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Low secondary resistance on coils

  • Thread starter Thread starter Anonymous
  • Start date Start date
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Anonymous

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Hey guys,

Is it a problem if I have low resistance on my secondary winding? I've replaced the caps (also tested them @ 5k Ohms).

Right now, my secondary resistance is 24k OHMs and my primary resistance is 4.7 Ohms. From searching through the forums it seems the my secondary should be within 30k-50k.

I'm running rich right now so I'm trying to narrow down the source.

Thanks!
 
I couldn't see how a low secondary resistance on your coils could cause your engine to run rich. Low resistance on the coils could be due to a short in the coil in which case you are probably looking at a difference in the correct voltage for the plug, this may cause you plug to run hot or cold I would imagine, but wouldn't actually effect the richness of the fuel mixture.

If it is your input on the coil than you are looking at an output voltage higher than what you would normally have on the spark, this could mean the plug will run hotter than normal (not a good thing).

If it is your output on the coil than you are looking at an output voltage lower than what you would normally have on the spark, this could mean you plug is running colder than normal.

Sorry, i don't remember if the secondary winding on a coil is the input or the output.
 
Sorry, I meant that it was making my plugs black and sooty.

If my problem wasn't ignition related, I would assume that I am running rich.

Thanks.
 
Yeah, figured as much. So it looks like you have found a very positive lead here (no pun intended). 30-40k down to 4 ohms is a very serious short, check to make sure it is nothing obvious and simple, such as wires leading into the coils themselves. If the short is within the coil, I don't think this is something you are going to be able to really fix, you will need a new coil.
 
Strange... I would have thought that a lower resistance on the secondary winding would mean that I would have a STRONGER spark.

Shows you what I know! 8O Thanks.
 
What does the spark look like at all four plugs in a dark area? Use very clean or new plugs, correctly gapped, correct factory supplied heat range.
Be sure the battery posts, ground, coil terminals and plug leads/caps are all clean and tight first. Be sure the battery has correct voltage and is filled correctly. If you have points, be sure they're clean, gapped, not pitted and join squarely. Then check the spark quality. Be sure the leads are in good condition and there's no arching going on under the tank. Check timing advance action.
Lots of reasons for dark/sooty plugs. Let us know how it goes.
 
The spark is blue, but it's not what I would call "fat". This is on new NGK B8ES plugs, correct gapping.

The battery is at about 12.7 volts and my coils are getting about 12.6 volts via a relay from the battery I recently setup. The coils USED to only get 11 volts.

I have points... I just replaced them and the condensers. I also replaced the wiring from the points to the next junction.

I've never seen any arcing but I will look tonight under darkness.

My timing is spot on as well as the advance.

Thanks for you help!
 
Is the bike stock? List any mod's.
If stock or mod's, what have you got for jetting?
What have you tried so far, besides the coil check, to fix this?
 
No, it's not stock.

I have a 4-1 exhaust with a Kerker pipe (sounds great). I also have Emgo-type pods.

I beleive the main jet is 117.5, but I will confirm this tonight.

I've been assuming that the carbs USED to be okay, so I didn't change anything there. One thing I noticed is that the PO was running B7ES plugs. I tried those also, but I'm still fairly dark.

2 months ago, I completely took the carbs apart and dipped them, cleaned them and replaced all of the gaskets and o-rings (from Mr Barr). And like I mentioned above... new plugs, new caps, new points and new condensers (sp?).

The only thing I have NOT done (I think) is sync the carbs because I don't have the tool.

I've checked compression cold and I have ~135 PSI across the board. I will be checking my valve clearances shortly.

Thanks again!
 
Oh... forgot... I also put new(er) intake boots and new o-rings with a dab of high-temp bearing grease.

I've done so many things that I'm losing track.
 
Well, you have to vacuum synch before you can get accurate plug reads.
But since yours are all dark and sooty, It sounds like your problem isn't related to vacuum, though it will need to be done.
Your problem isn't the main jet selection either. 117.5 should be too lean. Something closer to 125 is my guess.
But the rest of your jetting is still a mystery. With those mods, if you still run the stock jet needles, you should have them set at the richest position, which would be the e-clip in the lowest position. I'm assuming you have stock needles because any jet kit wouldn't have included 117.5 mains.
I really think the Emgo's are more trouble jetting and run richer than K&N's but that's my suggestion on the jet needles. Hopefully the PO re-installed the stock plastic jet needle spacers in the correct order. The thicker spacer goes on top the e-clip, thinner below. Reverse these and you'll be very rich in the setting above. Some people even forget to install them at all.
The pilot circuit may work with just screw adjustments. Try the pilot fuel screws (underneath) at 1 1/2 turns out for starters and then adjust the side air screws using the highest rpm method.
The float levels must be set correctly too.
Also be sure to remove the two floatbowl vent lines and leave the ports open to breath.
Then you have to get the carbs synched.
Throttle position will tell you what each jetting circuit needs. Do what the plugs say.
Open throttle for the main, 1/3 throttle for the jet needles, and slow steady riding of about 35 mph in 4th gear for the pilot circuit.
 
Just checked the main jet and it's actually 107.5. Is that stock??

I didn't have a chance to check the needle, but I recall it being at the lowest position (raised). I also don't remember seeing any spacers. Did the VM26 have those?? I don't see that on the fiches.

I would like to get the K&N as my pods are pretty old looking and I think the bike was stored outdoors for some time. K&Ns are just so expensive.

Floats are set to 26mm and the vents are open.

I will double check everything else as per your recommendations tomorrow and I will let you know.

Thanks very much for your assistance!
 
I believe 102.5 is stock main jet size for your model. I know it is for the '78/'79 models.
Yes, all VM carbs have those plastic spacers as described, above and below the jet needle e-clip. They protect against metal to metal contact.
If your needles are in the bottom position, that should work, even with the Emgo's. The next leaner position would be a 1/2 position change, or placing a .023" jetting spacer on top the e-clip in the current position. Test first.
If you're missing those spacers, actually the thicker one is called a "ring", you'll run very rich as I said. If they were installed in the wrong order, that too would cause richness.
Get this sorted out and re-test. If you still have any problems, generally too lean with the stock needles, you'll need a jet kit.
 
I still haven't taken my carbs apart but I would still like to know if my coils are within spec.

From searching through previous posts, they aren't. Should I go ahead and pickup some 90's Suzuki coils on the 'bay?
 
both coils show the lower resistance????????? Where are the points that you are testing them?????
 
From the caps. 1 to 4 and 2 to 3.

1-4 shows 23.3k Ohms and 2-3 shows 23.5k Ohms.
 
The coils on your bike work very much like a transformer in all practical electronic applications.

A coil with an equal number of windings on both sides causes the input and output voltages (primary is input, secondary is output) to be equal... if you reduce the number of windings on the output side you reduce the output voltage on that side, and logically if you increase it, you increase the output voltage (bearing in mind that power has to always be equal, so amperage if the factor here that compensates for that).

This is why your secondary resistance is higher, more windings in the coil cause for greater resistance from more wire being used in the coil than the primary, so your output voltage is actually measured as (primary voltage ~12v * secondary resistance / primary resistance). (This of course assumes the same type of wire material and guage on both ends, and though may not be pratical for actual output voltage it none the less proves my point)

Now if your secondary coils are shorting, you end up with a lower output voltage, meaning your spark becomes less blue and fat (amperage can increase too, be careful and don't shock yourself, could be fatal).
 
I dont believe that he gets improper resistance at the secondary side of BOTH COILS

I guess i should say i believe it buts something is wrong that is common to both coils but i dont know what. Both coils do not go bad at the same time with exactly the same secondary resistance.

8O i theeeenk!!!!!!!!! 8O
 
Just to add some extra data here, the coils are completely unplugged, but are still grounded via the chassis brackets.

THEEENK GUYS!! :P

Thanks!!
 
If they are aftermarket coils like Accel or Dyna your reading is fine.
 
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