The studs contained in the 2x Endplate Stud packs that I have been supplied by 2x different top Lambretta parts supliers are apparently the correct length but are completely useless .
The studs supplied are M7 x 26.5mm x 1mm pitch and when correctly fitted to the case they barely show above the level of the endplate. There is not even sufficient space to fit a thin 1mm washer let alone a flate washer, spring washer and nut !.........
The stud that is required to secure the endplate satisfactorily needs to be at least 32mm long preferably 35mm .(This goes for a M7 bolt if one should decide to use a bolt instead of a stud although great care will be needed if using a bolt so that the bolt does not bottom out before reaching full fixing torque.)
The crankcase endplate fixing holes are tapped to a depth of 12mm with a further 4-5mm insertion depth below that.. so a minimum thread insertion depth of 10mm and a maxmimum of 14mm would seem appropriate provided the case threads are cleaned and the holes cleared out.
To this we can add 9mm for the thickness of the endplate 0.5mm flat washer 1.5mm spring washer and 4.5mm for the special thin M7 end plate nuts . That gives a total of 25.5mm - 26.5mm .
The supplied studs are 26.5mm in length which would theoretically be just long enough with nothing to spare however there is a problem.
The threaded portion of the studs are approx 10mm but like all studs ,have a 2mm tapered lead in. This tapered portion of the thread contributes nothing to the strength of a fixing nut .We are therefore left with barely 8mm of thread to insert into the case which is clearly insufficient to secure the endplate when you bear in mind the magnitude of forces applied by the layshaft. In addition to this the fixing nut is likely to only have 2.5mm of effective thread to be secured to as the last 2mm of thread is tapered both ends
I suspect that the majority of endplate and hub failures are due to the endplate fixings failing due to insufficient stud thread insertion in the casing where builders , in order to leave sufficient stud projection to fit the endplate washers and fixing nut, unthread the studs too much leaving insufficient threads in the case. This is probably compounded by worn case threads and no application of threadlock .
So what is the answer ? ...., before someone says ‘fit bolts instead mate’ ....clearly if we wish to stick with studs we should consider fitting longer studs so that we can reliably and consistantly achieve a 10mm minimum thread insertion of the studs, in the case (preferably 12mm ) and still leave sufficient stud length to fit the plate , flat washer, spring washer and nut with say 3-4mm thread spare.
I would suggest that the ideal stud length would be between 32mm and 35mm the latter of which co-incidentally matches the Vespa cylinder head studs. M7 x 35mm 0.1mm pitch.
Happy days
[fbvid=]
endplate studs by John, on Flickr[/fbvid]
I know my post was rather long but I thought that I had made it clear that the maximum insertion was 8mm ? 
