classic motorcycle forum
Motorcycle Discussions => British Bikes => Topic started by: john11668 on May 02, 2018, 10:07:49 PM
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Hi folks
I understand that on the later B31 when an alternator was fitted , the cush drive was dispensed with!
Can this be done generally. Would it be a problem if there was no cush drive??
The main reason for the question is that we are looking to put an electric start on a tin chaincase bike . We are looking at an external pulley wheel with sealed sprag and we intend to try and fit a large (say 80T ) timing pulley. This will be a much simpler task if we don't have to contend with maintaining the cush drive function.
Would be happy to here from anyone who has tried this or knows any cause, or just impediment why this may not be done.
In the search function I saw electric start described as "wimpy". Not for a 70 year old who is 8 stone wet through it isnt ! ;)
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I understand that on the later B31 when an alternator was fitted , the cush drive was dispensed with!
Can this be done generally. Would it be a problem if there was no cush drive??
As I understand it, it was the crankshaft-mounted ramp-cam shock absorber that was dispensed with in order to fit the alternator and a cush-drive clutch assembly was then used.
https://www.draganfly.co.uk/index.php/a65anda50/category/909-4-spring-triumph-type-with-cush-drive
"'4 Spring Triumph' type with cush drive - used on alternator equipped 'B' and 'M' models from 1959."
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Yes, I would agree with that. I would think a big single bike with no cush-druve arrangements would be so horrible as to be unrideable.
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I would think a big single bike with no cush-druve arrangements would be so horrible as to be unrideable.
A lesson well learned from the earliest days! Here's the cush arrangement in my 1903 Columbia. It lives on a counter shaft in the normal clutch position. The previous year, the "cush" was achieved by mounting the engine drive sprocket clamped between two large washers, but otherwise unconnected to the mainshaft of the motor. It things got snatchy, the sprocket just slipped. Crude, and not very effective, but Indian used a similar arrangement on their back sprocket for a number of years.
"Something's gotta give!"
Leon
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Harley twins had no cush drive until the early 60s......although an accessory was available from about 1924 onwards......as regards the BSA,the 'orrible clutch is generally replaced with a Triumph four spring,IF you can find one.
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Have managed to retain the original cam cush drive with a rather compicated coupling around it but it seems to work and starts well . We need now to convert to 12 v in order to charge the battery . Have bought the 12 V armature for the dynamo and also the field coil , bearings and brushes . I am told that the existing regulator should suffice. Any thoughts
I have attached a pic of the arrangement . A Mk 2 version will do away with the idler and the jockey pulley for the belt
All original parts are retained so nothing is irreversible. All a bit non PC bit it permits the wee fella to continue enjoying his bike which is the object
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If you mean the original electro-mechanical regulator then no it wouldn't suffice for a 12V set-up. Fit a modern solid state dynamo reg like DVR2 (not to be confused with the crap AO VReg2 unit!)
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Supplier of parts said regulator cutout should be ok .
Would like to find someone who has done this conversion .
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Hi,
Rex is correct, you need a 12v regulator, I have converted several dynamo's to 12v
You can also get a 6v dynamo to charge a 12v battery with a suitable regulator, it needs to spin faster than a converted one to start charging though
A 6v regulator would not charge a 12 v battery
When buying the suggested DVR2 you need to specify that its a converted dynamo
Supplier of parts said regulator cutout should be ok
That statement is complete rubbish,
John
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One warning....fitting a 12 V generator to a magdyno can quickly ruin the magneto.....what rubbish ! say the experts!........well no,the slipping gear assy on the mag will heat up and cook the mag......disable the slipping gear.
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I've heard reports that a 6V dynamo being pushed to 12V by a reg conversion can sometimes get so hot that the comm solder connections start to melt and the solder is then flung off.
I'd prefer to fit a "proper" 12V dynamo personally, but then if the bike has a mag for ignition is a 12V conversion that necessary? I know bulbs and batteries are easier to come by in 12V but does anyone ride old bikes that much at night?
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The dynamo with new field coil , armature and brushes will be Identical to a 12 V model so I cant imagine any difficulty with solder melting. Unfortunately we are committed to 12 V for the starter ( could not find a 6v starter of any real power) so just want to make sure the battery keeps topped up on a daylight run. We dont make a habit of riding old bikes around in the dark although I suppose it is possible to be held up.
Not sure what the slipping gear does, or the relevance here . Will go for the solid state regulator . Wont spoil the ship for a ha'porth o' tar. Cant imagine there will be too much overheating on our country rides out, but will watch out for it .
I guess there have been a fair few 12 conversions and it it were a common problem it would be raised more frequently. As long as there is enough charge going in to keep the starter vigorous then that will be all we need .
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slipping gear would, I think, refer to the slipping clutch in the magdyno.? those fibre gears won't take a lot of stress.
Lots of other solutions to your 12v considering your engineering abilities, an alternator off a Citroen 2CV used to be favourite.
I had the same problem as you are solving here, but I solved it by buying a Piaggio Scooter ;D ;D
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Looks like an interesting project. Do you have any more technical details of the starter motor, gearing, sprag etc? You never know, my right knee may give out one of these days.....
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You never know, my right knee may give out one of these days
I solved it by buying a Piaggio Scooter ;D ;D
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slipping gear would, I think, refer to the slipping clutch in the magdyno.? those fibre gears won't take a lot of stress.
Lots of other solutions to your 12v considering your engineering abilities, an alternator off a Citroen 2CV used to be favourite.
I had the same problem as you are solving here, but I solved it by buying a Piaggio Scooter ;D ;D
More info might be usefull Mini me
Do you mean you used piaggio as a donor, or as a replacement for B31. Latter would not be considered a suitable solution by my mate .
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Looks like an interesting project. Do you have any more technical details of the starter motor, gearing, sprag etc? You never know, my right knee may give out one of these days.....
Will probably post all the details when we have had a couple of trips out and can be confident of no problems .
All the proprietry parts are available on the net . Some material from local merchants and a bit of work on the lathe and miller.
Second hand starter from Ebay (Kawasaki xzr 750 , 99p) which turned out to be wrong rotation so had to add the idler to reverse it . Found this easier than altering brushes . Gearing is initially 80/9 then further 2/1 at the belt giving a total of just under 18/1
With the long stroke it can baulk occasionally at tdc but a slight touch of the valve lifter gets over that.
Working on a Mk 2 with correct rotation ( Suzuki 750) and different adjustment so no idler is needed . Happy to guide anyone interested once we are happy that there are no unexpected problems.
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You never know, my right knee may give out one of these days
I solved it by buying a Piaggio Scooter ;D ;D
Not a knee problem here . Rider is just not heavy enough!
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A place where i worked used a Piaggio scooter to start a huge big Ruston and Hornsby 6cy diesel engine......the scooter was pivoted on the front,and the back wheel was lowered onto the big flywheel....it used to start up on a freezing cold night far quicker than the compressed air start supplied with the engine.....Scooters are powerful little things.
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I'm quite pleased with my Piaggio 125 , its an old mans bike that keeps an old man on two wheels. 80+mpg, 60mph screaming flat out, handles well, and reliable.
I can still kickstart a big single and have kept back 2 after getting rid of the surplus, but its impractical these days to leave an old vehicle unattended anywhere.
I have no info re the 2CV alternator, but the magdyno slipping clutch/fibre gear should be obvious if you remove the cover, if that is what you refer to?
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Hi All,
A major consideration when adding an electric leg to old brit iron is the quality (cranking amps) of the battery
Look at, http://www.startyourbsa.com/ and note the battery used
A proper battery will give a couple of hundred starts without recharging 8)
The Alton starter fitted to Vincents needs this battery to work even using the valve lifter
https://www.batteriesdirect.ie/magento/index.php/odyssey-pc680.html
A friend who has had two new hips has fitted a Honda car starter to his vintage black Ariel :o
He fitted a ring gear to the back of the clutch and fitted the starter behind the gearbox
Total loss battery (PC680) but it lasts for months between charges
John
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Makes the bike even heavier though? and compound the problem?
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Just following up on this . A couple of morning runs , maybe a hundred miles or so , and all seems to run well without excessive heating of the sprag. There was a smear of excess grease on the first short run and a tiny amount of drag on the timing sprocket, but just wiped off the excess grease which did nor reappear. The drag seems to have settled with running too.
The hub ( crankshaft extension) which now houses the cush drive causes maybe 1/8" more compression of the cush spring but this does not seem to affect the rideability.
The fact that it starts at the touch of a button does vastly enhance the riders enjoyment since the fear of stalling at a cross roads disappears.
All the original parts are still on the shelf for the day when it may need to be reverted to original.
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Just curious if I can upload a link to a video
https://www.youtube.com/watch?v=RsMitvkvEZA
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Good to hear the positive progress. The video doesn't work for me (gets a blank screen with an exclamation mark).
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Seems to be only available if you are logged in .
Will try a different site
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Try this ! You may need to turn volume up
https://www.youtube.com/watch?v=RsMitvkvEZA
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That worked - the starter's looking excellent. Maybe the slow running mixture's a bit off though......
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I suspect you are right Ian but the sound on the video is not good either. We are told that the carburettor is not correct for the model but it works and runs well on the road. We are on the lookout for the correct one but hens teeth spring to, mind