hello from a state of disassembly.

[lindie]

therein lies my prejudice. my oil tank has at one stage i believe been chromed and hence split from the steering head. the tank has countersinking on both sides and may feasibly be the correct one for the 1951 dated C headstock, but the bolts which all of were fed through left to right arent chamfered accordingly, and the nuts only kinda are,through i believe the procedure of being turned to tighten against the countersink of the tank. not that they all look the same either and the threads show wear on the inside that looks like they've been on and off more than once.

would the idea of a straight high tensile bolt and a "tapered to suit the tank" washer a-la old mercedes truck lugnut style work? if nothing else it'd be better than whats there now as though theres a clamping force applied on the left side through the bolt heads, you wouldn't really call it positive location.

 

[b'knighted]

Alternative headlug nut.

I have recently removed the forging from a C oiltank to replace it with a numbered headstock. Although the studs with countersunk nuts each end appeared original the point at which shear would occur is close to the end of the thread. That strikes me as the weakest part of the stud. The modification I should like to make is to replace the nuts with spigotted nuts with countersunk heads so that the spigot is in shear, similar in principle to the spigotted nuts holding the UFM to the head brackets. A thin, fully threaded stud would be used to hold these nuts in place. Three sixeenths BSF or even a heathen 6mm should be enough as there should be no side force on this stud in normal use. The head size should of course be standard, although that risks overtightening on a small thread.

If you decide to make some of these, do me a set.

Cheers, Ian

 

[donrapide]

If you do go ahead with the H.T. bolt replacement, as I did, the English/Imperial H.T. bolts are grade "R" which is the best compromise of shear strength and tensile strength.

UNF/UNC are stronger in tensile but not as good in shear. Allen cap headed bolts are not reccomended for this application.

You can have complete confidence in these Grade 'R' bolts particulary if you carefully turn the chamfer taking care not to 'nick' the bolt shank. And fit chamfered high tensile nuts, not B&Q quality!

Do take into account the small amount of clearance between the oil tank nuts and bolt heads. You need this clearance to allow for movement and all the cables, control and electrical. So any alternative fixing must be as slim as the original.

It would seem that your bolts are already out but if anyone reading this thinks to remove the original bolts, just to see or replace them be very careful. The bolts have been there for some 50 years and could/would be the very devil to remove. If no signs of red dust under the nuts, fretting corosion, leave well alone.

 

[lindie]

If you do go ahead with the H.T. bolt replacement, as I did, the English/Imperial H.T. bolts are grade "R" which is the best compromise of shear strength and tensile strength.

UNF/UNC are stronger in tensile but not as good in shear. Allen cap headed bolts are not reccomended for this application.

You can have complete confidence in these Grade 'R' bolts particulary if you carefully turn the chamfer taking care not to 'nick' the bolt shank. And fit chamfered high tensile nuts, not B&Q quality!

Do take into account the small amount of clearance between the oil tank nuts and bolt heads. You need this clearance to allow for movement and all the cables, control and electrical. So any alternative fixing must be as slim as the original.

It would seem that your bolts are already out but if anyone reading this thinks to remove the original bolts, just to see or replace them be very careful. The bolts have been there for some 50 years and could/would be the very devil to remove. If no signs of red dust under the nuts, fretting corosion, leave well alone.

sadly, if you'd call it that, the bolts were simplicity themself to remove. might have to get the fuel tank back to the bike to see what clearance i have and decide from there. will wait till it's painted i suppose.

thanks for the suggestion, glen.

 

[Tom Gaynor]

Headbolts

In the literature it is made clear that once built at the factory the UFM and headstock are to be regarded as one assembly, and splitting them at home isn't advised. If however they ARE split, and you replace the bolts, what you must NOT do is thin the heads from the underside. They ought to be forged bolts, and the underside of the head is where the strength is. I don't know which type mine are (1951 C Shadow), and since it is freezing, and dark, and snowing, I have no plans to harness up the dogs and mush over to the garage to find out. I'm sure you'll understand...

sadly if you'd call it that the bolts were simplicity themself to remove. might have to get the fuel tank back to the bike to see what clearance i have and decide from there. will wait till it's painted i suppose.

thanks for the suggestion, glen.

 

[clevtrev]

The part that usually wears is the countersink in the tank. You would need to find a sidecar machine that has had a well used life, and has slightly loose nuts.
There would not be enough load imposed by the tank to shear even a mild steel bolt, given the amount of bearing surface of the tank on to the bolt.

 

[lindie]

In the literature it is made clear that once built at the factory the UFM and headstock are to be regarded as one assembly, and splitting them at home isn't advised. If however they ARE split, and you replace the bolts, what you must NOT do is thin the heads from the underside. They ought to be forged bolts, and the underside of the head is where the strength is. I don't know which type mine are (1951 C Shadow), and since it is freezing, and dark, and snowing, I have no plans to harness up the dogs and mush over to the garage to find out. I'm sure you'll understand...

dogs?

sounds like you need an MZ my friend.

 

[Tom Gaynor]

Dogs and MZ's

There are of course people who say that MZ's ARE dogs, but I am not one of them. I ran a 301 in all weathers for about 5 years. Maintenance over the five years was less than burdensome, amounting to about 15 minutes in total. Now I don't have to ride in winter, so I don't.
Ian Hamilton, of Wearing Out a Vincent Faster fame, lived not far from me, and thrice rode from Glasgow to the South of France, on a Guzzi Le Mans, a Commando, and a 250 MZ. The MZ made the fastest journey times...

dogs?

sounds like you need an MZ my friend.

 

[lindie]

sorry tom. was meant to read as MZ's will go places that dogs fear to tread, and they'll start in any weather without needing to be harnessed up.

above pictures are of lindie's younger sister marlene from the continent.

 

[Tom Gaynor]

MZ's

There seems to be an affinity between Vin owners and MZ's. You have one of the good looking ones. Mine was hideous but highly functional.

sorry tom. was meant to read as MZ's will go places that dogs fear to tread, and they'll start in any weather without needing to be harnessed up.

above pictures are of lindie's younger sister marlene from the continent.