| Author |
Message |
    
A.Nicholas Cowan
New member
Username: nicksearcher
Post Number: 1
Registered: 06-2006
| | Posted on Wednesday, July 12, 2006 - 05:02 pm: | 
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every time I align the magneto click with top dead centre, or, 2" before TDC, the engine refuses to start. Checking the timing again after cranking the engine, the click and spark are well after TDC. Can anyone please suggest a solution to the drive evidently resetting the timing wrong? |
Peter Ogborne
Senior Member
Username: peterogborne
Post Number: 155
Registered: 09-2002
| | Posted on Wednesday, July 12, 2006 - 07:17 pm: |
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Nick......I assume you have a impulse magneto and they are a bugger to set. If it is not impulse then you must have a problem with the taper on the chain sprocket to cause it to slip. I will try and find some info on setting impulse magnetos ....somewher in my filing system!
Meanwhile some helpful person might beat me to it. |
A.Nicholas Cowan
Member
Username: nicksearcher
Post Number: 4
Registered: 06-2006
| | Posted on Monday, July 17, 2006 - 12:41 pm: |
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Thanks for the suggestion. I tried some 'Screwfix'on the taper, but although it held very tight, the timing is still resetting itself and engine won't start. There is a lot of end-play on the taper shaft, the rubber seal is damaged, and the drive shaft seems to jump at fairly frequent intervals when the engine is turned by hand and the shaft seems very loose. That suggests damage inside the unit. Can the magneto drive unit be got at by removing the two nuts on the casing? What is the likely cause and possible remedy if you know please? |
Peter Ogborne
Senior Member
Username: peterogborne
Post Number: 157
Registered: 09-2002
| | Posted on Monday, July 17, 2006 - 07:58 pm: |
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Nick ...sounds like you may have to pull it down . It could be a collapsed bearing on the shaft carrying the chain sprocket.
There is a chain drive to the magneto shaft then a gear drive to the pump shaft. If you have excess end play in the magneto drive shaft it sounds like a bearing has collaped. This could cause the chain to jump on the sprocket.maybe ,maybe.......
Have a look at this aspect for a start. |
A.Nicholas Cowan
Member
Username: nicksearcher
Post Number: 5
Registered: 06-2006
| | Posted on Wednesday, July 19, 2006 - 03:31 pm: |
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Thanks for your ideas, Peter. It looks as though I'll have to anchor and wait for a while yet if the wind dies. Please can anyone tell me whether I will have to remove the engine from the yacht to get at the magneto drive shaft and sprocket to renew the drive shaft bearings? The assembly appears to have a cover secured by two nuts, but maybe one has to dismantle further? |
Peter Ogborne
Senior Member
Username: peterogborne
Post Number: 158
Registered: 09-2002
| | Posted on Wednesday, July 19, 2006 - 07:21 pm: |
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In short,no.It can be done with the engine in situ.Take off the magneto,then take the two nuts off the coverplate,you can then pull the shaft out.
Lets know what you find. |
Tim Mulvey
Senior Member
Username: timmulvey
Post Number: 94
Registered: 05-2003
| | Posted on Thursday, July 20, 2006 - 04:02 am: |
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There is a cog on the shaft and a ball bearing race each end - you will see one when you take off the cover plate but to remove it you should also take off the water pump (held on by four 1/4BSF bolts) so you can then drive the shaft and bearing on the other end with a punch. I recently had experience with a collapsed bearing on the water pump end of the shaft. Also MAKE SURE that when you lift the magneto drive cog chain off that you slide in a piece of wire otherwise the chain will drop down into the crankcase and then you will be in trouble with the result that you will need to take off the gearbox etc to retrieve it. |
A.Nicholas Cowan
Member
Username: nicksearcher
Post Number: 6
Registered: 06-2006
| | Posted on Thursday, July 20, 2006 - 09:04 am: |
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Thanks ever so much, Peter and also Tim. As soon as I have, or have use of an Imperial socket set I will get going on the problem. Thanks for the warnings about losing the chain too! All the best, Nick. |
