Conrod balancing and timingside cam bush oil hole

To balance con rods you need to know the reciprocating mass and the rotating mass of the rod first. This requires knife edges and accurate scales, personally I'd leave alone, get a rod manufacturer to carry out the work or buy new rods from a reputable rod manufacturer.

Colin previously wrote:

Having got my rods to fit the crank i now need to balance them as they are not the same.I have narrowed the differenc to the big end caps so anyone know the best place to remove material from?Also when cleaning and checking the timingside crankcase i noticed that the oil hole for the camshaft was not in line with the oil feed hole in the crankcase.Its almost90degrees fromthe feed hole.Is this normal.If so i presume there is a scrollin the case or bush.Hope somone can let me know before i take the bush out to check.Many thanks,Colin.

Norton rods vary quite a bit. Matching them is a good idea and not difficult. This is not the same as balancing the crankshaft. Digital kitchen scales are accurate enough. Put the big end on the scales with the little end supported so that the rod is horizontal. Equalise the weights of the big ends by lightening the heaviest. Remove any obvious irregularities first, then work symetrically around the end. Then support the big ends and get the little ends matched. As you do this check that the total weights end up equal. I don't think you need worry about balancing the crankshaft. You are only likely to move the maximum vibration from one rotational speed to another.

There's about a 1/8th groove running around the outside circumference of the camshaft bush.

Cheers

Alan

Alright Colin,

I'm curious about the following, what do you mean by 'having got my rods to fit the crank' ? Can I assume they are not originally matched to the crank, if they were then why have you had fitment problems.Also do you know the history of the rods, mileage and usage.

Personally I'd go for a set of brand new rods from Steve Campbell at Thunder Engineering, Carillo orR&R for example. If your thinking new rods are expensive add up the cost of replacement rods, crankcases, barrels etc if one of your modified rods let go.

Simon.

Simon previously wrote:

Personally I'd go for a set of brand new rods from Steve Campbell at Thunder Engineering, Carillo orR&R for example.

Simon, I'm thinking about rods for a 99 engine I'm building. Have you used Lightning rods?

Cheers

Alan

Would Lightning rods fit a 99? I am sure the big end diameter is too large. BSA A7 rods will fit. I wish I had bought some when I had the chance of some NOS ones.

Gordon previously wrote:

Would Lightning rods fit a 99? I am sure the big end diameter is too large. BSA A7 rods will fit. I wish I had bought some when I had the chance of some NOS ones.

They apparently do 88 & 99 rods: Thunder Engineering Lightning Rods

Cheers

Alan

Aha - by Lightning rods you did not actually mean BSA Lightning... all is explained!

No not BSA rods but rods manufactured by Thunder Engineering in Leicester, see above link.

To answer Alan, I fitteda pair of the above rods in my Commando approx. 15,000 miles ago, they appear to be very well made with proper big end bolts. Phone Steve Campbell at Thunder and have a chat, nice bloke.

I couldn't get the link above to work - try copy & paste on this one; http://www.smedirectory.net/_id_02_Product_1052_21830_1051.html

Don't they look pretty? Shame no-one will be able to see them! I'm going to askthe price for a pair of rods for a 99 - just for a laugh!

Cheers, Lionel

PS: "Thunder" & "Lightning" - Geddit?

Lionel

I found their prices for Dommie rodsin OBM; £125 each = £250 pair + VAT @ 20% = £300 total. No mention of postal costs. Not bad I suppose, but is it worth it for a touring bike which will do less than 3000 miles per year, mostly at legal limits? Sorry! I'm not 18 any more and definitely mortal!

Cheers, Lionel

Having had con rod breakages during normal, sensible running (I too am getting older) I would suggest that £300 would be money well spent. Don't forget, the 99 rods are 50+ years old and they do have a finite fatigue life. Are they 50% through it or 99.9% through it? When a rod goes it can and frequently does destroy barrels, crankcases and camshaft too. Have you seen the price of replacing that lot? Are you feeling lucky?

Gordon.

An addendum: Aircraft too are made from aluminium alloy, not necessarily RR56 like Norton con rods, but the principle applies. So much depends on how the aluminium is stressed (or used in plain English). A Gloster Meteor had a fatigue life of 770 hrs when used in a low-level ground attack role (i.e. used hard). However, when target towing (i.e. used gently) the fatigue life was 10,000 hrs. So if you are quite sure your rods were in a bike used by an elderly vicar who never exceeded 3,000 rpm (2,500 on Sundays), your rods should be safe for years to come, if you are at all sensible. If, however, they came from a bike used by a teenage tearaway or raced (guilty on both counts, Your Honour), they may not have many fatigue cycles left...

Incidentally, so long as steel rods are not taken past their yield point (i.e. start to stretch), they just go on indefinitely. BSA specified very precise measurements for their steel con rods on racing Gold Stars, and if they show any stretch they must be replaced, otherwise just keep on racing.

Some people are still racing Rudges on their original 80 year old steel con rods. So it's not age (despite what I implied above) - it's how you treat them.

Gordon.

I shall probably take the 99 out for a ground attack sortie this morning to see if I have stopped the head gasket passing oil. I changed it yesterday to a composite one as the solid one was still leaking. I will try to keep your comments firmly at the back of my mind

Cheers

Alan

I think I'm more than OK with my original con-rods because they have only done about 30,000 miles from new! I am well used to Jaguar con-rods and they aren't a million miles different. With them you alwayshad to renew the nuts & bolts at a major overhaul though. Skimp on that and you could lose the entire engine! Trust me on this as I've seen it happen - on someone else's car, I'm glad to say! Sorry of course, but glad it wasn't mine!

I will polish mine and perhaps get them crack-tested.I will also go for crankbalancing to suit normal touring 'road legal' speeds - i.e. 80mph for motorways. I never have and never will race or do "track days". I didn't when I was 18 and certainly won't now I'm nearly 66! (Yeah - BORING!)

I'm not sure what to do about the slight split in one top barrel spigot though. I'll get Norman White to take a look at it and see what he thinks. Maybe a solid copper gasket will help support it? It went after its +.040" rebore.

Cheers, Lionel

Lionel Lexley previously wrote on Tuesday February 21st at 00:48hrs:

snip>

I'm not sure what to do about the slight split in one top barrel spigot though. I'll get Norman White to take a look at it and see what he thinks. Maybe a solid copper gasket will help support it? It went after its +.040" rebore.

Cheers, Lionel

Lionel,

For assembling a pre-114870 head & barrel with its barrel spigots machined off, rings were supplied from Plumstead for the 650SS & Atlas to retain compression.

Norvil list the rings for 650SS which will also fit a 99, with part number: 990613.

£10.50ea + whatever austerity levy applies.

Iâm sure there used to be a special type of flanged head gasket which also filled the space left from machining off the spigots, but I always take any memories from that era with a pinch of (erâ?) salt.

Paul

Thanks Paul (dunno how the spelling mistake of my surname occurred!). I will take that under advisement. I didn't realise that such a ring was available - I'll have to look it up in Norvil's listing. I assume it fills the gap left in the head which would normally be occupied by the barrel spigot? I'll have to checkout the cost of machining the barrels. I'm a pensioner now so I have to watch my pennies! LOL!

Iwas reading that there are three true signs of aging -1) Memory loss; 2) I can't rememeber the other two!

Cheers, Lionel

Lionel Yexley previously wrote on Tuesday Feb 21st at 20.46hrs:

Thanks Paul (dunno how the spelling mistake of my surname occurred!). I will take that under advisement. I didn't realise that such a ring was available - I'll have to look it up in Norvil's listing. I assume it fills the gap left in the head which would normally be occupied by the barrel spigot? I'll have to checkout the cost of machining the barrels. I'm a pensioner now so I have to watch my pennies! LOL!

Iwas reading that there are three true signs of aging -1) Memory loss; 2) I can't rememeber the other two!

Cheers, Lionel

Haha! Yup, I've got all four of them!

Yes, that's whatthose ringsdo. Then you're compression ratio doesn't drop to pea soup level.

Give Les Em' a call, during one of his afternoon surgeries. He'll happily summarise the job.

Taking the spigots down would be well within the capabilities of a trusted engine re-conditioner. Just the minimum, plus a touch to dress the deck, give the stud threads a slight counter-sink, take it home and nail it all together.....er, sorry.....carefully blue-print the reassembly procedure.

It was my sausage-fingers that did the typo of your name. Sorry.

Same symptoms you've got (.................................rememeber?)

Paul

I've had second thoughts about Thunder's rods. They appear to be machined from solid "billet" aluminium. If you've got a Commando you need to buy genuine Norton rods as they are forged, not machined. Sadly they don't fit a 99 Dommie!

Cheers, Lionel