Recondition carburettors

   I managed to get the bike running sometime ago however it was as lumpy as a lumpy thing. I checked the coils for sparks. Yes good sparks. Fuel flow? Yes good. It should I had cleaned the tank out, fitted inline fuel filters and use clean new fuel. If I put my hand over one of the carb inlets the engine picked up. Essentially the carbs were massively out of balance and no amount of adjustment on the few adjustment screws was going to correct the situation.I resolved the recondition the carbs. I reasoned that the carbs were 30 years old and one or both items could be corroded on the inside. Since carbs are sophisticated items and very built to fine tolerances this would likely be the reason for the lumpy running. I was hoping for the simple problem of a torn diaphragm. I priced the items. It turned out to be more cost effective to buy a refurbishment kit than buy the diaphragm only and hope that was the issue. Whilst I was about it a thought it might be nice to fit individual choke levers to the carburettor and do away with standard cable operation. More on this later.

 
I had toyed with the issue of getting an ulta-sonic bath to clean the carbs on the inside but I could not live with the cost. Of course I needed a large volume bath to contain the carburettor and they were expensive. I ordered the parts from Motoworks but not after extensive measuring and research to work out exactly which carburettors I had.

   Parts ordered and duly delivered they sat in their delivery bags for an age. I was worried that I would not be able to disassemble or reassemble the carbs. I picked up and mini set of sockets that came with screw driver bit to for the sockets. That meant I had small tools to tackle the intricate parts. I was also concerned that items to be replaced being brass might secured themselves to the Magnesium alloy of the carb body.
 


   I cleared my work bench, made sure there was plenty of light, got my mini tool kit, laid out the refurbishment components and made a brew! 

    To my great surprise and relief the screws and nuts came undone without much drama. Having the correct tools for the job helps. I remembered to take careful note which way round the moving parts worked. I removed one item at a time and worked as methodically as I am able until each component had been replaced.

  I had particular bother with the float needle. There are knack to removing it. The clip that held it in place was in a deep recess so I could not get at them. I worked out the way to twist the needle to expand the clip and slide it free. Luckily it went back in the same way. I discovered that the float needles were set to different heights. Well that is not going to help the engine run smoothly. They are now both the same setting, right or wrong they are the same. It was not surprising to find wear on any part that touched another part or any part that had been in contact with the fuel. The engine had been burning oil before it was refurbished and there was evidence of burnt oil residue of many of the parts.

   The final element of replacing the diaphragms proved to be tricky. The plastic grommet holding the diaphragm to the metal venturi slide was a very tight fit. However came away quiet easily but snapping it back in place was difficult. The shape of the lip retained the ring was such that with the extra thickness of the new diaphragm the metal lip and plastic ring worked against each other. Breaking either item would be expensive to replace. Hum what to do?

  Tea and a think. I figured if the plastic was to expand I might get the room I needed to snap the ring into place. Well how about I put the metal slide in the freezer for a while and I put the plastic ring in the bowl of boiling water. The former will shrink and the later expand. It might be enough.....and it was. The plastic ring fairly popped into place and captured the diaphragm inner edge as neatly as if it had been done in the factory.

    Next up was to fit the manual chokes. 80/7s have a choke lever

attached to the air box. Two cables run from the lever, one to each carb. The lever is always difficult to engage as the cables have a tight track to follow and get corroded. The conversion junks the cables and the lever. It was and easy job.














The new choke pulls simply slide into the vacant choke cable guide on the top of the carb: a small plastic insert fits into the guide to create resistance so the choke pull stays where it is positioned. The choke on the carb body is placed in the "on" position, the pull wire is fed through the capture bolt on the lever and the bolt done up. It is that simple.

  


The not so simple bit is that a decorative plate supplied with the kit. The plate blanks off the hole in the air box left by the missing choke lever. The blanking plate does not fit properly because the air box has been powder coated. It was either file of the powder coating on file down the shoulders of the blanking plate. Easy choice - the Dremmel made quick work of the Aluminum blanking plate. A couple of try outs and more Dremmel adjustments and the plate slipped snugly into position. A couple of turns with the Allen key and the plate was secured.      

Now to top up the battery and put it on charge.