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Discussion Starter #1 (Edited)
I should have spotted this earlier, but didn't.

I have what was a 724cc TR7RV. I bought it as a non runner. I rebuilt it last winter, and it runs very nicely. The alternator charges at maybe 14V and the battery is never flat. It starts first or at worst 2nd kick. It's as fine as I can tell.

Just fitted a new primary chain and an engine sprocket (see my posts in the What I did today...thread).

On fitting the stator I noticed that the rotor was protruding out of the stator on the sprocket side, by maybe 7 mm or so. I now think that's how it's been since I rebuilt it because I didn't notice. However, it runs fine, and charges, so the rotor protrusion does not seem to affect the AC production - but it cannot be right.

Checking the new Harris engine sprocket the depth from the outer face to the inner face on the outer side was about 0.8mm greater than the sprocket I've just taken off. The bike came with 2 distance spacers between the sprocket and the rotor, totalling about 13mm. Checking the parts book, there should be one spacer, and that should be 1/2" or 12.5mm. So, I have 2 spacers where there should be one (but the same total thickness), but more importantly, I think the rotor is maybe 5 to 10mm inboard of where it should be.

Looking at the photos, you can see a clean section and a slightly stained section of the rotor, where that stained section has been running inboard of the stator.

That can't be right. I can add spacers to move the rotor outboard so it would be better.

I don't understand how the rotor can be so far inboard and yet the parts all seem to be what they should be.

The new sprocket lines up apparently perfectly with the clutch, and the ends of the splines on both crank and sprocket are co-incident. I think the sprocket is located where it should be. The engine and clutch rotate apparently perfectly. It all seems OK.

The stator is I think where it should be because the stator mounting studs locate the primary cover where it should be - no excess stud length. It all fits.

I'm wondering if this is a 724/744cc issue and the crank was modified between the 2 versions, and the rotor location changed and previous owners have changed parts and I'm trying to work out what should have been.

I think this is easily fixed by spacing the rotor out a bit, but does anyone have any thoughts on this conundrum?

Thanks, Andy

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Hi Andy,
noticed that the rotor was protruding out of the stator on the sprocket side,
bike came with 2 distance spacers between the sprocket and the rotor, totalling about 13mm. Checking the parts book, there should be one spacer, and that should be 1/2" or 13.5mm. So, I have 2 spacers where there should be one (but the same total thickness), but more importantly, I think the rotor is maybe 5 to 10mm inboard of where it should be.
don't understand how the rotor can be so far inboard and yet the parts all seem to be what they should be.
You aren't the first to notice this, the misalignment of stator and rotor has featured regularly in Britbike forums for years; afaict, it was another of those minor cock-ups at Meriden they couldn't be arsed to fix. :(

Magnetically-electrically-ideally, the centre of the rotor should align with the centre of the stator; i.e. depending on the widths of the two components, either the rotor should stick out beyond the stator the same front and back, or the stator should stick out beyond the rotor the same front and back. However, if it's the stator's wider than the rotor, as long as the rotor width is fully within the stator's width, the centres of the two components need not align, they'll still function magnetically-electrically correctly. (y)

If there's a loose spacer between rotor and sprocket, the spacer's width should centre the rotor in the stator, not be some arbitrary width that clearly isn't correct.

rotor is maybe 5 to 10mm inboard of where it should be.
this is easily fixed by spacing the rotor out a bit,
Mmmm ...

. the rotor might actually be in the 'correct' position - if you move the rotor axially 'outboard', the most important thing to check is the rotor nut can still secure the rotor to the crank;

. it might be that it's actually the stator studs that were made incorrectly, moving the stator 'outboard'. :(

If you can and do move the rotor 'outboard', and the nut still secures it on the crank, then ensure the timing pointer in the outer chaincase doesn't gouge the rotor ...

wondering if this is a 724/744cc issue
:confused: Why, given the Forum's beaten the lack of '73 crank differences to death already?

As I say, you aren't the first to discover the problem (by many years) and, as long as owners persistently ignore the most basic internet tool ("Search"), regrettably you won't be the last (by a long way) ...

Hth.

Regards,
 

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Andy
Apologies in advance because, I did not get a resolution to this back then. It may not even be related, but

My last T140D always gave me a feeling that something wasn't quite right. I kept thinking I could hear an indistinct noise coming from the primary. At one stage I took the cover off and found this




Like you I couldn't think if my last Bonnie was the same. The (my) internet wasn't the same then and I only frequented one forum at that time so posted these pictures and asked advice. I never got anything to work on so left it as is...but could never shake the nagging doubt.

Anyway a year or so later I bought a new chain and sprocket set and went to remove the old ones. When I had removed the chain I noted I could move the front sprocket back and forth slightly. Not good thought I. When I removed the sprocket, this is what I found



I then spoke with the guys at Wilemans, and he said it would be due to a spacer missing causing some in and out movement and slowly chewing away the splines.
The crank was scrap, and I ended up selling the bike as a project as I didn't have the money to do a rebuild

As I said in the beginning, apologies for a wooly reply that may have nothing to do with your query, but if it helps, then........
 

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Discussion Starter #4
. the rotor might actually be in the 'correct' position - if you move the rotor axially 'outboard', the most important thing to check is the rotor nut can still secure the rotor to the crank;
Thx Stuart - the rotor could come outboard by 7mm or so easily as there's crank thread to spare.

Interesting that this is a regular issue - it hadn't occurred to me that I was being anything other than plain thick not to have spotted this alignment issue before. Difficult to conceive why Triumph did not fix this issue - it just looks so wrong, so wrong that I could not understand what I was looking at when the old and new engine sprockets were near as dammit identical.

I've ordered the 1/2" spacer and by mixing and matching I can get a better alignment I think, but I take your point about the timing pointer. I'll check that.
 

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Discussion Starter #5
Hi Jimmy,
Apologies in advance because, I did not get a resolution to this back then. It may not even be related, but...
No, I don't have that problem. My crank's fine.

I think Stuart's identified the issue - I'll see if I can improve the alignment with playing with spacers.
 

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Hi Andy, I’ve not seen 2 spacers there before.
I’ll have to check my notes to see what my spacer is.
The rotor is normally well out of alignment though.
On my bike’73 Tiger & the ‘73 Bonnie it will hit the pointer. All the T140 are like this.
Charging system works perfectly. Would centering make difference I don’t know.
Think of crank sprocket 3 row chain is sensitive to sprocket alignment. That has to be addressed first.
Don
 

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Hi Andy, The first spacer (kind of a cup washer) goes cup side against roller bearing is .080” thick.
Then sprocket alignment shims as needed. Available in .010 & .030” thicknesses.
Then the crank sprocket. I don’t know how thick mine is.
Then one thick spacer. On my ‘73 it’s .536” thick. On 73 Bonnie it’s .537” thick.
my bike & the examples of ‘73s did not come with gasket on inner cover.
I have .040” of shims to align sprocket. Putting in gasket moves clutch basket to right. So that case no or maybe .020” shims. I doubt that would effect charging anyway.
Don
 
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