The BSA A7-A10 Forum

Technical => Lucas, Electrical, Ignition => Topic started by: BSA Patty on 18.10. 2011 19:30

Title: Magneto problem
Post by: BSA Patty on 18.10. 2011 19:30
went for ride on golden flash 1955 bike running fine pull in for a break after thirty miles ready to go again guess what would not start,check the usual petrol ok,spark at plugs a bit weak though,kick away no response not a splutter,so last resort bump start yes of we go,in the back of my mind having read on your great site how mag coils break down when hot,try everything back home nothing,next morning bike stone cold,flood carb starts first kick,yep looks like a mag overhaul,spoke to expert agreed this is problem,so mag of bike,note rotation,no problem on removal,sent of ,timing next,happy ending i hope.
Title: Re: magneto problem
Post by: wilko on 18.10. 2011 20:02
Could be just your hot starting technique!
Title: Re: Magneto problem
Post by: LJ. on 19.10. 2011 10:47
I wanted to ask if you have a tufnel heat insulating spacer between the carb and head, but neither of my A10s have one and start perfectly when hot, so its not that. I wonder why the A10 does not need this and yet my M21 and B33 need these tufnels badly or they will NOT start due to the carb being so hot. I think Patty is correct and that the magneto needs a rewind and new condenser. Let us know of the improvement when its refitted.
Title: Re: Magneto problem
Post by: iansoady on 19.10. 2011 15:09
Mine needs a bit of a tickle when it's hot. I think it may be due to petrol in the jet well vapourising.
Title: Re: Magneto problem
Post by: BSA Patty on 19.10. 2011 20:04
thanks for your replys,nice to know help out there,sure its a rewind,will post outcome.
Title: Re: Magneto problem
Post by: rockthedog on 20.10. 2011 19:28
went for ride on golden flash 1955 bike running fine pull in for a break after thirty miles ready to go again guess what would not start,check the usual petrol ok,spark at plugs a bit weak though,kick away no response not a splutter,so last resort bump start yes of we go,in the back of my mind having read on your great site how mag coils break down when hot,try everything back home nothing,next morning bike stone cold,flood carb starts first kick,yep looks like a mag overhaul,spoke to expert agreed this is problem,so mag of bike,note rotation,no problem on removal,sent of ,timing next,happy ending i hope.
had same problem mag fixed and now all ok
Title: Re: Magneto problem
Post by: renos-a10 on 21.10. 2011 12:09
hi to all.
I have the same problem on bsa a10.I take off the magneto and sent to england for recondition.Now the problem solve.
Title: Re: Magneto problem
Post by: A10Boy on 24.10. 2011 10:46
My A10 did this once on a very hot day after I had ridden though town. Stopped for 5 minutes and it wouldn't start, I thought I had flooded it, took plugs out and they were bone dry. Gave it a real good tickle and it started immediately. That was two years ago and it never did it again. Like Ian says, probably fuel vapourising, I have a tufnel gasket to fit next time the carb is off.
Title: Re: Magneto problem
Post by: BSA Patty on 26.12. 2011 19:36
Fingers crossed problem sorted. Sent magneto for overhaul, work done rebuilding magneto including rewind coil, replacing slip ring, supplying left hand contact breaker assembly, run on test for three hours and guaranteed for three years however they said guarantee would be invalid if suppressed caps leads etc are used. Replaced on bike, next problem was auto advance unit. On removing from bike I noticed two horse shoe washers fitted believe one only to be used, sure enough when timing set advanced, retard unit unable to move without using a lot of pressure with my fingers. Being a plumber I have a strong grip, all them pipes you know! but, saying that the bike started fine, but no way was that unit working correctly.I know on other forums people have commented on this, but I sought further advice from someone whose business is re building these units for the classic bike market, he said the centre bolt had been overtightened thus belling out the threaded end onto magneto shaft so I sent it to him for overhaul. Fitted to the bike now, when fitted movement is just great, bike starts and runs fine, road test next when weather ok ,hope i haven't gone on too much and hope this is of help to someone else. Just like to wish everyone a happy and trouble free new year and to all those who replied to my original posts.