June 2021 and I have been mulling over doing another special, rather than a Restoration, which I did last time with an early Monster 900 . I have been riding around the last project I built, the Multistrada with the FCR carbs on it, which goes really well! My favourite bike to ride! One of the problems with it though is the single seat, my wife likes to come out on pillion sometimes… So I decided to build a scrambler/flat track/adventure type bike, with a dual seat on. I looked around for another 1000 DS Multistrada and this red one turned up at the right price. These are cheap to buy as many are suffering leaking and bubbling tanks, and faded LCD screens. I am still formulating ideas at the moment, but I have made a bit of a start so I have stripped it of all the parts I wont use so I can sell these on. but below is a rough mock up with a borrowed seat. Also a picture of the last 4 specials I have built over the last few years. This will be a slow build as I want to enjoy the summer!
Sometimes I just sit for a while and look at the silhouette of a build in the garage with the lights out… I did this the other night (my wife thinks I am mad!) and I kept coming to the conclusion that the tank is not what I want… So off to the bike breaker who lets me wonder around his BIG unit. I took a cardboard cut out of the shape I wanted with me, and some measurements… of the hundreds of tanks I looked at (surprising how many are now plastic!) , none were suitable, mainly due to the angle of the frame. On the last build I used a 999 tank which worked well, so I decided to try a shortened version on this build. I didn’t feel bad cutting this up as its so badly corroded, and it just goes to show what leaving a bike for a long period with ethanol based fuel in it does inside the tank. you can see from the light I am holding behind it that its actually perforated on the top! So its off to the blasters with it to see what state its in when it comes back…. I have a fall back, but its a perfect 999 tank, be a shame to cut it up... If the one comes back from the blasters and its too bad, I will probably use it to mock up, and see if I can find a dented one. My FCR 41's came this morning
well the tank came back from the blasters… as you can see its full of pin holes, and for the first time in over 40 years of repairing tanks I feel I have been beaten! there is no point in trying to repair this! I put a light inside to shop the extent of the corrosion. look after your tanks guys!
Started the frame modifications, just tacked up at the moment. On this build I want to keep the seat height right for me, but also allow for an under seat exhaust and a seat long enough for a pillion. I have replaced the shocker with a strut at the moment so I can see what things look like at max and min travel.
on my last build I run a pair of FCR carbs, it runs really well so for this build I chose the same carbs, but this time decided to bolt them together, and use a common split spindle to control the slides. this means I can use a single pull/ pull throttle arrangement, instead of the 4 cables system I used before. It also means I can run a TPS on the end of the spindle. I thought it would be easy, I got some 8mm silver steel for the spindle, and a couple of new bearings with seals instead of the closed cup bearings… unfortunately the threads on the locating pins into the spindle is an unusual thread and I couldn’t find a tap… so I had to make some new pins as well… All done now though, including a linkage in the middle so I can balance the carbs . I have also made some new velocity stacks to accommodate some foam filters… there is a few hours work in those! and a pile of swarf! Short video to demonstrate how I hand turn the bellmouth on the stacks!
To mount the carbs I needed to make some alloy custom manifolds. I made these using the pie /lobster cut method. I set the chop saw to 7 degrees and cut off a selection of pieces and tape them together until I have the right shape… I then mark the position of each and weld them together, ensuring I have good penetration, which I then grind off inside to make them smooth. the long bur in the picture is a beast to use! Onto the tank. I managed to source a very clean 999 tank, but of course this is too long for the build… so out came the angle grinder and off came the back! measure twice cut once!. I then fabricated a new back end and welded it into place. When welding stuff like this, everything needs to be clean for a good half inch either side of the weld, so I clean both sides with emery paper, and use to carb cleaner to ensure there is no grease… also wipe the welding rod with some as well… Once the back/side piece was in place I planished the sides so the new piece had the same radius as the tank. then I welded the bottom in. to test for leaks I use two methods… some dye penetrant and developer, and if it passes this test, I do a final check with air at just 3 PSI and squirt it with soapy water.
One of the most difficult things I find to make on a bike is the seat… this one i have used a different approach as (a) its a dual seat and (b) I am making the base out of aluminium. I mocked up what I wanted in cardboard first, and then transferred the patterns onto some 3mm aluminium. Then I seam welded it… It came out ok, be interesting to see what its like once its to the final shape and the foam and cover is on!
Next job will be the exhaust system but to do this I needed a silencer to get the mock up right… I wanted a small slim silencer, that was re-packable, and that I could fit a baffle come MOT time… and a bit retro/old school. I searched but couldn’t find any suitable, they were all too wide as I want an under seat, side mounted setup. so I modified a cheap (£16!) stainless steel one off eBay. I would have loved to have made one from scratch but don’t have a cone roller, and to buy a ready made stainless cone is expensive. the hardest part of making this was actually drilling three holes for the bolts to hold the end cone in. the stainless is incredibly hard! after blunting 3 new drills, and buying a cobalt drill and that not touching it, I ended up making a punch and die and punching the holes!
Thanks DucatiScud... I do have a few TCT drill bits but they chip so easily especially on thin stuff... I hate working with stainless! With the silencer finished I mounted it on the frame. I decided to make it rubber mounted to keep the vibrations down a bit. The collector was challenging… first one I made I was not happy with, so the second one I welded it on the inside with the TIG, which came out well and should flow OK. Stuck for a few days now as I need a couple of mandrel bends to finish it off.
That’s looks great, I just couldn’t master welding when I did it as part of my mechanics training sadly. I just wish that KTM had released the road going 790 with an under seat exhaust as the prototype was shown. The nearest I like of exhausts is the double from LeoVince pictured below.
the speedo/ rev counter I am going to use has a plastic case... which does not look good. I tried to get some tube the right diameter but it was too big or too small, so I cut 12mm out of some bigger stuff and seam welded it back up, using a piston ring clamp to pull it together to weld it. I knew it wouldn't look right with a flat bottom so I made a conical one by spinning it in the lathe. The alloy needs to be soft for this so I annealed it by heating it up to temperature, and letting it cool. A neat trick to know when its the right temperature is to use a Sharpie pen, and when its burn off and has disappeared, its the right temperature! a bearing on the end of a bar makes it easy! here is a short video...
The seat base is finished, added the rivinuts to hold it on, and made a bracket so it only bolts on at the rear so it comes off easily. The last build is a pain to remove the seat. just need to add the foam and sand it to shape. I am happy with the mock-up but cant decide if the front mudguard needs to go central or biased to the front, but that can wait a while. the exhaust is all but finished apart from polishing and adding the hoops for the springs.
many (many!) years ago I modified the frame on a Bultaco for a race seat. I put a complete back end on, much like what I have done here. I made very careful measurements using various fixings as datums, and welded it all up. soon as it was finished, and the seat on, it was evident that it didn’t sit straight on the bike. I was gutted as I had painted the frame. No one else noticed, but it bugged the hell out of me for years! I learned from this, these days, here is how I do it… I get the bike dead upright to a spirit level on the wheel, and then make sure the seat is level. seems to work! I have also made a new purchase... an auto darkening welding mask... why the hell I didn't buy one years ago I just don't know! its so much easier!
Thanks! With the new seat the rear foot pegs were too far back, and uncomfortable for her legs, so important to get this right! I have made some new hangers out of 10 and 12mm steel tube. I made a jig first so all the angles and bolt holes were correct, and it wouldn't move as I brazed it. this is my first time TIG brazing and I was worried about strength, so I did a test piece first and tried to break the joint... the parent metal broke before the joint so all is well there!
been taking a few days off and getting about a bit on the bike and in the car. I have to say Covid and the restrictions to normal life have got to me a bit! I got my parts back from the water jet cutter, another superb job! while I was there he was cutting through a 150mm block of exotic alloy, its fantastic how it just cuts through such thick metal. I designed the number plate bracket, the headlight brackets, and the number plate backing on CAD and sent it to him… a few days later I picked this up. I could have cut it by hand but this is so easy. I was going to sell the number plate, but I have decided to keep it… L90 fits the engine configuration! below is a short video of him cutting the plates
Strip down begins… the bike is now all in pieces and the frame and wheels are at the powder coaters. The engine is all in pieces as well ready to have the cases vapour blasted. Engine wise its all good apart from the exhaust valve guides which is a common problem on these engines… I need to replace the guides. Its easy to check if they are worn, here is a little video to show how to check them… the valve needs to “just” off its seat. Here is a puller I made to remove the gearbox bearings. I know you can buy blind bearing pullers (I have a set) but for the gearbox bearings on the Ducati engine they don’t work well as there is no inner race to pull on, and you end up pulling the rollers out and breaking the plastic cage! They are also expensive bearings to replace at £60 each…. This puller expands fully into the rollers as the bolt rides up the internal taper. Also a primary gear puller I made a few years ago, along with the dimensions for that. I know you can buy them also (£150… where is the fun in that) but this cost me £20 for the laser cutter to knock me out 5 sets! Happy to share the CAD drawing… checking for guide wear...
