OS 20 Max Gasket

[Andy J]

Can anyone advise the part number for a rear crankcase gasket to fit the above engine.

[Denis Watkins]

40 minutes left today on eBay

 

[Andy J]

Thanks Denis was watching that listing, but was not totally convinced it was for the OS 20.

[J D 8]

I just make this sort of thing from thin card. Damp the crank case with thin oil/ink and print outline on the card or gasket paper. Cut out with scalpel.  To tight to spend £6 on a tiny bit of paper.

[RottenRow]

1 hour ago, Andy Joyce said:

Thanks Denis was watching that listing, but was not totally convinced it was for the OS 20.

Andy,

 

If your engine is the old (crossflow) OS Max 20 then the 20FP gasket set shown probably won't fit it. They were different generations of engine.

As JD8 says, easy to make and rather satisfying too.... both making it yourself and saving the £6!

 

Brian.

[Andy J]

Agree with you both. Did think £6 was a little steep for such a small gasket.

[Engine Doctor]

A brown envelope is all that is needed for a backplate gasket. If too thick it will cause the plate to distort . Rub a piece of card on the case a rub fingers over it to get impression of the hole needed. Cut out wit new scalpel blade an fit onto backplate then push into engine. Push a thin sharpe screwdriver into holes to puncture paper and insert screws. Carefully trim off excess with paper with scalpel. Job done. 5 min and a few pounds better off.

[Andy J]

Thanks ED, was tempted to get my laser cutter out this morning and experiment with the settings to cut a hole of the correct diameter and then trim around it  when fitted.

[Engine Doctor]

A bit of a sledge hammer to crack a nut 🙂 but fun if your into 3D printing. That would be a good way of making a gasket from thin plastic like the later models use .

[Paul De Tourtoulon]

Paper over crankcase, rub a dirty finger over the paper to mark it out, 4 pen or pencil tip holes where the screws go and rub the end of a ball peine hammer ( or screw driver handle ) to make the bigger hole, cut around the edge with scissors, it's quicker than posting this on the forum !

Edited December 11, 2022 by Paul De Tourtoulon
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[Andy Stephenson]

An easier method is to cut a round hole in some card with a compass cutter that just fits over the boss of the back-plate. Cut the card a little over-size then assemble it with the card protruding out round the edge. Poke holes where the bolts go and screw them in and pinch them up tight. Then with a scalpel carefully cut the exact profile by running the blade around the back-plate.

[Andy J]

Had the laser cutter out this morning to cut some more dummy access panel rings out in solartex so quickly knocked up a GCODE file to cut a 25mm circle out of a brown envelope as suggested for a backplate gasket. Once I get some fresh screws from Model Fixings I will trim around the outside of the crankcase to finish the job.

If I had only brought my measurement aids into the house when I went up to the workshop to collect the engine this morning could have been a bit more adventurous and cut out the screw holes as well.

[dave windymiller]

+1 for brown paper with just one hole to fit the back plate.  

 

You can trim the protruding paper gasket from the assembled engine by burning it off with a pencil torch flame.  Perhaps add a bit of thinners or methylated spirit so it burns better.  Makes a perfect fit and no unsightly protrusions!!