Super Jet Ignition coil resistance

M

malte

Location
germany
Hi,

I have a SJ RN that has some backfire. Found out that the spark plugs have a resistance of 16.5 kOhm. Manual says max. is 4.7 kOHm. So I took apart the spark wires from the coil to replace them. Now I measured the resistance of the coil:
Primary 0.1 Ohm which is fine I think.
Secondary 4.1 kOhm - is that okay or is the coil broken?? (measured directly at the coil with no spark wires!)

Thanks and regards from Germany
malte
 
FlightPlanDan

FlightPlanDan

Don'tTrustAfartAfter50
Location
Crescent Beach, FL
Generally, replacing the coil and wires together is the way to go, if that's what's wrong. I've had backfire issues in the past that turned out to be a bad CDI. Been down the road of measuring resistance checking the stator... the average meter is not sufficient for measuring the readings spec'd in the service manual.
If you have a friend that will let you swap CDI's....... I'd do it.
An MSD costs the same or less than OEM.

Note: I fought it too long....lots of backfiring. It blew air leaks throughout my motor. Blue/Jetmaniac tore it down and fixed it for me.
The MSD solved the issue otherwise.
If you have separated the plug wires from the coil in the process of working on this, then I would consider getting a new set from Jetmaniac/JSS or OCD solutions.
 
FlightPlanDan

FlightPlanDan

Don'tTrustAfartAfter50
Location
Crescent Beach, FL
augustaf said:
I just measured 3 coils that had the wires removed: secondary windings = 4.132Kohm, 4.157 and 4.205 at room temperature. So the op should be fine.
Gerade die sekundaere Wicklung gemessen an drei verschiedenen Zuendspulen- Deine Messwerte sind gut!
Click to expand...
Fred, I'll always respect your opinion, even follow your advise blindly, but what does this mean?
Gerade die sekundaere Wicklung gemessen an drei verschiedenen Zuendspulen- Deine Messwerte sind gut!
 
M

malte

Location
germany
Thanks guys! Today I installed new wires together with new spark plugs. Engine runs better and backfiring is gone!

But still the spark seems weak to me. I noticed that my charge coil has only 400ohm and produces 21volt AC while cranking (full battery). Maybe CDI is getting to low voltage and that's the primary problem?

Just want to make sure everything is in good condition for the upcoming season... Which is btw much to short in cold Germany ;-)
 
OCD Solutions

OCD Solutions

Original, Clean and Dependable Solutions
Location
Rentz, GA
The 61X will have a pretty weak spark at cranking or idle with the hottest spark appearing around 3500 RPM.

What type of meter did you use to measure the AC voltage and at what RPM?

This is a very hard value to capture accurately with AC. Most quality meters are incapable of getting a true reading, much less cheap ones. The Yamaha shop manuals all recommend using a Direct or Peak Voltage Adapter for this reason, (DVA or PVA). With a peak voltage adapter, even a cheap meter will get you decent readings.

You can find a more in depth explanation here; http://www.boatingmag.com/boats/get-adapter-to-troubleshoot-cdi-ignitions

The output voltage of the charge coil will vary with RPM. I typically see 275-325 volts at an idle, it peaks slightly higher around 3500 RPM and then drops steadily as RPM increases from there. Around 8000 RPM, this value is down in the range of 150 volts. 150 Volts is about the lowest voltage that will still reliably fire the average coil. If your charge coil drops below 135VDC, you can expect to have issues firing the plugs and you should replace the coil.

If your charge coil is able to produce 150+ VDC throughout the entire RPM range but yet you still have weak or erratic spark, then look to your grounds, plugs, wires, caps or coil itself for an issue.
 
augustaf

augustaf

Location
central florida
Malte, seems you posted that you are working on a round nose SJ. Stock stator/ flywheel on that ski would be a 62T. The charge coil should measure at least 450 ohm. The charge coil is wound with very fine wire, sort of like angel hair, and since the actual working voltage is pretty high at rpm, it will "age" and the windings punch through. ( Wicklungs Schichten schlagen durch). I would say- from experience- that a 62T charge coil which reads 400 ohm is severely compromised, may work with a stock CDI- but not at all with a MSD enhancer or ATP Epic. Here in the US, charge coils may be bought from Yamaha (about $120 street), just solder in a new one.
Don't know what they cost in the EU.
 
Last edited:
M

mikespo12

Location
Connecticut
So my ski will do maybe 75% power in the water. I can't get to top speed. I changed the fuel lines, checked the carbs they're good, new plugs and spark plug boots. Riding it yesterday and out of no where the ski rode like a bat out of hell. Was running beautify. Throttle was 100% responsive then next thing you know it's back to riding how it was. I take it out of the water and bogs when I hammer it then back fires like crazy when it's at full throttle. Could this be a bad coil?
 
tylercannon

tylercannon

Location
Clearwater, Florida
mikespo12 said:
So my ski will do maybe 75% power in the water. I can't get to top speed. I changed the fuel lines, checked the carbs they're good, new plugs and spark plug boots. Riding it yesterday and out of no where the ski rode like a bat out of hell. Was running beautify. Throttle was 100% responsive then next thing you know it's back to riding how it was. I take it out of the water and bogs when I hammer it then back fires like crazy when it's at full throttle. Could this be a bad coil?
Click to expand...
What ended up being the issue?
 
You must log in or register to reply here.
Top Bottom