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Posted By: Ducknaldo Rotor type and marks... - 05/15/11 7:29 pm
Once again my friends 68 Bonneville with a later T140 engine has revealed something strange, at least to me.
The rotor has quite a few marks, but none of them seems to line up with 38 degrees.
If he lines up 38 degrees by using the timing plug hole, none of the marks line up with the timing pointer.
According to him, the rotor does not rotate on the crank.
Is this an original rotor and what are all the marks for if none of them is 38 degrees and aparantly not tdc either.
38 bdc is found by looking down the spark plug hole and thereby locating tdc and then rotating backwards until next crank hole line up through the timing plug hole, but no marks line up at both points.
I apologize for the bad picture, but he´s no wizard with his cellphone:)
Anyone who can shed some light on this rotor type and the marks?
I figure the solution will be to line up 38 through the timing plug hole and then making a new mark on the rotor and strobing this new mark.
[Linked Image]
Posted By: shel Re: Rotor type and marks... - 05/15/11 7:43 pm
My 76 T140V has the timing marks scribed into two raised pads opposite of one another. Is it possible his rotor is installed backwards and the timing marks are facing the engine?
Posted By: Ducknaldo Re: Rotor type and marks... - 05/15/11 7:48 pm
Mine is the same as yours and I thought all rotor´s were like that.

If it´s really on backwards, if that´s possible, why would there be marks on the backside?
Posted By: shel Re: Rotor type and marks... - 05/15/11 8:03 pm
It is possible to install the rotor backwards. I've never paid attention to the back of mine so I don't if it has marks on the back or not.
Posted By: Pete R - R.I.P. Re: Rotor type and marks... - 05/15/11 9:07 pm
That looks like a Trident rotor.Just put a new mark on it.
Posted By: L.A.B. Re: Rotor type and marks... - 05/15/11 10:20 pm
Yes, they are the Trident "A" and "B" timing marks (for early and late triple cranks none of which are in the correct position for a twin) just about visible through the blur.
Are there any timing marks on the other end of the rotor?
Posted By: RF Whatley Re: Rotor type and marks... - 05/16/11 4:52 pm
Whatever the reason, the rotor needs marking for strobe timing. He'll need to add his own with a center punch. Best way to do this is to fit a positive crank stop tool into the 38 deg BTDC hole to locate the crank, then add a single punch as close to the pointer as possible.

[Linked Image]

The tool is fitted where you see the brass object in the photo.

:bigt
Posted By: Stuart Re: Rotor type and marks... - 05/16/11 5:46 pm
Hi,

Fwiw, I'd whip the rotor off and see if the twin's timing marks are on the other side - they often are.

Btw, is the stator a two-wire single-phase one or has the whole alternator been replaced with a 3-phase?

Hth.

Regards,
Posted By: Ducknaldo Re: Rotor type and marks... - 05/16/11 9:41 pm
Hmm, I´m not sure, I´d have to ask him to check.
I think it´s the single-phase though, original for this engine.
The rotor was replaced a few years ago, because it was floating.
The owner now seems to recall having strobed the bike with this rotor, so probably the twin marks are there.
Now the bike has been completely rebuilt by a very capable... Nimbus mechanic:), hence all the kinks has to be ironed out.
I just hope he didn´t put 4 pistons into it:D

The gearbox was also incorrectly assembled and only 2 gears are working now.
Dunno if a Nimbus was a 2 gear bike:)
Posted By: btour Re: Rotor type and marks... - 05/16/11 9:48 pm
laughing
Posted By: shel Re: Rotor type and marks... - 05/17/11 12:00 am
Originally Posted by Stuart
Hi,

Fwiw, I'd whip the rotor off and see if the twin's timing marks are on the other side - they often are.

Btw, is the stator a two-wire single-phase one or has the whole alternator been replaced with a 3-phase?

Hth.

Regards,


My Trident rotor has the twin marks on one side. That's why I wondered if maybe his rotor was on backwards.
Posted By: Stuart Re: Rotor type and marks... - 05/17/11 3:15 am
Hi,

Originally Posted by Ducknaldo
The rotor was replaced a few years ago, because it was floating.

Ah! That'd be a good reason to expect the twin timing marks on the other side. I can't now remember whether my T160's original rotor also had the twin timing marks, because it's been gone the best part of thirty years, but certainly the rotor from the Lucas 3-phase that replaced it then has them all.

Hth.

Regards,
Posted By: Pete J 77T140 Re: Rotor type and marks... - 05/17/11 12:38 pm
Hey,

I just got a new rotor made by Wassell and the back side (side that goes toward the engine)looks just like your photo above.

Cheers,

Pete
Posted By: RF Whatley Re: Rotor type and marks... - 05/17/11 12:57 pm
Originally Posted by Stuart

Originally Posted by Ducknaldo
The rotor was replaced a few years ago, because it was floating.

Ah! That'd be a good reason to expect the twin timing marks on the other side.


That's like saying "There was no life on the moon, therefore it must be on Mars." laughing

And what if the rotor is off a Royal Enfield? It won't have marks for triples or twins.... on either side. And who is going to guarantee that the marks, if any, are in the correct position?

You guys are killing me. Assuming there are correctly placed strobe marks on the other side is a leap of faith requiring an astounding imagination.


You're also asking the OP to violate the first rule: If it ain't broke, then don't fix it.

Posted By: Ducknaldo Re: Rotor type and marks... - 05/17/11 1:26 pm
Hehe, Mr. Whatley.

As far as the rotor goes, you´re absolutely right, there´s no reason to turn it around, even though it´s quite certain that the twin marks are on the other side.
(He remembers having strobed it with this rotor, remember?)

It´s far easier to make new marks instead and that would ensure close to 100% perfection in the marks location.

I must say, that if I compare the two tasks, I would also just make a new mark, but that would be down to being lazy.
I offered him to borrow my crank tool next weekend and I figure that´s the way he´ll go.
Posted By: Jack Adams Re: Rotor type and marks... - 05/17/11 2:21 pm
As RF pointed out,It is easier to remark it AND it is "sure" to be right if you pay attention to what you are doing,so why even consider any other course of action? Jack
Posted By: Stuart Re: Rotor type and marks... - 05/17/11 2:54 pm
Hi Richard,

Originally Posted by RF Whatley
what if the rotor is off a Royal Enfield?

Originally Posted by Pete R
That looks like a Trident rotor.

Originally Posted by L.A.B.
they are the Trident "A" and "B" timing marks

Originally Posted by Stuart
I'd whip the rotor off and see if the twin's timing marks are on the other side

Originally Posted by RF Whatley
You guys are killing me. Assuming there are correctly placed strobe marks on the other side is a leap of faith requiring an astounding imagination.

No.

Ducknaldo has been registered for well over two years and has made 452 posts. You've already posted, "the rotor needs marking for strobe timing"; all I've assumed is he's not so stupid that I have to repeat your advice.

Originally Posted by RF Whatley
You're also asking the OP to violate the first rule: If it ain't broke, then don't fix it.

confused 'Course it's broke, the wrong timing marks are visible.

Ducknaldo can make new marks wherever he pleases but, given he's doing the bike for someone else who is unfamiliar and less-experienced with old Triumph twins, KISS is an at least equally-valid principle. If he checks for standard twin timing marks and, if they're present, he checks them, it's equally possible that they could be accurate. Then there won't be any need for even more marks ... or any need for the eventual owner to remember which marks are the 'right' ones ... and/or that anyone who subsequently works on the primary has to replace the rotor the 'wrong' way 'round ... yadda, yadda.

Hth.

Regards,
Posted By: Ducknaldo Re: Rotor type and marks... - 05/17/11 3:16 pm
You´re absolutely right Stuart.
I think we all know it would be the most correct way to go about this.
I have a very strong feeling though, that my friend, presented the options, will want to punch new marks.
It actually surprised me that Mr. Whatley suggested this solution.
Normally on this forum, the guru´s are the ones telling us mortal Triumph owners to do things the "correct" way and for good reason. It has to be noted in this situation that which ever solution chosen, would yield the same technical result and thereby making the decision partly "ethical", in lack of a better word.
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