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Discussion Starter · #1 ·
I have an oil leak from my alternator. bike has only done 370 miles and to wait for a seal from motogb will take ages. for the sake of three bolts im tempted to just change it myself. Anyone know what size o-ring will fit it exact without having to cut one down? Also is the alternator just simple bolt on bolt off
 

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Info below is taken from Errols awesome website Engenia's Benelli Tornado Novocentro Tre and linked to this forum (at top of this section)

Hope this helps...

Section: 3/32" (2.4mm)
Diameter of the base of the groove is 77mm
Accepting bore is 81mm

The O-ring seal on the alternator is not under great pressure, but it does tend to swell with age. When the alternator is removed, you may notice that the o-ring is quite slack in it's groove. If it is replaced in that state, chances are that the bore will cut it, as it slides back into position. The resulting oil leak is likely to be very small, but annoying - it took 2 days to make it's presence known (-;
The solution to the problem is to cut about 20mm out of the o-ring, and rejoin the ends with super-glue. When doing this, use a very sharp knife - a new scalpel is preferable - to ensure a clean, square cut. Slight mis-alignment is acceptable.
Also, when refitting, a small drop of superglue will hold the flexible couplings in place, long enough, so that they don't mis-align.
 

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Cheers. Im not a fan of cutting orings. It's adding a weak point.
Each to his own, but the alternator o-ring holds back next to no pressure, so joining that one is no issue.

I've never had a problem making my own o-rings out of o-ring cord. They have never opened up or leaked.
The cyanoacrylate joint is probably as strong as the o-ring material. It IS a molecular joint afterall.
 

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On my old Tornado I fitted one off a Basin Bottle Trap, it worked fine and didn't leak, certainly whilst I had it anyway ;)

I have spare ones if anyone else ever needs one :D



How much for the bottle trap I've got an o ring :doh: I had trouble sourcing o rings for injectors didn't want to risk cutting one on the fuel system.
 

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I have an oil leak from my alternator. bike has only done 370 miles and to wait for a seal from motogb will take ages. for the sake of three bolts im tempted to just change it myself. Anyone know what size o-ring will fit it exact without having to cut one down? Also is the alternator just simple bolt on bolt off
The alternator is only secured by three bolts, but there is an annoying coolant pipe that gets in the way. Use a e.g. a cable tie to pull it out of the way. The cush drive consists of 4 separate piece of rubber (or more if/when they disintegrate!) and there is almost no way they will stay in the right place by themselves when you try to refit the alternator. The answer is to 'glue' them in place with some grease, and even then it can a little tricky to get the alternator drive aligned with the one in the crankcase as you can't see either of them as you push the alternator in.

Whilst the alternator is out, check that the correct belleville washer has been fitted to the drive flange in the crankcase (the newer large washer instead of the old small washer or the lock tab), and that the bolt is correctly torqued.
 

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Discussion Starter · #11 ·
Each to his own, but the alternator o-ring holds back next to no pressure, so joining that one is no issue.

I've never had a problem making my own o-rings out of o-ring cord. They have never opened up or leaked.
The cyanoacrylate joint is probably as strong as the o-ring material. It IS a molecular joint afterall.
The aircraft engineer in me won't allow it. Stupid I know
 
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