Stainless steel cylinder head bolts

Hi,

I've used SS fixtures for thirty years on my ES2, Dommi and Commando with no problems whatsoever. I've used them in combination with aluminium alloy, mild steel and, of course, stainless and have never had any electrolytic reaction with any combination.As with any fitting, always use a bit of grease - 'Copaslip' -is the one usually recommended for SS. The only thing I've noticed is that they do tend to slacken off more than the original stuffwhen first fitted but 'nipping' them up after a couple of hundred miles or so after a rebuildnegates any further problems. Stu Rogers sell stainless stuff to fit elektron (magnesium) alloy cases on Manxes and if it doesn't react with that...................

Regards.

Ian.

Stainless steel bolts tend to have the threads cut rather than rolled, so the rolled threads tend to be stronger also stainless has a tendancy to gall ie. jamb, particularly when used with a stainless nut. Copaslip is the way ahead in these cases.

Hi Ralph

My Commando was fitted with stainless steel cylinder head bolts by the previous owner in the 90âs. I had the head off a couple of times, and found I spent the next couple of thousand miles re-tightening the nuts and bolts. Once they eventually settled down they held everything in place fine.

Last time I had the head off, I threw the stainless steel bolts, studs etc away and fitted standard parts. They were torqued up as usual, needed very little retightening after the initial warm up, and that was that. Much better. Of course they were rusty within a few weeks.

The previous owner had replaced many fasteners with stainless steel. This included the engine/cradle fixings. The bike developed a hell of a rattle one day, which was caused by the 3 cradle fixing bolts at the back of the engine popping their heads off. When I mentioned this to another club member he told me the same thing had happened to him in the past with stainless bolts. Then on another club run, a MK3 Commando developed a problem with the engine moving about all over the place and suffering a burnt out alternator â guess what, the same thing had happened.

I have removed most of the stainless steel bolts from highly stressed areas since then. Iâm not suggesting all stainless steel parts are unfit for purpose, but you must be sure they have been manufactured from a suitable grade of material. Preferably purchased from a trusted source.

Cheers

Jeff

There are several hundred types of high chrome ,high nickel,alloy steels,which resist corrosion to varying degrees.Stainless steel was a trade name of one early type." Stainless" fasteners with cut threads are typically produced by low volume cottage industry suppliers from unsuitable materials,the main requirement being free machining.Aircraft have nearly all "stainless " fittings.Fasteners made from heat treatable grades with rolled threads, can have tensile strengths in the 1200 Mpa range[SAE grade 8 is 1000Mpa ],and will be suitable for any motorcycle application.Its also well known that bolts and nuts made from high nickel grades will seize together.You wouldnt use cuphead woodbolts in you bike and expect them to work,so dont use stainless fittings with similar strength.Regards John.

The problem with stainless steel fasteners for British Motorcycle use is availability. Unlike aircraft, which are usually put together with fasteners with Unified threads, Brit bikes use a lot of CEI, BSF, BSW, and BA fasteners, all of which are technically obsolete threads and therefore not produced in a wide variety of materials. What I see most often where a material is specified is A2, which I believe to be what was called 18/8, 18% Cr and 8% Ni. I don't know who the "Cottage Industry" to which you are referring is, does it also make re-pop Manx Nortons?

I put my Commando together with specialised fasteners from a well known Norton parts supplier in the midlands, but I bought the more common nuts mail order from McMaster Carr and bolts from a hardware store in the town where I live. I have had no trouble with any of the fasteners.

The Electra is another story, which should be discussed on another message list, but the hunt goes on.

The old 18/8 stainless,type 304,is a soft austenitic grade suitable for use in boats ,fences ,mudguard brackets,etc not requiring much tensile strength,but taking a high polish,and with good corrosion resistance.Can be annealed ,but not hardened by heat treatment.Type 303 is a similar free machining grade.For fasteners such as head bolts,crankcase bolts, etc requiring high tensile strength , use heat treatable grades like 416 and 431,or the well known 440C.These grades contain no nickel,and do not seize in use.Precipitation hardening types like 17-4PH are also used. Regards John.

A blast from the past, I havent heard of Andy Molnar for many years.He was a pioneer making replacement parts for classic bikes,in the days when you d buy a bike just to get a couple of parts.Regards John.

The attached MS Word doc is a very nice advertisement for Andy Molnar's business, and I have never heard anything bad about his stainless products. I have bought a few things off him over the years. Andy is the man manufacturing re-pop Manx Nortons who I mentioned in my earlier post to this discussion.

Back in the 1990s, the NOC Tech Team became aware ofproblems that a good number of Nortonownerswere having with their bikes all pointing to duff replacement Stainless Steel parts.

Traders were finding that they could make fast bucks by jumping on the Stainless wagon and flogging a whole range of replacement parts to Norton owners. The main problembeing that many of these bits were nowhere near the correct specifications for the parts they were replacing and this in turn often resulted in expensive damage.

The most worrying of these was wheel spindles which either corroded quickly or just snapped. In both cases it was due to the wrong grade of Stainless being used in their manufacture.

The second major alert came with reports of rebuilt engines that kept blowing cylinder head gaskets. Where were all these duff gaskets coming from? Well the answer quite simply turnedout to be nowhere.......because the gaskets were not the problem. It was replacement head bolts made from Stainless Steel.

Most of these badhead bolts were overlong, when compared to originals and would bottom out inside the barrels before clamping up the head gasket.

Others weremanufactured with oversize threads that seized up on being torqued down and then often snapped when a removal was attempted.

The really bad news, with regard to this saga, was the fact that some big name suppliers got their fingures burned by also sellingquite a lot of the grot parts.

The message here is .........don't always assume that you get what you pay for.

Paul previously wrote:

All the posts here are interesting. Along with mentioning (some of) the various grades of stainless steel and the warnings re: All that glistersâ?â?...

Whilst some of this does not address Ralphâs original question, it has reminded me of a letter sent to Roadholder back in the early eighties by Andy Molnar.

Stainless items are big business on the auction circuit. I have seen one well known supplier of shrouds (NOT A.M.) proudly listing his wheel spindle raw-material as 431.

Many are the restorers who, when faced with having a critical yet unobtainable component specially made have thought: âWhy not have it done in stainlessâ?.?â

Iâve attached an edited version of the letter, copied to a Word.doc, for anyone interested.

With reference to the document posted by Paul, coincidentally the VMCC February magazine has just arrived. On page 51 it reads, "431 is most appropriate for wheel spindles.......to gain maximum strength it should be heat treated to BS970."

I am no metallurgist; does anyone know if the heat treatment changes AM's warning?

Cheers

Alan

Where corrosion is a problem, use stainless. Providing it has been put together with copper slip or equivalent it will come apart many years later. The places like head bolts etc rarely require stainless to be fitted, and standard items are usually trouble free and fit for purpose.

I have had a rear wheel spindle snap whilst joining the M275 from the M27 eastbound and though the bike was still ridable at speed as soon as I crossed the white lines it was very evident something was very wrong. It took some time to prise the bolt out as it had snapped at the top of the threads and just rested in the stub axle, I may still have it in the garage.

I will now not use stainless where tension or flex is needed, better to wrestle out a bent or seized fitting then being sat at home in plaster licking your wounds and counting the pound signs of a re-build.

Simply put," things change in thirty years". 431 is a free machining modded type stainless,different manufacturers use different formulas to arrive at a similar result . The formula may have been changed many times to solve faults that appear from time to time.When producing components in small batches,manufacturers tend to use a pre heat treated stock suitable for general use,yet still machinable.Hence the heat treatment may have no relevance to the particular requirements of the application.The alternative is to have the finished component heat treated to a particular spec,such as may indicated from experience and or testing.What testing? None,if its a hole in wall manufacturer,churning out bits to flog to the punters.The finished form of the part also has a great influence on failure in service,ie no abrupt changes in section,sharp runout of cut threads etc, stress raisers that cause failure in service.The best steel will fail quickly if these rules are ignored.Regards John.

The wheel spindle breakage is a problem I have heard about before. I have heard about it with both standard Norton spindles and stainless replacement parts. I want to change course of this discussion slightly to cover this matter.

The only bikes I hear about which break wheel spindles are later Commandos. I never heard of it happening on a Dominator, a Lightweight, a single or an early Commando. The point is what changed? The later Commandos had rubber cush drives built into the rear wheel, whereas all pre-Commando Nortons had the cush drive in the clutch centre. Early Commandos, like my 1969 S, do not have a cush drive at all, the rear wheel is just like the one on an Atlas or other earlier bike.

My thought is that the brake/sprocket moving around on its rubber cush drive adds bending force to the spindle, causing fatigue, which then leads to the spindle breaking at the weakest point.

Any thoughts on this one?

Colin.

Previously wrote:

Where corrosion is a problem, use stainless. Providing it has been put together with copper slip or equivalent it will come apart many years later. The places like head bolts etc rarely require stainless to be fitted, and standard items are usually trouble free and fit for purpose.

I have had a rear wheel spindle snap whilst joining the M275 from the M27 eastbound and though the bike was still ridable at speed as soon as I crossed the white lines it was very evident something was very wrong. It took some time to prise the bolt out as it had snapped at the top of the threads and just rested in the stub axle, I may still have it in the garage.

I will now not use stainless where tension or flex is needed, better to wrestle out a bent or seized fitting then being sat at home in plaster licking your wounds and counting the pound signs of a re-build.

The wheel spindle breakage is a problem I have heard about before. I have heard about it with both standard Norton spindles and stainless replacement parts. I want to change course of this discussion slightly to cover this matter.

The only bikes I hear about which break wheel spindles are later Commandos. I never heard of it happening on a Dominator, a Lightweight, a single or an early Commando. The point is what changed? The later Commandos had rubber cush drives built into the rear wheel, whereas all pre-Commando Nortons had the cush drive in the clutch centre. Early Commandos, like my 1969 S, do not have a cush drive at all, the rear wheel is just like the one on an Atlas or other earlier bike.

My thought is that the brake/sprocket moving around on its rubber cush drive adds bending force to the spindle, causing fatigue, which then leads to the spindle breaking at the weakest point.

Any thoughts on this one?

Colin.

Previously wrote:

Where corrosion is a problem, use stainless. Providing it has been put together with copper slip or equivalent it will come apart many years later. The places like head bolts etc rarely require stainless to be fitted, and standard items are usually trouble free and fit for purpose.

I have had a rear wheel spindle snap whilst joining the M275 from the M27 eastbound and though the bike was still ridable at speed as soon as I crossed the white lines it was very evident something was very wrong. It took some time to prise the bolt out as it had snapped at the top of the threads and just rested in the stub axle, I may still have it in the garage.

I will now not use stainless where tension or flex is needed, better to wrestle out a bent or seized fitting then being sat at home in plaster licking your wounds and counting the pound signs of a re-build.