The BSA A7-A10 Forum

Technical => Lucas, Electrical, Ignition => Topic started by: Thrang on 19.04. 2016 22:42

Title: weak spark
Post by: Thrang on 19.04. 2016 22:42
Evening all!
I'm new to A7's but have owned a fair few older Triumphs in the past so I'm no unfamiliar with using my foot to start a bike. Any way my Shooting Star has been a total pig to start, so I had a look at the system.
It produces a very weak spark when I kick it over but as a matter of course before I attempted to start the bike I stripped and cleaned the carb. Cleaned out the tank, change the oil and set the tappets to the Haynes manual specs. Checked the compression (and its good).

When I spotted the spark issue I replaced the points (and plugs) and set them up as in the (Haynes) manual.
The HT caps and leads look new, no sign of cracking or damage and have good connectivity.

However the battery is pretty crappy and after 2 hours on charge it only showed 2volts so I've ordered a replacement.

So my question is does the A7 magneto  dynamo set up require energising from the battery, or should it produce enough of a spark just off the boot? 

Cheers
Tony.
Title: Re: weak spark
Post by: Greybeard on 19.04. 2016 23:12
If the machine is standard then no battery is required; the magneto generates the sparks. Mag overhaul may be expensive but I found it to be well worth the money!
The battery only serves the horn and lights and should get charged by the dynamo.
Title: Re: weak spark
Post by: Joolstacho on 20.04. 2016 00:33
Agree, re-co magneto.
I chased a starting problem for years before I finally bit the bullet and had the mag re-co'd.
Easy starting was the result.
Title: Re: weak spark
Post by: Thrang on 20.04. 2016 01:09
Thanks chaps!

I'll give it a couple of weeks and see if its just me not having the 'knack' of starting her yet that's at fault. If I don't get the knack and its still a pain in the idiot I'll send the Mag off for a reconditioning. Got to say she's a lot of fun to ride once I have got her started. I went for my first proper ride, over the Kirkstone Pass and down the side of Ulswater this afternoon and the brakes were not as bad as I expected. The run back down the A6 from Penrith to Kendal was pure magic warm, sunny and hardly any traffic, it was absolutely brilliant. Well it was until I turned back into the Lakes and had to face all the drivers rubber necking the lovely views over Windermere rather than watching where they were going.

Tony   
Title: Re: weak spark
Post by: Greybeard on 20.04. 2016 05:15
I went for my first proper ride, over the Kirkstone Pass and down the side of Ulswater this afternoon and the brakes were not as bad as I expected. The run back down the A6 from Penrith to Kendal was pure magic warm, sunny and hardly any traffic, it was absolutely brilliant.
You lucky so-and-so! *smile*
Title: Re: weak spark
Post by: KiwiGF on 20.04. 2016 07:51
Before refurbish the mag which as the others say is  *pull hair out* expense I t would be worth checking you definitely have the right specification plug caps and plugs, you don't want either with resistors, if using a mag.

There's a few other things it might be worth checking like the brushes (including the earth one) and slip ring etc.

I've a BTH electronic mag which was a  *pull hair out* *pull hair out* *pull hair out* expense.
Title: Re: weak spark
Post by: RichardL on 20.04. 2016 08:20
Has anyone mentioned timing or asymmetrical point gaps? Also, there are a few thing you can do for yourself on the mag before committing to a complete rebuild, for example, replacement cap from Brightspark Magnetos. Checking and/or replacing the slip ring and/or the pick-up brushes.

I think I'll mention timing again, just for the heck of it.

Richard L.
Title: Re: weak spark
Post by: duTch on 20.04. 2016 08:41

 Ditto all the above, in particular;
 
Quote
I chased a starting problem for years before I finally bit the bullet and had the mag re-co'd.
Easy starting was the result.

 But check all the other above first, bad Maggie will likely fail in transit and/or be hard to start when hot (my experience)
Title: Re: weak spark
Post by: cyclobutch on 20.04. 2016 10:21
As ever I’m in accord with GB. My magneto was of unknown provenance so I figured I’d just get it done and then it was one less thing to worry about. So I threw money at the ‘problem’. I have a first kick starter and a magneto that I’m expecting to outlast me. 
Title: Re: weak spark
Post by: RichardL on 20.04. 2016 14:40
Ah. Money. Now, that's an interesting commodity, as is "Time".

Richard L.
Title: Re: weak spark
Post by: cyclobutch on 20.04. 2016 16:24
Indeed, I'm in the questionably fortunate position of being able to spend (some) money in order to save on what dwindling amount of time might be left to me. You rarely seem to have both. Swings and roundabouts I guess.
Title: Re: weak spark
Post by: worntorn on 21.04. 2016 04:57
My A10  SR magneto is going in for rebuild tomorrow. There are very few advantages to being 61 years old rather than 15 , as I was when I had a G80 with a duff mag. One big advantage in 61 is that at age 15 I could not afford to rebuild the mag and was forced to do a lot of kicking & bump starting.
At 61 I can spring for the good rebuild.
Nonethe less, watch me whimper when the bill comes in :-)

Glen
Title: Re: weak spark
Post by: Greybeard on 21.04. 2016 09:18
...dwindling amount of time might be left to me...
I really hope that comment has no deeper meaning to it!
Title: Re: weak spark
Post by: Topdad on 21.04. 2016 11:24
I was thinking exactly the same ??