Crankcase Joint-Prep and sealing

riptragle1953

Well Known and Active Forum User
Non-VOC Member
I'd do the usual soak, brush and scrub stuff in solvent and then a bead-blasting cabinet using fine plastic "grit"......... then wash the hell out of them with soap & water followed by high pressure air.
 

1660bob

Well Known and Active Forum User
VOC Member
Well I finally got the cases together and bolted up.Now I just have to figure where this G39AS thingy goes......ONLY JOKING!!!!- did have a senior moment though- got everything sealed and bolted up in a carefully choreographed operation of surgical cleanliness and military precision. I stood back to admire my work and reflect on how well it had gone:), that`s when i saw that the con rods were in the wrong cylinder mouths...........After much sweat and toil i got the joint apart and corrected my,er, oversight, but in my panic added more sealant and the end result was too much.Lesson learnt, all apart again and cleaned up for a fresh start.Sometimes you try too hard and concentrate on the detail so much that you can`t see the bloomin` obvious.
Anyway, job done now, I used the Threebond 1184 as recommended by ClevTrev in the end-its rubber base and ability to cope with uneven surfaces swayed it for me.Seems like good stuff.
I found that my cases were less than perfect, I could definately detect a little rock in a steel rule placed across the mating face, seemingly the divide beteween crank case and gearbox was a couple of thou proud and I suspect there will always be a little "spring" for the bolts to pull up on most cases.
This got me thinking, once bolted up, that centre joint needs to be left undisturbed, and yet at the rear lower end of the gearbox, case bolts `K` and `J` (MO41) get disturbed,`J` when removing the G1 cover to access gearchange mechanism/change sprockets etc,and perhaps less so,`K`, if you are removing the FT108 footrest plate for some reason.Either way, undesirable in my view.
I decided a simple mod was in order and so extended the threaded portion of the bolts sufficiently to accomodate a couple of home brewed spigot nuts to keep everything tight if ever G1 or FT108 are disturbed.Piccies below. `K` straightforward- a spigoted nut fits into G50, and the spacer/dowel FT109/ET163 assy bored out to accomodate the new spigot nut(i will make a new SS one piece one).
`J` is of course through a dowel that locates G1/G50, and a little more tricky.I made a sleeve nut to do the job of the ET163 dowel,just down a thou or so so as to locate but not be tight in the crankcase/G50/G1, with a shallow hexagon to facilitate tightening (made from same hex. sized bar as the standard 5/16ths nut 142).The dowel bore in G1 cover will have to be bored out at its outer end to accomodate the new hexagon part of the nut, but there is plenty of depth in there to do so whilst retaining its function.The sleeve nut hexagon JUST clears the opening for the G51 tin cover, if the flat of the nut is positioned to suit.What do you think??
 

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