The BSA A7-A10 Forum
Technical (Descriptive Topic Titles - Stay on Topic) => Lucas, Ignition, Charging, Electrical => Topic started by: Muzzleloader on 28.12. 2018 18:14
-
Hi.
My 1962 650cc Gold Flash is very difficult to start when hot and the kill switch will only cut out one cylinder. Have Checked cut out switch, wiring and magneto end cap and centre connection.
Starts cold easily and runs really smooth and plenty of power with no misfiring.
Comments greatly appreciated
Muzz
-
G'day Muzz, long time no see.
I'm no xpert on magies but that sounds very strange only cutting out one side. Could you be getting pre-ignition on one side making it "run on"? Could be a combination of timing/fuel & bias.
Cheers.
ps: Give us a clue as to here your located.
-
Location Herefordshire uk
-
Have a look at the earthing brush for the stopping problem.
The hot starting issue could very well be a failing capacitor.
-
G'day Muzz.
Thanks mate, you now have a flag.
Trev is most likely right but why would it only cut one side?
Cheers
-
Thanks for the replies. I have checked the carbon brush and continuity is good. I think an overhaul of the magneto is a good starting point. Will update at some point.
Ride safe wherever you are located
Muzz
-
Did you really check the earth brush and not the kill switch brush?
Some earth brushes are under a screwed-on holder, like this:
(https://i.imgur.com/6vYCnDV_d.jpg?maxwidth=640&shape=thumb&fidelity=medium.jpg)
-
I have had engines only cutting one cylinder.
It was the earth brush, maybe it was only contacting the armature in a limited area.
Usually the armatures have a distinct hollow in one spot which needs to be machined out.
-
G'day Fellas.
I remember my first problem with the A7 back in '81. She would start and run great but I couldn't stop her. Never had a Lucas magged bike before. Lucky the local library had a Lucas book. Yep that brush was gone.
Cheers
-
Just to pick up this thread.
My Flash has become a pig to start when hot. Fine when cold with no issues, but doesn't take too long to start spitting and backfiring on right hand pot. Took 40 mins to get it started when I filled up, but then ran ok for the next 100m with a few spitting and hesitancy moments. Was one moment when I thought it might pack up altogether, but it ran through it and I got home fine (didn't stop). Am I in for a maggy rebuild (hasn't been done since I owned it and I don't know if it's ever been done)? Earth brush looks fine, plugs and leads are fine - what do you all reckon?
One other quick question, what size are the front spindle clamp bolts and the mudguard studs on the lower fork leg.
Cheers all.
-
Have you already seen to all the service items?
-
G'day worty.
As TT suggests 1st give it all a good service.
Tappet clearance is the first thing I'd check. Then carb mixture, cold likes a rich mix hot doesn't. Then it's the maggy.
Cheers
-
Cheers guys.
So, plugs new, HT leads new with no frayed ends, earth brush and pickups cleaned and good condition, slip ring cleaned, points contact cleaned and dressed with correct gap.
Tappets have just been adjusted, I run 10 on inlet and 16 exhaust for max power (according to the handbook).
It does run a tad rich, always has and hasn't played up until now.
I'm really keen on keeping right on top of everything I can think of. Past posts have suggested fuel evaporation in the carb, but I did tickle it a bit with this in mind. I guess this wouldn't make it spit and backfire occasionally when on the road. It does generally seem better at higher speeds.
It was a very hot day here, around 30C and I'd just given it a 60m blast?? Funny how it fired up after 40 mins and even ticked over nicely.
-
G'day worty.
Give it another two thou on the inlet.
Cheers
-
Cheers Musky - so 12 and 16 - what'll that do performance wise?
-
Cheers Musky - so 12 and 16 - what'll that do performance wise?
Can't hurt to try. It ain't performing now ;)
Had similar when I first converted the A7SS to a A10 CR. Once hot she was down on power and wouldn't start till cooled off.
Cheers
-
Cheers Musky - cheeky question, do you know what size the front spindle clamp bolts are and the mudguard studs on the lower fork leg?
Nice to hear from you again.
Worty
-
G'day worty.
Wasn't that ? asked a few days ago? 42-5084 = 5/16 cei x 1, 7/16"
Cheers
-
It was mate, but I didn't get any replies - very much appreciated though. I've got a problem with a sheared mudguard stud and a stripped thread for the clamp bolt - got an adequate spare on at present but wanted to refurb the other. I guess the stud is welded on so I may need some expert help.
Cheers
-
Ok. Slip ring cleaned, new pickups, cleaned earth brush, new sparkies set at 16thou rather than 18thou, inlet at 12thou - exhaust at 16thou, points correct at 12thou. Kicked up first time cold. Am I right in guessing that, if I get spitting and backfiring now, I'm in for a maggy rebuild? Does seem weird to think that the maggy is failing only when it's very warm, but I note that this is fairly common.
What do you reckon??
-
Most magneto failures occur when they're hot. No idea why (no doubt groily can enlighten us). Maybe it's the condenser / capacitor more likely to fail when temp rises?
-
A correctly gapped contact breaker can still result in an error to the timing, if the drive gear was fitted with the gap incorrectly set initially. Opening the gap advances the timing, closing the gap retards it. So you need the correct points gap, armature correctly set, piston height set/backlash eliminated......then on with the drive gear with auto or manual set at full advance. Only then will you get the correct timing by the book. Which may then require a tweak depending on the fuel being used.
Erratic running/ misfiring. Number one suspect is steel points backplate type contact breaker spring touching the cam ring. Brass points carrier is a different electrical path. All detailed in previous posts.
Easy starting cold, with poor ignition, no starting and sudden ignition failure when hot are symptoms of a condenser on its last legs. The remedy is relatively inexpensive, and consists of substituting the well respected modern EasyCap for the failed electrolytic condenser originally fitted. If the magneto works well otherwise, and from the description it produces sparks in the right place, this will transform the magneto and add reliability for a reasonable cost.
Swarfy.
-
Points toward a failing condenser (no pun intended).
Timing was pretty good up until now. Ran smoothly, excellent acceleration, no issues. Timing was done by me and the geezer who helped rebuild the engine. Same thing applies to points backplate. Can't see how either of these issues have changed from when it was running really well until now.
Bike starts very easily from cold. Depending on how hot the ambient temp is, it starts misfiring after around 20-30m, especially on acceleration, this is becoming more common. Bike refused to start from very hot for around forty minutes last weekend, then fired up unexpectedly and ran on for another 100m with a fair few pops and bangs along the way.
I'm not competent enough to do a maggy rebuild myself. I also know there's a chip in the top of the slip ring. Priory Magnetos seem to offer a rebuild for around £300ish, don't know if that includes the EasyCap but it seems sensible to get this done. Ignition timing seems a right PITA, but may give it a shot. I've just created a thin rod which has the 11/32 markings on it for the btdc timing method, but I may get my mate to help out as he knows more about what he's doing than me.
To create my timing rod, I put a shrink insulator on the rod, put it up against a straight fixing bracket secured by one of the head steady bolts, made a cut on the insulator then measured the 11/32 with a digital Vernier gauge. I then cut the insulator again at that point and removed the section of insulator. That way, I get a nice edge on the insulator to measure the distance by instead of relying on a permanent marker.
Cheers in advance.