RITA reluctor gap issue

I recently revived a 1972 Interstate with a Combat engine and RITA ignition. It starts and runs, but seems much less responsive to the throttle than what I expected and am used to with my other Commando (71 Roadster). I know there could be many reasons for this, but I am focused on an ignition issue right now.

The issue I am experiencing is that there is just over .005" difference in the measurement of the air gaps between the pick-up pole and each of the lobes of the reluctor. This results in at least 2 problems: I can't get both within the .008"- .012" specified range, and similar to what 'ilf8ed' reported in his 2015 thread: https://accessnorton.com/NortonCommando/750-combat-top-speed-problem-2015.18379/#post-273591 I'm seeing 2 timing marks when I strobe it, indicating that the cylinders are firing at different times. This thread goes on to several other subjects, but at post #43 he indicates that he was able to solve his problem by re-seating the reluctor on the camshaft taper to get it balanced. I have tried that several times, with both orientations of the reluctor and the camshaft, always ending up with the differing gaps. The wider & narrower gaps move with the camshaft orientation, indicating to me that something is off with its rotation or the taper the reluctor mounts to.

Is this conclusion sound?

and

How could this problem be solved?
My thought is to take a little off one of the lobes of the reluctor, but then it would only be good for this engine.

Having worked with rita's for decades this indicates a common effect of a poor taper match from the rotor to the cam taper. Some machinist blueing or black sharpie to indicate the mismatch. A little fettleing could improve this. A dial indicator on the rotor body can also help find the mismatch. But ultimately the hack method is file the close rotor tip to make it the same as the other then swing the pickup to close up the gap to the spec.
Do you have a lucas rita triumph PU7 trigger? I have a little story if you do...

dynodave said:

Having worked with rita's for decades this indicates a common effect of a poor taper match from the rotor to the cam taper. Some machinist blueing or black sharpie to indicate the mismatch. A little fettleing could improve this. A dial indicator on the rotor body can also help find the mismatch. But ultimately the hack method is file the close rotor tip to make it the same as the other then swing the pickup to close up the gap to the spec.
Do you have a lucas rita triumph PU7 trigger? I have a little story if you do...

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I'll try to isolate the mismatch.

How would I know if I have a PU7 trigger?

NickZ said:

How would I know if I have a PU7 trigger?

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LUCAS manufactured and labeled comes off a triumph with OEM rita box
2 part ,pick up and rotor

IIRC the minstral made rita rotor is big on the beginning small end of the taper and bottoms with less support on the big end of the taper therefore it can rock (slightly) from side to side which causes the nonrepeatibility of rotor installation

dynodave said:

LUCAS manufactured and labeled comes off a triumph with OEM rita box
2 part ,pick up and rotor

IIRC the minstral made rita rotor is big on the beginning small end of the taper and bottoms with less support on the big end of the taper therefore it can rock (slightly) from side to side which causes the nonrepeatibility of rotor installation

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Here is what I have:

dynodave said:

Having worked with rita's for decades this indicates a common effect of a poor taper match from the rotor to the cam taper. Some machinist blueing or black sharpie to indicate the mismatch. A little fettleing could improve this. A dial indicator on the rotor body can also help find the mismatch. But ultimately the hack method is file the close rotor tip to make it the same as the other then swing the pickup to close up the gap to the spec.

Click to expand...

I put a dial indicator on the rotor (which I think is the same as what is called 'reluctor' in the installation instructions) and it measured very true, both on the taper part and the part where the lobes are. Everything stayed within +/- 0.001" of the starting value .when rotated in a V block (and in collet on my mill).
Everything points to the mismatch being a result of some characteristic of the cam taper, not the rotor. I'm going to take the pick-up plate out and try cleaning out the cam taper as best I can, but beyond that I've no ideas on how to make the cam taper better for this.
If that doesn't help, I will have to modify the rotor, and it seems to me it would be much easier to shorten one of the lobes than to try to modify its taper. Either way, I end up with a rotor that is paired with this cam.

MIne was finicky, not this bad.
The tapers don't match up well.
It's probably in the taper.
However, I have heard of bent cams........

MichaelB said:

MIne was finicky, not this bad.
The tapers don't match up well.
It's probably in the taper.
However, I have heard of bent cams........

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My thought as well. Bent cam could cause this.

Maybe you can source a different rotor to test?

Though it may take a month of Sundays via USPS...

gortnipper said:

Maybe you can source a different rotor to test?

Though it may take a month of Sundays via USPS...

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That is a good idea.

Any ideas where to source one?

NickZ said:

Either way, I end up with a rotor that is paired with this cam.

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NickZ said:

when rotated in a V block (and in collet on my mill).

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Iam not suspecting the items were not originally turned "round and concentrric with each other. But if the taper gradient is slightly wrong ,which is my claim, they will not mesh and seat concentrically. If you put a candle in a candle holder and the profiles do not match, the candle wobbles if pushed .
If you can tap the rotor with a plastic mallet and "move" the tip clearance then the taper is sloppy, a good cam and rotor will NOT move the setting.

NickZ said:

That is a good idea.

Any ideas where to source one?

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@dynodave ?

Did you try machinist blueing or black sharpie to indicate the taper mismatch?

Have you tried rotating the rotor 180º ?

cliffa said:

Have you tried rotating the rotor 180º ?

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Yes, I tried both orientations several times. The same gap difference repeated every time.

gortnipper said:

Did you try machinist blueing or black sharpie to indicate the taper mismatch?

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Yes, DD suggested this, and I used Dykem to check the match. Here are the results: