The BSA A7-A10 Forum

Technical => Lucas, Electrical, Ignition => Topic started by: BSA500 on 20.03. 2013 13:10

Title: Magneto issues?
Post by: BSA500 on 20.03. 2013 13:10
Hi,
I think by posting this I may be answering my own question. For quite a while the A7ss has had an annoying misfire/stutter when accelerating from approx 1/4 throttle upwards. I had put this down to a horrible worn slide-so worn it ticked and you could hear it over the engine. I replaced the carb with a spare which was the smaller 15/16 but had a resleeved body. The bike now ticked over and actually ran rich due to less air going around the old slide. Anyhows the annoying stutter/missing is still there. I experimented with different needle jets as the old one was a 107 but no improvement. Is there anything easy to try on the mag to check it out. Some other things I have done....
New plugs,new leads,no caps just direct wired to the plugs(rain does not effect them). I suspect its a rebuild/check over but it starts first kick, nice tick over-oh its better when the engine is cold( i know suggests mag as when its warmer its worse).
I do 26 miles a day every day so its not standing around. I f it needs a check/build it will go to Priory mags.BTW the dynamo he rebuilt for me is going great no issues all winter *smile*
Title: Re: Magneto issues?
Post by: muskrat on 20.03. 2013 18:40
 G'day BSA500, better when cold means it's rich and the stutter could be your slide cutaway or pilot jet (it affects the whole range not just idle).
I can't comment on the magie, I went lectric 20 years ago.
Cheers
Title: Re: Magneto issues?
Post by: Angus on 20.03. 2013 19:52
When my A7 was first brought back it had a misfire/stutter at about that point. Roger came and took it back. Fitted a larger carb (its to SS spec inside) and rejeted also dealt with induction bias
Title: Re: Magneto issues?
Post by: BSA500 on 20.03. 2013 20:06
I suppose I should rebuild the 1 inch carb first then. problem is it needs resleeving which then means you cannot try out different slides. I know I could buy a new carb but its only £50 against £150. Strange the stutter did not change when I swopped carbs I could try a smaller pilot as well at the moment I am using a 30 pilot.
Title: Re: Magneto issues?
Post by: A10Boy on 21.03. 2013 13:07
Have you clean the slip ring, set the points, replaced pick-ups etc? To me, if it's still doing it with a different carb fitted, it would be a mag issue.

Regards

Title: Re: Magneto issues?
Post by: BSA500 on 21.03. 2013 19:47
i will do the magneto checks but I did swop over the jets from one carb to another,so in theroy the same issues have been transferred over. The only differences being the smaller choke size 15/16 instead of 1 inch and a good fitting slide(resleeved). The biggest improvement was that now I have a tickover and she does not spitback or try to die when opening the throttle off idle. I think other than a quick check over of the mag would be to get the 1 inch carb resleeved and jetted according to the specs and go from there.
Title: Re: Magneto issues?
Post by: Topdad on 22.03. 2013 11:11
Always worth doing the standard stuff on the mag set it up ok then get the carb done ,sorry you're so far away I'd lend you my carb .Last time I rode to kent (1966 ) took me 14 hours . Anyone closer to help? best wishes Bob .
Title: Re: Magneto issues?
Post by: BSA500 on 22.03. 2013 11:52
Thanks for the offer. 14 hours blimey that is dedicated riding. Where abouts in Kent?
Title: Re: Magneto issues?
Post by: Topdad on 22.03. 2013 12:40
It was the last family holiday in 1966 ,my dear old mum and dad ( he being a true born cockney ) always took us to Ramsgate for our hols when we lived in Manchester ,we moved to liverpool and decided it would be nice to go again once more so I follwed him in there camper so quiet slow 45 max however the rain was of biblical proportions ,I had to be rescued by the firebrigade under a bridge in rudgley stone  mag was under water !!  ..kaput  but pulled it out dried it off used that new fangled (then )wd40 stuff  and bingo on our way again ,boy did I sleep when we got there!! strangely looking back I was rather pleased with myself , (......sorry e here I go again wind wondering of topic ) Finally remember visiting Manston to see the spit and hurri ,they were still outside then and looking very sorry but to be able to get that close ,feels like yesterday and certainly worth the 14 hours best wishe and hope you sort your misfire BobH.
Title: Re: Magneto issues?
Post by: BSA_54A10 on 22.03. 2013 20:24
Spend £ 30 on a colour tune and stop wearing your brain cells out.
With it you can look at the combustion colours as you open the throttle .
If the flame goes out & you can see the spark then you have a carb problem.
If the flame goes white ( lean ) or yellow ( rich ) you have a carb problem ( note it should go rich momentarially as you open the throttle )
If the flame goes out and you can not see a spark, or the spark is not constant then you have an ignition problem.

Of all the "special tools" in my tool chest this one gets the biggest work out.
Knocks down tracking problems in 1/2 and just about every one who watches me using it ends up buying one.

Just two tricks to remember.
1) run the bike from a lawnmower fuel tank hanging on a stand so you do not run the engine stationary for too long
2) lightly engage the rear brake & pop the box into a high gear to put a bit off a load on the engine

Bike Beesa
Trevor
Title: Re: Magneto issues?
Post by: bsa-bill on 22.03. 2013 22:08
Quote
If the flame goes out and you can not see a spark, or the spark is not constant then you have an ignition problem

spot on Trevor

it did and I had, as yet I've not had time to find out why but suspect a series of duff plugs and maybe Magneto condenser - all on a to do list
Meanwhile Pazon performs with distinction
Title: Re: Magneto issues?
Post by: Triton Thrasher on 23.03. 2013 09:52

Just two tricks to remember.
1) run the bike from a lawnmower fuel tank hanging on a stand so you do not run the engine stationary for too long

I don't understand. Don't run it too long, by pressing the kill button.

Quote
2) lightly engage the rear brake & pop the box into a high gear to put a bit off a load on the engine


Be aware of what will happen if you knock the bike off the stand, or get something caught in the chain.

I have landed myself with two Colortunes, which is good on a twin. The odd thing is, an ideal coloured flame at idle doesn't always seem to be so ideal when you go out and ride around on the bike. I ended up setting the idle mixture, by ear, for best running at a teeny-weeny throttle opening, held by the cable adjuster. I know that's wrong, in theory.

Mixture at bigger throttle openings isn't hard to get right by road testing.
Title: Re: Magneto issues?
Post by: bsa-bill on 23.03. 2013 10:23
Quote
I have landed myself with two Colortunes,

Lucky lad, I can see why for once overspending would be a big benefit, I will continue to swap mine from one side to the other until someone comes up with a good price, unfortunately when I got mine Halfords didn't do a bogof
Title: Re: Magneto issues?
Post by: Triton Thrasher on 23.03. 2013 10:30
Quote
I have landed myself with two Colortunes,

Lucky lad, I can see why for once overspending would be a big benefit, I will continue to swap mine from one side to the other until someone comes up with a good price, unfortunately when I got mine Halfords didn't do a bogof

The second one was cheap second-hand.
Title: Re: Magneto issues?
Post by: Spitfiremk9 on 23.03. 2013 10:57
Thanks Triton thrasher, forgotten I had one tucked away in the garage must dust it down and use it, regards Bobh
Title: Re: Magneto issues?
Post by: BSA_54A10 on 25.03. 2013 12:30
I don't actually use mine for tuning unless I am in deep trouble or way out of my depth ( most of the time ).
What I use it mostly for is fault finding.
Really good particularly on late A65's with the carby balance tube.
No need to touch any of the owners "tuning" and I can show them where they went wrong ,
just about every one that has fronted up at my place was running both pots at idle off one carb
Title: Re: Magneto issues?
Post by: mayes on 07.04. 2013 15:20
Hi Check that you are running on non resistance spark caps also I was caught out with the cut out switch not fully disconnecting witch gave a weaker spark when hot ,hope this helps Jon   
Title: Re: Magneto issues?
Post by: A10 JWO on 07.04. 2013 16:04
Spot on Mayes, A bloke from Hullbridge gave me that good advice as well. Watch those cut off switches on the KF2 Mag'
: )

Title: Re: Magneto issues?
Post by: BSA500 on 07.04. 2013 19:16
I have disconnected the wire and will check it out tomorrow on the way to work.Fingers crossed.
Title: Re: Magneto issues?
Post by: BSA500 on 08.04. 2013 09:17
No change. Just to recap.... Fresh plugs and leads, no supressed plugs or caps(in fact no caps wired direct to plugs). The stutter is still there regardless of carb fitted. Ticks over and revs a treat just the stuttering when accelerating hard and gets worse the warmer the engine gets. It has a nice long run into work each day 13 miles each way. I would like to see if anything changes as the weather warms up but it seems that's still a way off *sad2*. I still intend to have the 1 inch carb resleeved and new needle jets etc when funds allow just to hopefully rule that out.
Could this be a condenser on its way out,if it is its taking a damm long time to fail. As an aside I had to fit B7ES plugs as the others(B6ES) failed as NGK seem to in under a year. It now pinks which is why I used B6ES.
Title: Re: Magneto issues?
Post by: muskrat on 08.04. 2013 10:35
G'day BSA500. Retard the ignition a tad. A hotter plug won't help pinging, but it will help burn a richer mixture to combat pinging.
Is it a manual or auto advance?
Cheers
Title: Re: Magneto issues?
Post by: BSA500 on 08.04. 2013 12:28
Auto. Checked the weight action on the atu and that's fine will have a check on the timing when I have a chance to see if its not slipped or anything
Title: Re: Magneto issues?
Post by: a10gf on 08.04. 2013 12:31
Maybe worth to try a Brightspark EasyCap, see http://www.a7a10.net/forum/index.php?topic=5359.0
Title: Re: Magneto issues?
Post by: BSA500 on 08.04. 2013 13:09
Don't really want to start cutting the mag about unless I am sure there is a issue
Title: Re: Magneto issues?
Post by: A10Boy on 08.04. 2013 16:39
Thats a fair point, but it might just be the problem. Fitting a brightspark is easy, it will eliminate the dodgy condensor worry, and it will give you the reason to re-set your timing too. All for about 15 quid.  *smile*

No connection.
Title: Re: Magneto issues?
Post by: BSA500 on 09.04. 2013 12:24
That's  probably what I would end up with-no connection  *smile*. If it was the condenser, from previous experience, would it not be difficult to start, run rougher esp when hot. My only symptoms are the stutters under acceleration. She ticks over like a clock(better after fitting the spare carb),starts first/second kick even when hot and barring the stutters accelerates really well. There is no spit back but at the mo some pinking(timing?). I really must speak sweetly to she who holds the money about rebuilding the correct carb(1 inch not the current 15/16) and new needle/jet etc and going from there unless someone has any more possible reasons?
Title: Re: Magneto issues?
Post by: Triton Thrasher on 09.04. 2013 20:57
Missing under acceleration.

Can be a problem in the HT side of the ignition.  Close the plug gaps to about 8 thou. If that helps, well, at least you've eliminated the carburettor as the cause.
Title: Re: Magneto issues?
Post by: BSA500 on 10.04. 2013 08:40
Well it seems Triton Trasher wins todays prize. Closed the gaps and no stutter-hoorah. Of course this means there is an issue with the mag-boooo.
Title: Re: Magneto issues?
Post by: KenF on 10.04. 2013 17:14
Well done, TT.

BSA500, if you're after a mag troubleshooting guide, please pay a visit here http://brightsparkmagnetos.com/DIY (http://brightsparkmagnetos.com/DIY).

You may have a condenser problem, but I guess it's more likely to be a breakdown of the insulation around the HT winding or of the slip-ring or pick-up. Sometimes you can detect a pick-up problem by putting your hand on it while the engine's running (but don't try that if you've got a pacemaker). Breakdowns of the winding insulation or slip ring are more difficult to detect without stripping the thing down completely and using a magneto coil tester.

Best of luck.

Ken
http://brightsparkmagnetos.com (http://brightsparkmagnetos.com)
Title: Re: Magneto issues?
Post by: Triton Thrasher on 10.04. 2013 17:54
Well it seems Triton Trasher wins todays prize. Closed the gaps and no stutter-hoorah. Of course this means there is an issue with the mag-boooo.

I suppose you've eliminated the cheap possibilities like bad plugs, cracked pickups, HT lead or plug insulators tracking, buildup of oily stuff on pickups?
Title: Re: Magneto issues?
Post by: BSA500 on 10.04. 2013 18:42
Yep TT done all the cheap stuff.
Title: Re: Magneto issues?
Post by: Dunney on 18.04. 2013 19:49
Pinking observation is interesting.  Do you have a manual adv/ret mag?  Does the pinking diminish if you back off the timing a tad.  Have you timed the ignition on both pots to see how far out the two sides are.  Don't know what the tollerance is but it the slip ring is worn more on once side that the other it could be making a difference.

Dunney