Roderick
Darmah ignition pick-ups
Darmah ignition pick-ups
How likely is it that a Sprag clutch, that is starting to go, might affect the timing pickups. The engine has been kicking-back when using the K/S and, when using the electric start, I have heard a loud metallic clunk noise which I think is from the ring gear. Hence I am assuming the sprag is on it's way out. Now the engine won't fire up at all although I have spark and (fresh) fuel. Anyone have some wisdom to offer?
Roderick
Roderick
1980 Darmah in 'SS' trim
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hprice
- Cucciolo - the Lil Pup
- Posts: 13
- Joined: Wed May 12, 2004 5:27 am
- Location: Warwickshire, England
- Contact:
Ducati bevel engine matters
Roderick,
I also have a Duke of this ilk - a 1979 SD. I have had it since 1986 when it was a relatively low mileage bike. So far as noises from the sprag clutch on 'kickback' go, I have always treated a 'whizzing' sound as normal. The starter is geared down so that the crank turns a good deal slower that the motor. Therefore when it kicks back, the starter gearing and motor are spun up to a pretty good lick! Having not heard your noise, I cannot be sure if it is to 'my' noise that you refer. If the sprag clutch has had enough, I would expect you would know soon enough, as the crank would stall while the motor kept trying to turn it. Soon after acquiring mine I had it to pieces, mainly due to cogs 'jumping'. On removing the outer flywheel, all the clutch sprags fell out on the floor as the cage had disintegrated. I knew absolutely nothing about this as at the time it still started without problem, so I would not be hasty in condemning the poor thing. As for the kick-back, I would suggest two things having had similar problems. Shortly after I bought the Darmah, I moved to Worthing where I found a motorcycle mechanic by the name of Alf. He still has a workshop in that area, I've seen something on the web or in print about it. He advised me, since I was complaining about lumpy running, that for the Bosch ignition to work well, you need to have your crank de-magnetised form time to time!!! Well I wasn't crazy about removing the thing again, much less about trying to find someone with gear to de-magnetise it, so that never got done. However I was always suspicious that one cylinder was firing on full advance all the time, hence the viscious kick-back. Crank magnetisatin would, one might expect, affect both cylinders simultaneously. I'm afraid the bike fell into disuse due to a spell abroad and acquisition of another bike etc. One time when I did go out on it, the battery exploded (another story) taking out the entire charging and ignition systems. I shall therefore never be certain about the Bosch control units (RIP). I was sad, to say the least, but the up-side was that it gave me the excuse to try some other form of ignition control. I bought a couple of BOYER control units, not intended for 900 applications but 'close' in terms of advance curve. The truth is this system is still experimental even though it is a number of years since the disaster that precipitated it. In short, it is possible you have a problem with one of the control units which may need some scientific diagnosis. Try to detemine if it is one cylinder specifically with the problem (removing plug cap while kicking over with VERY STIFF footwear might reveal). I cannot think that problems in the starter clutch are likely to affect timing, unless maybe the engine has been mis-assembled Please don't hesitate to contact if you want a chat. I too can hear a loud metallic sound if it tries to fire on full advance, it hardly surprises me and the result is usually a limp for at least 24hrs! Yours etc.
I also have a Duke of this ilk - a 1979 SD. I have had it since 1986 when it was a relatively low mileage bike. So far as noises from the sprag clutch on 'kickback' go, I have always treated a 'whizzing' sound as normal. The starter is geared down so that the crank turns a good deal slower that the motor. Therefore when it kicks back, the starter gearing and motor are spun up to a pretty good lick! Having not heard your noise, I cannot be sure if it is to 'my' noise that you refer. If the sprag clutch has had enough, I would expect you would know soon enough, as the crank would stall while the motor kept trying to turn it. Soon after acquiring mine I had it to pieces, mainly due to cogs 'jumping'. On removing the outer flywheel, all the clutch sprags fell out on the floor as the cage had disintegrated. I knew absolutely nothing about this as at the time it still started without problem, so I would not be hasty in condemning the poor thing. As for the kick-back, I would suggest two things having had similar problems. Shortly after I bought the Darmah, I moved to Worthing where I found a motorcycle mechanic by the name of Alf. He still has a workshop in that area, I've seen something on the web or in print about it. He advised me, since I was complaining about lumpy running, that for the Bosch ignition to work well, you need to have your crank de-magnetised form time to time!!! Well I wasn't crazy about removing the thing again, much less about trying to find someone with gear to de-magnetise it, so that never got done. However I was always suspicious that one cylinder was firing on full advance all the time, hence the viscious kick-back. Crank magnetisatin would, one might expect, affect both cylinders simultaneously. I'm afraid the bike fell into disuse due to a spell abroad and acquisition of another bike etc. One time when I did go out on it, the battery exploded (another story) taking out the entire charging and ignition systems. I shall therefore never be certain about the Bosch control units (RIP). I was sad, to say the least, but the up-side was that it gave me the excuse to try some other form of ignition control. I bought a couple of BOYER control units, not intended for 900 applications but 'close' in terms of advance curve. The truth is this system is still experimental even though it is a number of years since the disaster that precipitated it. In short, it is possible you have a problem with one of the control units which may need some scientific diagnosis. Try to detemine if it is one cylinder specifically with the problem (removing plug cap while kicking over with VERY STIFF footwear might reveal). I cannot think that problems in the starter clutch are likely to affect timing, unless maybe the engine has been mis-assembled Please don't hesitate to contact if you want a chat. I too can hear a loud metallic sound if it tries to fire on full advance, it hardly surprises me and the result is usually a limp for at least 24hrs! Yours etc.
Hugh Price
Darmah, XK120 and some Alfas
Darmah, XK120 and some Alfas
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Laurie TwoValve
- Cucciolo - the Lil Pup
- Posts: 2
- Joined: Sat Apr 03, 2004 7:46 am
- Location: Scotland
If the sprag is on the way out you'll have lots of sparkly bits in the engine oil. These will go round the oilways and 1) take out all your roller bearings and 2) confuse your pick ups with slivers of old bearing forming "whiskers" around the pick ups rather like the magnetic sump plugs do.
The bearing is still a current component still being used on the 750 belt twin in production. ( but be warned it is increadibly costly) There is a cheaper alternative using a Rover/British Leyland automotive component
Its a Metro automatic gearbox "freewheel" part number 22A716 on microfich number AMU1868 but the outer edge of the cage must be machined down 0.5 mm to 65.5mm (pretty cheap to get done at a machine shop) this fix works out at about a third of the cost (in the uk anyway!)
The bearing is still a current component still being used on the 750 belt twin in production. ( but be warned it is increadibly costly) There is a cheaper alternative using a Rover/British Leyland automotive component
Its a Metro automatic gearbox "freewheel" part number 22A716 on microfich number AMU1868 but the outer edge of the cage must be machined down 0.5 mm to 65.5mm (pretty cheap to get done at a machine shop) this fix works out at about a third of the cost (in the uk anyway!)
LaurieTwoValve