Hello, I could do with a bit of help if anyone can assist please

My trials Cub, has a PVL electronic rotor connected to an Electrex world cdi coil pack, unfortunately the chap who built it is no longer with us, so there is no way I can verify this.

The two instructions from each manufacturer state different ignition settings BTDC

My question is: Which setting would be best to set the static timing, the Electrex world at 6.5mm BTDC or PVL 1.8-2.2mm BTDC?

I am led to believe that the PVL has little or no advance till 7000 rpm, but the Electrex world has the advance built into the coil pack

Can anyone positively confirm or deny the above

Any further help would be gratefully appreciated 

Many thanks 

That is a question you should refer to PVL and/or Electrex.  It's possible the combination of two different systems will provide a useful synergy -- or far from optimal results.

I don't know anything about the Tiger Cub, but a search revealed its stroke is 58.5mm. To calculate ignition advance in degrees from mm bTDC, you also need to know the rod length.  Guessing the rod length to be twice the stroke usually gives reasonable results.

6.5mm bTDC equates to about 35 degrees of advance.

2mm bTDC equates to about 19 degrees of advance.

Ultimately, the best ignition timing is the setting that yields the desired performance without signs of overheating and/or detonation.  Experimentation, riding feedback, and looking at the spark plug will guide you.

Very generally, advancing the timing gives a boost in low-RPM torque at the sacrifice of running well at high RPMs.

P.S. Advancing the static timing too far can make the bike difficult to start as it promotes "kicking back".

 

Edited March 6, 20251 yr by konrad

Hi Konrad, thanks for the reply, as it happens I have set both today the PVL and Electrex world recommendations with vastly different results 

After some experimentation I have now set it at TDC which gives me best of both worlds, clean slow speed running and the ability to allow it to “rev out”

Ill ride it on Sunday and see how it performs in real time

Thanks for taking the trouble to reply

All the very best 👍

Hope it works well for you on Sunday!  

I am curious about how you measure timing in mm bTDC on a 2-valve 4-stroke.  Are you removing the head?  If you have a timing light, I'd be curious what the PVL-Electrex hybrid is actually doing.