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?

[Lozza]

There isn't much difference between 1.6, 1 and 0.9 Ohms

[Viper666]

What happen to all the other comments?

[Graeme M]

Here:

http://ozvmx.com/community/index.php?topic=27481.msg268175

I posted twice...

[Viper666]

DUH!

There isn't much difference between 1.6, 1 and 0.9 Ohms

Unfortunately this is not the case. 1.6:1 is a difference of 60% huge difference & it not as simple in comparing 2 coils primary & secondary readings, even though this could work, you need to know the Impedence (Resistence) of the wire used in the windings. This is also crucial in the function of the coil. It could mean dozens of more windings &/or ratio.

Coils work on a primary to secondary windings ratios, i.e. 10,000:1 on cars gives you 12-15000 volt output to a 12-15v input.

So look at the difference in the secondary too.

That said it will probably work well enough to prove whether the coil is at fault or not but I would not run it for any length of time.

Graeme, try & get one off another IT because the CDI's for them are different to YZ. Again though a YZ one should prove it though.

Perko

[Graeme M]

What do you think about the pitbike coil? .9 ohms for the primary is within spec, but 4.2k ohms for the secondary is outside the spec of 5.9 +/- 20%, although not a lot (4.2 vs 4.7).

[Viper666]

That said it will probably work well enough to prove whether the coil is at fault or not but I would not run it for any length of time.

Try it, but dont run it for too long.

[Lozza]

DUH!

There isn't much difference between 1.6, 1 and 0.9 Ohms

Unfortunately this is not the case. 1.6:1 is a difference of 60% huge difference & it not as simple in comparing 2 coils primary & secondary readings, even though this could work, you need to know the Impedence (Resistence) of the wire used in the windings. This is also crucial in the function of the coil. It could mean dozens of more windings &/or ratio.

Coils work on a primary to secondary windings ratios, i.e. 10,000:1 on cars gives you 12-15000 volt output to a 12-15v input.

So look at the difference in the secondary too.

That said it will probably work well enough to prove whether the coil is at fault or not but I would not run it for any length of time.

Graeme, try & get one off another IT because the CDI's for them are different to YZ. Again though a YZ one should prove it though.

Perko

If you read a figure in Ohms  that is the resistance. An Ohm is not a big unit of measurement.