MGB GT fettling

Talk about your cars etc here. Keep it sort of sensible and on topic please.
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Scruffy Bodger
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Re: Scruffy's Scrappers

Post by Scruffy Bodger »

I can't believe I didn't think of that, stupid twat. I'll give it a try in a bit.
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Re: Scruffy's Scrappers

Post by DodgeRover »

Points and condenser would have been the first things I cleaned or replaced in the event of no spark.
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Re: Scruffy's Scrappers

Post by Scruffy Bodger »

DodgeRover wrote: Sat Sep 07, 2019 12:25 pm Points and condenser would have been the first things I cleaned or replaced in the event of no spark.
The first thing I did was file the points :-) I've also taken the coil and condenser off and checked it over with a 9v battery and it sparks ok with that, the plug is brand new.
I've just tried it with a bulb and get nothing, I also tried it on the other output from the dynamo to the lights, nothing on there either. Putting a multimeter on the output to the coil reads 1.5 ohms with the points open or closed, seems to make no difference so something can't be right. It's just odd as everything behind the flywheel looks like brand new, no signs of corrosion on any of it.
I've found a wiring diagram and it certainly is pretty simple!
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Re: Scruffy's Scrappers

Post by DodgeRover »

How are you wiring a bulb, the usual way is via the points and a battery to see if they are opening and closing.

You'll never get it spinning fast enough to light a bulb from the generator out without it running.
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Re: Scruffy's Scrappers

Post by Scruffy Bodger »

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I did wonder about that, ta. So how do a wire a battery into the circuit then?

I moved on from that earlier as another fucker turned up, they are breeding! This one doesn't run either and has no keys with it sadly. There's no kill switch on it so I've been working on the assumption that the key grounds out a wire to kill the spark, so I've disconnected the wiring harness, still no spark at the mo tho. The battery that came with it is very probably fucked as was made in 1989 iirc and was very low on fluid. I've added a bit of rainwater to it on the offchance it takes a bit of charge. A bit of googling suggests there's no points on this one tho. I think* it's using a PEI system from what I've found so far?
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Re: Scruffy's Scrappers

Post by DodgeRover »

Power up the coil circuit from a battery not the magneto and it should work.

PEI - Pointless Electronic Ignition, an acronym that caused much amusement at the time.
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Re: Scruffy's Scrappers

Post by Junkman »

It still does within the right circles.
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Re: Scruffy's Scrappers

Post by Scruffy Bodger »

I had another play with the orange one today, basically went over everything I did before. As they say, assumption is the mother of all fuckups! I'd only got the two plug caps to play with, after testing the one the other day I found it had a high resistance unless the plug was pushed very well home so I swapped it for the other. This seemed to improve matters straight away, except I still couldn't get it to fire. The spark also proved intermittent after a while. Sum of it was both caps were showing high resistance FFS. There was also a problem with the end of the lead too, I had to cut an inch off it to get a reliable reading on the multimeter.
After pouring some petrol straight into the bore, stripping the cable back and doing away with the cap the fucker fired on the second kick!!! It needs the tank taking off as it's full of rust now before going any further, I'll probably leave that for the owner to do. The kickstart is fucked too, all the splines have been smoothed off. I'll probably stick a dab of weld on it, a bit extreme maybe but I've no idea if a shaft would be available.
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Re: Scruffy's Scrappers

Post by DodgeRover »

I wouldn't weld it, put a picture up of how fucked it is, in an extreme you can fit a small cotter pin to stop it rotating.

With only 50cc to spin over it doesn't need to be mega strong, you may get away with cleaning up the splines and making sure it is nipped up good and tight.
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Re: Scruffy's Scrappers

Post by CLINT »

Great stuff. Justin's shite deserves its own thread really. I want the G Wagen
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