Honda NS125

Previously the carburettor had been removed and taken for cleaning by club mechanic Phil Howells.  It had now been cleaned and returned.  Dylan, and the two Graham’s worked on the bike. The first issue we faced was re-installing the throttle on the end of the cable.  The throttle cable fits in a small slotted hole in the throttle slide.  The spring that closes the throttle surrounds the cable and the bottom end of the spring seats on a flat metal plate.  The principle purpose of the plate is to prevent the throttle needle from rising up.  Initially I managed to thread the throttle cable through the wrong hole in the plate.  However this quickly became apparent and ten to fifteen minutes of patient cable waggling saw the throttle slide attached to the cable.  Dylan then worked patiently to fit the carburettor into the openings of the engine and engine air-filter hoses both of which had hardened a little and shrunken over time.  Now it was time to connect the temporary fuel bottle containing some petroil.  Turning on the fuel tap resulted in fuel spilling from two little spigots on the sides of the carb, that I assume are meant to have oil feed pipes connected to them.  In steps Graham (the other Graham) with the end of a screwdriver to tap the carburettor float bowl with.  Destiny shone on Graham and a few judicious taps later and the carburettor had stopped overflowing.   The bike’s battery had long since failed, so we took a chance and kicked it over relying on the ignition system to work without the aid of a battery.  Fortunately it did and without too many kicks it fired up in a cloud of acrid blue two stroke smoke.  Now it was time to take the bike outside and run it some more, before the hall filled totally with the blue haze.  Once outside, just a couple  of kicks were needed and it started and ran surprisingly well even managing something akin to a tickover. The engine sounds fine with no big end or main bearing rumble and no audible piston slap.  Of course it was only run for a short while, so a longer run if needed before we can be completely happy that all is OK inside the engine. I am dubious as to whether it will run cleanly under load as the throttle needle clip is missing and has been replaced by a lump of solder.  I have not seen this bodge before.  The problem is that lump of solder is much wider than the missing clip it has replaced. This in turn will lift the needle to a position equivalent to its highest position .  With the needle lifted like this it will allow more fuel out of the main/needle jets for any given throttle opening, thus making the mixture rich and probably giving rise to lumpy running.  As the bike was running outside fuel began to emerge from the overflow pipe on the bottom of the float bowl, so the carburettor will have to come off again.  It might just be a case of float height adjustment, a little dirt having found its way back under the float valve or  wear on the tip of the float valve.  More on that after our next workshop session.   

So things that this bike needs:-  A new throttle needle valve and clip; A new battery; a new choke cable; a new throttle and a new rear tyre if not both tyres.  The rear tyre is a fairly heavily worn but most importantly has significant cracks in the tread as a result of its age.