Advice needed re coil on IT175G

[Graeme M]

I have a problem with my 1980 IT175 - it starts but runs intermittently and then simply stops. It will fire up OK, but then runs bad. I have tested all electrics and all checks out, next step is to pull the carb and check it out.

However, in testing the ignition coil I found the primary winding measured at 1.6 ohms rather than the factory spec 1.00 (+/- 10%). The secondary was fine at 5.88k ohms (factory spec is 5.9k ohms +/- 20%).  I have a pitbike coil that will fit just fine, but it tests at .9 and 4.18.

First, does the high reading on the stock coils primary mean there's any problem, and second would the pitbike coil be fine with those numbers?

[SON]

Was the plug cap still fitted to the HT lead?

[OverTheHill]

Hi, without thinking too deeply [sleep time over here], 'does' sounds electrical & my first port of call [apart from obvious things like plug or cap] would be the stator source [ign charge] coil. Without looking it up i'd say 350 ohms give or take a little. You'd be surprised what bad fitting multi plug connectors can do too, if in doubt replace with good crimp on individual ones. All a bit of an [un]educated guess on my part. But, if it starts easy & keeps running but misfiring it's probably not that sorry as usually are hard to start through low voltage. Starting to bamboozle myself but i suppose changing the main coil under the tank is easiest to eliminate [or hopefully fixes it]. Raced A 175G back when new & loved it, mate had a PE175 & we were pretty evenly matched. That's reminded me i have an IT200 hidden under other junk--time to resurrect it, put a tt600 front end in to be able to wheel around as boy bought it as a basket case to use the disc front end in the 490--sorry, another long story. Someone else might have better ideas for your IT175 & hope you get it sorted. Cheers.

[Graeme M]

All the stator coils check out perfectly, earths are good. SON, I checked the coils with and without caps, differences were small. Could be kill switch I spose but it's new.

[Viper666]

Did you do a short test on your leads first?
The leads themselves can test up to .6 ohms depending on quality & condition.
Even though outside specs it doesn't seem too bad.
I'm assuming it WAS running OK?
I would suspect either the pulse or charge coil. Even though you say they checked out OK this is done not under load or running condition.
Test again & move/tap the coils to see it there is an intermittent break.
Also my YZ 125 did exactly the same & was just a loose earth terminal on the coil.

Viper666

[SON]

Start with the plug cap it's the cheapest then the coil  try the cheapy they work ok,
next go back to the low speed coil they can test OK but fail intermittently,
wave a heat gun over it and warm it up, take another set of readings

[Viper666]

wave a heat gun over it and warm it up

Forgot to mention that!

[Graeme M]

Thanks, some good suggestions there. I have considered the stator might be failing under load or once warm, but but was hoping to find something else. It just suddenly started to play up at CD9, was running fine before that. I'll keep hunting. And try that pitbike coil.

[SON]

wave a heat gun over it and warm it up

Forgot to mention that!

Does two jobs
Possibly exposes an intermittent fault when hot
Possibly reestablishes continuity in internal connection

[Andrew L]

https://docs.google.com/file/d/0B0BD_MkiU7JpSzItZDJiUTBjdzQ/edit?pli=1

Could be usefull has info how to test and what values you should have and some symptoms of failures hope it helps.

If it the pulser coil this could be your solution and you will eliminate the pulser from future issues.

http://www.rexs-speedshop.com/epages/es143131.sf/en_GB/?ObjectPath=/Shops/es143131/Products/DT3-PL

[OverTheHill]

a peak voltage meter is a real handy item to have & the source charge coil should put out about 160 peak volts at kickstart speed, with plug out if you like, to keep it turning easier but should reach that with plug in if it's a good one. The pulse trigger coil should do only a couple of volts but maybe a bit more. In saying that if it's starts & runs it's probably not that problem. So, um um um, try hooking up the ohms meter with flywheel off & heat both coils [source & trigger] with say a paint stripper gun on 'low heat' & watch the resistance to see if it suddenly drops back considerably. Did test a problem DT200 that did just that once. Good Luck.

[mitch75]

Yes use the pit bike coil should be fine for testing.