crank shims are they necessary

[tavspeed]

hi all,just split a indian crank, to which i am going to fit a vespa ape rod,the 2 webs measure as near as dammit 12.5 mm each,the ape rod measures 15.39mm,which gives 40.39mm,add in .25mm for clearance so you have 40.64mm.
the rod came with 2 1.0 mm shims.
if it is ok to run without shims i could build the crank as it will fit comfortably in the crankase,i have nearly 42mm between the mag flange face and opposing crankcase face.
i could get 0.5mm shims if i need them but the crank would end up 41.64mm wide,or i have .5mm machined off the web faces.
i am going to tig the pin which i turned down to 40mm,wish i had waited and made it 41mm,anyway which is the best way to proceed,

fit .5mm shims and the pin would be approx 0.8mm short in the webs both ends and tigged

fit shims to machined webs and tig

fit without shims and tig,

cheers all.

[wack 63]

It all depends what you intend to run the crank in.Personally I wouldn't use .5 shims ,they seem to wear quicker and have seen one wipe out a Imola kit when it wore through.1mm shims are better but you will need to machine the webs to get the clearance which then gives the pin less purchase,swings and roundabouts. High revving motors I would use shims but not worry about them in a milder motor unless doing many miles a year then a check every now and then to see how things are wearing.

[tavspeed]

thanks for the advice wack63,crank is going in a suzuki 230 engine,with a taffspeed exhaust,so isnt going to be a high revving screamer,so i will take your advice and build the crank without shims,do you think .25mm is right with the clearances,i.e .125mm either side.also have been advised to cut a slot in the big end eye for lubrication,as the ape rod only has 2 small recesses on the circumference,whereas the indian rod has multiple recesses and 2 slots,wouldyou advise cutting a slot for lubrication,cheers

[gaz_powell]

i`ve got an rd400 rodded indian webs no shims - its not in use yet but will going in a ts1 200 i`m going to build

no shims used came out at 12.5+12.5(webs)+16(rod)+0.25(clearance) = 41.25 and fits okay

No shims were used with this rod at the advise of a very experienced local crank builder he was confident that this type of rod and webs didi not need them - however when he built my rd250 rodded one into mec webs he used the shims.

we used the indian pin and not the solid one that came with the rod kit and the rod i got had recesses and 2 cut outs in the big end - it was a pattern rod from TKR

Overall width of 40.5mm + is what you are aiming for, any smaller & the flywheel may rub the pick up