CB250 rebuild part 9

**30/3/2019**

This entry is all about the oval holes in the motor and my struggle with them.

**13/4/2019**

It is also about gasket scraping and cleaning. Honda appear to use an adhesive called "shellac" (or something very similar) which sticks the gaskets in place and also leaves behind an incredibly hard/durable brown varnish-y layer that is really difficult to scrape off. The steel plate around the alternator wasn't so bad though.

Thank goodness for power tools.

**23/4/2019**

After a lot of thinking/pondering/outright wonderment I decided that the best course of action was to drill out the existing holes from 10mm to 12mm and then sleeve them down. Some googling revealed I could buy 1mm thick steel cylinders that I could fit into the new enlarged holes:

https://simplybearings.co.uk/shop/Bearings-Wrapped-Steel-Bushes-Plain-Wrapped-Steel-Bushes-Plain-Wrapped-Steel-Bearing-Bushes/c3_4701_4702_4542/index.html

https://simplybearings.co.uk/shop/Bearings-Wrapped-Steel-Bushes-Flanged-Wrapped-Steel-Bushes/c3_4701_4703/index.html

The holes for the dowel pins are already 10mm and are not destroyed (even at the front!) because the dowels are steel and also in the middle so avoided the worst of the movement around the mounting bolts:

While not seeming too bad the holes at the rear of the motor must also be oval, if they weren't then the engine wouldn't be allowed to move about!

However not all the mounting holes have dowels in them, such as the lower front mounting point which is basically destroyed:

It turns out that this hole is 12mm anyway and just has a small/short taper in it which goes down to 8mm - such a tiny contact patch and yet the engine is a stressed member of the frame!? I think if I drill the dowel one first I can then use the front mounting bracket to semi-accurately gauge where to drill through the lower mount. All is not lost.

Full of enthusiasm I purchased 10mm, 11mm and 12mm drill bits from Screwfix (£19.50!!) to ensure they were sharp and straight. The 10mm bit fitted nicely into the new sleeves, which would mean I could line the hole up with the drill until it easily slid up and down and I would know I was drilling in the centre. Once it was lined up I could go up to 11mm and then 12mm as long as everything stayed in place.

Right, let's get to it! The pillar drill is a bit smaller/shonkier than I remembered..

So, knock the sleeve/bush/dowel into the hole for the usual dowel (this was a tight fit):

Check that the drill still fits and the sleeve hasn't been crushed together..

This is where things started to fall apart. The tiny little platform of the tiny little drill was too small to hold the case in a position where I could drill the hole. So I tried to use the base instead which also didn't work.

I tried an alternative setup to try and get the case flat but it was no good.

So I gave it up as a bad job and went back to pondering.

In the middle of May I realised we have a bunch of trained mechanical engineers and a hefty pillar drill at work! I explained to the apprentice (in his late 20s!) what I wanted and that it was of critical importance that he NOT, UNDER ANY CIRCUMSTANCES ruin the holes that the dowels fit into. I could see this wasn't going in. I could see he wasn't listening, and even if he did listen he would never understand. As soon as my back was turned he got the 12mm and, by eye, attacked the rear dowel-hole. The case was immediately scrap. He also then insisted on cleaning it which washed a lot of grit into all the bearings and then left them all dry so they're gone too. The only saving grace is that this was the left case and it is the right case that has the engine number on it. Still a shame though.

I later found out from a much more experienced engineer that the drill is knackered anyway and has a decent wobble on it so the hole was never going to be exact. I'm now mulling over buying another left case and a pillar drill so I can do the work myself, as it should be done - properly and with care. At the time of writing (12/11/19) the frame is sat outside under a cover being engulfed by cobwebs and snail poo while the engine parts are sat in a box. What a waste.