newbie in need of ideas!!!

ddranged

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Hello, new to the site and relitively new to bikes. anyway i have a 73 that i am in the middle of chopping up, and i hear so much about how cool these bikes are i had to buy another one right now in order to ride now. anyway a couple weeks ago bought an 82 xs and well the guy that had it before me said he had the bike rewired, tank lined, and carbs rebuild and drove the bike for 3-4 days and then parked and i bought 7 months later. after sitting he fired it up and the bike will only throttle up to about 3000 rpm and it just bogs down and will back fire. i bought it cheap assuming it was carb issues but the bike idles ok just wont rev up (even warm and on the road) so i took the carbs off and cleaned them again and still no difference. so i tinker a lil more and well my battery goes bad. i cant kick it over or anything, well i hooked a battery jump box to it (and it kept saying check battery when on any charge setting) and when i put it to engine start it fired right up and would rev through the entire rpm band no problems like a new bike. im puzzled as to why forcing high amperage to it would make it run fine. i have tested the rectifier via instructions online and that seems fine. any help would be uber sweet. thanks in advance.
 
- if the batt is going flat youve probably got a charging problem...try checking your brushes

- have a quick sqizz here too
 
Also remember that your 82 has the TCI ignition. It doesn't want to run very well when the battery is flat, especially if the alternator isn't charging.

And for sure, while you're in there checking your brushes, leave one of them loose and check the resistance across the alternator rotor's slip rings. You want to see somewhere between 4 to 7 ohms. It is very common for these rotors to fail. Custom Rewind in Alabama does excellent work rewinding these rotors. There are probably other folks who also do a good job, but Custom Rewind is the service I used for my '81's rotor, and I've been very happy with their replacement.
 
thanks for the info. i will check that later tonight. the thing that worries me is that i put a good agm battery in it and it acted the same way. but i am almost positive the alternator isnt charging because even when it is runnin at idle or even at 3000 rpm (the max it will rev due to this issue) it didnt get above 12.9vdc. can this all really be the result of the alt not charging, or is there something else. i did test for spark and it seemed weak, but as i said earlier i am new to bikes. would it be a waste of time to swap the ign coils with some i believe are good, are is it even possible that would be it as well. thanks in advance.
 
dont swap out the coils unless you have the right ones for your bike. you can fry your cdi if you put the wrong ones in. test your rotor as described above. Sounds like its not working. also, check the length of your brushes. if you are super lucky, you might just need new rotor brushes.
http://www.mikesxs.net/products-29.html#products
 
thanks for the info. i will check that later tonight. the thing that worries me is that i put a good agm battery in it and it acted the same way. but i am almost positive the alternator isnt charging because even when it is runnin at idle or even at 3000 rpm (the max it will rev due to this issue) it didnt get above 12.9vdc. can this all really be the result of the alt not charging, or is there something else. i did test for spark and it seemed weak, but as i said earlier i am new to bikes. would it be a waste of time to swap the ign coils with some i believe are good, are is it even possible that would be it as well. thanks in advance.

If you're getting 12.9 vdc, then the system is probably charging stlll, but just barely. The resistance readings across the rotor slip rings may give you some indication.

An easy way to tell if your charging system is working properly -- no tools required -- is to aim your headlight at a reflective surface, then gun your engine. You should see the reflection get brighter. If this isn't happening, then it ain't putting out enough juice.

Having said all that though, I've never run into a situation where my bike wouldn't run over a certain rpm with the battery still having at least 12 volts (I ran that bike for a couple years with total loss ignition, and just put it on the maintenance charger whenever I got home.) The one time I was out riding and it wouldn't run anymore because the battery had discharged too far, it felt almost like it was running out of gas. And even then, all it took was about five minutes with the battery hooked up via jumper cables to my car to give it a sufficient charge such that it ran normally the rest of the way home.

So I'm inclined to think the charging matter is separate from this rpm ceiling you're experiencing.
 
If your voltage is low Your TCI can do strange things. Thats why it ran ok with your jump box.
Your "good" AGM battery may not be so good. Was it fully charged when you tried it? It may have been low or dead. A low battery can make it look like it's not charging. The alternator needs a good battery to work right.
 
I didnt get a chance to check the brushes or meter the coils yet but i own a car audio shop and it was a brand new battery off the display and tried two different batteries. any other ideas. or is there a way to test the tci box?
 
The brushes literally take 10 minutes to check, do it. changed two today, shift lever, two screws on the cover. one screw per brush. Note the weird way the brush wire gets wrapped around the tab. the brush furthest from the crank normally wears fastest. a worn brush can easily cause flaky charging even if it isn't down to service limits, 3/8" IIRC.
 
Even a new battery right off the shelf can be low. Check the batteries voltage. If it don't read better than 12 volts it needs charging before you try it.
The way to check the TCI box is to check everything else in the ignition, If everything else checks good the TCI is bad by default. There are no bench test for the TCI box itself.
 
Is there a way to check the coils? i remember reading a post about metering from one plug cap to the other, is that true on my 82? when i did it came up as testing 27.53 ohm. is that about right. i will check the brushes tonight. thanks
 
On your meter, what range setting was it on?
On the 20k scale it will read 27.53 which is 27,530 ohms.
In the Clymer book it says the reading should be 10,500 - 15,500. from lead to lead. This is without the plug caps. With good caps, at 5000 ohms each, should get 25,500 to 35,500.
I have an 82 coil in hand that test out 11,570 without plug caps.
I get a reading of 30,100 with one set of caps, so these caps are 9,265 ohms each. This set is too high. My other set I get no reading, so these caps are bad too.
I think your coil and caps are just fine.
Also you can ohm out the primary side, the two wires where the coil plugs into the harness, a red/white and orange wire, it should be 2.5 ohms.
Check it on your meters lowest ohm range, often 200. Before you test the primary touch the leads together and see what reading you get. Just subtract this reading from what you get when testing.
Most meters have a bit of a reading on this low a setting because they are reading the resistance in the leads themselves.
One of my meters gets .1, the other gets .4.
If i check the primary on my coil with one meter I get 2.6 ohms. 2.6 - .1 = 2.5. The other meter reads 2.9 ohms, 2.9 -.4 = 2.5. Right where it should be.
If you haven't used a meter much, getting a few resisters from Radio Shack, in various resistances to practice with is a good idea. Take two 10 ohm resisters, hook them end to end, in series, you will get a reading of 20 ohms. Hook them side by side, in parallel, you will get a 5 ohm reading.
 
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