborne.

Mike

PROBLEM SOLVED

I returned the Boyer for test, checked OK. Thought I found a bad spade connector, corrected. It was evident that the right pot was trying to start and the left doing all the back firing, would not however start. I had good sparks L&R touching stator plate wires and kicking with plate connected, what could be wrong? I remember from my RAF days the Gen Fitt boys had a plug cleaner and tester that simulated compression. That was it, the left pot plug, Champion, was breaking down under compression. Two new NGKs and sweet result. I had been convinced the problem was elsewhere because I could see nice blue sparks, a lesson learned.

Submitted by julian_wells on Sun, 17/06/2018

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Great news!

Previously michael_wallace wrote:

PROBLEM SOLVED

I returned the Boyer for test, checked OK. Thought I found a bad spade connector, corrected. It was evident that the right pot was trying to start and the left doing all the back firing, would not however start. I had good sparks L&R touching stator plate wires and kicking with plate connected, what could be wrong? I remember from my RAF days the Gen Fitt boys had a plug cleaner and tester that simulated compression. That was it, the left pot plug, Champion, was breaking down under compression. Two new NGKs and sweet result. I had been convinced the problem was elsewhere because I could see nice blue sparks, a lesson learned.

 



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