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Checking stator coils on 1978 Yamaha IT 175

17 Oct 2020 15:11
TomTom1
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Checking stator coils on 1978 Yamaha IT 175 #1
Hi, new to forum ...cannot get this bike to properly start reliably and bogs down under load. New top end, new seals, new genuine Mikuni carb, pressure checked for leaks etc. Gets a spark when cranking over, but would like to check the resistance of the TWO source coils, sandwiched together with a smaller one on top. Lighting coil is ok and pulser coil checks out. Please any insight would be most appreciated! Timing etc all checks out...this is maddening. Is one coil for low rpm and the other high rpm?

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17 Oct 2020 17:26 17 Oct 2020 17:27 by RT325.
RT325
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Checking stator coils on 1978 Yamaha IT 175 #2
Welcome from NZ down under.
I'd guess by experience but nothing else that around 350 for the main source & 100 for the small one. Be good to hear & see a video. I'm hung up on restricted exhausts lately!!, kills any useful power up in the revs to the point of stopping the motor if you blocked the end off totally. Well, probably wouldn't stop it if it's not totally sealed at every joint--but!!. I had a burnt out one of those, minus 4th gear. Ran great with little work to get it going & had a lot of fun on it. Was an insurance writeoff. Often wondered if it was torched deliberately when i cranked it up & 'bugger', 4th gear's poked. Me being a tight #$%^ i remove the offending gear & carried on doing quick changes lol. Come to think of it--the exhaust was clean--burnt out in the fire.

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17 Oct 2020 17:59
TomTom1
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Checking stator coils on 1978 Yamaha IT 175 #3
Thanks for the information, any idea which coil is low speed and which is high? BTW see your PM had a convincing victory. My wife spent 3 months in your spectacular country years ago, itching to make a return visit!

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17 Oct 2020 19:17
MarkT
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Checking stator coils on 1978 Yamaha IT 175 #4
I knew I had the specs someplace... finally found them

The pulsar coil (White/red and Black) should be 12.4 ohms

High speed source coil (Red and Black) should be 13.6 ohms

Low speed source coil (Brown and Black) should be 420 ohms

+/- 10% @ 68deg F.

1963 YG1-T, 1965 MG1-T, Allstate 250, 1970 CT1b, 1971 R5, 1973 AT3MX, 1974 TS400L, 1975 RD350, 1976 DT175C, 1976 Husqvarna 250CR, 1981 DT175G, 1988 DT50, 1990 "Super" DT50, 1991 RT180, 2017 XT250
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17 Oct 2020 20:24
RT325
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Checking stator coils on 1978 Yamaha IT 175 #5
Haha, i'm not sure what's so great about our country tucked away miles from everyone else & costing heaps to get stuff sent here, but thanks. Happy your wife liked it though. Must've been nice weather. Winter gets a bit depressing like most places i suppose, & with the Covid lockdown of course. But been very lucky with Covid partly due to our relatively small population. Cheers.
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18 Oct 2020 08:10
TomTom1
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Checking stator coils on 1978 Yamaha IT 175 #6
Thanks for those specs, give me a good starting point. Will also check high tension coil, cap as well! Much appreciated.

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18 Oct 2020 09:20
TomTom1
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Checking stator coils on 1978 Yamaha IT 175 #7
Ok Pulsar coil checks 12.4 ohms, low speed about 375 ohms, and high speed I am getting no reading, open loop? Am I to assume there is an internal short somewhere and might this cause poor starting etc? Electronics are not my forte, also I see a part # 2A78551120, for a lot of money, but wondering if a Yamaha P/N 4BC 8551120 for lot less money is interchangeable? Any thoughts? Thanks again

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