The BSA A7-A10 Forum

Technical => A7 & A10 Engine => Topic started by: Terryb on 11.06. 2015 20:21

Title: A7 Shooter Suddenly Not Starting
Post by: Terryb on 11.06. 2015 20:21
Hi All here's a teaser.

I have an 1955 At Shooting Star, which up to a few weeks ago, run like a dream, started almost without looking at her. Then the other day had a ride out to Didcot Railway Museum (about 40miles) and on the return had to switch over to the reserve, so popped into a service station. Put two gallons of petrol in and then tried to start it and failed. After checking the usual things like spark and petrol flow, still wouldn't fire up. After about 20 mins of kicking her over, just about to call for the yellow taxi she started. So without delay rode on home. Next day went to my usual bike meet about 10 mile, left there and called in to see a relative, came out and she would start again. Same thing, good spark and petrol flow but dead as a DoDo. After 10 mins this time she started, rode home and I'm now scratch my head on what to check? Any idea's or has anybody had the same happen?

The only bad experience I had prior to this was that about 4 weeks ago, I accidently put a gallon of diesel in by mistake, obviously wouldn't start. Got the yellow taxi home. Flushed out the tank and carb, cleaned the plugs put new petrol in her and away she went. Since then the only maintenance has been to adjust the tappets.
Title: Re: A7 Shooter Suddenly Not Starting
Post by: Greybeard on 11.06. 2015 20:26
Check that the fuel cap air hole is not blocked. DAMHIK!
Title: Re: A7 Shooter Suddenly Not Starting
Post by: chaterlea25 on 11.06. 2015 22:47
Hi Terry,
Where are you checking the fuel flow? check by removing the cap at the bottom of the carb
Its possible that crap from the tank bottom flowed down when on reserve?

Did you fit new plugs after running on the diesel mix?? if not do

HTH
John
Title: Re: A7 Shooter Suddenly Not Starting
Post by: beezermacc on 12.06. 2015 10:05
Sounds like classic magneto failure to me. Probably capacitor gone.
Title: Re: A7 Shooter Suddenly Not Starting
Post by: Terryb on 12.06. 2015 10:42
I'm almost sure there is no crap in the float chamber, there's a filter on the banjo connection and I've recently cleaned the tank when it had diesel in it.

Could be worth trying a change of plugs. The magneto has only done 4K since it was rebuilt and I had a healthy spark.

My money is on a possible fuel airlock, its the only connections which have been disturbed, every think else is as was.
Title: Re: A7 Shooter Suddenly Not Starting
Post by: edboy on 12.06. 2015 20:30
another favourite is the kill button staying on/sticking sometimes. overwise mag problem i d say
Title: Re: A7 Shooter Suddenly Not Starting
Post by: paulmbsa on 13.06. 2015 19:57
Mag u/s condenser gone
Title: Re: A7 Shooter Suddenly Not Starting
Post by: duTch on 14.06. 2015 00:06
  Terry, I'm a bit confused...
 
Quote
..... After 10 mins this time she started, rode home and I'm now scratch my head on what to check? Any idea's or has anybody had the same happen?

The only bad experience I had prior to this was that about 4 weeks ago, I accidently put a gallon of diesel in by mistake, obviously wouldn't start. Got the yellow taxi home. Flushed out the tank and carb, cleaned the plugs put new petrol in her and away she went. Since then the only maintenance has been to adjust the tappets.

   ..so is there still a problem?

   I had a similar, where it just stopped one day on the way to the races....picked it up in the U-beaut blue Ute later- after living in denial for ten years that it was anything but the maggie, I had it rebuilt-; immediate fix(condenser shot, plus ugly old wires ), and no problem since (but I had refurbed the carby in the process).

 Having said that though, if it finally starts and runs fine, maybe the idle mixture is a bit out of whack, or float level a bit high...?

Title: Re: A7 Shooter Suddenly Not Starting
Post by: bikerboy on 28.06. 2015 01:24
Sounds like mag to me do you only get the problem when the engine is hot?
Title: Re: A7 Shooter Suddenly Not Starting
Post by: Terryb on 28.06. 2015 19:31
Hi,

Sorry for the late reply, but been away. If as you say it is the mag/condenser, how come that during the period of not firing, when I checked for a spark on either plugs I was getting a big fat spark?
Title: Re: A7 Shooter Suddenly Not Starting
Post by: bikerboy on 01.07. 2015 03:38
Terry

I had exactly the same after about 20 miles my bike died and would not start until it cooled. I had a spark when I tested it but it still never went. Classic mag failure so I am assured. Got the mag done and its now as good as gold
Title: Re: A7 Shooter Suddenly Not Starting
Post by: worntorn on 01.07. 2015 07:56
"Hi,Sorry for the late reply, but been away. If as you say it is the mag/condenser, how come that during the period of not firing, when I checked for a spark on either plugs I was getting a big fat spark?"

It's possible to have a spark show at atmospheric pressure but still no spark when under compression. This situation is pretty common with a weak spark.
Title: Re: A7 Shooter Suddenly Not Starting
Post by: Terryb on 06.07. 2015 17:12
OK Guy's I give up and leaning towards thinking its the Mag. I've just cleaned the fuel system, so I plan to make a test run tomorrow.

Having never had a go at re-timing a twin with a Mag and manual A/R and being a coward I'm leaning towards Thorspark Electronic Ignition Conversion. I've read all the messages regarding battery power, but as I do little or no night riding and the bike is mainly used for club runs, its looking like the cheaper option. Equally if I do decide to be brave at a later date I can always exchange the armature and re-commission it.

I'll post my decision soon! Thanks one and all.
Title: Re: A7 Shooter Suddenly Not Starting
Post by: Triton Thrasher on 06.07. 2015 18:04
Thorspark doesn't look much cheaper than a Tony Cooper mag rebuild.

Also has no electronic auto advance.
Title: Re: A7 Shooter Suddenly Not Starting
Post by: beezermacc on 06.07. 2015 19:02
Thorspark doesn't look much cheaper than a Tony Cooper mag rebuild.

Also has no electronic auto advance.
..... or Priory Magnetos
Title: Re: A7 Shooter Suddenly Not Starting
Post by: Terryb on 11.07. 2015 13:01
Hi All,

Yes, you were right it looks like classic mag failure. Did my test run this morning 20 miles, then home, went like a dream. Parked it on the drive for about 5 mins. Tried to start her, nothing. Left her about 30 mins. started first time.

Decided to give a Thorspark 6v version a try. Thanks very much for the advice guy's. What would I do without this Forum. Cheers
Title: Re: A7 Shooter Suddenly Not Starting
Post by: Rocket Racer on 11.07. 2015 23:52
on the upside a dodgy mag will stop someone starting your bike and riding off while your in the shops and gives you an excuse to relax with a drink of your choice and enjoy the scenery. Almost a feature courtesy of Lucas products, if you decide to stop you stay stopped... Good to hear you've got it sorted.
Nothing worse than not being able to start the pride and joy when you've got an admiring audience that then quietly wanders off shaking heads about old pommie rubbish  *problem*
Title: Re: A7 Shooter Suddenly Not Starting
Post by: jachenbach on 12.07. 2015 13:23
re: checking for spark. It's entirely possible to have a good spark when laying the plug on the cylinder head, but not getting it when the plug is in the engine. It takes more energy to jump the gap under compression. Seeing as they're cheap and easy (and spares are good to have anyway) I always start with swapping plugs for a problem of this type.