CB125T2 from 1980

[Spitfire]

This is looking great, keep it up

Cheers

Dennis

[peteuk]

Cheers Dennis. It's turning out pretty good. It's a costly hobby tho this ere bike renovation. Also I've yet to try and start it as I don't have a spark to the plugs so I'll let you know what the engine is like when I get to that stage

[peteuk]

Hi everyone. A quick update. I've now got the electrics something like and managed to get a spark to plugs and points. However, the thing will not start. It does the odd fart but other than that I'm left with an aching thigh after all the kicking over. I'm thinking it's possibly fuel to the plugs. When i take out the plugs (which along with the points are new), there is a hint of a whiff of petrol on them but they're certainly not soaked. Could it be a carburettor problem. The bike is a twin and I couldn't find any original carbs so bought 2 singles. As far as I know, and I could be wrong, the original were 2 singles with a linkage joining the choke arms together so that when one choke is operated it engages the second one as well. So I've made s little arm myself to link the 2 choke arms. Am I missing something. Thanks in advance.

[K2-K6]

Spray a little carb/brake/cleaner or ezeestart down each carb,  usually gets them firing and starts to drag a little fuel out of the float bowls to give it a bit more appetite to running.

[Woodside]

im finding these days when plugs have got really soaked they are wrecked especially NGK...
my cb450 and cl450 were the main culprits
when i put new in it would fire first kick...
the guy who bought the cb rang me a couple of days after i dropped it off as he couldnt get it started again new plugs and it was off...he was giving the throttle a load when kicking ...it liked to be left to its own devices

[peteuk]

K2-k6 you mentioned spraying carb cleaner etc down the carbs but where from. Do I take the air filter off and spray from that route or do i take the throttle cables off and spray down the barrel of the carb ?. Cheers

[K2-K6]

Yes take air filter out ( especially if it's foam) and just spray into carb throat from there. Get it ready to go,  give a quick spray and try starting. I don't usually continue to spray as you're trying to start, just enough vapor will work and you don't want it saturated with this stuff.

General precaution when spraying flammable stuff around is to do it outside. You don't spray enough for real risk but sensible to be practical about it.

If it runs on this and then stops it shows you've not got petrol in flammable mixture enough to make it catch. Usually all things being ok they'll go and continue to run on their own fuel.

[peteuk]

Okay mate I'll give it a go. Thanks for the advice

[peteuk]

K2-k6, tried the carb cleaner spray but didn't make any difference. Still the odd fart of a combustion but nothing more than that. Not sure what to do next. I've checked the timing for the 18th time and it's okay.

[K2-K6]

Something a bit odd then. Usually with that stuff anything will at least run momentarily if everything but the fuel is ok.

I'm not familiar with ignition setup, timing strategy or firing order for these engines so you may need more input from someone with direct experience to find a way forward.

 Just a quick thought, It's not possible to get the timing 180 degrees out is it?

[Rob62]

You mentioned the condensers earlier on. Are you sure they are wired in correctly?... I’d be looking for an ignition fault as suggested by k2-k6.

[K2-K6]

It seems that you're not far off getting it running but must be something tripping it up.

Something woodside mentioned back there abit about the plugs being wet. I know you said they smelt lightly of petrol but if they've wetted enough not to spark then it could stop you progressing. I've you've got anything else you could run them in it may help with diagnosis.

I contrived to get some NGK plugs in a car wet,  it wouldn't go at all apart from a couple of coughs. It's fuel injected so I had to pull the fuel pump fuse and crank it with the throttle propped wide open until it cleared but it did fire and the plugs are fine still. It took me ages to realise I'd flooded it and after taking hours going through it found that nothing was out of place.

[peteuk]

K2_k6 you read my mind cos I was just coming on here to ask that very question. What if I've coupled the coils into the wrong power lead. Normally with double coils there is a blue and an earth on one coil and a yellow and earth on the other so you couple them up the right way into the harness. The coils are identical other than this.on my bike, both coils had a blue and an earth. Could it be that I've coupled them up back to front causing 180 degrees misalignment.

[K2-K6]

My "offsite" knowledge of the twins is not up to scratch so a few questions.

Is there just the one set of points,  if so then you can't connect them wrong I think. The power into them is just straight from the loom switched through the ignition and has kill switch. As an extra check you can wire straight from the battery positive to bypass the other kit,  leave a loose connection though in case it starts and goes too fast you can pull it off to isolate.

The coils firing is via the earth through the points. One set of points equals firing both coils. If you've two sets of points then you can connect the earths to the wrong set and fire them 180 out,  so that's something to verify.

[peteuk]

K2 yes there are 2 sets of points and 2 coils. Are you saying that the earth is not common and by plugging in to wrong earth connection can cause 180 degree out