Heavyweight rear mudguard conundrum

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Jdraper
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Joined: Mon Mar 07, 2011 9:41 am
Location: BUCKS UK

Heavyweight rear mudguard conundrum

Post by Jdraper »

When I got my AJS 18S many years ago, it was in a sorry state with a bitsa rear mudguard. I sourced a reasonable looking replacement, with a hinged rear section, but there are some subtle changes to the details of these units and associated grab rail. The first problem is that the mudguard does not have a big enough hole for the special 'bucket' nut that goes through the sidewall of the guard and engages with the grab rail as it screws onto the long top Jampot mounting bolt. No signs of repair, but the hole is just big enough for the suspension bolt to pass through. This means I have to use an ordinary nut to secure the mudguard.

The second minor issue is that the hinged section of the 'guard is secured to the grab rail by two bolts either side. These have 5/16" 22 Tpi thread, with the one securing the rear hinged portion having a stepped shoulder to allow the bolt to be loosened enough to allow the hinge to work, without removing the bolt. The second bolt securing the grab rail to the non hinged section should be a plain 5/16" bolt. Now the issue I have found is that the grab rails I have sourced only have a hole big enough for a 1/4" bolt - the pictures should help here.

Although I have made the current bits work together, does any one know if there are two types of grab rail? Ones with a 5/16" hole and ones with a 1/4" hole. Also any ideas what year the mudguard I have may actually be from! I am interested to understand the subtle differences from year to year, singles to twins and lightweight to heavyweights..

Jeremy
(just curious)
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SPRIDDLER
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Re: Heavyweight rear mudguard conundrum

Post by SPRIDDLER »

I had to refer to your Profile to find the year of your bike.
I believe the '55 models are known as an 'interim' year with features for that year only.
Be aware that the '55 models were produced from Sept 1st 1954 and only until Aug 31st 1955.
However, the 1955 Spares List pages 16 and 36 have (rather poor) illustrations of the frame parts and mudguard (enlarge them) and lists the bolt types and sizes, but the hand drawn illustrations weren't always updated year to year:
http://archives.jampot.dk/book/Spares_l ... ingles.pdf

Is your 'curiosity' ref the differences just for frames or generally?
Year by year changes can be found in the individual Spares Lists and are also documented in many places but here's just one example of where they can be found by searching with the keyword 'Changes' in this website's Technical Articles (top right of this page):
http://www.jampot.com/article_search.as ... rch&num=10
Last edited by SPRIDDLER on Sun May 31, 2020 12:35 pm, edited 9 times in total.
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clive
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Re: Heavyweight rear mudguard conundrum

Post by clive »

There were more than two types of grab-rail. During lockdown you could go through the spares lists and see how many times the part number changes!
clive
if it ain't broke don't fix
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ajscomboman
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Re: Heavyweight rear mudguard conundrum

Post by ajscomboman »

There was a pair of the very early grab rails on sale on the facebook website recently. As mentioned the holes are totally different compared to the later types.
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