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.

A problem sorted

I have been having a lot of trouble getting the brake rotors to line up with the callipers. I had a chat with the chaps at Motorworks about fork yokes. Click HERE for their website. They suggested I took some pictures and email to them. Well....I got the camera out and went into the garage. I had a hard look at the forks to try and work out where the problem is. I have done this several times before. The difference is that this times the penny dropped. 

I am ashamed to reveal I had put the forks on back to front. The fix was easy enough to do. Seat off, Tanks off, front wheel out, mudguard off, callipers off, handle bars off and finally the forks. The big fork end bolts had to come off then I undid the bottom yoke pinch bolts. I knocked a wedge in the pinch bolt slot which opened the yokes to make removing the stanchions. I swapped the stanchions over and started to reassemble the front of the bike. Whilst I had the fork leg top out  I took the opportunity to fit the auxiliary instrument pods brackets which fit on the top of the top yoke and held in place by the top yoke bolt. I put the handle bars back on which was a bit fiddly. Then I jacked the stand up to put the mud guard at a easy working height. Then the bike was jacked up to the top level to fit the wheel. The wheel went on but the brake rotors still did line up correctly. It was not out by much. Whilst have a chin scratch I saw that I had left in the spacers between the rotor  and the wheel body. I took off the discs and removed the spacers. Then a few minutes later the discs were bolted back in place. It was no surprise that the wheel slipped into place between the fork legs and neatly into the callipers. The wheel spindle was fitted and the pinch bolt nipped up. It took a few minutes the adjust the eccentric cams within the callipers. The wheels and brakes now spin freely. I finished off by topping up the battery electrolyte, refitting the tank and the seat. 

That is the last of the mechanical jobs. I have an electrical problem to fix. Then just a small job to fit a instrument pod but I am not which pod is to house.

Oil leak

I had to move the bike today. I started the bike up by putting the choke full on, turn the petrol taps on and hit the starter button. The engine turned over many times before it reluctantly chugged into life, one cylinder at a time. Once running it chugged along. The carbs are badly in need of balancing and when they are in balance it should run much more smoothly. I have bought a strobe timing light and need to use it on the bike to tweak the ignition. That too will make the bike run smoother.

Oil started dribbling onto the floor from the bike as it warmed up. I had a look. It was easy to spot the leak. The gasket on the oil filter cover is leaking. I will have to let the engine cool down before I start that job.

Side Panels

I picked up the final few bits and pieces that matter. I have a new favorite supplier, SAS in Shepshed. Click HERE for website. I had to file out the middle of the copper washer for the sump plug because I could not get the exact one. Given the alternative of waiting until late next week it was worth a bit of Dremell action. With the washer filed out to the exact size and sump plug refitted, I topped up the engine oil and then gave the sump plug an extra tweak. I was pleased to find it was not leaking.

Next up was to fill each suspension leg with the right amount of oil. Many years ago I picked up a 60mm syringe. It is just the job for measuring out the oil and for squirting the oil into the tiny filler hole on the top of the suspension leg. 230mm in each leg later, filler caps replaced and top covers tapped on, that job was done too. I had to cut cable ties that held the wires from each switch cluster in order to get access to the top of the suspension legs. It was a small job to refit the cable ties once the oil top up was completed.

I had bought an auxillary power socket some time ago. I decided today was the day to fit it. It went on well enough but it was a fiddle to route and connect the wires. I had to find a longer bolt for the battery terminal to accept the additional connectors. That job done I replaced the tool tray. The wires made the tray fit a little more snug.

The next job was to fit the clutch side hand grip. I wound a couple of turns of insulating tape round the handle bar and forced the grip on. It went on nice and tight but I can see it being a bugger to get off when I decide to connect the heater elements.

After that it was a nuts and bolts check. I moved the Landy so I could get the bike out of the garage. With the bike on the drive, choke lever engaged, I thumbed the starter button the engine turned over but it would not fire. I bit of coaxing and it did fire but just on the one cylinder. I bit of thought then a removed the float bowl from the none firing cylinder to find it was dry...no petrol. I was quite chuffed as I thought the engine sounded short of gas rather than short of spark. I flipped the floats a couple of time which made the petrol flow. I quickly replaced the float bowl since petrol was p*ssing out all over the drive. I thumbed the starter button again and this time she fired. The BM ran strongly if lumpy. The carbs definitely need balancing.

I pulled the clutch lever in and tried to engage a gear but nothing happened. I engaged a gear and dropped the clutch but the back wheel did not turn. I ran up the gear box and down again without success. I imagine all kinds of issues, incorrect clutch installation, iffy gearbox. I put those thoughts to the back of my mind and got a couple of spanners to adjust the free play on the clutch actuator rod. That did the trick. With the engine now idling off the choke I took a chance, dropped the bike off the stand. hooked first gear, revs and clutch out. As with all BM's off this vintage the torque lifted the bike and we were off. Just to the top of the street and back. A result. A couple of issue became apparent but the key thing is the bike runs, suspension and brakes work, and the bike feels quite balanced i.e. the wheels are in line. As it has been raining today and I spilled some petrol. The drive is covered with rainbow patches of petrol. It is still raining so the patches will wash off.

After my tentative trip to the top of the street I adjusted the back brake then left the bike to idle on the drive. The bike was up to temperature. The bike idled evenly over the twenty minutes it stood there. A checked over the bike afterwards to find, more accurately not to find any leaks. I gave the sump plug an eighth of a turn to stop the last little bit of an oil drip.

Asa final act I got the side panel down and fitted each one. The near side panel required my to remove the hand grip from the frame. . It was th work of a moment. With the tricky panel sorted I fitted the off-side panel too and hooked the rubber band between them. Job done th e bike was put back on the stand and a final job list created.

Getting there

I sent for a new set of brake front pads from Motorworks. I was convinced I had the wrong pads as the front brake was binding on the disc and they were dragging the pads from there seating. The new pads were exactly the same as the ones on the bike. So that means the problem is else where. I re-read the manual. I figured it might be the adjustment of the caliper via the eccentric cam. Once the wheel was re-fitted I adjusted the calipers. That seemed to do the job. Unfortunately the bike is the wrong way round on the stand.

With the bike turned round I tackled the gear box and sump plug. I dropped the oil from the engine. The new oil pressure switch stopped part of the oil leak but the sump plug was still dripping. I took the sump plug out but that means you lose the oil too. The crush washer was not doing its job. I did not a washer to fit so I could not refilled the engine. Next up was the gear box oil. I took the drain plug out. There was no oil in the gearbox but the plug, which is magnetic, was covered in gunge. I cleaned the plug , as luck would have it, I had a crush washer in stock which I fitted when the plug was replaced. To top the oil up I had to remove the foot peg. That done I measured out the oil, 800cc of SAE 90's and squeezed it into the plug hole. When the oil level is right it dribbles out of the filler plug hole. It dribbled therefore it was full. I replaced the filler plug then the foot peg which just happens to have the gear selector attached.

I got the manual out to make a note of the oil volume for the engine. I need 2 3/4 litres of SAE 10/40's and the note the volume of the fork oil which is 280cc per leg of SAE 5's. Now I just have to go and buy the oil.

A quickie

Having sorted out the items on the near side of the bike I had to turn it around again. It was really heavy again. Only when I got the bike back on the stand did I find out that the rear tyre was flat. I pumped it up to 35 psi. I will check it again in a few days to see if it held pressure.

I had a quick look at the bevel box. I cleaned and refitted the drain plug. I knew I had SAE90 oil in the cupboard. I checked the amount of oil in the carton. It was exactly the amount that is required by the bevel box. I filled the bevel box and fitted the filler plug.

Whilst had a minute I tightened up the bolts for the off side horn. I also cable tied the sleeved cables up to the clutch switch block.

Break Through Day

The first job of the day was to turn the bike round on the stand. The bike is heavier than I remember. It might be because the front brakes are binding.

Today was another break through day. I managed to fit the side stand spring. First time round I used a cable tie and a lever. The cable tie snapped. Next I used two cable ties and a lever. I just managed to to get the spring over the toggle on the side stand. Job done and it works properly. It only took three years to sort it out.


I had decided that the issue with the rear indicators and stop/tail lights was a wiring loom. After more than an hour of deliberation I discovered the fault. It was a issue dodgy earth. Fixing the fault was straight forward if fiddly. I also had to dismantle the rear light /indicator cluster, I cleaned it and carefully reassembled the cluster whist testing each step. Finally it was together and working. I then had to reassemble the loom and refit the relays, organise the wiring in the headlight shell and then refit the head light cluster. At each stage I tested the lights to ensure they worked. I an glad to say they did.

I fitted the near side horn and secured the wiring. It looks neat and the horns work....very loudly. With the horns fitted I then fitted the petrol tank. It was a bit of a fiddle. I hooked up the fuel lines. It is ready for fuel. Some of which I have in a Jerry can in Degsy. I cut a piece of insulating tape to length and stuck it to the rear sub frame to protect it from the seat hinge whilst fitting of the seat. I then fitted the seat. The seat needs a little work but money does not allow for such extravagances.

I discovered a new vendor from a magazine. They are SAS which have a branch in Shepshed. Click HERE from web site. I went along and found a deep 22mm socket which would allowed me to remove and replace the oil pressure switch. I did indeed replace the oil switch. The switch worked fine it allowed oil to pour out through the insulator even under static conditions. I hope the new one, now fitted, does a better job.

Unless I can get a set of instrument pods I will have to remove the Voltmeter and Clock. As it is they are dangling off the headlight shell.