ALLEN MILLYARD
With all the lockdown nonsense, it’s time for Allen to get on with the motor build of his splendid Kawasaki Super Six.
Allen is back on with his six-cylinder Kawasaki.
With the current lockdown relaxed a bit it was really nice to be able to go out for a ride on a few of my bikes, especially my Z1 Super Six. I started by riding it on short trips local to home. I always put the engine through many heat cycles from cold to hot to help the welded cases and other parts normalise and settle down as part of commissioning the bike.
After about 100 miles I removed the tank and tightened the cylinder head nuts, which is an easy job on the Z1 engine because they are all accessible with the cam-cover in place. While the tank was off I checked the throttle linkage on the carbs to see if anything had come loose. There was a slight lumpiness on light throttle openings and a bit of popping in the exhaust at idle; it felt like one cylinder was missing or not running at all. When the throttle was opened past a quarter of a turn it seemed to chime in and run smoothly. The throttle linkage was fine so maybe it could be a blocked pilot jet on one cylinder. I checked the header pipe temperatures with my optical thermometer and header three was much cooler, then the other five. It is possible to remove the float bowls from the carbs while the carbs are mounted on the bike, so I removed number three. It was full of petrol so there was not a flow issue. I then removed the pilot jet and looked up through it at a light and it was definitely blocked. A quick blast with my air-line removed the obstruction.
I had recently bought some clock cleaning acid for cleaning brass clock parts so I made up the solution as instructed on the bottle and dropped in the jet. After a few minutes it started to fizz and I could see it changing colour to a bright shine. I removed the jet, rinsed it in some clean water and dried it off with my airline. I re-fitted the jet, replaced the float bowl and tank and then fired up the engine; it was now running much nicer at
idle. The bike has now clocked up around 250 miles of short trips, including one longer trip of 96 miles, and is happy cruising at 70mph with the engine spinning at just 3500rpm in top gear with its 16-29T gearing. I’ve taken it to 5000rpm in lower gears just to hear the sound, but there is no need to wind it up because it pulls like a train in top from 20mph. On the last ride I noticed the handling wasn’t quite right and it felt odd in the corners, so I pulled over to check the bike and noticed the rear tyre had deflated a bit. Luckily I was only a mile or so from home and got home just as it went flat. The rear wheel on a Z1 can be removed easily without taking off the exhaust by first removing the two end caps on the swinging arm, then loosening the wheel spindle nut, and the wheel will slide backwards out of the bike. I removed the tube and couldn’t find any trace of a puncture so I replaced it with a new heavyduty tube and it has been fine since.
Back to the engine build. Last month I explained how I made the cams and have also been filming the process for my Youtube channel which was fun, but usually means doing things several times to cover all angles. With the camshafts finished, it’s time to build the top-end of the engine, so the first thing I did was to
give the head a good clean. I use bike general cleaner and a jet washer to blast off any swarf and grit that may be present, paying special attention to oil ways. This is a great thing to do on a hot day because you usually end up quite wet! I dry the head by warming it up in my gas BBQ to ensure all the water has evaporated, then I give it a blow over with the air-line, again including all the oil ways.
With the head clean I then cleaned and checked the valves, springs and collets ready for assembly. Before the valves could be fitted I needed to grind them into their respective seats using grinding paste and a suction stick. A smear of grinding paste is applied to the valve and then the valve is placed into the head and rotated back and forth using the suction stick between your hands while lightly pressing down.
This can be a lengthy process, but luckily my engine has good valves and seats and they cleaned up easily. I fitted a set of new valve stem seals, pressing them down firmly on to each valve guide. The valves were then inserted in each valve guide, carefully pushing them in with a drop of oil on the stem. It’s important to put the valves in carefully because the valve stem seal can easily be damaged. I then fit the valve springs and caps and, using my Dad’s old valve spring compressor, I fitted all the collets. I remember as a boy using this tool when helping him de-coke his Austin A60, which was a regular job back then but is virtually unheard of these days.
The head was then placed on to the engine, sliding it down gently engaging all the studs, which are different lengths on the Z1 engine, being careful not to pinch the central cam-chain tunnel oil seal. The head bolts were tightened and the cam-chain retrieved from the lower crankcases with an extending magnet ready to fit the cams. The cams rest on 12 split shell bearings and are clamped in place with retaining caps.
The valve timing is set up as a standard four cylinder Z1, except the two central pistons need to be positioned at bottom dead centre to use the original timing marks on the cam sprockets. I then counted 28 links from the second chain link above the head top face on the front of the exhaust camshaft sprocket to the 28T marker on the inlet camshaft sprocket. With the camshafts fitted and timed I carefully turned the engine over two revolutions, feeling for any tight spots, and was pleased it was all smooth. I checked the valve clearances with feeler gauges and most of the valves were in specification, and after swapping a few shims all clearances were good and I could fit the cam cover. I then fitted a set of spark plugs and kicked over the engine with its kick-start lever and it felt good with even compression pulses.