Model31 splitting crank case

[eric650]

Hello it looks like I'm going to have to replace the big ends and small ends on my Model31 any tips on splitting the crankcase and removing the gudgeon pins from the pistons it appears that the inboard circlip is always obstructed by the other piston any tips on methods and special tools and any little dodges will be much appreciated. Thanks in advance Eric

[1608]

Hi Eric, doubtless you will be inundated with advice on this one. However, for starters removing the pistons is a doddle. If you are relatively new to dismantling an engine my advice would be to clear a good space on a separate top to the work bench so you can lay things out on a clean surface. Have a permanent marker handy and write on or label bits and pieces as you go. As for the pistons:- Place the engine at TDC and remove the heads and both barrels. When removing the barrels place a cloth over the crank case mouths to stop any broken rings or debris entering the engine ( just in case you find that there is no b/end play) and decide not to split the engine. Remove both outboard gudgeon pin circlips and push a long screwdriver through one gudgeon pin and up against the other pin and push out. You may have to heat the piston a little to expand it just enough to allow the pin to move. Try not to let the con-rods drop against the crank case as this could bruise the rod and in extreme cases lead to the rod being weakened. If there are any such marks already on the rods from previous clumsy work then the marks or bruises should be smoothed out using fine emery and finishing with metal polish.Thats enough to be getting on with. Don't forget to mark the pistons so they go back in the same barrel and face the same direction.