bike wont start gilera 125.help please :)

OK, I just wanted to confirm 100% what coil you have and it's a bog standard one with a live wire and an earth. Some fancy ones have a trigger circuit in them as well and that might have complicated the plan a bit.

Go ahead and test the coil by putting 12v to the terminal of the coil that the purple wire goes onto and then quickly taker it on and off again to see if the plug sparks when you remove the 12v. It should do and that will rule out a duff ignition coil.

 

ok im just going to give my battery a full charge then gonna give that a go

 

Any news?

 

- NO EXPERT

you say you have no spark from your new CDI - have you tryed a new spark plug. I fixed a lawn mower once that had no spark with a new plug because it was all dirty because the owner didn’t have the strength to start the thing and always flooded the engine resulting in the plug dieing

Sorry if this is just a stupid reply but it was the first think i though of when i read you had no spark

 

@ Merlin i yes i removed the purple wire from the coil terminal and got a wire and put it from my battery 12v to the coil terminal like you said and every time i touched the coil terminal , i didn't get a spark from the spark plug the live wire sparked when i touched it to the coil terminal and seemed to getting hot

 

OK, so it seems that the coil has gone dead short, so that's why it's not sparking. You should get a spark when you remove the wire after putting 12v to it as that's what the CDI (or a set of contact breaker points on an older bike) does. I'd expect a bit of sparking when you put 12v on but it only needs to be there for a split second to charge the coil before you can remove it to create the spark at the plug. Was the spark plug earthed to the engine or frame when you did this? If it was, then I'd say that the coil was knackered. Luckily they aren't expensive.

The Science Bit

The ignition coil works a lot like a transformer, as it takes 12 volts on the low tension winding and generates hundreds of volts on the high tension winding inside the coil. Think of it like a house mains transformer that you'd have for Christmas Tree lights, but working in reverse.

Once the coil has charged up to the hundreds of volts, removing the 12v feed creates an induction in the secondary coil as the 12v drops away. Those hundreds of volts have to go somewhere, right? Then it's quite handy that we've provided a nice short path to earth, via the spark plug gap. The high tension voltage discharges to the spark plug just like lightning - it's a lot of voltage, but not much current in Amps.

Does that make things any clearer?

 

well i dont no if its earthed , i just ook the purple wire of the coil and touched the live on and off it like you said while he spark plug was out the top end and just in the spark plug holder looking to see if it sparked, no spark only spark was the wire touching the coil terminal and geting hot

 

Touch the spark plug body on the engine or a clean metal bolt to ensure an earth and complete the circuit then try again. Hold the spark plug cap with your hand, not the plug body, or you might end up being the earth!

As soon as you take the 12v away the plug should spark. If you get zilch then it's knackered.

 

ok il try that tomorrow so keep the spark plug in the cap but touch the bottom metal part of the spark plug on the frame and try ok

 

Yep, you got it. You only need the 12v on for a split second, to prevent the wire from getting hot.

 

ok well i just retryed that with the plug earthed, and the plug sparked like twice out of about 10 trys it didnt spark every time i applied the 12 v

 

OK, so it's sparking, although it may be about to fail and that's why it's not sparking 100%. I think you need to replace the coil and then we can turn to the other electrics that feed it.

 

ok will order a new coil in few days, and go from there

 

brand new coil just arrived, now when i check for a spark i can see a lil spark coming out the spark plug now, so i put spark plug back into the top end... does this have to be very tight? cos i didn't do it too tight cos im abit worried about over tightening bolts , anyway still got the no fuel going to the carb still , so i tryed a bit of easy start and it sounds like it wants to fire up so the sparks back i got a new fuel tape here also what ive not fitted yet as i dont no if thats my issue

 

I'd fit the manual fuel tap and take the doubt about it out of the equation. If the original is a vacuum operated tap, don't forget to seal off the pipe from the manifold that goes to the tap as it's not needed any more.

The spark plug needs to be finger tight then a little 'tweak' with the spark plug spanner to nip it up tight. It doesn't need massive amounts of force.

 

here is the fuel tap i currently have http://www.ajsutton.co.uk/product/PIAGGIO/577881/FUEL TAP RUNNER?gclid=CO3F8qbOyr8CFZKWtAodFxgAog
and i have a new one of these also , i think it is vacuum operated
so what would i have to do get a new fuel tap thats manual

 

Fit one of these, it's a straight swap for the original and just blank off the vacuum pipe.

https://www.scooter-attack.com/shop...Tap-Piaggio-Aprilia-Gilera-Manual-1-hose.html

http://www.scooter-works.co.uk/piaggio-manual-fuel-tap-valve.html

 

ok is it ok to use a manual one on a gilera runner? and would i just always leave it open...bit confused and when u say blank of the pipe what do you mean?

 

ok cant get bike to start, got the petrol coming to the carb now from the fuel tap, when i kick it , it sounds like it wants to start , but isnt, maybe its flooded... bit confused

 

Take the plug out and look to see if it's wet with fuel. Sometimes, you have to give the choke a hand (quite literally) by taking the pipe off to the air filter and cover the carb throat with the palm of your hand to increase the vacuum and suck fuel through. You may flood it the first time, but if the plug gets wet with fuel, you know it's getting there.

If you fit the manual tap, the pipe that goes to the side of the original vacuum tap is redundant and not needed any more. Seal it off by folding it over and securing the folded pipe end with a cable tie to make sure that air doesn't get in.

Have you done a compression test with this engine? If the piston is scored or the piston rings are shot, then you may not have enough compression to get it started. Just a thought.