cb125 superdream coil wiring

salem1987 · Scooby Slapper Joined: 10 Sep 2013 Karma :

Hi, just a quick question as i can't figure it out from my haynes.

Which coil goes to which plug on a superdream?

Ive got a Black and yellow wire and a Black a blue wire which were disconnected when the bike wasn't starting to clean contacts etc and i stupidly didnt make a note.

The bike still isn't firing up after swapping them over to see which combination works, so i think its a fueling issue now but i need to be sure ive got the coils right!

Cheers

Taught2BCauti... · World Chat Champion Joined: 12 Jan 2012 Karma :

Not familiar with the machine, but does it have 2 sets of contacts, or do both coils fire together (lost spark)?

Try removing both spark plugs and rotating the engine by hand, or pushing it forward in 2nd gear.

Stop when you see one spark plug fire, and check which piston is near the top of it's cylinder.

The plug and coil that just fired, belongs with that cylinder.

The other piston should be near the bottom, and goes with the other plug and coil.

If they both fire at the same time, it doesn't matter which way they go.
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bikenut · World Chat Champion Joined: 21 Nov 2011 Karma :

one for Teflon mike really as he is a cb125 guru and knows the subject well ( respect ).......

so your is a tdc?? or a t?? just cant remember which one is which these days......one will have the pistons going up and down in phase or together....both cylinders at tdc at the same time....with a twin lead ht coil......

but suspect yours is an out of phase type where one piston is at tdc with the other a bdc .....2 cdi 's and 2 coils........

from memory the flywheel cover has a slotted inspection plug near the top..........you will see severl;a marks....find "LT" meaning left time.

with plugs removed ( be carefull use a small socket not a half inch drive.........and remove by hand when plug is slack, else danger of fouling the head and thread damage, refit by hand also... ) on the left hand side, watchn the valves open........watch the inlet open then close then LT will appear....this means the left cylinder is about to fire. LF Meaning left fire........ now all you need to know is which lead wire is for the left cylinder. see wiring diagram......back in a bit or remove the flywheel cover and suss out that way

see the wiring diagram in the Haynes manual.....cant find one on here....it should say which is for the left and right cyl........do you have a red neon plug cap?
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Teflon-Mike · tl;dr Joined: 01 Jun 2010 Karma :

There are some minutiae even I do not commit t memory....
LT wires to the coils are both, black ISTR with different colour twists....
If it doesn't start.. I just swap the LT feeds between coils.... it's easier than swapping the plug caps.. ad certainly quicker than trying to trace the trigger wiring on the schematic.... if it starts... was wrong way before!

Bike-Nut... He said it was a 'Super-Dream', which if correctly badged makes it a CB125TD-C; the earlier, 6v points engine, twin-shock CB125T was just badged 'Twin'; later 12v Mono-Shock, dropped the 'Super-Dream' badging TD-E was badged 'T-Deluxe' for a change of spec that amounted to little more than the addition of a separate number plate lamp and relocated rear reflector; The TD-J was simply badged CB125T again; for quite a lot of changes, that included cast wheels and tubeless tyres, and a 'H-Vo' toothed cam-chain. All the 'Benly' CB125 twins, have 180, one-up-one-down crank; its the rest of the Benly 'family' the CM's & CD's that have the 360, two-up-two-down cranks.
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salem1987 · Scooby Slapper Joined: 10 Sep 2013 Karma :

thanks for the replies. It is a 180 twin yes with two coils etc. Superdream style.

After numerous attempts putting fuel down the head and swapping coils over i am getting nothing. Spark is excellent with fresh plugs and everything seems to be in order fuel and air wise.

Now the big thing is that the bike went onto 1 cylinder with 12 miles to go on my commute. Found the problem was an ancient HT lead which was arcing to the engine through one of the clips on the engine.
Replaced both leads for fresh ones, cleaned all contacts and tested everything with a multimeter. In theory it should work.
But,
the big thing I have not checked is compression and I'm unable too just yet.
The bike was bought from a very reliable source and has recently had a rebore and pistons. (its been run in properly too..)

Could the 12 miles of 1 cylinder crawling home have caused some serious issues compression wise?

salem1987 · Scooby Slapper Joined: 10 Sep 2013 Karma :

tef i just worked out the wiring from your cam chain/tappet guide on your website. One of the photos clearly shows the black and yellow wire going to the left cylinder.

Thanks!

Teflon-Mike · tl;dr Joined: 01 Jun 2010 Karma :

From the photo's on the tappet adjustment Shocked

THAT is taking teflonits to an extreme!

12 miles on one pot, with a dead spark? Well, you would have got a it of bore-wash from pumping charge and not burning it, that could miutely accelerate bore/ring wear; but 12 miles? Unless yo did'em at 14K rpm 1st 'cos of the power loss.. doubt its done much.

When you say you fitted new HT lead.... THERE is where I suspect problem lies.... Take it you have OE coils with screw-in HT lead, to 'just' replace the lead, on its own...

What did you use? Where did you get it? it WASN'T per-Chance carbon-core car Lead from Halfrauds was it? Doesn't really take well to screw in conections that stuff.... Did you do both sides? Did you use new plug caps, did you avoid the coil's clamp ring, round the HT lead, that's usually baked brittle, cracking so it does't grip the lead?

BUT Best Bet... screwing on new HT you have twisted the screw the coil the old housing and broke the contact on the back of it....

Would still give good spark in free air, cos it's double arcing; first across the break inside the coil case, the across the plug gap... under compression, doesn't have the juice to make the second jump... Try a continuity test from the plug-cap to the coil-earth....
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My Webby'Tef's-tQ, loads of stuff about my bikes, my Land-Rovers, and the stuff I do with them!
Current Bikes:'Honda VF1000F' ;'CB750F2N' ;'CB125TD ( 6 3 of em!)'; 'Montesa Cota 248'. Learner FAQ's:= 'U want to Ride a Motorbike! Where Do U start?'

CaNsA · Super Spammer Joined: 02 Jan 2008 Karma :

bikenut · World Chat Champion Joined: 21 Nov 2011 Karma :

buttonitise dude.....don't worry....you will be old one day. :karma: lt is left time or tdc....lf is left fire.......... :karma:
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CaNsA · Super Spammer Joined: 02 Jan 2008 Karma :

salem1987 · Scooby Slapper Joined: 10 Sep 2013 Karma :

Leads and caps on both sides now yes. Using just bog standard lead off a roll which ive used on many bikes.
Tried the bike again today and it fired straight up.
The bike is purely used as a winter hack and i'm wondering if waters been getting somewhere i didn't spot. Its been left to dry for about a week until today.

Carbs are totally out of balance and at the wrong mixture now after all the fiddling so thats the next thing to sort out.

Had a CG125 engine ready to bolt in too (bodge in) but looks like the old twin will live another day for now...

Cheers