The BSA A7-A10 Forum
Technical (Descriptive Topic Titles - Stay on Topic) => Lucas, Ignition, Charging, Electrical => Topic started by: bigwol on 19.07. 2012 11:46
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Hi guys, recently bought my first BSA, 1959 A7.
Due to one or two factors only took it round the block a couple of times and all was fine. Used it yesterday for the first time "in anger" so to speak and after 12 miles or so she lost power and eventually came to a stop. I checked spark as best i could and didnt seem to be great to be honest but when she cooled down restarted so I headed home with the same result. Cooled her off again and got back to base and she is now on the ramp. Blue spark at plug when cold and starts ok. (flood carb no choke fores first or second kick)
There is some oil appearing at the top of the head, so my question is most likely cause? Magneto breaking down when hot? Condenser same thing? Or something more sinister like losing compression when hot?
One more thing, as she had wet sumped I topped up the oil before setting off. When hot after first breakdown the level was around an inch below the top of the tank, is this too high? Where should the level be?
Any advice will be much appreciated.
Dave
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Hello & welcome. Moved the post to the lucas board, ref. your main question\problem.
Very probable you've got a heat problem with the mag, maybe open circuit in armature winding when hot and expanding, and ok when cold and contracting (...how did I learn about that :O)
About the condenser, take a look at this http://www.a7a10.net/forum/index.php/topic,5359.0.html
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Thanks for the welcome a10gf, and the reply.
I have heard of the "brightsparks" external condeser (I have run a couple of AMC's for a year or so, so although new to BSA'a not a complete novice with classic brit iron) and would certainly consider it if I need to replace the condenser, however if it's a windings issue will probably send the mag away for refurbishment. Either that or look at electronic ignition although I do like the mag system, not least as you can start and run with a dead battery if needed.
I'm not 100% certain it is mag yet, will investigate further including run the thing till it plays up and check the spark hot again, but it only seems to do it after 10 to 15 miles and being made to work. Another avenue I will check is compression hot and cold and take a look at the carb to see if there are issues there.
It doesnt missfire so much as lose power which gradually gets worse. No popping back or spitting, just more and more gutless untill it stops completely. Just wondered if anyone else had similar problems so I could get a few pointers.
Regarding the oil level, while I doubt a high level would cause problems like this can you give me a clue as to correct level?
Thanks
Dave
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Hi big wool, first thing I would look at for this type of fault is to see that there is a thick insulating gasket between the carb and the head to prevent heat transfer to the carb.
All. The best Goldy
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Oil on the head is often from the rocker box or out of the plug hole if the spark plug isn't seated properly or blowing back from the exhaust port. I'll send you a p.m. re the mag. Welcome to the board.
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regarding the oil level my "BSA Instruction manual" printed 1964 states 5 1/2 pints as the capacity of the oil tank for the A7 (and A10). Maybe you can fill the tank and mark the level before it has a chance to wet sump!
Rick D
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Sounds very much like the magneto. My A7 was playing up in a similar fashion. Have picked up the bike today after having the magneto reconditioned & all's well. It is a different bike altogether.
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G'day bigwol, welcome,
to throw another possible cause is the tappet clearance too close. They close up when hot and prop the valves open a tad = loss of power. Stop and cool down, all fine again till hot.
Cheers
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Hi big wool, first thing I would look at for this type of fault is to see that there is a thick insulating gasket between the carb and the head to prevent heat transfer to the carb.
All. The best Goldy
Hi Goldy, the manifold has a fairly long neck which may do that job like some of the amal carb models but i'll check the gasket situation, without looking I can't recall if there is a "bakelite" type spacer as on my AMC's. Again, i need to check and see if it should have one of those?
I have a few things to look into, will keep the forum informed as to progress.
Bigwol
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regarding the oil level my "BSA Instruction manual" printed 1964 states 5 1/2 pints as the capacity of the oil tank for the A7 (and A10). Maybe you can fill the tank and mark the level before it has a chance to wet sump!
Rick D
Thanks Rick, 5 1/2 pints seems a lot for that little tank but i'll give it a try.
Bigwol
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Sounds very much like the magneto. My A7 was playing up in a similar fashion. Have picked up the bike today after having the magneto reconditioned & all's well. It is a different bike altogether.
Hi Stu, yes it does sound like a mag winding breaking down. Where did you have your one refurbished?
Bigwol
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G'day bigwol, welcome,
to throw another possible cause is the tappet clearance too close. They close up when hot and prop the valves open a tad = loss of power. Stop and cool down, all fine again till hot.
Cheers
Yes muskrat, someone else has suggested tight tappets may be to blame. Don't suppose you know what the clearances should be?
Bigwol
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Funny you should mention this.
My first A 10 did exactly the same thing.
I would get off, clean the carb, clean the points, clean the slip ring ,dither around a bit then it would go off like a rocket only to repeat the same performance about an hour or so latter.
A bit latter on I found out that if I did nothing for 20 minutes I got exactly the same results.
Meanwhile My friends thought that I was an "Ace" mechanic because I could always fix the thing and when it did go it went with a capital W.
One day on the way to the surf it did its usual but would not start after the usual milk shake & fag break.
When I pulled out the brushes they did look a little past it & as I was a short walk from a sparkie I went down & got a new pair of brushes .
He assures me that they were correct but when I went to put them in they were totally different to what was in there so I took them back complaining that they were wrong this time armed with an original for comarison.
He looked at these and laughed " Usually Lucas maggys don't run very well with Bosh brushes in them ".
Luck I was by my self.
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Hi all.
One more option to throw into the debate, tight valve guides. Had a customer once who's A10 was doing the same thing as yours. Fine and dandy when cold but after about 20 miles, and normally after a good thrash, would start to lose power and finally grind to a halt. Fag break for 20 minutes and away she would go again. Turned out to be the exhaust valve guide was too tight on tolerance, as the engine got hot the valve started to nip up in the guide.
Regards Chris.
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G'day Bigwol, tappet clearances cold, iron head 10 in 16 ex, alloy head 8 in 12 ex.
I run my alloy head A7 at 8 and 12 but the alloy head A10 needs 10 and 14 to stop it happening.
Cheers
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G'day Bigwol, tappet clearances cold, iron head 10 in 16 ex, alloy head 8 in 12 ex.
I run my alloy head A7 at 8 and 12 but the alloy head A10 needs 10 and 14 to stop it happening.
Cheers
Many thanks Muskrat
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Hi bigwol, welcome to the forum. There are guys on here with a mine of information, so, keep asking!
I had my magneto reconditioned by a guy named Paul Lydford. He did a dynamo for me several years back & his workmanship is first class.
He lives in Shaftesbury, Wilts (1 Maple Close to be precise) but he has a business namely APL Magnetos. Phone no. 01747 852136. His normal turn round time is about 2 weeks. As far as charges are concerned, I can't help you on this as the work on my A7 was done as part of a warranty issue after buying the bike from a dealer. The dealer paid for the magneto to be reconditioned.
When cold the bike would start, run & tick over, but when hot, would tend to misfire & would not idle or start. It is the all too well known symptoms of a magneto condenser failing when hot. They seem to have a varied life span, mine lasted 51 years so, for once, we must congratulate Joseph Lucas!
Have a chat with Paul. He is very helpful. If you have not removed a magneto before & it has an automatic advance unit, then the securing nut is also the puller. Read about it before trying to remove.
Hope this helps
Regards
Stu
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Thanks for the welcome Stu. There is no sign of a missfire with my bike, just gradual loss of power till it stops. No coughing spluttering farting or banging!
The mag was refurbed for the PO about a year ago so should be ok. The guy who did it has been great saying if it turns out to be the mag he will sort it under guarantee. My next step is to have the carb off and see if there is any crap in there and clean it out, tank too if needed. If the tanks off i'll check the tappetts and compression and see where we go from there.
Good job i have some holiday coming up!
Dave
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Hello, Bigwol.
Your problem puts me in mind of some trouble I had on a B31. The hole in the fuel tank cap was blocked, it ran well at low speeds but ran out of steam when asked to keep up on a club run. Clearing the breather hole cured the problem. Hope yours is as simple.
Regards.
Raindodger
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Hello, Bigwol.
Your problem puts me in mind of some trouble I had on a B31. The hole in the fuel tank cap was blocked, it ran well at low speeds but ran out of steam when asked to keep up on a club run. Clearing the breather hole cured the problem. Hope yours is as simple.
Regards.
Raindodger
Hadn't thought of that one Raindodger, a mate of mine had the same thing happen on his Matchless G12. (Someone had put blue tack in the hole!) Will give it a look see.
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Update guys.
Yesterday I got a few hours in the shed and looked the A7 over.
No sign of anything in the carb other than petrol. Same with the tank.
I did find the HT leads a little loose at the Mag and the rubber plug caps could be in better condition so will order new leads and caps but doubt they were the cause.
Checked the tappetts. Way too tight for 10 and 16 as for iron head. Re-set them and fired it up and wow, ran at way too high revs for tick over, i'd guess at 2000? Took carb back off, rechecked cable route but still the same. Seems it must have ran rough - because of the tappetts? (although there was clearance when cold of some kind) - so someone had not only wound the slide stop up but also the cable adjuster! Re-set throttle cable, stop and air screw and she ticks over like a watch. Was going to go for a decent ride this morning to see if I've cured it but of course it's peeing down!
Will keep you all informed, and thanks again to all who replied and posted suggestions, much appreciated.
Bigwol.
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If you go out anyway, it won't get hot enough to stop anyway....(water cooled) .??
But if it did that'd be a bitch= time for hot toddies!
Hope that's the prob tho', and good on ya for persevering, good luck& cheers
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Bigwol,
You should adjust the tappets as per the camshaft fitted, not the head material.
Trev.
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Bigwol,
You should adjust the tappets as per the camshaft fitted, not the head material.
Trev.
Absolutely Trev, to the best of my knowledge it's a standard engine, and as it came from the factory. (Numbers match the old green log book)
I did about 60 miles round trip yesterday, stopping roughly mid way for a tea and a sausage sandwich, and it was fine. Not as hot a day as last week when i had the issues though.
Someone loaned me a copy of "BSA A7 & A10 Twins, Super Profile, by Owen Wright, a Haynes tome. Looking at the spec sheet in that from '58 A7 tappetts are 8 thou both inlet and exhaust and from '59 all models were fitted with the "sports" cams from the Shooting Star variant. Shooting Star model tappetts are listed as 8 thou in and 10thou ex. from '58. It's all very confusing!
I will run it as it is at the moment and see how she performs on hot days (assumming we get any more) and see if I have recurrence of the problem. I may even try re-setting the tappetts as listed and see if it returns. I also have a Haynes on order and will try to get along to the local OC section meeting at some point.
I've had to fit a replacement light switch and for the life of me cannot see a way of wiring it so the side lamp goes out when the headlights are live. Couldnt follow the old wiring as the switch fell apart in the headlamp shell when the bacolite disintigrated! At least it's road legal.
I have to say it does ride nice!
Again thanks to those who contributed to helping me sort it out.
Bigwol
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scuse my ignorance chaps but why should the clearance at the tappets be differrent because the cam lifts higher, I know it is cause BSA said so.
Is it due not to the camshaft profile but because with that camshaft the engine might run hotter and isn't that why it has an alloy head to keep it cooler
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Still not had a chance to give the A7 a damn good thrashing to see if the problem has been cured. Took it in for MOT in the week, passed with flying colours - and promptly got a puncture which I just havnt had time to fix. *sad2*
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scuse my ignorance chaps but why should the clearance at the tappets be differrent because the cam lifts higher, I know it is cause BSA said so.
Is it due not to the camshaft profile but because with that camshaft the engine might run hotter and isn't that why it has an alloy head to keep it cooler
I think it has something to do with the cam profile rather than the max lift. The cam may also have quietening ramps etc, so follow manufacturer's recommendation when setting the tappets.
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Hi. Had the same problem with my A7. just did'nt want to start when hot so i fitted a Brightspark condenser, problem cured.Cheers Ian.
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Not having the best of luck with my first BSA guys, got the puncture sorted the other week, took it to work (about a 20mile run each way,) and she is noisy and has a fair bit of oil on the drive side cylinder. I suspect a big end on the way out so will not run her again until i've investigated. Are these a noisy engine? I was at a show the other week when someone started up what i think was a C15 and that sounded pretty awful too, the guy rode away on it and didnt seem that bothered. Maybe my AMC's are just quieter bikes!
When i get time - never seem to get any of that - I'll take the head off and see if the conrods move on the journals. Will keep you posted .....
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Well if you run your BSA alongside a Triumph you shouldn't be able to hear yours.
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Well if you run your BSA alongside a Triumph you shouldn't be able to hear yours.
*yeah*
In that case i definately have problems! *problem*
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The iron head engines are normally pretty quiet.
Trev.
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The iron head engines are normally pretty quiet.
Trev.
The A7 is much noisier than my AJS twin, not going to mess about will take it to bits and make sure all is well, or put it right. I know the PO did very little work on it mechanically but he didn't own it for very long. Will give me something to do over winter anyway *whistle*