Bad/no idle=bad coil

More problems, or possibly THE problem?. As outlined in my previous threads I am having a bad/no idle problem with my '82 550 Maxim. I removed and sealed the carb holders(have new ones coming) and resynced the carbs, no fix. Removed and rebuilt the carbs, set float levels,idle mix, and resync - no fix. New fuel filter, clean and open petcock, and fresh fuel. The way it's acting it has to be a fuel issue but I went over the entire fuel system and it is like new clean. I know I need a new battery so I decide to check the rest of the electrical system just for s's and g's. Charging system checked out right in the middle of the specs, all connections clean, starter and alt brushes clean and like new. Ignition, pickups- 610 ohms for both- perfect. Coil primaries- 2.51 ohms-low but good, secondaries- coil 1/4-11160 ohms, coil 2/3- open/ no reading. With engine running- pull plug wire from #2- no change, pull from #3- minor change. I think this bad coil was most of the problem from the start but disguised itself as a fuel problem. So I will get a new battery, Dyna DC1-1 coils, Dyna DW300 wires, and NKG DR8EIX iridium plugs and hopefully this will get me back on the road. Bad coil after only 9800 miles.?!

 

It's still 25 years old.

 

True they are old. The new parts will fix it up- when I get the spare cash. Damn teenagers are going to bankrupt me yet.

 

It feels pretty good to finally figure out the root cause of a problem...congrats.

 

Just something I've been wondering. Is it possible to have no reading on the spark plug wires and still get the bike running? Or am I just testing my wires incorrectly?

 

That is what's strange. Before I put a meter on the coils, I pulled all the plugs and checked for spark- easy things first. Number 2 and 3 had a brighter spark out of the cylinder than 1 and 4 that is why I suspected a fuel system problem. According to my local dealer the plug wire ends need to be removed to get an accurate reading on the secondaries. The ends can be left on and the resistance of the ends subtracted from the reading.

 

beardking yes a broken conductor in the wire will spark the plug and read open with a meter
i think the resistance of the plug caps is low like 5 or 10 ohms no need to remove them to read 11K ohms

 

Nope. Not unusual.
You can get put the probes across the low side and get ZIP!
You can read the Plug wires and get specs.

The coils still fire and the bike will run great.
I used to argue about it with a lead tech every time we'd test a bike for spark.

Nothing showing on the low-side test has sold a whole bunch of new aftermarket coils to many not needing coils.

It's why some Rev-Limiters won't work on FACTORY ignitions without additional resistors added, in line, to the coil low-side hook-ups.

 

Primaries for both coils checked good- 2.51 ohms.With the resistor ends removed the secondary on the 1/4 coil was 11160 ohms and the 2/3 coil was open. The resistor caps all checked at 9.5 to 10.1 ohms. With the engine running I pulled the plug wire off of #2 or #3 and there was virtually no change in the idle. When I pulled the wire from #1 or #4 the engine coughed and died. This would indicate a bad coil and cause my poor idle, correct?

 

so far as i can tell all that has been proven is #2 #3 don't work too well
switch coils 23 to 14 and 14 to 23 now if the problem follows the coils
stand up and shout bingo

 

Picked up a pair of used coils yesterday for $45.00 from these folks Cycle Therapy. The guy bench tested them in front of me before he let me have them- never seen a junk yard do that with electrical parts before and I have been going to bone yards for 20 some years for car parts. It's only going to be in the low 30's with snow so I dont' know if I will put them on to day or not. Also went to the Yamaha dealer and got new wire ends for $3.00 each. They didn't have 10k ends, only 5k, and the older parts guy said to use 5k even though the book says 10k as I will get a slightly hotter spark and a little easer starting.
If this don't fix the problem I don't know where else to look as everything else checks good or has ben rebuilt.
Time to go to work now, have a good day.

 

Just for shits and giggles I thought I had my intake rubbers sealed properly also...but, then I sprayed ether (starting fluid) at each of them while it was running and the rpms climbed up to about 2 on the #4 cylinder, so I found the problem with rough idling. Took the intake rubber off and sealed it with Marine Goop and put'r back together and ZING! It runs so smooooooooooooooooth now!
SO, just saying you may want to check those boots out again. You may not have them sealed like I thought I did! Just a thought. >PD<

 

Got the replacement coils in as well as a new battery and what a difference. It starts so much qiucker now that everything is working right. Now I just have to track down a 12mm color tune for a reasonable price of find someone local who has one and do some fine tuning. I did three passes on the carb sync to make sure it was as close as I could get it with my ancient vacume gage. The mix screws are just shy of three turns out but i'm not to positive of that setting as the idle is not dead smooth,close but not as smooth as I think it should be. So the next step is grease the wheel bearings and headset bearings and wait for warmer weather.

 

Fozzie, don't forget: you have to check the valve clearances and correct as needed before you synch.....or you're wasting your time. I know it's a bummer, but......

I did EVERYTHING to my bike...cleaned the carbs 4 times, rebuilt them, new coils, new intake boots, plugs, plug wires, etc. etc. Could never get it to run/idle/off-idle smoothly. Bike only had 11K miles on it. No need to adjust the valves!

Finally opened up the valve cover, all of them were right on....except #4, and both the intake and exhaust were too tight.

Now it syncs perfectly, easily, and runs like a top.

 

Already checked the valve lash and all were within spec. I also did a compression test and it was at 134 lowest and 139 highest. Changed the oil and filter- was dirty but had no sludge or metel on the drain plug. I am using Wolfs Head 20W50 dino for now. The bike has 9800 miles,I'll change the oil again at 10,000 and at 12,000 I'll check the valves again and switch to Royal Purple synthetic. I think the bumpy idle might be just some diryt combustion chambers from trying to tune with a weak dying coil. It's supposed to be in the low to mid 40's tomorrow so I'll be able to take it out for a ride and clean it out, wanted to today but low 30's was just to cold.
I'm sick of this weather already. :x :x

 

I took it out for spin today and it is much better. Has a very slight hesitation right off idle until it has fully warmed up(about ten minutes or so) then seems to run pretty good. It seems to smoke a fair bit when cold but that might be from the seafoam in the gas, it's not oil smoke. I might pull the tank and drain it into my lawnmower can and get some fresh gas if it ever warms up. Needs some fine tuning but it's drivable now.
Just a tip- A quilted flannel does nothing to keep you warm in 35 degree temps at 40 mph!! BURRRRRR