Dominator big end nuts

Reusing big end nuts is not normally recommended. They should be 5/16" by 26tpi, reduced hexagon with anti-vibration insert or similar - and usually centre punched andwith a drop of loctite. The con rods if original will be RR56 alloy. So use the new NOC supplied ones. Might be worth renewing the big end bolts while you are at it.

Gordon's right - best to always renew the bigend bolts and nuts together. It's not as if you should be stripping them apart very often. A mate of mine, when he was an RAC recovery man, once attended a blown Jaguar on a motorway. Its engine was destroyed by a piston & rod(or perhaps more than one?) parting company from the big ends at speed. It went through the side of the cast steel engine block! It was because someone had replaced the bigend bearings but not the bolts! "Spoiling the ship...." etc. False economy - like my Bro's propshaft nearly falling off at the front end (Seriously dodgy!) of his Triumph 2.5 PI (That's a car!) after a garage had replaced a universal joint but NOT the nyloc nuts! They are designed as a "use once only" item. They were, and still are, cheap so don't do it! Cheers, Lionel

In an ideal world I'm sure it would be good advice to renew big end bolts and nuts every time. However there's too much confusion being put about by two Norton parts suppliers at the moment over which Commando big end bolts are safe to use, each rubbishing the other's version. I don't know what the position is with regard to Dominator bolts.

I have a note (did I get it from John Hudson's video?) that it's OK to re-use big end bolts, and even, I think, nuts.

And RGM state "Big end bolts can be re-used providing there is no sign of stretching or nicks/marks. Big end nuts should not be re-used".

Recently I bought a set of the small hexagon 5/16" Cycle thread big end nuts. One of them stripped at about 10 lb/ft when I was carefully torquing it up to the recommended 15 lb/ft, and the others don't look much better. I've now ordered a set from a well-known West Midlands supplier because the last ones I had from him were more substantial (1/4 Whit rather than 3/16 Whit spanner size).

I'm hoping my old bolts will continue to be OK. As far as I know, they're the 52 year-old originals. I'd like to replace the bolts but how can I be confident the quality would be any better than the small nuts?

You want locking nuts - aerotight all-metal rather than nylon insert varieties. Wouldn't want one to come loose! Not forgetting the loctite for belt and braces.

Rob......You are correct about the video and John Hudson's opinions re crankshaft bolts and nuts. He was not too impressed by the quality of spares available, for Norton engines, in the 80s and 90s. His view being that, generally, the original parts were made to a much higher standard than the replacement gear then available. Some New Old Stock being the exception.

He accepted that it was 'good engineering' to replace the big end nuts but that, often, the old ones could be used for one more rebuild. The bolts he always checked for stretching or damage in the threaded region and binned any that looked dodgy.

All of my rebuilt crankshafts have used recycled parts and none have ever let go.......even when suffering the extremes of 'Track Day' outings. However, if I rebuild a bottom end for someone else then I will use new bolts and nuts purchased from a good supplier.

"A good supplier".

I'm sure all four of the main Norton parts suppliers I've tried consider themselves to be good, if not the best. Are you prepared to say which one(s) you trust? Should I assume you mean only AN and their small number of agents?

Maybe it's bad etiquette here to name names, but give us a clue...

I believe the saying goes something like....'you pays yer money and you takes yer choice.'

I buy my bits from different suppliers, depending on what I need. But there is no real guarantee, on quality, from any of them. My experience of the BIG 4, over the last 20 years, does not make any of them a general favourite for me. Even purchasing parts with the Green blob inside the packet, from this group,has not provided any better quality than the likes of eBay.

Inrecent times, this has included a fork bush refurbishment kit, kick start, ignition switch, valve colletts, valve guides and an Isolastic kit. All with serious faults.

I used to try and buy my bits from suppliers who stated that they were selling me British made gear. That didn't work out very well. Especially items like chains and sprockets.

My last purchase ,of engine goodies, was from BritBits on the south coast. He seems to have an endless supply of NOS or good quality alternatives.

Yes, 'Aero' nuts (so called because they are used on aircraft) are the only type to use on bigends. In the olden days they were castellated nuts with split-pins.'Nyloc' would berisky as they are not intended for use in hot areas. I'm not going to risk finding out what the softening point of nylon is! Whether or not you re-use bolts and nuts depends on how often you do a complete stripdown and how much you thrash the old nail! If less than once a year you might as well use new.