MICRON 2.8 REBORE REPAIR

 

here's the engine as we received it from Adrian.

Well lets get on with the job................

Here it is all stripped down and ready for assessment.

First step is to make the piston and contra-piston blanks and the tooling to make and fit them to the nicely rebored liner.

Upon dismantling the con-rod assembly a rather large problem was discovered, unless Micron deliberately made a two piece gudgeon pin.

O dear..................

 So we will start with Adrians damaged crankcase,replacing it with one that we found whilst rummaging through our parts bins, then move on to cleaning up the back plate ready for reassembly.

Next it's clean up the crankshaft measure and check that there's no wear. All good there, so we'll refit the original crank back into our replacement case and assemble the front end. The prop washer and nut are far to shabby for us to allow out the door so these will be replaced at the same time.

 

 Here's the finished new con-rod and the piston blank and contra piston blank all ready for machining up to fit.

New con-rod fitted to the engine and awaiting the rebored liner and new piston etc.

As usual we have added lube holes to both the little and big ends of the rod as this greatly improves lubrication to these bearing surfaces and creates a much longer lasting engine.

 Here's the new contra piston all finished and ready to install.

 

And installed.

Next up is to finish the new piston and lap to fit.

Here's the new and old for comparison.

And fitted up to the engine.

Now we just need to make a new cylinder base gasket and it's onto final assembly.

 Just to satisfy our curiosity we took the time to weigh the original conrod/piston assembly and compared it to our replacement parts to ensure that the new parts were in fact a bit lighter than the original overweight items.

The original assembly weighed in at 18 grams and our replacement parts came in at just 12 grams, so a bit of weight saved in the reciprocating mass department,

Gasket is all done and the cylinder liner assembly is final assembled onto the case assembly ready for the cylinder head and tank assembly.

 

Cylinder head is all cleaned and ready to refit to the engine.

We have also replaced the fuel tank assembly with a like new item from our parts store as the original tank had been butchered by some lovely person and was shortened considerably.

Now all that's lacking is a prop and some fuel, fairly certain we can sort that tho.

Off to the test stand we go...............

 

And again after a few more runs......

Restart check.