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Dynamo/Alternator

pifinch

Well Known and Active Website User
VOC Member
Lady and me have been together for over 30 years, Lucas dynamo on a series C, I fitted a JG unit in 1974, it has been fine until now, the dynamo has finally spilled its guts & I have bought a Alton - Looks great but the Lucas 'mo had a tapered spacer, the parts list shows a shim for the miller unit, the Alton fits too snug to the primary chain, I have no knowledge of miller dynamos, do I need PD19 or am I better of using a large dia. o ring to effect a seal? any help welcome. THANKS.
 

bcc99

New Website User
Non-VOC Member
Alton

I recently fitted an Alton alternator to my Series C. I fitted only the oil thrower (PD28) and sprocket (PD15/1), as per the instructions, and found alignment was quite straightforward. I was able to slide the alternator from left to right in the clamp, to position the sprocket in the middle of the central chain run, then rotate the alternator body to achieve clearance, which I checked with the clamp fully tightened and the chain in various positions, and under tension from the kick-start. The instructions state the gap should be 10 thou, but I couldn't think of an easy way to measure this. I just checked that the sprocket could be moved slightly, independently of the primary chain, in all positions. All seems fine (after only 57 miles!).
 

Monkeypants

Well Known and Active Website User
VOC Member
You can purchase sheet cork in various thicknesses and this can be used to make a seal/spacer for the Alton. To do this, cut a ring of cork to fit between the Alton and the flange on the engine casting. This cork seal will be a narrow ring laying right at the outside dia. of the Alton. If you look at the Alton and look at the engine casting the dimension for the dia and width of the cork will be obvious.
You may have to do some trial and error with different cork thicknesses in order to get the appropriate thickness such that when the Alton with cork fitted is pushed up tight to the engine casting, making a seal, the sprocket is centered on the width of the primary chain rollers.

It has been suggested to me that it would be a good plan to put a tiny groove across the face at the top side of the cork seal in order to allow primary case air pressure to escape as things heat up. Otherwise it is possible that positive pressure could be created in the primary, and this could cause the primary case to leak oil.
I did not put the groove in and I have had no problem with primary leakage, however.
In fact, I used the cork seal described above on my Miller to cure leakage I had around that unit. When I switched to the Alton, there wasn't room for the cork since in the case of the Alton, the sprocket sat nicely in center with unit pushed up tight, metal to metal. I used a heavy bodied anerobic sealer on the flange instead.

It sounds like your situation with the Alton is similar to the way my Miller lined up, so some thickness of cork should fit the bill.
 
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bcc99

New Website User
Non-VOC Member
Alton part 2

In light of the posting by wormtorn I looked again at my Alton installation. There is clearly a gap of 1/8" between the alternator and inner chaincase. I had assumed that the combination of oil thrower PD28 and oil ring ET164 were sufficient to prevent significant loss of oil - neither the parts list or Know Thy Beast mention the use of cork gaskets. Reading further in KTB, in a section referring to series D, there is mention of an alloy adaptor, PD32, which fits in the gap between Lucas E3L and inner chaincase, and which may be skimmed if necessary to obtain the correct sprocket alignment (implying that the dynamo should sit right up against this). The use of silicone sealant / strategic drilling is also mentioned as a means of preventing oil seepage. Although there is no sign of leakage, and my primary chaincase still contains the right amount of oil (I just checked), I have only ridden 57 miles since the conversion so perhaps should reconsider. In which case, cork seems like the way to go (as the gap is too big for sealant).
 
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Monkeypants

Well Known and Active Website User
VOC Member
The cork fix was suggested to me by John McDougall.

The first time I took my top-end apart and removed the Miller i noticed some oil laying on the crankcase under the dynamo. I asked John about this and he informed me that most of the countless Vincent twins he has rebuilt have had oil under the dynamo, found upon teardown. This appears to be oil which finds it's way past the flinger. The cork takes care of it quite nicely.
 

Pete Appleton

VOC Hon. Social Secretary
VOC Member
VOC Forum Administrator
Alton Oil leaks

I tried 'O' rings and cork gaskets with little success. In the end I put a 1/4 " bead of ordinary silicone sealant around the end of my Alton and pushed it inwards until the sprocket was in the middle of the primary chain and did the clamp up. 7000 miles later - still no leaks.
The obvious worry when using copious quantities of silicone is the danger of any excess finding its way in to the oil system. This is not a worry in the primary case as there are no oil ways to block.
The other comment that I would make is please dont smother it in that horrible orange muck. Buy some clear stuff from a builders merchant, it works just as well and looks nicer.

Pete
 

Mickthevin

Well Known and Active Website User
Non-VOC Member
Just Been Reading All The Comments Regarding Altons As I Have Been Having Probs With My Lights - See Lights Thread
So You Spend £300 Odd Quid On A Piece Of Kit That Solves All Your Problems And You Still Have To Bugger Around Making It Fit And Oil Tight
I Was On The Point Of Ordering One But Bi Am Now Having Second Thoughts
Am I Being Unrealistic In Expecting Something To Just Bolt On

Mick
 

nkt267

Well Known and Active Website User
VOC Member
On a Comet you do away with the seal and use silicone sealant and you may even have to shim it for pinion clearance. If mine ever comes back I might be able to try it again.
 

Monkeypants

Well Known and Active Website User
VOC Member
Really there is no difficulty in fitting the Alton.
The oil getting past the flinger is a problem with the Vincent, not the Alton. As I mentioned earlier, nearly every engine John has stripped has had a little oil laying under the dynamo, and most of these probably had their factory Miller or Lucas in place.

Vincents do tend to leak a lot of oil ,there is no doubt. Factory workers from the 40s and 50s talk about the ever present oil leakage problems, so we know that they leaked when new. My Rider's Handbook lists the "oil mileage" as one imperial gallon in 1500 miles! I wonder how much of this number was to allow for the inevitable leakage?

Over the years various people have found ways to cure most of these leaks such that today it is possible to have a dry Vincent. Possible but extremely rare! I was just at the IOM and had a look at all of the bikes after the lap. The vast majority had oil streaming down the crankcases and laying in pools underneath the engine/transmission.

If one keeps at it and uses all of the collective wisdom on the subject, most of these leaks, including the dynamo leak, can be fixed.
 

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