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Hello again. I am in the final stages of my 1970 Triumph bobber build. Exhaust is on and tightened up and now am just installing the Boyer rotor and timing. I am confused with where the timing mark should be in relation to the pointer on the primary cover.

I removed the plug at the rear of the cylinder barrels and found one of the notches, but not sure if there are two of these.

With the notch i found, the pointer on the primary is dead on the line in the raised pyramid block on the rotor.

Is this 38' TDC or is this TDC.
Thanks
John

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By no means an expert, but if the "TDC tool" is in the slot that sets makes it 38 degrees for static and your looking on the cam side for the magnets in the boyers little windows in the plate. The marks on the rotor are for timing light at 2000 rpm. Hope that doesn't confuse thing further


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Not sure if you should have one or two slots in your 70 crank

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Originally Posted by DAMadd
The marks on the rotor are for timing light at 2000 rpm.

Assuming it's the usual "Boyer" Micro-MkIII/IV.
http://www.boyerbransden.com/pdf/KIT00052.pdf
"Connect the strobe lamp and time with the engine running up to 4000 R.P.M."


Originally Posted by AngloBike
Not sure if you should have one or two slots in your 70 crank

Should be two (TDC and 38° BTDC) slots.

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I should have prefaced my comment with: the Boyer sheet that came with your ignition tells you that. Also Imy last static timing was a mk III on an a65t 68 and my triumph is a 65 thus my actual preface--not an expert. If there is 2 timing slots on a 70 then anything goes without the service manual all good eventually more knowledgeable folks will chime in. Good luck


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@Waterloo I really hope this helps

When I did the timing on my 73 T140.

When your timing plug tool is in the slot in the crank, I used a small screwdriver) and the the pointer is aligned, this is TDC. I also used a pencil in the spark plug hole. As you approach the TDC you will see the pencil raise, it will be or should be at its highest point at TDC. Doing this along with the timing mark plug made this whole thing make sense to me.

1. remove your spark plugs, and raise the rear wheel.
2. rotate your wheel very slowly backwards, leave your timing tool in the plug and let it gently touch that crank journal.
3. it will fall into the next slot. This slot is the 38deg before TDC. I used small black paintbrush and drew a line on the rotor at the primary cover pointer.
4. this is now where you line up the Boyer rotor. I found it a helpful starting point to have the magnets at like 1 o'clock and 7 o'clock positions
5. line up the little holes on the stator plate of the Boyer. tighten it down, not worlds strongest man tight, but decently.
6. put in the plugs, and give it a fire. It should run.
7. now you do the static timing, and rotate the stator plate to then with the engine running you watch that black line you drew, and try to get it to line up with the pointer on the cover while you HOLD the rev at 4k.

if memory serves, rotating the Boyer stator plate clockwise moves the "timing mark" counter clockwise during the static timing.


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I should also add,

Don't break off the timing tool in the plug. And when you rotate the stator plate to either advance or retard the timing, small movements of the plate work best. Like for me it was like a few mm in either direction made huge differences. The first time I did this with a friend, and it was really helpful to have someone hold the timing light, and keep an eye on the rotor mark.

The second time I did it by myself, and it was a bit more difficult. Had the timing light like duct taped to a chair. Ha.

And not sure if you know, but its more accurate if you run the timing light off a second battery, not off of the bikes own energy. Its also helpful to not melt the wires leading to the timing gun (this is where the friend also comes into play)


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73 TR7RV. Before I moved my stator, I checked to see where it was set. Turns out at 5,000 RPM, it was advanced to approx.40+ degrees. After dialing it back to the mark (38 degrees) it runs much better and doesn't carbon foul the plugs when running close to the redline.

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Hi Seanalex; you did it wrong. The mark in the rotor is 38º BTDC.

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Originally Posted by reverb
Hi Seanalex; you did it wrong. The mark in the rotor is 38º BTDC.

Originally Posted by seanlex
3. it will fall into the next slot. This slot is the 38deg before TDC. I used small black paintbrush and drew a line on the rotor at the primary cover pointer.

Seanlex got it right, he was working off the slots machined in the flywheel, 2 slots TDC and 38 BTDC. He then made a mark on the rotor which is good practise in case the rotor has been changed or was marked wrongly.

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Hi Kommando; the error is here: "When your timing plug tool is in the slot in the crank, I used a small screwdriver) and the the pointer is aligned, this is TDC. "

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There are 2 slots in the flywheel, one at TDC and second at 38 BTDC, he references both in his write up.

Quote
3. it will fall into the next slot. This slot is the 38deg before TDC. I used small black paintbrush and drew a line on the rotor at the primary cover pointer

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...we are looking like guys that do not know how to read...the pointer of the primary cover points to the rotor mark at 38BTDC
TDC has no mark. He wrote bad; then confused more the other guy with the explanation that you quoted.

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Crank flywheel not rotor, the crank flywheel has 2 notches, one at TDC and one at 38 BTDC, on the timing side crankcase is a plug which when removed you screw in the timing plug which will drop down into both slots.

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...of course; but HE said: "pointer" not "plug". Mark on the rotor is 38BTDC. Is not semantics. He wrote bad; confused the other guy and many more in the Future.
So, as you know; for reference, the timing plug is just that; the flywheel has the two slots for TDC and 38º. The rotor mark is 38º (and that is what is important)
If you put the plug on the TDC you will not have the rotor aligned and that is what matters.
Simple like that.

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For What It's Worth - I once found a flywheel that had been installed backwards on the crankshaft.

So, there APPEARED to be no timing dimple and no TDC dimple. The problem was, the TDC dimple was on the "wrong" side of the flywheel, and the timing dimple was in the AFTER TDC position (also on the wrong side)...

Last edited by GrandPaul; 11/25/21 1:55 pm.

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For what it's worth , I agree with Seanalex and Kommando .

seanalex uses and identifies the tdc flywheel stop ( while also checking piston travel )
as the first step ,
to finding and using the second 38° btdc flywheel stop ...
now the TDC stop can not be confused with the timing stop .

The second timing stop
should correspond to rotor-scribe and primary cover timing pin ( if the rotor is keyed correctly )

Is it necessary to find and use the TDC stop first , if you know the 38° stop and rotor-key broach are spot on
to a timing pin ?
no , you take a short cut . ( Reverbs perspective ? )... just cut to the chase.

You can approach the problem from the different end .
You could use the back wheel in-gear method , turning the engine over slowly
watching the rotor-mark clocking-around closer-and-closer to the timing-pin
until the flywheel stop drops into its slot .

.. if it's been a while , it cant hurt to use both stops as this can help visualize what's going on and when .
Especially as ignition timing this days is often a fit and forget process
... meaning I forgot what I did last time , I better not take shortcuts .

If your rotor is close, but couple of degrees off .
Look to see at the flywheel /rotor brooches aren't knackered
or that the rotor hub has started to move and spin against its softer outside casting .

Last edited by quinten; 11/25/21 8:25 pm.
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Hi Quinten; I was not talking about methods I was talking about that the other member wrote the thing bad. The rotor mark is the 38º not the TDC.

Then; if you and others want to talk about method; the only time you need (in these later models) the TDC on the rotor (you need to do a mark there) is if you have n stroboscopic light without some features; so you need to check on TDC new mark (but the crank in 38º) then check but most lights can do without that complication.
I needed to check at 30; 32 and 34 degrees because I have a dual plug head.

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reverb , i re-read seanalex' post for the 4th and 5th time , and you are right .


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