Sparx 3 phase alt set up... Rotor question

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jeremy0201

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Jun 13, 2008
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Hello all, I have a quick question I am not quite understanding the rotor set up in regards to timing... So the rotor has two marks on it but its also keyed so it will only fit one way.. does this mean that the mark is tdc mark or am I completely confused? I am in the middle of an alt upgrade trispark install and complete rewire from scratch harness to negative ground.. I want to set it up so I can strobe it in the future and know everything is correct... Thanks Jeremy
 
Here's what I would do---rotate the engine so the left side piston is comming up on the compression stroke---rotate untill the piston is almost to TDC--look at the rotor and see which mark is almost in line with the mark----use this mark. To be more precise---fabricate a degree wheel to find true TDC and then remark the rotor--these are sometimes off by a few degrees due to manufacturing tolerances.---you can use a file to smooth off the raised portion of the rotor then scribe a new mark.
 
When I installed my sparx rotor (after getting it machined so that it would fit the crankshaft) I just put it on and hoped, upon the basis that if there were two opposing timing marks on the rotor, and a single timing mark on the primary cover, the marks must surely match for timing with a strobe light.

So far as I am aware there is no issue with timing; but it worked well enough that I have not bothered checking it with a strobe as yet.

Can I be wrong with that approach?
 
Timing marks in the cover are often off by several degrees. Mine were off by almost 5 degrees!! So much better to make your own timing marks with a degree wheel as FMJ suggests. Then you know it's right. You may get lucky and find yours are right on, but then you know for sure.
 
Chris T said:
When I installed my sparx rotor (after getting it machined so that it would fit the crankshaft) I just put it on and hoped, upon the basis that if there were two opposing timing marks on the rotor, and a single timing mark on the primary cover, the marks must surely match for timing with a strobe light.

So far as I am aware there is no issue with timing; but it worked well enough that I have not bothered checking it with a strobe as yet.

Can I be wrong with that approach?
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If it's running fine and your happy no problem----but that doesn't make it 100% spot on. Only if your kind of a perfectionist would it matter much. MOPO.
Probably 1000's are just like yours.
 
I was always under he impression that the 2 marks were there so you would be able to hook your timing light up to either spark plug.They are 180 degrees opposite of each other are they not.My bike has a Boyer on it and set the timing through the points cover 28 degrees at 3000rpm.This also matches up with the little degree scale that you can see through the front inspection plug in the primary case.
 
750nort said:
I was always under he impression that the 2 marks were there so you would be able to hook your timing light up to either spark plug.They are 180 degrees opposite of each other are they not.
Click to expand...

They are 180 apart, but on a 360 degree four stroke vertical twin, the same rotor mark would be used for both cylinders - regardless of whether it had points or electronic ignition.
 
When I replaced my original Lucas unit with one timing mark with the Sparx unit with two ,I was told by my supplier that the Sparx has two because it can be used on other models of bikes with different timing degrees. So if your motor has been static timed one of those marks will be close enough so you can start your bike and then strobe time it later if necessary.
All of my triumph's have original Lucas units that have two timing marks.......


Tim_S
 
Tim_S said:
When I replaced my original Lucas unit with one timing mark with the Sparx unit with two ,I was told by my supplier that the Sparx has two because it can be used on other models of bikes with different timing degrees.
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Either your supplier didn't explain it very well - or they didn't know what they were talking about.

A 180 degree vertical twin would obviously need a rotor with two marks 180 degrees apart. However it appears the two mark rotor was adopted as the standard item during the mid-seventies when Triumph decided to shift the position of the ignition timing pointer by 180 degrees on their 750 twins, therefore a rotor with two timing marks would be suitable for both applications.
 
LAB I would love to stump you one day! Joke.

But thanks, your explanation has satisfied my curiosity of the two marks on the rotor. I think there were also other timing marks on some Triumph's as well. From memory the T150 had A & B marks just to add some confusion.

Cheers Richard
 
stockie2 said:
I think there were also other timing marks on some Triumph's as well. From memory the T150 had A & B marks just to add some confusion.
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Lucas rotors often have the timing marks for triples at the opposite end.

Originally there were three timing marks for triples, but to provide better emergency starting, the alternator rotor keyway of the triple crankshafts was repositioned and another set of timing marks added to the rotor, the "A" marks then being used for the early type crank and the "B" marks for late cranks - however the "A&B" marked rotors were apparently fitted some while before the modified crankshafts were introduced.

One Triumph Service Bulletin "2/73 (Triple)" quotes the change of crankshaft occurring at T150 serial "AH 1603" (AH = '73 model, built Jan. 1973), and Hurricane "XH 01842"(XH = '73 model, Dec. '72 build but Hurricanes built in 'Jan '73 often had the XH Dec. '72 build date code prefix :roll: ).

Another Triumph Service Bulletin (429) notes the change of crank occurring at serial "PG 01603" for the Trident and "PG 1842" for the Hurricane however the AH/XH date codes would seem to be correct and not "PG".
 
Well I thank everyone for helping me clear this up.. So I am going to find TDC again, mark the rotor mark closest to the top position and hope for the best.. If theres an issue I 'll create my own mark... Thanks all. Jeremy
 
jeremy0201 said:
Well I thank everyone for helping me clear this up.. So I am going to find TDC again, mark the rotor mark closest to the top position and hope for the best.. If theres an issue I 'll create my own mark...
Click to expand...

You will probably have to make your own TDC mark - as there is no static "TDC mark".

What you really need to check is whether the ignition timing scale is set accurately - so the rotor timing mark lines up with the 28 degree mark on the scale when the crank is set at 28 deg. BTDC (or 31 @ 31 deg. for some electronic ignitions) as ultimately it's 28 (or 31) degrees BTDC that has to be found.
 
That rotor,with the two marks, sure is a handy thing. When I installed the Boyer ignition on my Commando I managed to time it with the wrong mark and wasted most of an afternoon trying to figure out why the damnn thing wouldn't run. A great lesson in being thorough and paying attention, it won't happen again(I hope).
 
So I think I have the same issue with the sparx setup. I set the rotor @28 deg as the piston was rising on the primary cover scale but I'm not convinced its actually 28deg as the Tri-spark didnt register it. How do I verify accuracy of this.I have the gist of it but 100% sure as i've never done it so please correct where necessary.Heres what I'm thinking
I've downloaded the degree wheel its needs to be glued to something solid and cut out and attached. Where?
I find TDC with a dial indicator by halving the start and end movements of the piston as it rises and falls
wire attached to frame or something acting as a pointer the degree wheel is repositioned to "0" Top center on the wheel and lock it in.
Moving the wheel to 28deg and see what appears at the primary window scale?
 
I printed my degree circle on a stiff piece of paper and glued a golf tee to the center, and just pressed it into the crank where you put the puller. I fashioned a wire pointer off of the inner cover stud with a bracket and a nut. I marked the stator with a knife edge lined up with the rotor mark when I got TDC and 28°.

Dave
69S
 
speirmoor said:
I set the rotor @28 deg as the piston was rising on the primary cover scale but I'm not convinced its actually 28deg as the Tri-spark didnt register it. How do I verify accuracy of this.
Click to expand...

Your Commando is an 850 Mk3 isn't it? So it should have the crankcase timing aperture and 28 degree BTDC timing slot in the crankshaft?

Sparx 3 phase alt set up... Rotor question

Sparx 3 phase alt set up... Rotor question
 
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