1985 maxim x 750 ignition coils

Hello. My bike has become hard to start so i started digging. Both ignition coil primary winds are 3.5 or 3.6 ohms at room temp of 24 celcius. My book says 2.7 +/-20% at 20 celcius. Would the higher room temp cause my higher reading or are mine in need of replacing?

 

I did some poking around on the internet and found an equation to calculate the increase in resistance with the increase in room temp. It seems with an increase on 4c the resistance would increase from 2.7 to 2.74 as the tolorance. With this being said my coils appear to be out of tolorance.

My next question is would an increased resistance of 0.9. Ohms cause my problem with difficult starts?

 

Someone has to know this. What does the primary windings do and what does the secondary windings do?

 

Ignition coils are basically a step-up transformer. You're taking a small voltage (which goes into the primary winding) and making it into a bigger one (which comes out of the secondary winding and goes to the plug wires).

You've given measurements for the primary winding -- what about the secondary? A few years back I had a hard starting issue with my 750; the secondary on one coil was way up to 80K. The problem magically disappeared when I replaced them.

 

Meter leads can account for 0 or up to 1-ish ohms. Zero your calculation by connecting the leads together to see what they read in Ohms.

Then subtract that amount from the test across the primary.

And like Schmuck said, primary takes little voltage and converts it to high voltage, which the plugs use.

Causes for hard to start: failing battery, clogged jets in carb, dirty air filter, bad plugs, extra resistance in plug wires, worn brushes, old plugs, etc. Could be bad gas, or gummy carb. Both may be fixed with a little seafoam in the tank for a few fill-ups.

I'm gonna hazard a guess, that if both primaries are that close, then they are probably still good. Problem may lie elsewhere.

 

Thanks for the tip with the meter. I didn't know that. I'll check again when I get home next week. I didn't check the secondaries as I couldn't figure out how to get the plug wires off. Any tips?

I have to check my valves too but am slowly going through the whole bike.

Thanks again.

 

To remove spark plug caps, simply unscrew them off of the wires. You should find it hard first, you could use small pliers to help brake them free. DOnt try to remove the wires from the coils. You don't have to anyhow.

To measure the secondary resistance, first remove the plug caps as I described and then probe your meter leads in the plug wire ends. Repeat for the other coil. You don't have to pull the coils off of the bike, but they should be disconnected from the circuit.