Aprilia RS 125/ KTM 640 LC4 Supermono

Started some of the work on the winter rebuild and wanted to test another Tacho, however now thw starter spins but doesn't engage. Suspect the Sprag clutch. Ordered flywheel puller. Got it apart and garter spring knackered so replaced it and re-assembled still the same. Took t out again and on closer inspection, the cage that holds it all together is broken due to rear on one side. The tabs on the circlip are supposed to be retained on the outer ring   but these bits have worn off so circlip is not retained. Ordered new Sprag (freewheel clutch) £70 from Fowlers. Not taking chance on Chinese Ebay jobbie.

The latest trip to Mallory on 5th November was a complete success. It went well all day and completed all 6 sessions. Had a couple of things to adjust during the day but nothing that was a problem. The front end was very good, could really push it into corners, (we had cold and wet and cold and dry). Only small slip was rear coming out of the hairpin. The back end shock was disappointing. It needs a decent shock with correct spring rate and both ways damping. I might add a ring to this one to give a bit more preload but something better is needed long term. The corner speed was really impressive, had the confidence to push round the outside of loads of riders round Gerrards. Little bit conservative as temp never got over 9 deg. Its fairly gentle on tyres and fuel.  Could be a a keeper for me, its light and nimble and changes direction so easily, I found I could be very precise in corner entry and hit an apex very cleanly. Few things to do in the winter;- May need a sprag clutch at

Well, I took it to Mallory on Friday having spent most of Thursday fettling. I made up a booster battery pack and fitted a new spark plug . I discovered that the ferrule on top of the spark plug was missing so it wasn't making good contact with the cap. that explained a few issues with starting and running. It now starts much easier. At Mallory all was good. It started well and ran well. Got through noise test at 92db with a baffle. Did the first session and it went really well, it stopped well handled ok and pulled well. However when I pulled in, a puddle of oil formed underneath which was from the rear shock. I pumped the rest out and tied some cloth round it to soak any up. I then decided to to add some fuel to the tank. I think the inside of the upper portion of the tank was coated in Dust/mould / crap I don't know what, but adding fuel loosened it all up and turned it into pond water. Since then it wouldn't run for more than half a lap before stopping. 30 seconds late

Good news, latest test run was a success. Appears to be getting full power now and runs pretty well. Have booked first track day for friday 6th oct at Mallory. Still a couple of jobs to do. Th R6 Master cylinder that i was expecting to be 16mm was 14mm. so i have now ordered a TRX850 Master cylinder. The gearbox output shaft seal is slightly weeping so have ordered the parts to do that. Currently the front sprocket is 16T and rear is 41T, the front is limited for space and i don't fancy fitting the 17T, ill run it at Mallory as is and maybe put a 38T on the back depending on that day. No repeats of the Solenoid saga so far, think the sputnik solenoid may have fixed it.

Got a short test in last week on a quiet bit of road at a secret location, It started and ran ok, but once moving it was clear that it is only running properly at part throttle. Back at base and a bit more research and it looks like i have some ports on the carb blocked or unblocked since i removed the air valve gizmo. The large port on top of diaphragm cap needs to be blanked so that vacuum from inside carb body can open the slide. I had it open. The port on right hand side of carb is actually a vent for the float chamber so needs to be open. I had it blocked. The metal pipe elbow from the top of carb body needs to be open as this vents the space below vac diaphragm to allow slide movement, i had that blocked too. Should be better now. Hope to get another test in later this week. I have ordered an R6 Master cylinder for front brake and some new EBC track pads. The Master cylinder is 16mm where the old one is 13mm i think.

Been busy again recently. Decided to try to get to the bottom of the starter solenoid problem. Stripped back the wiring loom and stripped out all the wires I don't need and most of the spare connectors. Re-bound it and fitted the biggest solenoid available, which is good for 150A continuous!. Shouldn't be a problem welding them shut now, and so far so good. T

Well I took it to Rockingham, Went lunchtime so I could have a tinker. Seemed to be running ok but had a slight coolant leak. Took tank off and fixed that.  Decided to give it a run through the tunnel and back. seemed ok but really low on power, got me through the tunnel and up the hill to the turn area then stalled about 3 times, coasted back to tunnel and eventually got it started and limped through the tunnel and back to car. Stalled just at the car and then the starter started cranking of its own accord. Got to the new master switch and turned it off. Loaded up and went home. Bit miffed. Calmed down a bit now, 1 there must be a fault somewhere in the wiring that is giving false signals to starter system. 2 The relay must be under specified to keep fusing closed like it has. Engine - either I got the cam fitted one tooth out or it has an air leak/ fuel restriction. May have to wait a while as I have other things to do that I have been putting off for a while. Keep checking

Update. Did the rebuild of the cooling system and the thermo housing can be moved 180 deg so the large outlet faces down, which gives a better hose run to the rad and gets rid of the airlock u bend. Fitted new starter relay ran the engine to check cooling and shut it down before I gassed myself in the workshop. Few seconds later it started cranking again while my back was turned. Got the battery cable off but it was too late the ni-cad battery hade a hissing sound and a nasty smell, so I think that is dead now. I have thought long and hard and am convinced I have the wiring correct. I am going to try to free off the relay and  put battery on with a crocodile clip (quick release ) and jiggle the wiring round and see if I can find the fault.

It has been running but its not circulating water. Discovered I got two hoses on wrong pump connections. Going to re do the cooling system as I got rid of the thermostat I can now ditch one of the smaller pipes. That one circulates the water through engine before stat opens. Ideally i'll turn the outlet housing 180 deg to get a better hose run and make it easier to get air out. Bigger disaster was while running it the starter kicked in, hit the kill switch which stopped it firing but it was still cranking, turned ign off but still cranking. Cranked itself flat before I could get to a battery lead. Starter solenoid must have welded itself on. Suspect cheap aftermarket solenoid, may be under specified. Ordered KTM replacement. Fortunately new Li Ion battery recovered with a charge.

Made some good progress during last week. I couldn't get the back brake to bleed. A master cylinder kit was £30+, so i bought an after market cylinder for £36. Finally got it bled. Chain arrived and thats on now, so i took it to a garden away from home to give it a bit of a run round, just on grass. It went ok, but was leaking oil like a fountain. Mostly from the breather pipe on the front rocker cover. i had about 6 inch of pipe on it but it was spraying out the top of that. There was another leak from the cover gasket and one bolt that was missing its copper washer. Another oil union was weeping too, so a bit more fettling needed. I also decided to remove the thermostat to get a better idea of the running temp as i don't want to have a fan. Gave the scabby matt black bodywork a quick tidy up. Proper bodywork is coming once i have got it all running and properly tested. Got some new grips and a used screen in the post today. I ordered the correct mesh screen that go

Had a week off but got back to it at the weekend. New Lithium battery now fitted, saving 3kg over standard and much smaller. Tidied up the wiring. Took the heat gun to the base of the tanhk and pushed in the bits that were fouling the head and carb, so that fits now. Put some fuel in and that is ok now. Gear lever linkage back on. Started fitting rear brake but couldn't get it to bleed through. Fluid leaking past master cylinder seal so thought I would get a seal kit, but for around the same price you can get a complete after market unit, so that's on order.

Next up was to be to start it up for a quick run check, but I accidentally pulled the four wires off the spade connections on the starter solenoid. After several days of fiddling and head scratching I eventually worked it out, put everything back together and Bingo, a dashboard light, then the starter kicked in. Put some fuel and in a temp dripe feed thingy, choke on hit the button and hey presto she runs. Quite well too. Here it is at present.   May need to fit a bigger fuel tank at some stage. But its a huge relief to have it running at last.

The Vcoil went in ok followed by new sump plug, oil changed and oil cooler zip tied on. Need to refill the cooler as there is a small leak at the lower union as I didn't have any new copper washers, I have some now. The cooler is best filled while on its side with the banjos uppermost.

Oh dear Another bodge uncovered. Thought I would just drain the oil last night. Main plug came out after a good whack with mallet on bar, way overtightened but intact. Smaller plug on right of pic is under gearbox, started to turn and then continued to turn. Stripped thread, tried pulling and turning but no good. Going to have to drill and tap plug and make a puller to get decent pressure on to unscrew it. Ordered vcoil kit and new plug.

I've been sorting out the oil system this week, however the oil cooler I got from Triumph tiger has 14 mm  banjo connectors and I didn't realize how difficult this made things. I ended up having to machine some adaptors to convert from M10 fine to M14 fine. Both odd size threads. Here's what I ended up with. Have yet to assemble and fit it as I need to change oil and filters as well, maybe this week.

The front end is finished now. New Disc fitted, new wheel bearings new brake hose and bled. It should stop now, all I need to do is make it go!. Cooling system is done, I used the RS125 header tank and blocked off the large outlet and machined a new smaller outlet from a M8 bolt. Next is the oil system. I have an oil cooler from Triumph tiger that is a nice size. Unfortunately it comes with M14 banjo bolts. cant find any adaptors in the M14 coarse thread to M10 fine that I need. so it looks like a bit more lathe time to make some.

The last pic of the front end is pretty much as is now, only difference is it all fits and the wheel goes round. Disc found to be 2.9mm so way below min wear, have ordered a better one, New wheel bearings were being fitted last night till I hit my thumb instead of the drift. Ouch! I'll finish that off when the bleeding stops. Had to take a bit off the caliper mounting lugs, also off the lugs on the forks. Spacers for the disc 3mm out from wheel and a couple of mm off back of caliper body. So now Caliper clears wheel spokes, Caliper is central over disc and wheel is central between forks. Made Axle out of RS/GSXR and machined new alloy collar for non disc side. New tyre fitted on a nice sunny day in the garden last weekend. Just a few new fasteners to come this week and I can bolt it up for the final time. Brake line from RS was too short so one coming soon 625mm long and that's about it, hopefully. This conversion is just about do-able but its not easy. If you are shy about

Been busy doing some engineering this week. Fitting the forks is a breeze as they fit in the rs triple clamps, however the rest is not so easy. There is an option on the forks of 4 pot or 6 pot calliper, well it would be rude not to i thought. not sure if the 4 pot would have been simpler but its not been easy. The GSXR wheel almost certainly wouldn't fit as the RS tyre doesn't have more than about 5mm clearance each side. The calliper fitted with the wheel centralised clangs on the wheel webs.  I took the calliper apart and removed a piston on the back half and measured the casting thickness at 6mm so i machined 2mm off the back of that, took a few mm off the back of the calliper mounts and likewise on the fork mounts, its nearly there, i'll get some small spacers maybe 4mm to space off the disc and we should be about there. The axle is another story. GSXR axle is 25mm RS is 20mm. You can't get bearings with 25mm id to fit in the RS wheel so it needs a s

Been busy again today rebuilt the forks. Watched you tube video from Del boys garage for doing the seals on USD forks, however when i got into it these are different design and need a puller to compress the spring in order to get at the lock nut. Made a gizmo to grip the top sleeve and used straps to compress the spring. All done but took most of the day, new seals and 7,5 weight oil.

Needed to take front wheel out and had a bit of a job. Every single fastener had either seized or broken, had to drill most bolts out. Gave up with calliper bolts as severely rounded off. Thats the trouble with RS125's every young lad has worked on them with a mulgrip tool selection. I wanted a decent front end an tis isn't it. Felt like one leg hasn't even got a spring in it. Did a fair bit of research to see what would fit. Decided the best value were GRXR, lots of them are virtually identical so will fit the triple clamps. These are GSXR 750 SRAD and were advertised on eBay as "Horrible condition, worst on Ebay" Decided to have a punt at £29.99 inc post, and they came today. They are all there and straight, nothing broken or cracked, few broken bolts but nothing i can't fix. Need new seals and dust seals, they came today too. I cleaned one of the lowers up and it looks good, the sliders are good too.

Been working on cooling system now exhaust is done. Bought TDM850 Rad which has a pressure cap thinking i wouldn't need a separate expansion tank. Now the rad is mounted as high as i can get it, the filler is not the highest point on the system so will need a small expansion tank to fill from. Ordered a RS125 one that should do the job. Fitted some hoses but need some more bends to plumb the red in neatly. Its very congested and tricky round the water pump area.

Just finished the exhaust, I used the 2-1 section from BMW F800S plus the rear section, a bit of old Ducati 749 pipe for the link pipe and the rest i fabricated from 38mm stainless Mandrel bends. I got 105 deg for the top bends and 55 deg for the bottom bends. I had to cut close to the bend for the top to get the downpipes close to the engine. In doing this i found the pipe wouldn't slip over the exhaust stubs. The diameter of the tube is reduced in the bend and a couple of inches either side. I had to weld a short section of straight pipe at the manifold end, bit fiddly getting correct angle. All fits ok, have strengthened can hanger now and will make a support underneath next. I managed to weld using a stick welder, i now have a small inverter that goes down to about 20 amps. Made these welds at 30-35 amps using 1.6mm stainless rods.

Finally after 2 weeks of waiting the bottom bends have arrived. Just spent a couple of hours fitting the first, ill do the other one tomorrow and then thats the exhaust about sorted. Ill make a slightly longer link pipe to move the can a bit further back. The other thing that arrived today is a pair of Metz M7 RR tyres from trackday tyres, they look almost new so for £100 were a bargain. Date codes show late 2014 which is ok by me.

Still waiting for pipe bends to arrive, have ordered 105 deg top sections, and 55 deg lower sections. In the meantime i have done some work on the back section. Made a can hanger and a joint for the link pipe which spaces the can a bit further back. Gives a bit more clearance from footrest. I think its just about workable. Heel is quite close to link pipe but i might have to add a heat shield.

First try Exhaust, MK 2 coming next when Mandrel bent sections arrive.