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C: Clutch Comet Primary Drive Q's?


Jez Nemeth

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VOC Member
Got an 18T on the gear box drive at present -46 rear, there's some play there for sure -cloudy on calling these ratios in the primary though Chris. Not conversant with that stuff -and want to get close to standard, highway/touring speeds ideally -that was going to be the topic for next post! But does need to be considered at this point of course...
 

Oldhaven

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Check the drain plug area on the outer cover with a larger front pulley. I had to do some material removal with even the smaller Newby pulley and belt.

 

Jez Nemeth

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That's bloody close! But looking through the inspection cover -got about 1/8" space, phew. Be easier with a 25mm wide belt, possibly up to 30mm but no more... how wide is the belt you have?
Assuming its and alloy pulley + integrated flanges/guides, might be a bit thicker than the pulley I measured -that came to 35mm total thickness, 30mm belt, figured I could reduce belt down to 25mm width if problematic.
 
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vibrac

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On the flash which is the only installation with a conventional inner I needed a 1/4" spacer in place of a gasket I used a piece of 3 ply with the edge painted silver I keep meaning to take a gasket to my water cutter man to get one cut in 8 mm alloy
On the egli ( oops that 3 not 2 belt drives) I have a plain alloy plate at the back a primary cover on the front and a 1" wide strip supported by the screws in between. On the racing comet I just have a light alloy sheet cover with a open clutch
 

Jez Nemeth

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Love it! Did think about an 8mm alloy 'gasket' if upping the belt width, standard cover though, what's a good width Vibrac?
 

Jez Nemeth

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just connecting the dots here ...'oldracer', that gorgeous comet? Reason I bought mine in the first place if its one of yours...anyway, any problems with over-heating with belts? Less heat the wider they are? -possibly in racing I'm thinking, but not so likely for road use -kind of like the protection from stones of a full cover etc...mindyou have a Scooby STi sitting in the back of an 80's T25 VW, belt open and never had issues and done big miles across Europe at speed, engine does face backwards though!
 
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Chris Launders

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I run 27 or 30mm belts on two 750 pre unit Triumphs and a Norton Atlas no problem and a 40mm one on the Norvin with Mk11s etc, only the Atlas has chaincases though. I've had the earliest on for about 30 years. A Haywood drive on one Triumph and I don't know what the other is as I didn't fit it plus Norvil Commando ones on the Norvin and Atlas. As regards gearing it's really the overall gearing that matters a little lowering of the primary ratio and raising of the secondary won't matter. I have a couple of bikes with big JAP engines and Norton boxes and I have 24t gearbox sprockets on to get the gearing up as their case too big an engine sprocket and the engine wouldn't turn over fast enough on the kickstart to start.
 

Jez Nemeth

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Good to know Chris -thanks for info. Mindful that the inner primary case, gearbox side where I have the 18t drive sprocket, on the gearbox mainsheet, looks to only be able to take up to a 21-22t at most without mr dremmel getting involved -be fine I suppose. The belt I was looking at was a 25mm width one, whole caboodle fit neatly into the case then, its road going, around 32hp so I think no real need to fit a wider belt for racing purposes? Not sure if that equates, but its not hugely powerful I wouldn't have thought. Ideally with final drive, rather get the ratio pretty spot first throw, rather than an endless and potentially expensive exercise in 'guess the ratio'...done that too many times, fingers burnt and all that.

Kickstart rotation!!! Eeek. Never even considered that one -thanks for flagging that up. Phew
 
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vibrac

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Here is my Egli Comet Primary the cover had been butchered by someone who wanted the ESA 'dome' and had drilled it off with a ring of holes I converted it to a forward air scoop to get some air into the case (exit at rear) bit of bling really to use up a scrap item since Inever had heating problems with the Flash but then 20-30 mins is about max running time for that .
You can see there is no inner chaincase just a alloy plate for all pickup points and prop stand. You can just see the 1" strip spacer
27409
 

Jez Nemeth

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VOC Member
Like the scoop! Things folx do...when I got my basket case, and knew little about Vincents, other than uncle had one when I was a kid near Tamworth NSW, remember the figure from the tank. Soon came to realise that the basket had some bloody big holes in it. RFM had two broken ends and the pivot bearing casting cut of??!!! (did think about making one, pig Iron casting etc...Have equipment, just don't have bucket loads of the most precious component -time), Anyway money saved from projects like this, new rear stay castings sold on F-bay the other day too, in the pot towards a new RFM eventually. Enjoying the ride of putting it together, with all the challenges -"Zen and the art of Vincent Maintenance" so to speak.
Airflow, good to have on a road machine? -You put yours properly through their paces mind, I'm looking at the Monmouthshire/Gloucestershire/South West and Welsh hills -A/B roads, just plain all day meandering.
 

Black Flash

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I used a belt conversion from norvil on my comet. The front "sprocket" I machined in my mill to accept the pd4 with the help of a 25 ton press. If using this arrangement I had to widen the clutch cover with a welded on strip of alloy all way round.
If you do so please don't forget to use the commando type clutch lever in your gearbox, the atlas type has not enough lift for the diaphragm spring.
While it worked okay I changed back to chain with a self fabricated clutch conversion [yam clutch] with Peter Barker making the cush rubbers for me.
I simply changed as I found the cover to wide to look beautiful, so purely cosmetic reasons.
Bernd
 

Jez Nemeth

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VOC Member
The back road from Rhayader to Devil's Bridge is a ripper, but mind the sheep!
That's one is defo on the plan. Miss the roads of NSW, but when the sun shines, Wales has some amazing roads, spaces and places - mostly empty too...bar sheep!

Weighed up all advice, really appreciate all the help and information.
So bit the bullet. 54 tooth AT10 Clutch Basket fitted with sealed bearing, 30 Tooth front pulley 32mm belt width- Retaining stock 1.8 standard ratio, and with a smaller diameter drive pulley at 3" 6/8 (96mm) than the 106mm I had in mind. New AT10 (Red Gen3) Belts available in every possible length/width, and relatively inexpensive too, they'll be around for years -have no wish to build in obsolescence. I'll fit the pulley before ordering correct belt. Basket is slightly smaller than the standard Norton Commando one, so gearbox won't need to be jammed tightly to the back of the engine casing to clear some of the fixing bolt flanges for fitting the Primary cover, it will just fit better, and should be able to use the range of the tension adjusters fully (1 1/2") Moved the clutch cable boss yesterday accordingly, and alu welded up the hole in the gearbox cover, tap a new hole later after work for the cable adjuster and that should all be good - I'd love a Newbie system...but had complete clutch internals already, so it just made sense to do it this way than buy a whole new system. If all goes pear shape, be the first to be knocking at Bob's door...
 

Jez Nemeth

Well Known and Active Website User
VOC Member
I used a belt conversion from norvil on my comet. The front "sprocket" I machined in my mill to accept the pd4 with the help of a 25 ton press. If using this arrangement I had to widen the clutch cover with a welded on strip of alloy all way round.
If you do so please don't forget to use the commando type clutch lever in your gearbox, the atlas type has not enough lift for the diaphragm spring.
While it worked okay I changed back to chain with a self fabricated clutch conversion [yam clutch] with Peter Barker making the cush rubbers for me.
I simply changed as I found the cover to wide to look beautiful, so purely cosmetic reasons.
Bernd
Thought of that one Bernd -but good point ..a mate mentioned to me there might not be enough 'pull', checked it against a commando one -bit of luck, had a Commando lever in place! Might it be a Norton owner's mod? (even thought about lengthening it a bit too, cut, weld, temper...). Think the Clutch should be ok, its just that cush system, or rather lack of one which is having me scratch the rain detector. Can't think of what I've got close to 25 tons hanging round the house to do what you've done there :) . Looked at Yammies, Hondas and Suzie clutches, there seemed some possibilities -Ben and Steve over at Conways/Godden do a loverly one with their Honda kit.
Trying to keep standard case if possible, if everything works out it should all fit, otherwise its an 8mm thick 6082 'gasket' Vibrac mentioned.

Ordered a mild steel pulley for 32mm Belt (it was a choice between 25,27,32), AT10mm pitch, 37mm (Outer flange to Flange width) - 93mm OD (bonus meant I could go wider with belt, stated 96mm on web, but actually 93mm?), and has a boss of 50mm OD -13mm depth that I can turn down. Be here in 10 days. Only real issue is if my old 1920's Drummond lathe will cope with turning down the bits, or do it at work, when I have the time...

Question though, did you find it harsh in use when you had the belt on it? Don't remember Commando Clutches being discussed as exemplary examples of clutch technology, but they can be refined...that Comet Mongrel post is good for that.. Commando Lever + Alloy Boss, be fettled drilled and tapped later...Friday night,
my wheelie bin goes out more than I do...
27413
 

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Jez Nemeth

Well Known and Active Website User
VOC Member
Belt Clutch basket arrived -cheap, much lighter and fits with a little more room as hoped -full 1 1/2" adjustment, mild grinding of one bolt flange at top of full range, not absolutely necessary but just to be safe, but all good. 1st fitted, 2nd at full outward adjustment. Anybody looking for a standard Norton Clutch basket pm me...
CD85EF14-049A-4DBE-9455-D174A0B353C2.jpeg5294413A-132D-4FFA-BA20-488C32D24D3F.jpeg
 

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