LCGB Forums

Is it necessary to re-torque the cylinder head nuts at about 100 miles after a rebuild ? If so has anyone ever found that the nuts have come loose at all.The reason I ask is that of all the motorcycles I've owned and rebuilt none have suggested re-torqueing the head nuts/bolts.

Would say advised rather than necessary. The gaskets compress and after a few heat cycles it's worthwhile.

Broadly I'd check ALL the crucial fasteners after a shakedown period.

I run the engine up to temp 2 or 3 times with the head cowl off letting it cool each time then re-torque.

I know I'm going to get lambasted for this but I would say no. In my first period of scootering , mid 60's to mid 80's I never did re-check head torque but since I re-started and everyone seems to advise it I have done but never noticed any movement of the torque wrench. In my work as a mechanic I have never felt I had moved head bolts/nuts on tractor first services either. But I suppose there is always a first time.

you've not said if it's an alloy (eg mugello / rb etc) or cast iron??

If alloy then its a necessity in my book, seen far too many holed pistons due to leaking head gaskets due to not being retorqued.

I rebuilt my mugello early this year (piston ring replacement etc) and when I retorqued each of the 4 nuts had lost between 4 and 7 foot lbs!

As said, gaskets do compress but if your engine has been built without head or base gaskets then there is nothing to compress imho.

On my Imola I re torqued after about 500miles from new and it needed it and then left it until after about another 2500 miles on the way back from IOW when had big air leak only to find the head nuts loose. As the Imola has the secondary nuts on the head it actually leaked at the base where I am not using base gasket( to obtain the right squish). I reckon if I had re torqued previously I would have got home..

Although it won't completely remove the need for re-torquing the head, I'm using nord-loks which will stop them from backing off.

They will still lose tension (which is what we really want; torque is almost irrelevant in reality) if the gaskets compress further after the initial build.

Nord-loks are 'kin dear, but they're also 'kin excellent at stopping fasteners from coming undone.

bike grim wrote:On my Imola I re torqued after about 500miles from new and it needed it and then left it until after about another 2500 miles on the way back from IOW when had big air leak only to find the head nuts loose. As the Imola has the secondary nuts on the head it actually leaked at the base where I am not using base gasket( to obtain the right squish). I reckon if I had re torqued previously I would have got home..

That would suggest to me that there is some kind of fault in the design and/or build of the kit.To re-torque after 500 miles and find that the head nuts needed it,first of all at what point between 0 and 500 miles did they come loose,secondly if the the head nuts had been re-torqued after 100 miles,at what point between 100 and 2500 would they have come loose and how would you be able to tell,apart from when its to late and the damage is done.

I`m with Tractorman on this one

I make sure that the studs are in tight, use deep nuts, thick flat, thick spring washers and torque to 20lbs/ft - all set ups have base and head gaskets (on both ali and cast barrels)

never had a problem - but I never have a problem with exhaust stub nuts - again flat/spring/deep nuts torqued up

if you read about re torque distance it ranges from 50-500miles depending on individuals/dealers.

Got an rb20 rebuild on bench (haven't started stripping it yet) but will be applying the above to that.

I was under the impression that the re-torque was to do with the cylinder studs as well. They stretch? A quick search on google gives answers to this age old problem

nickw wrote: A quick search on google gives answers to this age old problem

And probably as many varying opinions...

So many choices

Eden wrote:I run the engine up to temp 2 or 3 times with the head cowl off letting it cool each time then re-torque.

Just as a matter of interest,after going through this procedure did you ever find that any of the cylinder head nuts had come loose at all.

Dunno about the 50-500 mile thing I'd never heard of any figure other than 100 personally

Cambridge Lambretta 50 miles
AF Rayspeed 500 at first service

Are people using spring/wavy washers ? I see loads of cylinder stud/nut sets that only have flats included.

Parts manual shows wavy washer straight to head.

I have only ever used flat washers although I don't see a problem with wavy ones. I wouldn't consider using nordlocks as they can be a nightmare to get off and I wouldn't want to have to reck the thread of the stud to get them off.

I do re torque at around 100 miles or sooner. The only time I have ever had an issue where I really did need to re torque was on an alloy barrel. Ts1 and SR were no problem but v3 Mugello that was a different story. This was a few years back now. May have been to do with the barrel warping.

In The "Official Lambretta Home Workshop Manual" it says to use spring washers and torque to 15 ft/lb.

In another Lambretta printout it is recomended to re-torque head nuts at first service 500 miles.

I don't do it that way, instead I use large flat washers with spring washers ontop and toque to 20-21 ft/lb and re-torque after 24 hours then again after a couple of heat cycles. This seems to work we'll.

Storkfoot wrote:I have only ever used flat washers although I don't see a problem with wavy ones. I wouldn't consider using nordlocks as they can be a nightmare to get off and I wouldn't want to have to reck the thread of the stud to get them off.

I do re torque at around 100 miles or sooner. The only time I have ever had an issue where I really did need to re torque was on an alloy barrel. Ts1 and SR were no problem but v3 Mugello that was a different story. This was a few years back now. May have been to do with the barrel warping.

Nord-loks can be a tricky to get off if they rust so I use stainless ones. They cost stupid money but I steal them from work so I don't care.

I'd still use them even if I had to pay though. They're a first class product.

If you can't get them off you need to get down the gym.

Do you know where you can buy stainless M8 nor-lock nuts?