Black Widow - engine overhaul

There were some weird, wunderful and especially worrying sounds coming from the engine for some time. I chose to ignore them.
I wanted to go on a little trip to Denmark. I did not have time to open the engine, and have the crank done before, (yes - I was pretty sure something was wrong with the connecting rods) so I decided to just risk it anyway, and take it easy. The sidecar outfit got me there ... and back ... a trip of about 3500 km.
Two weeks later was a rallye of the Dutch yamaha 650 twin klub, and I decided to risk that too. Another 700 km. Well - you guessed it ... it got me there and back.
By now the engine was sounding like someone rolling a metal dustbin full of metal balls down the driveway. To get it started when cold I needed to pour a little bit of oil through the plugholes to get a decent compression.
I actually measured it ...

throttle closed: L 2.5 bar R 2.5 bar
throttle open : L 7.5 bar R 6.5 bar
After adding a drop of oil through the plughole - to help the piston rings seal like they should ...
throttle closed: L 7.5 bar R 5.5 bar
throttle open: L 9.0 bar R 8.5 bar

Conclussion - when the compression is that bad it will hardly start when it is cold. Piston rings are probably suffering from metal fatigue from overheating, or the cylinder bore has grooves in it.

Anyway ... time for an overhaul! You will not believe what I have come across so far in this engine! I am amazed it did not fall apart!

Making a mess of the garage, which I try to keep tidy. Getting the engine out went fairly quick - a personal record for me. One and a half hour later I had the engine out - sitting next to the bike. I did however wait til the next day to get some help from my neighbour to lift it and put it in the engine stand I have. I used to do this alone. Getting older means more back aches, and more common sense to avoid back aches!

Opening the engine was a bit of a rush job ... I wanted to go to Holland to the Rotterdam meeting of the Dutch Yamaha 650 klub and take the engine to a specialist who is nearby, saving me a long and boring trip. It did however mean I had to take the car, but then ... the sidecar doesn't look like it is going anywhere.

So off comes the head, cylinder, and side cases ...

To my amazement the left hand big end had like 2 mm of play! I guess we can safely assume that was the source of some of the noise!
Later I got the bad news the crank pin where the big end bearing is, is no longer for sale from Yamaha! This will be a real problem! No worries yet though, I have a couple of sources where I might find one.

But that's not all ... it gets worse ...

Look at this picture and try and spot what is wrong.

Yes ... that ball bearing should have a cage keeping the balls evenly spaced. I found some metal junk on the magnetic plugs ... not for the first time I might add ... but first time in an engine of my own.

Small end on the right hand showed scuff marks too - so that is gonna be scrapped as well.

And to my amazement, the crank was totally out of line, the right hand, which is supported by the ball bearing, was like 2 mm out of line. Probably a broken ball bearing makes it go out of line, or the other way around, it going out of line puts so much force on the ball bearing that it has to break like this.

Here you can see what happens too if the ball bearing is broken. The crank has side play - and the crank start scuffing the engine case.

I have not checked the primary gears yet - but expect problems there too!

Where the bearings of the gearbox are in the case, light scuffing can be seen. Nothing drastic, but I am gonna try and avoid it. I'm thinking of using a little bit of bearing loctite on those spots.

Now you realise why the crank bearings have those little pins making sure they cannot rotate in the cases.

The engine cases are corroded, and here you can see the carbs leaking gas left it's marks. Not much I can do about it.

I played with the idea of sandblasting the cases. Luckely I talked this through with a specialist.
1. Never ever sandblast an engine in parts. The sand gets everywhere, including the oil ways. You can rinse and degrease all you want, it will find it's way into the engine when you put it back together. And it can potentially ruin a fresh overhauled engine! The tip I got - when the engine is ready, plug the holes (exhaust, intake and breather) and have it blasted as a whole.
2. The quality of aluminum Yamaha used contains a lot of Zinc. It corrodes very easely and turns white. Unless you can paint it, this will not stay nice for very long.

Yeah - difficult to see in this pic - but something was very wrong with the 5th gear of the gearbox.
I had a hell of a time trying to get a decent close-up and found this is way beyond the digital camera I got. 1.3 megapixel witout optical zoom of any kind.

This is what would be acceptable. Unfortunately it is from the side that is in use when you use the engine brake.

This is in fact an accident waiting to happen. The teeth of the gear would have broken off under stress.
The cause? I think the metal pieces from the broken ball bearing of the crank got between the teeth and were grinded to a pulp ... which explains why I did not find a lot of it in the engine casings. Weird enough the other gear was not damaged nearly as bad as this. It was in fact still 'usable' I would say. I did change both though - just to be sure!

Before I get questions on how I managed to make the pics ...
I used the dv cam - nearly on maximum zoom ... and used a 300 Watt and a 650 Watt video lamp pointing at the white ceiling. I used dv capturing soft to show the image on the screen - and used a small screen capture tool to make it into jpeg's.
Yes - a lot of work - but well worth it ... and I think about the only way to get the detail necessary for this kind of shot.

Here is how to check the interference fit - or side play of the gears, and that they can't lock up. The special bearing with the little thingie in the cases hold them in place. Making a small bush so the gear shaft is held to the side, like if the clutch and sprocket were on it.

I found a lot of side play. And also a lot of play on the big gear of the first gear. (left under in the picture) I'll see to make a new bronze bushing for that, as it can't be ordered seperately from Yamaha.

Yamaha only has one thickness of spacer, 1 mm. I'm gonna see if I can get some grinded down to smaller thickness, so I can minimize side play of the gears.