Scooterotica

I've heard of SIL cranks being an ideal to upgrade to be used in tuned engines. I have a few questions.
What is required to make them suitable?
Which cranks are suitable and if buying a 2nd hand one, how can you tell if it's the correct type and a good donor?

interested too , i know sccoter resto's do a sil crank with jap bearings for 90 quid

you just need a jap rod and you want the 22mm not the 22.9 or whatever the strange one is.

jb can do these as can most others. replay are doing a 61mm mec crank with a yam rod for me.

minotaur wrote:interested too , i know sccoter resto's do a sil crank with jap bearings for 90 quid

the 110 jap rod or longer makes a smoother motor, sr may be just replacing the bearing for that money

i use a converted SIL crank in one of my TS1`s

gp200 22mm big end and have them rebuilt with an rd350 rod kit which is 110mm long therefore you need a 3mm packplate- things to keep an eye on though is the rod thickness they a thicker by 1mm than standard and then you put in a thrust washer 0.5mm each side - i get the crank webs machined down to suit so the crank is the same overall size when completed - i have heard of them put together without the washers straight into the webs

alternatively I have an SIL crank converted with an AF rod kit at 107mm - no machining, no packer required

both options make for a very good crank at a realistic price

hope this helps

I would of thought it was better to machine the RD350 (or RD400) big end width to match that of the Sil big end than to do the crank webs as this would help reduce the risk of twisting.
But I am no engineer so maybe not..lol

aussie

the bearing with the rod kit is 16mm wide so that dictates - I had the crank pin welded
but i`ve seen plenty done without welding - i have a crank (MEC) that the late Jon Betts (SES)did which was done in the same way