kiwiade

My TY175 lost spark so I thought I'd check the primary and secondary winding resistances of the ignition coil. The manual states 6k ohm for secondary winding resistance (between HT lead and coil earth) and 4 to 5 ohm for primary winding resistance (between small black wire and coil earth). The secondary resistance was fine, but I've run into problems measuring the primary. To start with, I put the red lead on the thin black wire and black lead on the coil earth and the meter showed an open circuit, but when I swapped the leads over it read about 2.5 Mohm resistance. Strange, conducts one way but not the other - methinks maybe there's a diode in there. Sure enough, the ty175 manual shows a diode inside the coil to prevent the motor running backwards. I read up a bit on testing diodes and found that modern digital meters only put out a small test voltage to measure resistance, and that voltage is not enough to make a diode "forward biased" (i.e. conductive). Most silicon based diodes need >0.7 volts to begin conducting and my meter only puts out 0.5 volts to measure resistance. Hence, when trying to measure the primary coil resistance with a digital multi meter, all I'm measuring is the high resistance of the diode while it is in a nonconducting state. Apparently older analogue meters use higher test voltages to measure resistance so would work in this case. Has anyone else come across this? Cheers, Ade

Hi folks, Were the ty50's any good compared to the ty80? There's a couple of ty50's in pieces for sale here and they might be good for my two sons to learn on (aged 7 and 9). Then again by the time I get them running the boys might be aged 17 and 19!! Cheers, Ade

Hi there, I've just bought a 1978 ty175 "project" to restore and eventually ride here in NZ. It's had a hard life, with many parts flogged out (swingarm bushes, wobbly gear selector shaft, stuffed chain & sprockets, wobbly steering head bearings to name a few) but a sound engine. Anyway, there's a rear sprocket for sale on here (http://www.trademe.co.nz/Browse/Listing.aspx?id=148004261) that has 54 teeth, while the sprocket on the bike now has 47 teeth. Would a 54 tooth sprocket be suitable? Presumably it will simply lower all the gearing. The sprocket suits a 428 size chain. Thanks in advance of many more questions .... Ade.