Twin spark heads ignition timing

[how much for a service!]

Hi
Going to have a go at checking the ignition timing on my 100gs. It has had a twin spark conversion and I read somewhere about the timing needing to be set slightly retarded?
Also what spark plugs are recommended for the bottom short reach one tried motorworks but they were not sure
Cheers

 

[Beemerboff]

Mine goes OK with D6HA plugs and around 26/ 27 degrees advance, but I have a Boyer Micropower ignition and 12 mm plugs, and there isnt a lot of choice in that size.

I set the timing by test, pulling hard up a decent sort of hill, but a dyno will do at a pinch.

Just retarding the timing on a stock system as the PO had done didn't work at all on this bike- the Boyer just transformed it.

 

[Rob Farmer]

I spent ages fanning about with a twin plug mod I had carried out, tried all the mods and settings suggested - bending ears in the bean can and various other timing settings all to no effect, gave up in the end and justset it all back to standard settings. As beemerboff suggests the Boyer micro power is the only way to go.

What size thread do you have for the lower plug?

 

[how much for a service!]

I spent ages fanning about with a twin plug mod I had carried out, tried all the mods and settings suggested - bending ears in the bean can and various other timing settings all to no effect, gave up in the end and justset it all back to standard settings. As beemerboff suggests the Boyer micro power is the only way to go.

What size thread do you have for the lower plug?

The lower plug is 14mm w5ac now I have taken a closer look at it
Only wanted to check the timing to try to cure the popping back on the overrun
Checked the exhaust all seems ok
Seems to have standard ignition although it has had quite a few mods done to it
(Didn't save the list off the original ad )
It belonged to hustler and then gadget before him but neither of them did the mods
Pic of top plug attached

 

[how much for a service!]

Lower plug

 

[how much for a service!]

Plugs

Having read a bit this afternoon think I might need a hotter plug in the lower
Like a w7ac?

 

[Beemerboff]

My D6HA looks a grade cool too, but a 7 is hard to find in 12 mm.

 

[chasbmw]

I use a hotter running plug in bthe bottom position oth my twin plugged airheads. iridium is even better. The bottom plugs seem to pick up all the crap.

In terms of timing at full advance you should be about 4 degrees retarded from stock if the top of the F (z) markis just about to disappear into the bottom of the crank window at fully advanced then you should be OK.