Scooterotica

I've come a cross most Lambretta problems in my years of scootering but this one has go me baffled. I have recently convert my bike to full DC on the lighting circuit using the following. New BGM 120w DC stator, New BGM flywheel, Wassal regulator, 12v 9amp battery, Beedspeed TV series 1 style ignition switch. On the ignition side a new CDi unit & HT lead. When all was connected I had great lights, horn and power to run a rev counted and Sat Nav. All sounds good. But this is the Gremlin I am baffled with. After first running the bike all seemed ok, engine fine but a bit groggy at bottom end, lights ect fine. I then took it for a duno run. This was also to sort out the groggy bottom end. After five runs and a nice curve on the graph things were looking good. Until run six when the power just died at mid range. Tried again but it wouldn't run high revs.
I rode it home and started to investigate the problem. I first tied a new CDi but it was still erratic at bottom end and reluctant to rev. It was only when I had disconnected the battery while getting to the CDi that I discovered that with the battery disconnected all ran fine. Yes,, with the battery disconnected the engine runs smooth and revs fine, but connect the battery and it starts to splutter and difficult to rev. So I tried a different flywheel. Did the same. Disconnected the ignition switch but still did the same. I have removed the stator and tested it, green 505 ohms, red 105 ohms, white to earth 0. Check condition of the stator wires all look fine and undamaged.
So why when my battery is connected dose the engine splutter but runs fine when disconnected. If anyone one has any suggestions please please let me know as this is baffling me.

Regards
Tombretta

Do the lights and the battery appear to be working ok? just wondering if it was shorting out? The ignition and lighting use separate coils on the stator and they are not connected electrically but I wonder if a short in the lighting circuits could affect to magnetism of the flywheel I'm way out of my depth here, electrical theory and flux didn't make much sense when I was 16 and at college and the intervening years haven't improved it

Tom , don t take this the wrong way, I thought the DC stator was including two yellows on the BGM , as the other set up sounds like a short and when the battery is disconnected it runs OK, what about the Rev counter ???? as they were supposed to be a continual feed from the battery ( according to my set up) hope this puts you on course to solve it.......

Hi, the light all work fine from the battery when connected with and without the engine running. They also work but a bit dimmer with the battery disconnected and the engine running.
The BGM stator does have two yellows, both of which are then connected to the two yellows from the Wassal Reg, red to the battery.
The rev counter is connected to a continual feed from the battery and via the ignition switch for on and off.

I checked the stator last night including removing the cable sleeve and checking the wires for any damage. None! Going to try a different stator tonight.

Regards

Tom

Tom

Hi! I'd try with an easy test. Remove the battery from scooter and disconnect the regulator black wire from earth. Conect the red and black wires from the regulator to the battery (but keeping the battery isolated from anything). Then connect a 35w lamp to the battery,start the engine and see what happens.
If the engine revs well with this "external" battery circuit,the bulb shines and the battery is being charged, then your stator and regulator are fine and you have a shortcircuit somewhere, or something being badly earthed and maybe earthing through the CDI. Good luck!

Hi All, thanks for the help. I have managed to sort the problem. Still not 100% sure what the cause was. But this what I did.
After try various things like disconnecting the ignition switch, changing the flywheel. If have put it down to one of two things or both. I removed the new BGM Dc stator tested it, all readings ok. Inspected it, looks ok. I then removed all the connectors and removed the plastic sleeve from the wires. Inspected, but found nothing. Resleeved the wires and put the connectors back. After fitting I try the engine and it seemed better but not 100%. So the only other thing that came to mine as it is is the only point were the two system meet is the earths. I did have at the time the earths from the regulator, CDi & Advance/retard connected to the same point. After moving all of the to separate points everything works fine. I have road tested the bike all week and all ok.
I never thought that possibly to many earths at one point could have an effect. I still don't know if it does, may be some can confirm this. All I know is it seem to make some affect.

Many thanks and happy riding,

Regards
Tom