classic motorcycle forum
Motorcycle Discussions => British Bikes => Topic started by: marty 31 on September 23, 2018, 10:55:15 AM
-
my 1969 lightning has been professionally rebuilt and now on the road, it starts fine, and runs fine, but when its fully hot, stopped then re started its a pig to get going, it has brand new consentric carbs, the correct jets set to the makers settings, but the plugs always look sooty and damp, one thing that has been pointed out is there is no heat spacers between the carbs and manifold, just a gasket, could this be the problem? or would dropping the needle in the carbs one (last) notch help? thanks in advance for any advice and help.
-
one thing that has been pointed out is there is no heat spacers between the carbs and manifold, just a gasket, could this be the problem?
Yes, it could be, or at least the lack of heat spacers won't be helping matters so I suggest you fit them because they should be there (70-7821 according to the parts list).
https://www.draganfly.co.uk/index.php/bsa/bsa/a50-a-a65/1969/category/313-69-cylinder-barrel-valves
or would dropping the needle in the carbs one (last) notch help?
The Lightning needles should be at the No.1 weakest position (clip in the top groove) according to the '69 - '70 factory manual.
-
my needle settings are set second last setting(2nd weakest) so I will try dropping them, also look at my parts list and try and get spacers, as the carbs seem very hot, after fully warmed up, thanks for the advice
-
also look at my parts list and try and get spacers,
There should also be an O-ring (622/101) on the carb side of each spacer.
https://www.draganfly.co.uk/index.php/bsa/bsa/a50-a-a65/concentric-carburetter
-
after looking at the parts list, the heat spacer looks more like a thick gasket, would that be right? or as I was expecting would it be a proper spacer? ie maybe 10-15mm thick or so?
-
after looking at the parts list, the heat spacer looks more like a thick gasket, would that be right?
I'm not sure but if they were then the originals could have been an asbestos composite material which you wouldn't necessarily want and probably aren't available now.
or as I was expecting would it be a proper spacer? ie maybe 10-15mm thick or so?
The thicker the better but I don't think the studs would be long enough for ones 10-15mm thick and the 70-7821 spacers available are thinner.
-
It depends on the insulation properties of the material. I think a material called tufnol (?) is effective at about 3mm thick. It's only to stop conducted heat between the flanges and minimise fuel evaporation.
-
Hitchcocks among others stock Tufnol spacers.
-
think I have the 3mm ones from a srm gasket set, good job for sunday, tank off, fiddly carbs adjusted, and gaskets fitted, then if dry go go go, thanks for the much appreciated advice and I will update the outcome
-
You describe the classic symptoms of a dying ignition system, that is, starts well when cold but a pig when hot. This is something that is nigh impossible to pick up beforehand and only starts to show after a good run when the engine is well and truly hot. Your professional rebuilder would have had little chance of picking it up given the limited miles they are able to put on a bike before it is returned to it's owner.
By all means do everything that has been suggested above. They will all help ease the burden on the ignition a little and are sensible suggestions anyway but they won't effect a permanent cure. The approaching cooler weather will also help as the engine will take longer to get really hot. The real test will come on the first hot day of next summer and you do your first long ride of the season.
If you can find an ancient old time mechanic ask him how often are carburettor problems cured by sorting out the ignition. He will have entertaining stories to tell you.
Best of luck with the beastie.
-
I'd agree if it was a magneto setup but would be less sure it was ignition on a coil job, especially as you effectively have 2 completely separate systems for the 2 cylinders.
Having said that, new HT leads and plug caps are cheap enough and always worth changing. I would not suspect capacitors as they usually cause bad starting in all conditions.
The above assumes it still has the standard points / coil arrangement.
-
it has been changed to electronic ignition (before I bought it) and the engine hadn't been run by the engine builder, I set it up with all settings by the book, my manual stated the carb needle setting was second from the top (2nd weakest ) but is has been pointed out that another book states top notch so as the plugs always seem sooty and damp it might be worth a try, thanks for any advice
-
Not so Ian, heat failure occurs in all variety of spark ignition systems regardless of how the spark is generated. In fact the last time I experienced it was on a Triumph TR7 fitted with an aftermarket electronic system displaying exactly the symptoms Marty 31 complains of.
Electronic ignition is an improvement but it is subject to the same woes as all the previous systems-just not as often.
Whatever the case, I'm sure Marty 31 will learn a lot sorting it out.
-
True, but with 2 coils how likely is it that both will have the same problem?
But I wouldn't rule it out.
-
I just hope we finally get to hear the end of the story. With so many of these queries they trail away to nothing. We're left guessing.
A happy ending always goes down well.
-
Very true. Gives me sleepless nights.....
-
and I hope a happy ending is not to far away, its getting to be a embarrassment pulling up at the local sunday bikers meeting café standing talking for a hour, then kicking my little hart out, then a massive cheer when it rocks up, I will update, and thanks again
-
The moment its difficult to start, try putting a NEW set of plugs in it.
Perhaps not outside the cafe though....
And study if the plugs you take out are wet or dry.
-
Try turning off the fuel as soon as you stop the motor.......A hot flooded motor is near impossible to start,and that sounds like what is happening here.........As for the cheer,a friend of mine used to get a cheer when his bike started outside the pub,but the really big cheer was when it caught fire.
-
If the "magic box" is under the tank it might be getting hot when the bike is standing after a run. Just a thought.
-
the problem persists, carbs needles lifted to weaken mix, resulted in running like a complete pig, so resorted in returning to makers settings starts and runs like a complete dream, but when heated up to normal running temp, just wont fire until a cardiac arrest is on the cards, then when it fires up it runs like a dream, the bike runs on electronic ignition and is timed bang on, so next try is going to be new 12 volt coils, does anybody agree and advise this? or am I just wasting just more hard earned money?
-
the bike runs on electronic ignition and is timed bang on, so next try is going to be new 12 volt coils, does anybody agree and advise this?
As it has "electronic ignition" (which make/type?) then it's more likely to require two 6V coils (connected in series or one 12V dual coil) for best performance.
or am I just wasting just more hard earned money?
Possibly.
-
the bike runs on electronic ignition and is timed bang on, so next try is going to be new 12 volt coils, does anybody agree and advise this?
As it has "electronic ignition" (which make/type?) then it's more likely to require two 6V coils (connected in series or one 12V dual coil) for best performance.
or am I just wasting just more hard earned money?
its boyer ignition with a duel small modern type coils which I assume is 12 volt as the rest of the bike, its a lot of years since I messed with brits but to me the spark always looked small, it also has a management box, that worries me because, how does one know if its working correctly? the engine is mechanically sound as its had a srm rebuild, so has to be either carbs or as I now suspect electrical :'(
Possibly.
-
how does one know if its working correctly
Engines are a number of 'systems', so each system has to be working - hopefully each at its best.
Spark plugs are a vital link in the chain - have you checked the plug gaps. ?
Reducing the plug gaps down is always a 1st step if you suspect that the spark is weak.
If this improves things, you know its (probably) in this area...
Determining the voltage of those coils might be useful to know too.
-
its boyer ignition with a duel small modern type coils
which I assume is 12 volt as the rest of the bike, its a lot of years since I messed with brits but to me the spark always looked small,
Which Boyer ignition?
The only Boyer ignition to use the miniature coils is the digital (blue box) Micro-Power ignition.
If it is the Micro Power then it would normally have one dual output 12V miniature coil.
(http://www.boyerbransden.com/mp.jpg)
Other Boyer systems such as Micro-MkIII, Micro MkIV, (both black box) and Micro Digital (red box) must use conventional coils, normally either two 6V coils connected in series or one conventional 12V dual output coil.
it also has a management box,
What make/type of "management box"? I assume you mean a regulator/rectifier?
-
its boyer ignition with a duel small modern type coils
which I assume is 12 volt as the rest of the bike, its a lot of years since I messed with brits but to me the spark always looked small,
Which Boyer ignition?
The only Boyer ignition to use the miniature coils is the digital (blue box) Micro-Power ignition.
If it is the Micro Power then it would normally have one dual output 12V miniature coil.
(http://www.boyerbransden.com/mp.jpg)
Other Boyer systems such as Micro-MkIII, Micro MkIV, (both black box) and Micro Digital (red box) must use conventional coils, normally either two 6V coils connected in series or one conventional 12V dual output coil.
it also has a management box,
What make/type of "management box"? I assume you mean a regulator/rectifier?
its blue box, the exact kit you have kindly shown, the exact same coils etc the modern type regulator/rectifier dosent seem to have a makers name on it, these modern add ons are all a good idea but bypass the makers manual, and the more ore less cheap process of elimination, thanx for the help so far, another thought is could the earth on the coils be maybe not good enough? as they are not earthed direct from the fixing because they had to be cable tied to the frame and couldn't be fixed to it,
-
its blue box, the exact kit you have kindly shown, the exact same coils etc
You say "coils"? I assume you mean the single dual output coil as shown in the picture and not two separate single output coils?
If you do actually mean two separate single coils then how are they wired?
the modern type regulator/rectifier dosent seem to have a makers name on it, these modern add ons are all a good idea but bypass the makers manual,
Does charging system appear to be working normally? Have you checked the voltage (both battery and charging)?
another thought is could the earth on the coils be maybe not good enough? as they are not earthed direct from the fixing because they had to be cable tied to the frame and couldn't be fixed to it,
According to the Micro-Power instructions (below), only the (+) terminal (of the dual coil) has to be earthed (the coil body is plastic) and only if positive earth.
http://www.boyerbransden.com/pdf/KIT00281.pdf
-
its blue box, the exact kit you have kindly shown, the exact same coils etc
You say "coils"? I assume you mean the single dual output coil as shown in the picture and not two separate single output coils?
If you do actually mean two separate single coils then how are they wired?
the modern type regulator/rectifier dosent seem to have a makers name on it, these modern add ons are all a good idea but bypass the makers manual,
Does charging system appear to be working normally? Have you checked the voltage (both battery and charging)?
another thought is could the earth on the coils be maybe not good enough? as they are not earthed direct from the fixing because they had to be cable tied to the frame and couldn't be fixed to it,
According to the Micro-Power instructions (below), only the (+) terminal (of the dual coil) has to be earthed (the coil body is plastic) and only if positive earth.
http://www.boyerbransden.com/pdf/KIT00281.pdf
yeah duel output exact one in the pic, and it has a new battery that charges fine, also its wired same as the makers diagram positive earth
-
a update on my lightning problem, the coils were changed, the bike suddenly developed a sporadic misfire, fitting heat retarding spacers between the carbs and head resulted in the carbs being noticeably cooler, changing the coils back to the original, resulted in the bike now starting first or second kick, hot or cold, after changing the oil, replacing the gaskets between the sump plate and the casings and being mega careful, the bike is now 100% oil tight, running superb, starting and running correctly (hot and cold) a pleasure to ride, a success story, thank you to all involved in giving advice, all helping in the end result.
-
Good news, thanks for coming back.