timing moving with different sparkplugs

[tonydevon]

ok, Im having a right mare.

I have made new mark right on edge of flywheel, used positive stop and worked back my TDC, so now all the markings are round at about 3 oclock on the flange, top part was so marked up with years of timing marks that I wanted to start fresh.

so TDC marked, then 15,17,19,21 and 24 all scribed, then slitting disc on dremel to get nice groove, spray with white paint,wipe clean and leave paint in the grooves

proper job, starting to feel like I know what Im doing.

fire motor up, warm it up, strobe the timing.

it was a bit spluttery so I changed the plug,

this is where it got weird, tried multiple times with 2 different strobes

BR8ES and B8ES,the timing moved when the plugs were changed???

[bristolmod]

The "R" indicates a "Resistor" plug. You should not be using that type but the "standard" plug as far as I am aware.

Could it be that the inbuilt resistor is delaying the spark by a miniscule amount?

Which plug is causing the timing to move "later" is it the "R" type plug?

Chris

[Yanker]

You do know you need to be checking the timing with the engine running at 2000 to 3000rpm minimum and not at tickover?

As BM/Chris says this may well show up otherwise...combined with a 'resistor' cap

Hopefully there is no difference at 1/4 throttle! (shouldn't be anyways)!

[Minority]

The "R" indicates a "Resistor" plug. You should not be using that type but the "standard" plug as far as I am aware.

Chris

Unless of course you are running the SIP speedo, then it is mandatory

Interesting result though! How many degrees difference does it make?

[Dryballs]

An engine and ignition guru in our parts reckons you should use nothing but resistor plugs. It protects your cdi

[nelson pk]

I think you will find the resistor plug will not make a difference regarding timing.
If it is static timing, strobe it and gently turn the throttle a smidgen while doing this until the timing mark is steady and not juddery. Also if its static give it a few more revs, say between 3000 and 4000 and it is likely that it will advance or retard a tiny bit. This is where you want timing set to.
If you increase the revs and the timing jumps around you have an electrical problem.

[wack 63]

I have found that using a resistor plug and cap does retard the timing, which could come in handy when out on a run and the motor starts pinking.

[tonydevon]

Thanks guys.

i have to extend the slots in my bgm stator but im getting there.

2nd kick and it fired up. well chuffed.
idle and just above its at 17 degree. pick revs up to 3-4k and it drops to 16. but cant get the 15 i been told to se. out with dremel.

will get a mtech at first opportunity to play with it