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ET ignition problem - rotor position? #782023 08/20/19 9:49 am
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splittie65 Offline OP
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I have a 67 TR6C and have neared completion of it.....and am dying to get the engine started and the bike on the road!
But I have no spark mad

All the componants are new, except the rotor.
New wiring loom, new stator, new ET coils, new condensors, new non-resistor spark plug caps, new spark plugs, new points (6CA system), nos 5 degree Advance Retard unit.........
The front primary cog is set in the correct place (previous thread) and the rotor is potioned on the 'S' peg.

I have tried setting the points opening at 37 degrees BTC using both a degree wheel method and the JRC Engineering method of measuring the height of the piston from TDC.

I have read magnetoman's thread regarding ET ignition.
The only discrepancy I can find is the location of the rotor / stator postion mentioned in this thread....see attached photo below.
( I have painted black on the rotor where the magnets are, and white where the stator metal is eposed)

The retarded postion is as the diagram, but not the advanced.
Is this likely to be my problem?......or any other suggestions.

[Linked Image from i.ibb.co]

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Re: ET ignition problem - rotor position? [Re: splittie65] #782025 08/20/19 11:47 am
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I don't think it's your problem.
As you've got a 5 deg advance, the difference at the crank will be 10 deg. That looks about right to my eye.
MM's diagram shows the maximum mis-alignment of rotor and stator poles for functioning at full advance, that looks about 25 deg (judged from the gap between poles being 60 deg).
Could be the rotor magnetism is drastically weak (you've seen if it easily lifts its own weight on a spanner?), or it's an electrical fault with the stator or wiring.
The points surfaces have been cleaned of any storage preservative?

Re: ET ignition problem - rotor position? [Re: koan58] #782042 08/20/19 1:43 pm
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quinten Online Happy
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Quote
All the componants are new, except the rotor


You have gone to the trouble of replacing all the other ET components,

What makes you think the 50 year old rotor is good ?

Re: ET ignition problem - rotor position? [Re: quinten] #782057 08/20/19 6:22 pm
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splittie65 Offline OP
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Koan58, I'm not sure the magnetism is that good, however I did read somewhere that it is unlikely to be the problem.... but still possible.

Quinten, find me a good / new one and I'll buy it!

Re: ET ignition problem - rotor position? [Re: splittie65] #782059 08/20/19 7:02 pm
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I did mine. It’s around 10 o’clock. The best thing you can do is ditch the 4ca points plate and get a 6ca. Makes adjusting the point so much easier.
I did the jrc one to set timing and it worked perfectly. Make sure you have the aau advanced when doing this. I took the aau bolt out and used to different size copper washer to hold it open with the bolt snugged up.

Last edited by Mori55; 08/20/19 7:04 pm.
Re: ET ignition problem - rotor position? [Re: splittie65] #782060 08/20/19 7:03 pm
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I sent mine to joe hunt in California and he remagnitized It for me.

Re: ET ignition problem - rotor position? [Re: splittie65] #782061 08/20/19 7:10 pm
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If you don’t get the points opening just right you’ll have no spark.
I took the plugs out and hand kick while sitting the plug on the head. About wore my arm out. Make sure plug is gapped right and your points are gapped correctly. Instead of paper to put in the points I used a continuity meter that beeped when the points broke contact.
ET points 014-016, plugs 018

Re: ET ignition problem - rotor position? [Re: splittie65] #782062 08/20/19 7:17 pm
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With the 6ca plate you can move each set of points individually instead getting a happy medium. Each set of points has a screw for setting gap and a screw that move each individual set for timing.
It fits right in. I moved the condensers up to the coil bracket.
[Linked Image from i.postimg.cc]

Re: ET ignition problem - rotor position? [Re: splittie65] #782063 08/20/19 7:24 pm
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Make you have the alternator rotor gap all the way around at .008. Just get a feeler guage and slide around the gap. Tap studs if needed to get right.

Re: ET ignition problem - rotor position? [Re: splittie65] #782068 08/20/19 9:10 pm
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Mori_ I think he has got 6CA points already.

Dave

Last edited by dave jones; 08/20/19 9:11 pm.
Re: ET ignition problem - rotor position? [Re: splittie65] #782069 08/20/19 9:11 pm
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Oh didn’t notice. Sorry

Re: ET ignition problem - rotor position? [Re: Mori55] #782074 08/20/19 10:49 pm
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Quote
Quinten, find me a good / new one and I'll buy it!

The ET rotor is a normal pattern rotor with dowel holes.
Buy a new normal rotor .
And drill the ET dowels holes on the back face .

The holes are located around the magnetic neutral area ... 60° offset from the magnetic centers .
In the soft aluminum potting .(safe and easy drilling )
The magnetic centers and neutral centers can also be indexed off of the broached key
Which is centered on a magnetic north magnet .
The poles alternate north , south, north , south ...around the circumference .

The holes are drilled in the neutral area between a north and south magnet... not a south and north magnet .

My measurements show

The ( S )hole is 2° off magnetic center , biased towards the south magnet
The ( M ) hole is on magnetic neutral center
The ( R ) hole is 2° off magnetic center , biased towards the north magnet

Or indexed off the center hole Broach ... as zero degees ... and using a rotary table .

The ( S ) is 32° ... clockwise
The ( M ) is 150°
The ( R ) is 268°
I never got as far as actual table indexing , i went a different path
these are just the numbers i came up with from eyeballing the problem.
Preliminary numbers... so dont take these to the bank .

.
.

Re: ET ignition problem - rotor position? [Re: splittie65] #782080 08/20/19 11:50 pm
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Why not just remagnitize it ? That’s what had done.

Last edited by Mori55; 08/20/19 11:51 pm.
Re: ET ignition problem - rotor position? [Re: splittie65] #782081 08/20/19 11:54 pm
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Re: ET ignition problem - rotor position? [Re: splittie65] #782082 08/21/19 12:06 am
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Hi Splittie,
I've just tried closer viewing of your contact breaker pics. Unfortunately they are rather low resolution, and taken at a somewhat downward angle rather than straight on.
Even so, in both pics the left contact already looks well open, whereas it should be JUST opening. If this is true, the timing will be considerably advanced from where it should be, which will reduce spark intensity at kick speeds.
Ignore this if what I see is just an artefact of the photography.

A magnetically weakened rotor will most definitely impact upon ignition performance.
Was the rotor kept inside the stator during the machine's hibernation? Kept separately, it will lose magnetism bigtime. Even kept ideally, such an old rotor is likely to be significantly below par, try the crude check to see if it will easily hold itself to a steel object.

Note MM's emphasis on:

"As this drawing shows if the sprocket is removed it should be replaced on the splines such that the peg protruding from it is at the approx. 9:00 position with the engine at TDC in order for the phase of the voltage output of the ET stator to be correct. Although there are 6 splines on the crankshaft and 6 magnets on the rotor, if placement is off by 1 (or 3 or 5) splines the polarity of the output voltage waveform will be reversed. However, later BSA and Triumph manuals don't mention this detail so the polarity of the tip of the spark plug could be reversed with less than optimum results"

It is always possible for a "conspiracy of details" to add, and result in failure to spark. For instance, a weaker rotor, the above wrong polarity and timing out could conspire in such a way.

Re: ET ignition problem - rotor position? [Re: Mori55] #782117 08/21/19 9:46 am
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splittie65 Offline OP
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Originally Posted by koan58

Could be the rotor magnetism is drastically weak (you've seen if it easily lifts its own weight on a spanner?)


I just took the rotor off, and the rotor will pick up a spanner......but I can't pick up the rotor with a spanner.
There's no way it will support its own weight.

Could this be my problem?

Originally Posted by Mori55
I sent mine to joe hunt in California and he remagnitized It for me.


Unfortunately I live in the UK........so I'll have to find someone more local.

Yesterday I found a NOS one in good condition on the USA eBay and thought I'd check mine first.......of course now i've done that, it has been sold!

I'm not sure my skills in locating the holes and drilling them in a standard rotor are good enough. Plus looking at pictures of them, the magnets look much wider leaving little gap between them....would this not affect the ET ignition?

Re: ET ignition problem - rotor position? [Re: splittie65] #782119 08/21/19 10:11 am
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Quote
I just took the rotor off, and the rotor will pick up a spanner......but I can't pick up the rotor with a spanner.
There's no way it will support its own weight.

Could this be my problem?


Yes it should be able to support its own weight ie picked up by a large spanner.

A O Services in the UK can remag a rotor.

Re: ET ignition problem - rotor position? [Re: quinten] #782131 08/21/19 12:24 pm
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Originally Posted by quinten
Quote
Quinten, find me a good / new one and I'll buy it!

The ET rotor is a normal pattern rotor with dowel holes.
Buy a new normal rotor .
And drill the ET dowels holes on the back face .


.
.



The last (new Lucas/wassel) rotor I bought has the dowl holes in the back for the locating peg as far as I can tell.


beerchug
Re: ET ignition problem - rotor position? [Re: splittie65] #782133 08/21/19 1:18 pm
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After having mine redone. It’ll pick up everything on sight. Large wrenches etc. it’s actually hard to pry stuff off it.

Re: ET ignition problem - rotor position? [Re: splittie65] #782135 08/21/19 1:23 pm
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I just looked up new Lucas rotors. They all said not ET. I’d get remagnitized. I know I wouldn't be comfortable drilling hole. And if you get s used one , how do you that won’t be weak

Re: ET ignition problem - rotor position? [Re: splittie65] #782138 08/21/19 2:09 pm
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splittie65 Offline OP
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Found somewhere that will re-magnatise the rotor.......125 miles away....but they said just drop in and they'll do it there and then while I wait.
£15 + VAT.....not bad I think, so I'll be off there tommorrow.

https://villiersservices.co.uk

Re: ET ignition problem - rotor position? [Re: splittie65] #782140 08/21/19 2:50 pm
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Nice ! Let us know how it works out.

Re: ET ignition problem - rotor position? [Re: splittie65] #782141 08/21/19 2:56 pm
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Lucas originally shipped their replacement rotors with steel bands that served as 'keepers' for the magnets. I have a NOS rotor in the garage I won't take the time to dig out to check, but I remember the band as being ~1/16"-thick and springy enough to hold in place but still be easily slipped off.

Within milliseconds of a keeper being removed from an Alnico magnet the magnetization will drop to a lower value from which it won't recover unless it is remagnetized. Luckily, Alnico is strong enough that this remaining magnetization will be good enough. But, if you want better than good enough you will have such a band with you into which the rotor will be slipped as it is removed from the magnetizer (i.e. never without either the poles of the magnetizer or the band being in contact with the rotor, even for a millisecond), transport it home, then slip it from the ring as you push it into the stator (again, never without either the band or the stator being in contact with it).

It will work even if you don't do this, but the difference this will make with an ET system will be a lower rpm needed to kick start it and the full 35 W of blazing headlamp power when under way. With a battery/coil system it will mean more Watts of charging power.

Re: ET ignition problem - rotor position? [Re: Magnetoman] #782142 08/21/19 3:15 pm
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MM, I have the old stator that I replaced, which I'm using as a keeper while the rotor is off the bike. Hope this helps.

The holes on the back of the rotor don't look to be in the best of condition, so if I find a NOS or very good used I might still replace in time.
(Although the 'S' one looks the best.....and that's what I'm using)

Re: ET ignition problem - rotor position? [Re: splittie65] #782145 08/21/19 3:24 pm
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Originally Posted by splittie65
MM, I have the old stator that I replaced, which I'm using as a keeper while the rotor is off the bike. Hope this helps.
It won't hurt, but it won't help. If you removed the rotor and immediately placed it in a spare stator, that was at least 1000x too slow to do any good.

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