Scooterotica

I've used them before but the guy didn't put on the shims on, this time he did. The crank is nicely through on the drive side but on the flywheel side I've got 5 gaskets in and it's still compressing the crank, how many could you go to???

Is it a Yamaha 110 rod? Don't those need to be machined down to go between Lambretta webs?

Yes a Yamaha one, 3rd one I've used. The only difference this time was the shims are on and they don't look too thick. Maybe I got the wrong rod but thought they were all the same.

My rod was machined down to 15mm width and the total across the webs is 40.8mm

i believe you need to machine the webs

As it is now, the conrod will not be running in the centre of the cylinder and casing so it needs a crank strip and the webs machining evenly on each. From memory the rod is 16mm wide + 2x1mm shims+0.5 clearance =18.5mm. The webs are then machined so the crank width when assembled is around 40.5mm. The pin also needs turning down to the same.

I've measured the crank mentioned and its 43.25, too wide. Measured a few other cranks LI and GP and they are all around 40.5. The shim looks about 1+ mm. The lad did one before without the shims and it worked great and the engine is still going strong. I know people say, 'yes and no' about the shims but if he took them out I guess it might be okay, like the old one he did for me?

If you remove 2x 1mm shims you still end up too wide plus over time the conrod wears a groove in the webs. You could try linishing the rod .5ish each side but the bearing needs to be done the same , if possible, to avoid trapping it.