Ignition timimg silk 700s m2

[Eric Ratcliffe]

Hi,
Some confusion, regarding piston setting before top dead centre.
1979 handbook,that came with the bike says 0.300" btdc. ( 7.62 mm )
Your site quotes, 7mm btdc for mk1, 5mm for btdc for mk2.

[gasman]

That's the info I had, what is your engine number again because I have had the latest porting done on my new liners and the bike has no power, the ports are copied from Clives master pattern so that should be ok. I'm wondering if the timing has to be well advanced to use these port configurations. I was using 5mm at max advance. If your engine is a late engine then i'm going to try the more advanced position. It's all a learning curve, Kev

[Eric Ratcliffe]

Hi Gasman.

Bike was bought in Feb 79, the engine # is 700s/2/103.

[gasman]

Eric, go for your handbook figure, I have just set mine at 8mm btdc and went for a run, before at 5mm I got 55 - 60 mph absolutely flat out with it set at 8mm I got 75mph in third, I didn't want to go any faster as not in biking gear and still running in. Kev

[Smokey_Paul]

I agree with that mine is 136 engine so later and set the same.

[Hendred]

Just to add a little more to the confusion, my late MKII (engine 126, 38mm carb.) original handbook quotes 0.2" or 5mm advance and seems to go well on this setting.  The bike is dated April 1979 and the handbook is for the MKII dated May 1977 with many hand revisions.  If you have the handbook for the bike go for the settings in it - they seem to work!  

The 0.3" advance is equivalent to 37.5 deg. btdc according to the handbook - this hasn't been amended in my handbook book as obviously at 0.2" the advance in degrees will be less.  I'm messing around with trigonometry to try and work out the advance in degress for 0.2"advance.  It's proving an interesting exercise - there is one assumption - the conrods are all the same length in all engines?