Correct resistance for coil?

Kigsby · Post by **Kigsby** » Thu Jan 19, 2012 8:45 pm

Having trouble getting the bike to start. Tried several different plugs and getting a weak spark. I tested the coil and with it set for ohms on 200 (not 200k) it reads 3.9-4.0 Set on 2000 it reads 003. Is the coil bad? I've never used the meter for anything other than testing the battery so I don't know if I'm using the meter correctly to test ohms.

brewsky · Post by **brewsky** » Fri Jan 20, 2012 5:46 am

That should be ok.
Have you removed the plug caps and trimmed the wires back?
Are you getting 12 volts at the coil?
Was it starting ok previously?
If you are getting spark, I would look elsewhere for a problem first.
Fuel flow, timing set, valves adjusted?

Kigsby · Post by **Kigsby** » Fri Jan 20, 2012 10:50 am

brewsky wrote:That should be ok.
Have you removed the plug caps and trimmed the wires back?
Are you getting 12 volts at the coil?
Was it starting ok previously?
If you are getting spark, I would look elsewhere for a problem first.
Fuel flow, timing set, valves adjusted?

I was working my way from the battery. Battery is fully charged, I'm getting 12 volts at the coil, but wasn't sure how to test the coil itself. I found some articles on it and tested positive to negative and got 3.9 - 4.0. Don't know if I'm testing the secondary wrong because I'm getting 0.00 (meter lead on the coil pole, other lead in the plug hole)?

I'm trimming the plug caps tomorrow (just read about that in another post too)
It wasn't starting before. Cleaned the carb, still not starting
Fuel is flowing to carb, but the spark plugs are dry. I'm doing a compression test and the timing this weekend and I have to read up on how to adjust the valves. Haven't done that before.

Kigsby · Post by **Kigsby** » Fri Jan 20, 2012 1:27 pm

I found this on the web from Bill Silver for the next person looking for the resistance level...

The single coil is double ended and needs both plugs grounded to test. Check the primary resistance values on the coil, which should be about 4.5 ohms on the two small wires, disconnected from the harness. If that is correct, then you may have either a broken lead on the secondary (plug wires) circuit, or it is shorting out somewhere between the coil and the plugs. Do not use resistor plug caps or plugs on these bikes. Non-resistor caps and regular D8HA NGK spark plugs should be fine.

Are you sure you aren't fuel fouling the plugs due to a dirt carburetor? Is the ignition timing set correctly. Check it running with a dynamic timing light to check spark advance curve. Don't let spark timing excess the II marks on the rotor, which is 45-48 degrees BTDC.

If the coil is bad, try a new DYNA coil with correct resistance value around 4.5 ohms. Check your old spark plug wires, too, to see if they are cracked/broken somewhere inside the frame. If you have the original coil, the leads will unscrew from the coil tower so you can remove/replace the leads with some solid core plug wire from a tractor shop or some race shops.

Bill Silver

ironangel · Post by **ironangel** » Fri Jan 20, 2012 2:56 pm

Good find!! you should be in the ball park with your coil

brewsky · Post by **brewsky** » Fri Jan 20, 2012 3:19 pm

If the spark plugs are dry after trying to start with the choke on, then you are prob not getting fuel thru the carb.

Shoot a little carb cleaner in the open end of the carb (choke off) before trying to start, then try to start it again with choke on.

If it fires and runs a couple seconds and quits, you will know it is a fuel issue. Maybe slow jet stopped up?

Kigsby · Post by **Kigsby** » Fri Jan 20, 2012 3:28 pm

Thank you Brewsky! I'll try that. I just cleaned the carb, and blew out everything with compressed air but who knows, maybe something got in there and clogged it up again. I am willing to try all suggestions! I'm spending all day Saturday checking everything I can think of!

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Correct resistance for coil?

Correct resistance for coil?