It was a relatively quiet session in the workshop but never the less some progress was made...
Honda CBR1000F...
The petrol leak from between carburettors 3 and 4 had not been quelled, so off came the carburettors once more. It still seemed most likely that the seals on the fuel feed tee-piece between the carburettors needed replacement, so Graham undid the nuts on the ends of the two long threaded rods that kept the carburettors together. This allowed carburettor 4 could be removed. The pair of seals did not look too bad but they slipped in and out of their openings very easily. The float bowls of the same pair of carburettors were also removed to inspect the rubber seal fitted between the carburettor and the float bowl. Whilst the seals were intact they seemed quite thin and it looked as though someone in the past had supplemented them with some clear sealant, so perhaps it was time for some of those new seals as well.
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| Would the seals end the fuel leak? |
Yamaha TX500...
Phil R and Dave continued their work on the engine on the bench. Once the cylinder head was temporarily sat in place the cam chain was fed round the sprockets on the two cam shafts. The arrangement of the camshafts found in the TX500 is often referred to as double overhead camshafts. It is a very common arrangement these days on four stroke motorcycle engines. Our artificially intelligent freind Copilot tells us that...
A double overhead camshaft (DOHC) is a type of engine configuration that uses two camshafts located in the cylinder head above the combustion chamber—one for controlling the intake valves and the other for the exhaust valves.
🔧 How they Work
- Each camshaft has lobes (cams) that push against the valves to open them at precise times.
- Springs return the valves to their closed position.
- This setup allows for four valves per cylinder—two for intake and two for exhaust—which improves airflow and combustion efficiency.
🚗 Benefits of DOHC Engines
- Improved performance: Better airflow means more power and higher RPM capability.
- Greater fuel efficiency: Optimized valve timing helps engines run more efficiently.
- Cleaner emissions: More precise control over combustion reduces pollutants.
- Enhanced tuning potential: Ideal for performance upgrades and variable valve timing systems.
Unfortuately the way the chain had been cut when the engine was stripped, meant the chain was now to short (As I have mentioned many times before I am sure.)
Another issue was discovered during this session. It was the fact that the shaft turning the cam that opens the ignition system's contact breaker points, wobbled around like a spoon in Jelly where it protruded through the engine's clutch cover. Removing the cover revealed that it didn't contain a bearing to keep the shaft in place. Graham scratched his head for a while and then, once the clutch cover had been pulled off, noticed two large unused bolt holes. This set him thinking that there must have been something fitted to the engine using those bolts. Flicking through the manual he eventually found just one picture giving a clue what was missing. It was an alumium outrigger containing the bearing that should be supporting the afore mentioned shaft. The hunt then began in search of the missing outrigger. It wasn't located during the session, so the search would have to continue.
At the end of the session as Graham was tidying up his gaze fell on a chain sitting on top of a green plastic lid not too far from the engine which looked strikingly similar to that which they had found to be too short. He had no idea where it came from but it looked suspiciously like another cam chain. The links were the same size, it was made by the same company. It had the extra link in place meaning it may even be long enough to fit properly. This would allow the ends of the chain to be joined using one of the joining links, the club had purchased some time ago for the engine. If it was a spare cam chain, why hadn't we seen it, it had been sat their in plain sight. Hopefully we would find out at the next session that it did indeed fit properly.
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| Cast your eyes to the chain on the green lid - was it hiding in plain sight? |
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| The two chains laid side by side for comparison, the longer one is closer to the camera. |
Honda 650 VIGOR...
The replacement rear brake disc had arrived from the Ebay vendor and fitted correctly onto the wheel of Mal's bike There then followed a bit of struggle to get the wheel spindle fitted back into the rear wheel. Independently everything slid in place as expected but when it was time to slide the spindle through the wheel, rear brake caliper mount and the swinging arm, the spindle repeatedly got so far and then refused to budge. After several attempts Jon applied a little extra encouragement with a mallet and finally the spindle slid fully home. Ultimately it had to be removed one more time to get the chain adjusters in the correct position so that the adjustment marks could be seen. The rear brake caliper hadn't as yet been removed from its carrier and was not yet moving as it should do meaning the inner brake pad was rubbing on the disc just a little too firmly. In time the caliper would have to come off the pins it was mounted on so they could be freed up and grease applied, to keep them freed up. In the mean time it was great to see the bike back on its wheels. Keiran and the team made an attempt to get the engine running but it declined to play ball on this occasion, that would have to wait for another session.
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| Mal's Honda Vigor back on two wheels. |
