I was hoping I wouldn't have to do this. I had bought the Corporal with the idea that it could make the best of a bad job, as far as 'The Heap' was concerned. You may remember, that was the bike I originally bought for Donna as 'her' project, but after stripping it down, was discovered to have a hacked up frame, and had to be 'scrapped'.
Idea behind buying 'The Corporal' was to use the supposedly 'good' engine from 'The Heap' in a bike that to all extents and purposes, was a tidy, serviceable little bike, with long Tax and Test on it, but an engine seized through owner numptyness!
Well that 'long' tax and test is about to expire, and after a LOT more work than the bike was supposed to need, I came to the conclusion that that supposedly 'good' engine wasn't much cop either!
Just before Christmas we put the unpainted bodywork back on the bike, for Donna to use to get to and from on, and to give us a chance to 'de niggle' it. There have been many niggles. Mostly trying to get it to run well, and an awful lot of attention has been paid to the carburettors. Anyway, after just two journeys to Leicester, amounting to some 40 miles, both of which returned on the back of the car..... I had another short test ride, and concluded I was going to HAVE to look more closely into the engine.
Good points were it ran, and the gearbox was sweet enough, and the clutch nice, so all boded well for the 'bottom end'. But clouds of smoke, getting worse, from the exhaust, REALLY suggested that a top end rebuild was in order. Not 'messing about', with just two weeks of MOT left, and wanting to get it 'sorted' before that ran out, I ordered a brand new barrel and piston kit off e-bay.
I could have waited until I had the engine apart, and inspected everything, then maybe had the cylinders rebored and fitted new over sized pistons. But its as broad as its long really, and a barrel and piston kit is just as economical, and I figured a pretty good bet it would be needed. When I actually got in there, well? Main problems seemed to be that the piston rings were 'shot' and the valve stem seals were hard as mouldy cheese, and the valve seats were rather 'cruddy'. I could have 'got away' with just new piston rings, and new valve guides, but that would only have taken half the wear away. Actual cylinder wasn't TOO bad... but wasn't brilliant either.
So, getting on with the job. First thing, engine BACK out the frame! AGAIN. Then down to business.
The step-by step process is detailed in HOW To: (Honda CB/CD/CM 125/200 'Benley' Series Engine) Top end Rebuild, so I wont repeat it here, but provide the high-lights!
On the Bench, Rocker cover removed and getting the rockers off.
Removing the cam chain is err... fiddly! But then the cam can be withdrawn from the sprocket and head, and the head and barrel stripped off.
The head was stripped, and the valve guides checked, then the valves 'lapped'. A damn tedious little job, made tortuous by the diddy little valves that are smaller than the lapping stick's 'sucker'! But once done, can be re-assembled with new valve stem seals, ready to go back on.
Another annoyingly dexterous job is fitting the new piston rings to the new pistons, and remembering to fit the inner circlips before putting them on the con-rods!
THEN, as it says in the book, re-assembly is simply the reverse of removal! YEAH! RIGHT! To time in the cam, you have to fiddle that ruddy cam-chain on and off and on and off a half a dozen or more times! It is NOT FUN!
But eventually it comes together! And it was back in and running within two days! Which I thought was pretty good going!
And I hoped NEVER to have to do it again..... only fate loves a laugh!
NEXT: Part 10 - The Corpral's Stripes