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- Oct 28, 2014
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has anyone bought this? I can't see enough of it to tell how it works.
I use it. I put the engine at TDC, put the disc on the rotor (nothing required for it to stick), and align the TDC slot in the disc with the timing mark on the rotor. Then I put a mark on the stator inline with the 30 degree mark on the disc. Then I remove the disc, put the primary cover on and record how much it is off, if any. If you don't have the timing device in the primary cover that mark on the stator can be your timing mark.has anyone bought this? I can't see enough of it to tell how it works.
It does require you to carefully turn the engine to TDC. A piston stop being my preferred method. Once TDC is accurately established, the tool lets you accurately find 20, 30, and 40 degrees before TDC. A degree wheel is not required. The accuracy of the rotor mark makes no difference - wherever it is when the engine is at TDC is TDC.If it does not require a degree wheel and a piston stop to determine TDC, it is not any more accurate than the factory scale...which may or may not be accurate. Remember that the factory scale has THREE variables...
1. The precise positioning of the outer chain case cover- you can make it shift a couple of degrees as you install the chain case cover.
2. The marking of the alternator Rotor by Lucas (or whoever)
3. the positioning of the woodruff key in the crankshaft by Norton or whoever.
All three must be exact to produce exact timing. Only a piston stop and degree wheel can verify it. Anything else is just "approximating." OTOH, unless you REALLY CARE, a couple of degrees error on a street motor won't make enough difference to make any difference.
Air bubbles, dial indicators, etc are not accurate if you want precise timing. BUT, again, for a stock Norton, I can't imagine that it matters much.
Held in place by double sided tape and removed once the primary cover scale is checked and calibrated.Is the idea to leave the plate on permanently... or remove once checked??
I'm not sure I understand your point.
I'm not sure I understand your point.
This plate calibrates the markings on the stator and primary cover scale.
The scale is well known to be inaccurate and in my personal case 2.5 degrees out.
Hi. It's a time since I went through the exercise but I do remember finding TDC with a positive stop and then orienting the disc.It is surmising the rotor mark which is being worked off is accurate which it might or might not be.
The problem or not is the stock scale has no TDC to verify easily.
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I elected to positive stop TDC on the short block, transfer that TDC position to the mounted stator then machine (rotary table) the needed ignition timing degree graduations into it.
(Trying multiple outer primary covers out of curiosity with the stock scale returned 1.5 degrees off as the maximum inaccuracy which was a surprise)
I can see the merit in that AN 'tool to at least have some easy idea of what is going on.
TDC positive stop verified and the rotor circumference divided by 360 would soon give a degree's in mm measurement also.
Hi. It's a time since I went through the exercise but I do remember finding TDC with a positive stop and then orienting the disc.
If I read your post correctly you have essentially turned the rotor into the disc marking up the rotor using the dividing head. A good method.
Yep I agree a solid stop either side of tdc and split the difference with a dial guage is the only way to get a precise tdc in my opinionSome things I like to know for sure and timing is one of them.
What I did is use a positive stop bar either side of TDC with the cylinder head off, the TDC line on the rotor transferred to the stator for two marks split on the rotary table to get a marked TDC. The timing graduations were then machined into the green potting of the charging stator body up to 32 degree's.
This was when I was moving the stator and rotor inboard around 12 mm to suit the duplex primary so was there anyway.
All it means to me is, set a timing mark with the light and it will be very close to confirmed actual.