TDC indicator tool,point setting?

[potto]

Bought the tool off In Motion came with no instructions but it seems straight forward enough (I think),I see conflicting info on here regarding setting ,my Spanish manual says 2.7mm BTDC is that when the points are fully open or do you set with points just open @ 1.8mm???.

Bike starts ok or do I leave it??? not sure,can't have the timing wrong and kicking back as my leg is finally recovering after the last big incident .

Thanks in advance.

[keychange]

I have a 247 and could never get a good outcome with 2.5 mm measure (for the 247)  - once I switched to using a paper timing disc it was perfect and hasn't been touched in last 5 years.

[bultobill]

Its a while since I have done points but the bit your interested in is when the points initially open as thats when the spark occurs remember changing the amount they open will also alter the timing slightly.Sorry cant help with the numbers though.

[oldaz]

8 hours ago, potto said:

manual says 2.7mm BTDC is that when the points are fully open or do you set with points just open @ 1.8mm???

On every other brand of engine I know, the measurement is only accurate when the points just open - so I interpret that as spark to fire at 2.7mm BTDC. They also specify points gap as a range, so points at the wide setting will fire slightly ahead of points at the narrow setting. In those engines where you "can't" adjust the timing, you can often get =/- about 2 degrees by points adjustment and still be in range. It's all smoke and mirrors, lol.

[potto]

10 hours ago, oldaz said:

On every other brand of engine I know, the measurement is only accurate when the points just open - so I interpret that as spark to fire at 2.7mm BTDC. They also specify points gap as a range, so points at the wide setting will fire slightly ahead of points at the narrow setting. In those engines where you "can't" adjust the timing, you can often get =/- about 2 degrees by points adjustment and still be in range. It's all smoke and mirrors, lol.

Thanks for the replies,old brain has taken all onboard ,will check today,cheers.

[feetupfun]

The reason that an ideal points gap, or an ideal range for the gap to fall within is specified by the manufacturer, is because the sizing of the capacitor is chosen to match that gap (and the area of the contact surfaces of the points). The actual gap is not particularly important in the scheme of things, but the position of the piston/crankshaft when the points start to open is very important.

On some bikes you can rotate the backing plate or change the points gap to adjust the timing and on other bikes you can only change the points gap to adjust the timing. As you move the backing plate away from the mid position in either direction, the voltage being generated in the stator coil (the primary circuit) at the time the points open will be (slightly) lessened, compared to if the backing plate is in the mid position. This means that if you want the strongest spark, keep the stator near the mid position and get the timing right by adjusting the points.

[nigel dabster]

on my old bultacos i always set the timing by the points gap. I assume that the gap is in the range as thats where it was set originally, and can be crossed checked after.

This ensures the btdc with a simple make or break light sets the timing.

Monts must be the same im sure.