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Hi Guys
I am just finishing up a restoration on a 1970 TR6R and have a question regarding the installation of a Boyer ignition.

According to the instructions, it looks like I need to set the timing mark to 38 degrees advance when setting up the ignition rotor position. I thought that the last time I did this, I used the centre timing mark on the rotor on the primary side. I have attached photos showing my "white mark at what I believe is 38 degrees advance, but would like confirmation from someone who installs these systems more often then I do.
Thanks
John

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The line on the Lucas rotor sets the pistons 38° before top dead center when it lines up with the pointer.

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Absolutley JohnH +1.

All assuming that the rotor is located with a key on the crank.

I think your model should have a timing plug in the case lightly rear centre of the cylinders, which can be used to confirm TDC and 38 BTDC by slots in the crank flywheel.

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Don't know what that white line is for and it's at least 4 degrees wide. Not very accurate for timing..


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there may be 2 locating notches ground in the crank
it look like youre located to the wrong notch .
[Linked Image from i.ebayimg.com]
as pictured , you're off by 38 degrees

Last edited by quinten; 04/16/21 8:20 pm.
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Originally Posted by quinten
there may be 2 locating notches ground in the crank
it look like youre located to the wrong notch .
[Linked Image from i.ebayimg.com]
as pictured , you're off by 38 degrees

There shouldn't be a crank notch at that white paint mark position.

One notch is at 38 degrees BTDC when the scribed line on the raised pad should line up with the pointer.

[Linked Image from i.postimg.cc]

[Linked Image from i.postimg.cc]

The other is at TDC which is on the opposite side of the raised pad to the white mark.

Last edited by L.A.B.; 04/16/21 8:54 pm.
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“there may be 2 locating notches ground in the crank
it look like youre located to the wrong notch .”

We haven’t heard that the OP is using ANY notch at all. He’s looking at the alternator rotor.
The white mark is (at a rough guess) 38 deg advanced of the proper mark on the rotor.

If it were 38 deg in the other direction, it could be understood as a TDC mark, as it is it is meaningless (say ~76 deg BTDC).

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Do what John Healy says


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I’ve tinkered with a few bikes that have had wallowed key fits between rotor and crank.

In this instance the rotor mark is less dependable, especially for static timing with points.

However, torquing of the rotor nut tends to leave the rotor in its most retarded position, also the revving of the motor tends to put it that way too.
So once its torqued down, I’m happy to take that as a reference point, even if that point has moved slightly with reference to the crank position.

That is why I would always check the accuracy of the mark on the rotor, which is easily done if the engine has the plug in the case, a bit more trouble without, so then using piston stop and disc.

But if you’re gonna do it, do it once properly, leaving no doubts, is my suggestion.

BTW, I’ve never had an engine that had the luxury of a timing plug (ie a unit motor) so I’m making a large assumption that those timing holes/slots in the crankcase are actually accurate.

Has anyone actually tested the accuracy of that crank setting mechanism against a degree wheel?

Cheers

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Originally Posted by L.A.B.
Originally Posted by quinten
there may be 2 locating notches ground in the crank
it look like youre located to the wrong notch .
[Linked Image from i.ebayimg.com]
as pictured , you're off by 38 degrees

There shouldn't be a crank notch at that white paint mark position.

One notch is at 38 degrees BTDC when the scribed line on the raised pad should line up with the pointer.

[Linked Image from i.postimg.cc]

[Linked Image from i.postimg.cc]

The other is at TDC which is on the opposite side of the raised pad to the white mark.

you are correct . i did the contortions in my head , and got it exactly backwards .

a tdc mark added/painted would be after the raised pad scribe had passed the pointer .
the white mark is by new guesstimate 38° before 38° Btdc , and of little use .

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There is another thing that catches people out. That is the latest iteration of the Lucas alternator rotor has two tining lines 180° apart. This is a left over from the BSA Bandit and Triumph Fury 350cc bikes that never saw the light of day. This was needed because these bikes had 180° crankshafts. The 38° Before top dead center timing mark, used for the 500, 650 and 750 twin models, was the one opposite the keyway slot.

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Hi WaterlooJohn, I’ve set Boyer on 70 Tiger. If it has 70 flywheel it has 2 notches for tdc tool. TDC & 38B. End of day you should own this tool.

I’ve been burned a few times where in real life hash mark lined up to pointer is not actually 38B. Rotor slipped on center. Even so production tolerances can give 1-2 deg error. This is very common.

Easiest way is remove plugs, put in top gear, bike on center stand. Rotate motor looking in spark plug hole to tdc. Stick tool in flywheel & zig zag rear wheel until rod drops into slot. That’s tdc. Again piston will be all the way up. Memorize how it looks. Pull rod up & backwards turn wheel letting rod gently drag on flywheel until it drops into 38B groove.

Practice this a few times to get a feel for it.

With tool rod in 48 slot look at rotor. Hash mark should line up with pointer. Spot on is the ideal. Usually not though. If you’re within 3/32” or so. Scribe a line & use that as the real 38 line. If your hash mark is way off, rotor has slipped on its center, keyway bad or the like. Remove rotor & inspect. If key/ keyway are good, rotor has slipped on center. This is a failure. Needs new rotor. Verify/remark new rotor line. Don’t think it’s good!

Once you learn the true 38 & mark, use the mark & pointer to set timing. Back up motor 3/8” if so. Gently go forward & stop at 38 line. This compensates for backlash in timing gears.

Now set the Boyer pick up plate lining up bottom hole with paint dot as you were doing.

Start motor & strobe time. 4000rpm.

Motor gets hot fast strobe timing. Put fan in front of motor.

With points full advance was 2000. With Boyer it’s 3500rpm. You’ll see the line stops moving at full advance. I go a bit more rpm to be sure. Thus the 4000.

Should you run out of slot on pick up plate, you have to move rotor in cam shaft. The direction you need more slot. Then star all over with aligning white dot & strobe timing.

If... you verify 38. Move motor forwards to 38 line. Center slots on pick up plate, Then lock rotor into cam. Back up motor, forwards to 38 line. Verify dot center of hole, you’ll find strobe timing will be easy & you won’t run out of slot.

None of this is complicated. It’s a step by step process that starts with verifying 38B mark is actually 38. Skip a step you’re looking for troubles.

Who knows what white line is? If 38 rotor is junk.

Coil wiring is easy. Just follow picture in instructions.
Is your bike positive ground? Make sure you look at positive ground hook up I tape over the incorrect illustrations & instructions so I don’t get confused. A mistake in wiring can smoke the unit.

Some coils are marked 15 & 1. 15 is +, 1 is -.
Don

Last edited by TR7RVMan; 04/17/21 9:51 pm. Reason: Changed sentence

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Originally Posted by koan58
Has anyone actually tested the accuracy of that crank setting mechanism against a degree wheel?
Not with a degree wheel, but I have confirmed that the mark on the rotor lines up when I lock the engine with the proper tool in the crank web.


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Thank you all for your input, it is great to have this forum as a resource.

My biggest mistake was looking at a private you tube video which advised that 38' bdc lined up with the screw hole beside the pointer ... thus the incorrect white mark.

I took the advice and started all over with finding the slot on the flywheel to line up the timing mark on the rotor and then re-set the Boyer plate and rotor to line up accordingly. I have added photos for reference.

Thanks
John

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