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Oil filter cover bolt seized

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meerkat:
Flushed with success after passing the MOT I ran the bike for a few miles prior to changing the oil.
After dropping the oil which looked quite old I tried to undo the retaining bolt for a filter change.
Closer examination showed the head to be slightly rounded off and seemingly immoveable with a bihex socket. The bolt appears to be the larger head type and previous attempts had obviously been made to move it judging by the chisel marks on the flange.

Where to start for the best ?
If I arc welded a bar to the head of the bolt, would I need to isolate the alternator and remove the battery, or would it be better to grind the head off the bolt in order to remove the cover and filter, then renew the bolt ?

Has anyone had this problem and found an easy option ?

hairygit:
DONT grind the head off the bolt! There is a small but significant risk of metal filings getting into the housing, and a risk of damaging the housing itself. A far safer option is to buy or borrow a "wall drive" socket (14mm for standard bolt or 17mm for aftermarket), as these drive the flats on the bolt, so even if the points are rounded, 99 out of a 100 times they will get it off. I have a socket set called "metrinch", bought it about 25 years ago, and as they hold the flats, they work on both imperial and metric bolts/nuts. I seem to recall machine mart do a similar set of wall drive sockets for a reasonable price (certainly less than a replacement bolt or housing!) If you cant get one of those, try hammering a slightly smaller socket onto the bolt, then put a couple of tack welds between the socket and bolt flange (a mate did this to his 500/4 about 20 years ago, and left the socket welded in place, no problems since! ;D

PatM:
Ive welded a 17mm head nut to the remains of the stud before and that served me for a few years! I used arc and the electrics survived it. Whatever you do, dont do it when the engines cold- they are buggers to get out once they are bound and these measures seem harsh but necessary sometimes!

matthewmosse:
a few firm flat on / square raps with a steel hammer, then a wall drive sockett, and normally that'll do it. Ive had some luck with stilsons / pipe wrenches both on the actual nut portion or on the flange in some cases but be sure that you have a good quality set that are not worn or rounded/ rusted as then they'll round things off worse. Failing that, a size smaller bi hex sockett hammered on often has luck - the hammering often jars things loose. After that it's weld on a sockett / old bit of metal etc time. Unless you have a rounded off 17 mil sockett and fancy filing it to a 16mm it will be new bolt time.

meerkat:
Thanks for your encouraging replies. You guys are brilliant !

After reading your responses I searched for my old Melco metric hexagon socket set previously destined for a car boot sale.
A couple of sharp taps with a light hammer to get the socket on and a long wrench finally loosened the bolt.
PHEW !
The filter was in the worst state ever seen and must have been in for years.
Here's a picture of the bolt below. I'll build up the head and flange by welding before reshaping it.
Many thanks again for all your help.

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