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dan williams

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About dan williams

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    Advanced Member
  • Birthday 08/05/1958

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  • Bike
    '13 EVO, '18 fugly
  • Club
    NETA, Seacoast Trials Club, East Coast Hoppers

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  • Location
    North Reading Mass USA
  • Gender
    Male

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  1. Yup you are correct. The ignition coil is basically an autotransformer that steps that 200-300V up to tens of thousands of volts. The old point systems had primary voltages that were somewhat lower. Basically running a current through the primary side of the ignition coil and setting up a magnetic field that would collapse when the points open. The collapse would develop the secondary voltage for the spark. Instead of running a constant current through the ignition coil CDI systems store the charge on a capacitor. On the Beta CDI I disassembled it was a 400V polystyrene cap. When the timing pulse is given the energy in the cap is dumped into the coil through an SCR or Triac which is a high current latching electric switch. So through the rotation of the cycle the capacitor gets charged, the trigger pulse fires the SCR which dumps current into the ignition coil building a magnetic field and generating the high voltage for the spark. The advantage over points is you can control the ignition curve very precisely and since you are able to generate a spark on the rising edge of the building magnetic field you can sustain spark on the falling edge giving a longer duration spark.
  2. Wow. That’s somethng new.
  3. Did they lengthen the kick starter or did somebody just not put it on right at the factory. Doesn't seem to fit in the notch in the pipe as it used to.
  4. New boots are pretty cheap and just screw into the wire. Just cut the wire ~5mm and screw the new boot on. The older ignition systems have three types of coils. 4-6 big coils with heavy wire to power the lights/fan ~16-20 volts ac A coil that provides the power to the CDI. These have smaller wire with more turns to generate ~100-300 volts ac. This charges the capacitor in the CDI (capacitor discharge ignition) and powers the electronics in the CDI. Most modern ones contain a uController. Basically a one chip microprocessor. The last coil is the trigger coil. This coil is a small coil whose sole job is to send a pulse to the CDI at a certain point in the engine rotation to tell the CDI to dump the charge stored in the capacitor through the ignition coil to make a spark. Some systems used two trigger coils to tell the uController how much advance was needed based on engine speed. if you look at your flywheel you will see one or two odd magnets that look split. These are the trigger magnets. The trigger coils are oriented in such a way that they don't generate a signal from the magnetic field of the other magnets in the flywheel. Typically it's the trigger coils that go bad so the CDI charges up but never fires. On the newer bikes the trigger coils/magnets have been replaced with Hall effect sensors. These live outside the flywheel in that little pod where the cable exits the case. There is a notch in the flywheel that trips the Hall effect sensor to generate the timing pulse. This is the same system used in cars. OK that's my major geek out for the day.
  5. It sounds like something pushed the pistons back into the caliper. A bent rotor will do that as will badly worn wheel bearings or even picking up a small rock or piece of wood that gets jammed into the brake pads. to make sure there are no leaks while parked grab a handfull of front brake and hold it to see if it goes soft after a bit. If it does then you have a leak somewhere in the system. Could be a seal in the caliper or master cylinder. If the lever stays firm I'd check the front rotor for true and check for play in the wheel bearings. Also pull the caliper off the rotor and look for anything on the pads that doesn't belong there. Obviously check your fluid level and make sure caliper bolts are tight and the lever has enough free play to open the reservoir port in the master cylinder.
  6. Going back to this as a friend had a GasGas with a PWK28 that did the same thing. Bounce the front end and the bike would die. Nose down and the bike would sputter and die. Fixed by replacing the carb. I had hoped to do a postmortem on the carb but the dealer who replaced it already disassembled it for parts. Very curious.
  7. Yeah much of what's in this thread is completely wrong. The double blip is simply a technique where the first blip of the throttle lifts the front wheel to the top of an obstacle. The second blip drives the rear wheel into the base of the obstacle. This is effective for small obstacles up to about 1/2 the wheelbase of the bike. The Jap Zap (yes it was first deveoped by a Japanese rider) is intended to get up higher obstacles by intentionally running the front wheel into the face of the obstacle at a height that will store maximum energy in the springs and using the rebound of both suspensions to lift the entire motorcycle. Essentially when it is done correctly the front wheel is vectored straight up followed by the rear wheel which impacts the obstacle near the same point as the front wheel. This allows the rider to climb obstacles greater than the wheelbase of the bike. The technique where the rear wheel contacts first is called a splatter and it involves violent compression of the rear suspension and sometimes a "kicker" to get more lift. Splatters require dumping the clutch at high revs to get the bike to rotate after lift-off to contact the obstacle rear wheel first at some altitude above the base of the obstacle. The size of obstacle you can get up with a splatter is solely limited by how high you can jump, hence the kicker, and the size of your, er... cajones
  8. That's great. One thing I noticed on my bike after I did the bleeding is the braking was weak until I had some time on the bike. I attributed this to the mechanics of the caliper. Basically the pistons are self calibrating. They can move a small distance but are pulled back from engagement by the O-rings. Exceed the elastic limit and they slide in the O-ring which is the self adjusting bit. Until they have moved in the O-ring far enough it's possible to have them contact the rotor but pull back too far to be in the proper working range. The clearances are so small that it's amazing it works as well as it does. This could explain why the weight trick helps the feel as constant pressure forces the piston/O-ring position closer to the rotor and gives more time for the O-ring to move on the piston. I could see this causing a bit of drag too if the piston slides a bit past the optimum position. Ain't mechanical engineering fun!
  9. Hmmmm did you use any kind of anti-squeal rubber goo on the back of the pads? Are the pads properly planar to the disk? I'm wondering if there could be something putting the pads at an angle to the rotor.
  10. That is a wild looking disk. Just like the pads different disk materials will have different friction characteristics. I don't have any new ideas other than alignment of the caliper. I'll keep my brain running and maybe it'll pop into gear and spit out a new idea but for now I've spewed out all I can think of.
  11. It sounds like your master cylinder is working as it should so now we move to the mechanical realm of possible misalignment of the caliper, bent disk or one piston sticking causing only one pad to move towards engagement (fairly common on older calipers that haven't been rebuilt in a while). The calipers aren't bad to rebuild. Fiddly but not really difficult. Can you pull your rear wheel to check if your disk is true and see if it is easy to push both of the pistons back into the caliper. Firm steady pressure should slide the pistons back into their bores. If both move freely then the caliper is probably good. If only one piston is moving it will do exactly as you are describing as the one working piston will chase the disk into engagement with the other pad rather than meeting in the middle at the disk. Caliper rebuild kits will include pistons, squarish looking O-rings and possibly a small O-ring that goes between the two caliper halves if it is a split caliper. By far the biggest pain in rebuilding a caliper is getting a stuck piston out of the bore. Once you've decided to go the rebuild route you're kinda committed anyway so you can take the caliper and use the pedal to pump the pistons out of their bores before you disconnect the caliper from the brake line. They're going to want to come out one side first so a small C-clamp is helpful to let you chase out one piston to where it is about to come out clamp it in place and then the other will move. Otherwise one pops out and it's pliers and swearing time to get the other one out. I find two main sorts of spooge in the caliper. Corrosion of the aluminum which seems to be an effect of moisture absorbed into the brake fluid and what appears to be a crust of the fine dust that sneaks in along the side of the piston. When I rebuilt my current rear caliper it was the silicate dust that packed into the O-ring groove and also built up in the corners of the bore. What worked like a charm to clean it out of the bore and grooves was a dental pick. I swear a set of these should be in every tool box. If you're careful you can pick out the crud without scratching the aluminum bore of the caliper. I've noticed replacement pistons usually seem just a bit smaller than stock. I'm not sure why that is but it could just be random chance from a small sample. Once the caliper bore is clean, fit the O-rings, put a little assembly lube on the pistons and slide them in. They will protest until you get them past the edge of the O-ring. Then you're in for the bleeding session again. On my bike I got to this point and figured I might as well do the whole system and rebuild the master cylinder as I had a kit on hand. Cleaned out the bore of the master cylinder and put the new piston in and it stuck. Badly. Nice lesson in manufacturing tolerances. I had to pull the master cylinder off and run a cotton wheel with polishing compound through the bore to get the new piston to fit. That was a real pain. Polish, flush, fit, polish, flush, fit until everything got along. Please let us know what you find. Knowledge shared is knowledge multiplied. Edit: Ah I didn't see you replaced the caliper. Well it's still worth checking to make sure your disk is in the center and both pistons are meeting in the middle.
  12. The problem is usually air trapped in the system. Air is an elastic medium (or at least much more than the brake fluid, Gas vs. liquid distance between molecules type of stuff) so when the pedal is depressed some of that fluid displacement is taken up compressing the air bubbles and doesn't generate the same force on the pads. Remove the gas from the fluid and you remove most of the problem. The only possible effect I can think of from putting a weight on the pedal to keep the fluid under pressure forces the gas in the system into solution with the brake fluid. Like CO2 in a bottle of soda. Once the pressure is released the gas will come out of solution. Try the bleeding from the top banjo bolt at the master cylinder. It's fast, it's easy and my guess is it will help. Since I just rebuilt the rear system on my '13 EVO (rear master and caliper) a month ago I can tell you it was the last step that finally got my brakes back to where they belong. Another issue could be contaminated pads/rotor. It's fairly common to get chain lube over spray or just finger grease on the pads and they lose a lot of their grip. Brake cleaner helps as does heating the pads to burn off any organics that may contaminate them. You can really heat up the metallic pads and they'll still be good. Just don't do it on the bike as you'll damage the seals in the caliper. I took a MAPP torch to mine and they were fine but I eventually told myself to cut loose with a buck and buy some new ones. The reason I don't recommend the pressure on any of the hydraulic systems on a bike is simply they are not designed for it. They are designed for short term application and it is possible to cause long term plastic deformation of the seals which will wear them faster. Fluid will weep past seals every time there is a pressure differential. In normal usage the amount of fluid that gets past the seals is so small that it will evaporate long before you would ever notice it. So a small amount of leakage from a seal under constant pressure that isn't designed for such duty is not surprising but it won't hurt to keep an eye on it. So I think it best that you start with the cheap (free) and easy bleed the caliper first with the bleed nipple just to be sure there is no air hiding in that high spot then bleed by cracking the banjo bolt at the top of the master cylinder. I think that will cure the majority of your problem. If that doesn't work then go ahead and try the other guy's tricks. I promise I won't have a tantrum.
  13. Oh that hurts Heather.
  14. Rear brakes on the Beta are a pain to bleed as the air gets trapped in the highest part of the system in the banjo bolt at the top of the master cylinder. Hanging weight on the pedal will only force fluid under pressure past the piston seal and possibly damage the seal. Try bleeding the rear by pressurizing the system and while holding the pedal down crack the banjo bolt. Tighten the bolt, repressurize and repeat. It usually takes four or five repeats to chase the air out. Refill the resevior and it should be better. There really should be a bleeder valve at the top of the master cylinder.
  15. Except if you try an EVO you are going to wonder how you ever rode the Techno🙂