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scifi

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About scifi

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  • Bike
    TY175

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    N Wales

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  1. I must admit that I have never seen any actual figures for Villiers engines, and the Villiers guys who are selling new 'Challenger' engines don't know what state of tune they are using. The only thing I remember being told was to remove 1/8 inch off the top of the exhaust port, and about the same from the inlet side skirt of the piston, to make a Racing type engine. ( Also to leave the transfer ports alone.) You mention 'opening and closing' timings... they are the same for two strokes..!
  2. Sounds as if the engine is trying to do the opposite of what you have done, and cancels out your polarity at higher revs... Or did you just short circuit the thermostat..? .
  3. scifi

    Won't rev?

    If water gets into the electronics, all is not lost, as long as it was clean water. Clean water will evaporate leaving no residue, unlike dirty water that will leave a conducing coat of dirt. So if the circuits have got wet, you need to place them in a dry warm spot for several days, a week maybe. I once dropped a Sony radio into a bath, the only component that I could not dry was the tuning capacitor, that I renewed for £3. .
  4. It's probably because of the heat generated in the Power Supply. Not enough to cause the fan to be fully on, but too much to be without the fan. The heat sink will take time to heat up and cool down.
  5. Hi all, just wondering if anyone knows if speedway bikes still use 350x19 trials tyres, and if they do, where do they get them. I think that some of the older trials bike conversions, such as Bantam Trials bikes, would only take a 350 tyre, without extensive widening modifications to the rear suspension.
  6. Quote,,,, Measured peak voltage raises until about 3rd or 4th kick and then stays around 20V. Voltage raising is presumably due to capacitor charging in peak voltage adapter. While taking measurements all loads were disconnected (in this case CDI). I think this points to the problem. You are charging the CDI Capacitor, but the CDI is not discharging it to make a spark. Probably the CDI discharge transistor (or Thyrister.) has gone open circuit. .
  7. The plug gap seems a bit close, why not the usual 25 thou. Also if it's an old plug, it might spark out of the cylinder, but not when under compression. Is it auto-decompressor..? .
  8. Quote... I went to a powder coating place today just to see what they could do and they wanted $150.00. I know some people like powder coating, but I avoid it like the plague, because once the water gets behind it through a crack or chip, it corrodes the metal from within. So in a couple of years time it can totally rust through a frame tube, unseen by anyone. .
  9. scifi

    Too smoky!

    Are you sure it is oil smoke...? Looks a lot like water vapour to me, either from wash water getting into the exhaust padding, or you not running it at max for over an hour (which is the norm for trials bikes.). You could try holding an ice cold can of beer in the vapour, does water condense on the can..? .
  10. Think of it as a change of gear speeds, so instead of 1st, 2nd, 3rd, 4th etc. You now have.. 3/4, 1 3/4, 2 3/4, 3 3/4 etc.... Much the same as old motor cars had an overdrive, which added half a gear. In agriculture, some tractors have three gearboxes, Rabbit and Snail, then 1,2,3,4th, and then Hi / Lo. .
  11. You have probably got the slow end too rich, and the top end too weak. But I can't understand what you mean by 'bogs down and cuts out' at high revs.. Bogging down means too rich ( four stroking.) and cutting out means too weak... take your pick. Just for reference, a TY175 uses a 240 main jet. If you need to measure your jets, see how far a thin tapered needle enters the jet, and compare it with the Bing jet.
  12. Ok, thanks for the teeth numbers, it looks as if the scrambles A to B uses a different tooth profile as they don't add up to 50. So if you want to know your overall ratios, you need to multiply / divide four cog teeth. 1st H/G x A/B 3.17 (trials.) 2nd D/C x A/B 2.44 3rd F/E x A/B 1.63 4th is 1:1 as C Dog Locks to A Looking at the BSA publication, it suggests different selector forks and spring for the different ratios. When I last swopped cogs (1970s) I don't think I changed any of that.
  13. Bit confused about what you are saying about 4th gear. Surely it is 1:1, basically straight in, through the dogs, and straight out. Only 1st 2nd and 3rd go via the lay-shaft. ( Also the total of the number of meshed teeth always = 50t.)
  14. Also just thought of another one... If footing is needed, put your foot in front of the front wheel spindle, that gives more time as the bike travels forward.
  15. Lost just one mark in a trial when the sandy rut that my front wheel was in did not put me at the right spot for the next rock, so had to dab to lift the front over the rock. On the next laps the rut had worn into the correct direction. I also find that tacking rocky stream sections quickly, reduces the desire to put your foot down.
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