Satruday November 15th 2025

 Yamaha Virago 535 - Our new project.

First pictures of our new project (Supplied by its owner)

Only 8546 miles if the speedo can be believed.

First pictures of our new project (Supplied by its owner)

Extreme corrosion in some places - but we can deal with it!

Jo and Graham collected our latest project from the village of Garnant roughly 22 miles east of Carmarthen on the southern edge of the Black Mountains.  The lady that kindly donated it to us had last used it during Covid and it had stood idle outside the house ever since then. The log book indicated that when she bought it, it had had 7 previous keepers.  The speedo indicated that it had covered just over eight and half thousand miles. The ravages of the Welsh weather had done their damndest to ruin what was an attractive motorcycle and lots of work would be needed to bring it back to anywhere near its former glory.   In the workshop a battery was connected up and attempts were made to start the bike.  After a while it started to make encouraging noises but it wouldn’t start.  The twin carburettors were eagerly removed and stripped.  They seemed clean enough inside.  They are quite unusual because they are ‘downdraft’ carbs where the throttle bores are vertical with the float bowls attached to the side of the carb instead of the common horizontal throttle bore with the float bowl underneath.   It very quickly became apparent that one key component was entirely missing from one of the carburettors - the needle valve. The rising and falling of the carb’s float opens and closes the needle valve keeping the fuel level in the float bowl roughly constant. Had any fuel reached the carburettor that was missing its needle, the level would simply have carried on rising till it overflowed, flooding that cylinder and leaking from the carb’s overflow onto the floor beneath.  Think about a toilet cistern with a missing ballcock valve. 

A good (if slightly dull) explanation of how the floats/needle valve control fuel level and hence fuel flow can be found in https://youtu.be/PBpdbIhmzZA?si=SwFz0MpLhb8iIEc-

The video shows a downdraught carburettor.  In the carb shown it has a fixed venturi and uses a fuel pump to pump fuel into the venturi when sudden openings of the throttle cause the vacuum to drop. Carburettors like those fitted to the Virago and lot of other motorcycles, are what they call constant velocity carbs. (CV Carbs).  In CV carbs the vacuum from the intake is applied above a diaphragm that lifts a slide up against a spring. The slide rises in proportion to the amount of vacuum being applied above it.  When the throttle is suddenly opened wide the vacuum falls until the engine speed increases.  This means the slide does not rise immediately and the velocity of the air flow under it remains constant, hence the name ‘Constant Velocity Carburettor.’   

Some of the rubber bungs in the carbs designed to plug galleries containing various jets had shrunk a little over time and would benefit from replacement as would the float bowl seals. 

The ravages of the weather had stripped the paint from the swinging arm which was now heavily corroded and in need of TLC if not replacement.  The exhaust collector box was also in a sorry state and probably in need of replacement. The chrome plated wheel rims and their spokes had begun to corrode and time would also have to be spent polishing the heavily corroded aluminium engine cases.  The paintwork on the fuel tank and sidepanels wasn’t in bad a state but would attention as well. It was just the sort of project we loved.

Members’ bikes…

Kawasaki ER6…

Some time ago Chris had submitted a request for help form to get help servicing his ER6. Prior to bringing it in Chris had spent a lot of time over several weeks helping to remove and replace and remove and replace and remove and replace the CBR1000F carburettors.  He had also helped with their strip down and overhaul. Chris bought all the parts and consumables he needed with him ready for the service. Club mechanic Phil oversaw the service work that included such things as an oil and filter change, spark plug change and air filter change to name but a few of the many things done. A little more needed doing by the end of the session so the bike stayed with us for another week. Graham was curious to find that there were no HT leads and coils fitted to the bike.  Instead a pair of small wires went to the top of each plug cap.  Club mechanic Phil informed him that in modern engines the coil is built into the plug cap to increase reliability. Well live and learn!

Suzuki DR125 (Engine only)

Guy had submitted a Request For Help with his engine because he had recently found some worrying metal swarf clinging to the gauze filter that sits at the bottom of the engine. During the session Guy worked with Phil R.  They removed the cylinder head and cylinder barrel gaining access to the piston.  He also bought with him a spare cylinder barrel that had come with the bike. The spare barrel gave a major clue on where the swarf had come from, with a large chunk missing out of the bottom of the barrel.  The swarf was no doubt a mix of cylinder barrel and piston.  The piston fitted to the engine had done a few miles but looked sound enough.  However the two uppermost piston rings were sticking in their grooves.  Graham assisted in the process of removing them with the aid of a feeler gauge blade to ease them out and over the piston ring ‘lands’.  These are the bits of piston between the piston ring grooves. Care is always needed when prying stuck rings out of their grooves as they are generally brittle when twisted. Having cleaned the piston rings and their grooves all the piston rings including the three piece oil control ring were reinstalled and the cylinder refitted. The crankshaft rotated smoothly and couldn’t be shaken up and down, so the main bearings seemed ok.  Likewise the big end bearing didn’t have excessive side to side play and couldn’t be shaken up and down, so was almost certainly in good order. Graham suggested it would be worth checking that the inlet and exhaust valves did not leak, so guy poured some fluid into the upturned combustion chamber and waited.  Quite quickly the fluid could be seen running out of the exhaust port.  A valve spring compressor was located and the valve springs carefully removed once the valve spring collets had been pried out. The valve seat was a little pitted so Guy ‘ lapped it in’ using a valve lapping tool and some grinding paste, being careful not to make the valve seat too wide. Making the valve seat wider than the manufacturer’s specification, could reduce the pressure per square inch on the valve seat to the point where it wouldn’t be gas tight.  When the time came to put the cylinder head back on, another obstacle presented itself.  As the piston reached top dead centre it could be heard to hit the cylinder head. The cylinder head was quickly taken off again.  Luckily it was only secured by 6 nuts.   The head gasket that had been fitted to the engine, seemed to be two separate metal gaskets.  Because only one them had been reinstalled the head was now too close to the piston. Luckily, guy had a gasket set to hand.  It contained a new head gasket.  It was thicker than those fitted to the engine. Once installed the engine turned over silently and was almost ready to go back in the bike. 

In other workshop news…

Dave W completed the third and final set of racking.  All that needed to be now was to secure the three sets of shelving together and somehow secure to the wall behind them.

Gareth worked on designs for various vinyl stickers, these included the beginnings of a design for the vinyl version of the club logo and a variety of coloured dots that would later be used to colour code the tool box and the tools that go within them so they wouldn’t keep getting put back in the wrong places. 

Graham bought in the club’s new heavy duty motorcycle ramp to make it easier to get bikes in and out of vans and also on and off the mobile museum.