Symptoms of bad coils or Condensor??

[XS650D]

I noticed on the weekend that once the bike warms up or after going for a ride that
while idleing will start to cut out or miss from one side to the other and eventually completely cutout like I turned the key off,it will fire rite back up easily then start to do it again.It also will backfire on deceleration and adding extra fuel with the fuel screws dosent really help.Its definitely not fuel related,i clean and reset the points,cheaked timing,valves and battery volts all good,could this be a coil going when it gets hot or possibly condenser or other electrical issue.Love this old bike but shit it has a lot off issues.Plugs are nice and clean ,new wires and caps 2000 k ago.Stumped on this one can u point me in the rite direction please thx

 

[5twins]

Observe the points while the bike is idling and acting up. Are they sparking like crazy? If so, the condensers have gone bad. If it only acts up when hot, then yes, it could be a coil going bad too. But, I don't think it would start right back up immediately if the coil was at fault. Usually you have to let the bike cool down some before that bad coil will work OK again.

 

[XS650D]

OK,Thx 5 Twins,will cheak tonite. Do Condensors go bad frequently. I had installed a new Mikes unit last season,as the original was suspect after 40 years .The Mikes unit fried early this season and had similar symptoms but not exactly the same, one cylinder would act up only so I flipped the wires on the Condensor and prob changed sides so I new.Now I am having a similar issue literally 1000 kilometers later but now both sides act up back and forth they will cutout and idle will drop,if they cut out at the same time the engine quits and have to restart.What would be causing these condensors to fry or have such a short life.

 

[5twins]

I don't know what would cause the condensers to go bad so quickly. It could just be a really poor quality replacement. Mike's isn't noted for quality, lol. If you still have the originals, I would put them back in. A condenser has no moving parts and some will last darn near forever.

 

[5twins]

I just thought of something else. Do you have the factory ground wire on the condensers? Apparently Yamaha thought it was needed, besides them just being screwed to the motor mount.

 

[XS650D]

Yes it does have the ground wire attached,could that cause issues.

 

[weaselbeak]

Could just be carb issues as well. Check for decent fire on a grounded plug, if OK you are most likely looking at a good carb clean & tune.

 

[XS650D]

ok finally got around to testing bike,I tested battery after bike sitting for a week not run,battery was down to 12.2 volts.I checked volts at orange coil wire to a good ground (did not use brown wire at ground,will it make a diff) for each coil with key on,got 11.8 on one side and 10.5 on other,Appears to be a bad coil,they are original but bike has low miles.Is there any other way to test that lower side coil to confirm or should i just get a new one.Thx

 

[5twins]

There are coil testing procedures in the shop manual .....

 

[XS650D]

Thx 5Twin,i have a Clymer,ill look tonite and try and figure it out.I take it that the spec drawing u send is for testing coil not hooked up which is kinda what I was looking for,rules out my wireing being at fault.Great stuff!!

 

[XS650D]

Clymer manual i have has no testing info for coils. I tested ohms for primary 3.9 and secondary 8.12 but when i check volts with key on get 10.3 volts thats with battery showing approx 12 volts (it needs a charge) other side now 11.6 volts..I was expecting a bad reading for ohms .What am i missing here.Does this mean that the coil is good or bad.
Testing volts is under a load were the ohm test is not i guess.

 

[TwoManyXS1Bs]

Looks like your 'coil voltage' test is revealing too much voltage drop in the wiring between the battery and coils...

 

[5twins]

For the secondary, 8K means 8000. If you're only getting 8.12, that could be a problem, lol. If you meant 8.12K then that's fine, within spec. But, if you're measuring the coils cold, they may test fine but still be bad once they heat up. Testing them once the bike is hot and acting up would probably give a better indication of their condition.

I'm not sure why you're testing volts on the power feed wires to the coils. That won't help diagnose coil condition at all. But, it can show a problem, and yours might have it - low power to the coils. You should see near battery voltage at the coils. If you're losing a couple volts, that usually indicates dirty or bad connections somewhere between the battery and the coils. With low volts to the coils, they produce a weak spark. Your readings don't make a lot of sense though. Those two red or red/white power feed wires to your coils "Y" off the same wire and should read the same. Maybe the "Y" connection is bad on that one side that only reads 10.3 volts?

 

[XS650D]

Yes 8.12K LOL! I may not be testing correctly when testing the volts though.What i am doing is disconnecting the orange wire from the coil,leaving the brown wire hooked up and checking the volts off the orange wire attached to coil. One side 10.3 other side 11.6.
What is that telling me,bad coil or bad wiring? Should i be testing the power on the red/white wire disconnected from orange from coil? Suck at electrical and my manual is useless for this.

 

[5twins]

Yes, disconnect the red/white wire from the coil, then measure it. You're trying to find out the difference between voltage at the battery and at the red/white wire. As I said, it should be near the same, maybe a few tenths of a volt lower. If it's a couple volts lower, you're losing voltage somewhere along the path. Common trouble spots can be the contacts in the ignition switch, contacts in the kill switch, or any of the plug connections.

 

[ThatXS650Guy]

I'm going thru this as well. 3 of the past four times I've taken the 650 out I come home on one cylinder. Pull the plug and it shows no spark. An hour later, sparking like crazy. Classic coil going bad symptoms.

 

[XS650D]

Found the problem,was the brown wire bullet connection to the red/white wire on one side was not getting a good connection,I cheaked red/white and got approx .3 lower than battery.With these crappy bullet connectors i guess thats not bad.The strange thing is the connection looked pretty good and was tight but whe i pulled it out and reinserted it all was good again.Strange! Bike ran like crap though.Thx for stayin with me on this 5T,I almost bought new coils and condensor!

 

[5twins]

These are old bikes and the wiring needs a good going through on pretty much all of them. If you don't have it already, get yourself a tube of dielectric grease to coat the connectors after you clean them. For cleaning, I use an assortment of Dremel wire brushes. You'll want the 428 or 530 for the external stuff like male bullets, and the 443 to get into the female bullets .....

 

[XS650D]

Already have the grease and Dremel tool but need to get the 443 and do the inner connectors,Thx

 

[robweeve]

There are coil testing procedures in the shop manual .....

I've been reading some confusing info on other sites about testing the secondaries. I've seen a few where they say connect the voltage tester to both cable caps at the same time and other places say make contact to one primary wire while making contact with one spark plug cable What are your thoughts on this? thanks