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Berticus
Joined: 20 Jul 2008
Posts: 1
Location: Brussels
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 Posted: Sat Aug 16, 2008 6:07 am Post subject: Podtronics and the 2MC Cacitor |
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I am about to replace the recifier and zener diode with a podtronics box but I was wondering whether the 2MC capacitor could go as well.
I have had an intermittent ignition problem that I can't find so I am using it as an excuse to replace everything, except I forgot about the capacitor. If it were failing short circuit I suppose it could be the problem couldn't it? |
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L.A.B.
Moderator
Joined: 20 Nov 2004
Posts: 1842
Location: Norfolk, UK
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| Posted: Sat Aug 16, 2008 7:22 am Post subject: |
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| The 2MC capacitor is there so that a bike can be started if the battery was flat or not even fitted, so technically you don't actually need it, just make sure you connect any Brown/Blue wires together that were originally connected to the 2MC unit. |
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worntorn
Joined: 22 Dec 2006
Posts: 168
Location: Langley, B.C.
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| Posted: Sun Aug 17, 2008 6:57 am Post subject: |
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I've never been able to get my Boyer equipped bike to start with the battery much below 12 volts. Even with 12.5 volts in the battery, the bike will not cold start with the electric starter. It will whirl over at a high rate but not fire. In this situation , when I give up on the electric starter and use the kick start it starts in half a kick. I've learned that this is typical of Boyer ignition , it requires pretty close to 12volts to make a strong spark.
If the bike has much less than 12 volts in the battery, say 11 volts when tested, then even with just the kickstart(no voltage drop from starter) it will bang and pop but will not start.
Clearly the non-start problem when cold and using the starter is because the electric starter turning over the cold engine causes a large voltage drop which is too much for the Boyer. I think others on this site have discussed the same problem with their Boyer equipped MK111s.
The 2mc capacitor is in the system, but does not seem to help with low voltage starting when Boyer ignition is used.
I am sure that with the original setup the 2mc capacitor was of use; with points and coil the voltage is not so critical, the system will still produce a reasonable spark with much less than full voltage.
This is my theory from observation of my Commando, but really this is a question I have been wanting to ask of others;
Will your Boyer equipped bike kick start from the 2mc starting capacitor with a dead battery or no battery? |
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79x100
Joined: 19 May 2006
Posts: 689
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| Posted: Sun Aug 17, 2008 7:40 am Post subject: |
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| worntorn wrote: | | Will your Boyer equipped bike kick start from the 2mc starting capacitor with a dead battery or no battery? |
Absoutely not ! At 10v it will be bruising the bones in my foot, trying to tear another chunk of cartilage out of my knee and doing its best to punt me over the handlebars !
I assume that the capacitor is ensuring a spark but the Boyer needs a steady supply or it gets its advance / retard knickers in a twist.  |
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L.A.B.
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Joined: 20 Nov 2004
Posts: 1842
Location: Norfolk, UK
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| Posted: Sun Aug 17, 2008 8:47 am Post subject: |
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With the battery disconnected, the plugs connected to the plug caps and resting on the cylinder head, I can just about generate enough cranking speed with the kickstarter to get sparks on my MkIII with the 2MC, however with an additional set of plugs fitted in the plug holes (simulating the compression resistance) with the original plugs still resting on the head I can't spin it fast enough to get sparks.
With an AGM battery, heavier gauge starter wires and 4 brush conversion, my Boyer equipped 850 MkIII bursts into life from cold, even after it has been left for weeks, in fact it starts far easier with the electric starter than it does with the kickstart. |
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worntorn
Joined: 22 Dec 2006
Posts: 168
Location: Langley, B.C.
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| Posted: Sun Aug 17, 2008 9:44 am Post subject: |
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L.A.B, I have the four pole conversion however I think the starter wires are original. My battery may also be a little lower in cranking power than yours. Either of those factors could be enough to mess up the Boyer for cold starting on the electric starter.
I should add that as long as the battery has 12 volts the bike is a very easy kick starter, cold or hot usually just one kick. Because it's an easy kick starter, I don't really mind the fact that the electric starter is useless to me for cold starting.
The bike fires up instantly on the electric start when warm, however in this instance cranking effort is less(less voltage drop) plus the battery is probably up half a volt from where it might be if the bike has been sitting for a couple of weeks. |
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Corona850
Joined: 09 May 2008
Posts: 25
Location: Corona, CA
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| Posted: Tue Aug 19, 2008 8:50 am Post subject: |
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| worntorn wrote: | The 2mc capacitor is in the system, but does not seem to help with low voltage starting when Boyer ignition is used.
I am sure that with the original setup the 2mc capacitor was of use; with points and coil the voltage is not so critical, the system will still produce a reasonable spark with much less than full voltage. |
The 2MC capacitors have a short useful life. If you have the original it is very likely knackered by now. See this article by R F Whately for some useful info.
http://www.gabma.us/elec/lucas_2mc.pdf
If you buy a replacement 2MC (such as those that an infamous vendor in Chicago was selling on ebay recently) they're useless because they're old stock. Whately's article says the life is "limited to about 30 years." I've read elsewhere that the life is more like 5 years.
I rewired my bike to use a podtronics. I eliminated the 2MC and I am using a Boyer (old style, not digital). Works fine and starts 1st or 2nd kick most times. |
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ML
Joined: 29 Jul 2007
Posts: 43
Location: Melbourne, Australia
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| Posted: Wed Aug 20, 2008 4:24 am Post subject: |
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Worntorn wrote:
Will your Boyer equipped bike kick start from the 2mc starting capacitor with a dead battery or no battery?
I have a stock 850 Mk2 with the 2MC and a Boyer analogue ignition and have on two occassions: Started and run the bike for 5 miles before I realised I had the battery fuse in my pocket! And next left the ignition on for a week and started the bike on the 3rd kick with the battery at 4.5V.
I don't understand any of this. My Bonnie would not even cough under 11.5V
Mick |
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norbsa48503
Joined: 07 Apr 2004
Posts: 995
Location: Flint, Michigan
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| Posted: Wed Aug 20, 2008 5:43 am Post subject: |
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I have been told by folks who know more than I.(not hard) that the a 2MC Not a Lucas one and not a Sparks one but an industrial one in good working form can be a positive force in the electrical system. Bad ones suck the battery down and make the system all work badly. But a good one works like a filter giving a studier DC output from the converted AC off the rectifier.
Do you have to have them? no Do they help when they are working? Yes.
An LED tail light cuts down the constant demand and helps just as much IMO.
So I do both when I can. |
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The Unapproachable Norton Commando
At the end of 1967 the Norton Commando was announced.
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