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backfire
http://www.international2cvfriends.com/forum/viewtopic.php?f=7&t=5598		 Page 1 of 1
Author:  bobh [ March 25th, 2015, 11:37 am ]
Post subject:  backfire
My AK2 suddenly started drinking oil, then eventually became almost impossible to start. Plugs well sooted up, changed plugs but when it ran, it backfires and no power. Fearing the worst, I have got another engine lined up BUT, when I took the old engine to bits, there is 1.0mm play on the top piston ring (Ie: groove width is +1.0mm more than the ring thickness) and the other is 0.6mm. The engine did have a good old rattle which I wrongly assumed to be the big end rattle.
So having said all that, why the backfire? The ign timing hadn't slipped but When I took the contact points off, they were very badly pitted on one side, pointy on the other, I guess the 'new' condenser is shot. Could this be the real cause of the backfires ?
What do you reckon guys?
Author:  citroenboat [ March 25th, 2015, 12:27 pm ]
Post subject:  Re: backfire
Apart from the oil it sounds like the problems I had; which turned out to be ignition switch, 123ignition, condenser, plug leads & coil (and for all I know points as well), which took me 3 months and numerous changes of componants to solve because when I changed sumat the problem went away partially or for a few miles & then returned. Every componant had some sort of problem. Very frustrating.
But I do have 2 coils who's problems I isolated thru this; one of which fails classically (won't start when hot) but also causes the engine to die @ tickover when hot and another which starts fine but then causes backfiring & spitting thru the carb, no power @ all until it warms up when the engine runs fine on it.
So it might not be one problem, and it might be hiding inside another problem - I got sidetracked by suspecting the carb in this saga too... :oops:
Author:  AZL57 [ March 26th, 2015, 11:18 pm ]
Post subject:  Re: backfire
if the points are burned the condenser is indeed gone. The new ones are of very poor quality helas....
Author:  bobh [ March 27th, 2015, 9:56 am ]
Post subject:  Re: backfire
I think you are right about condensers - Mine on the Austin 7 don't seem to last. Is it because they are not used enough ?? Would it be better to use a straightforward 'electronic' condenser, in which case does anyone know what spec we should look for. I suppose electronic ignition reduces the load on the points, but its an expensive way around a basic problem.
BobH.
Author:  Taskos [ March 27th, 2015, 10:59 am ]
Post subject:  Re: backfire
Spikes on the points surface is a sure sign of perished condenser.

The capacity should read more than 0,27μF.
The voltage rating must have been in the thousands area,
considering the size of the original capacitor.
Author:  AZL57 [ March 27th, 2015, 6:00 pm ]
Post subject:  Re: backfire
Has nothing to do with using much or not. It's just rubbish quality. On my 1957 one i have the same condensor since 20 years no problems at all. But it is still a genuine old stock one...
Author:  Sean [ March 27th, 2015, 6:30 pm ]
Post subject:  Re: backfire
bobh wrote:
I think you are right about condensers - Mine on the Austin 7 don't seem to last. Is it because they are not used enough ?? Would it be better to use a straightforward 'electronic' condenser, in which case does anyone know what spec we should look for. I suppose electronic ignition reduces the load on the points, but its an expensive way around a basic problem.
BobH.


Vellaman kit is cheap enough and does away with the condensor
Author:  bobh [ May 14th, 2015, 10:05 am ]
Post subject:  Re: backfire
Well, it wasn't the points ! ! Took the engine out (It had always had a good rattle which I took for big ends). On stripping down, the piston ring grooves were 1mm wider than the rings (worst case), other side only 0.75mm! That may have caused a "pumping action" letting fuel bypass the rings and all sorts. Cure for this one was a replacement engine - thanks Den. New engine is so so quiet - I had to lift the bonnet to check it was running.
Author:  lpgo [ May 14th, 2015, 10:45 am ]
Post subject:  Re: backfire
bobh wrote:
New engine is so so quiet - I had to lift the bonnet to check it was running.


:lol: :lol: :lol: :lol: :lol:
Author:  azuiper [ May 22nd, 2015, 11:20 pm ]
Post subject:  Re: backfire
Quote:
New engine is so so quiet - I had to lift the bonnet to check it was running.


... the best understatement I have heard for a long time ... :lol: :shock: :lol:
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