'82 750 Maxim charging battery unreliably

Hey Guys,

I've fixed the majority of the electrics, still got the turn signals not blinking below 2.5k rpm but I believe it's due to the spring in the housing being coated in rust (cleaned one of them thoroughly and it was quite a bit brighter). The major issue I'm having right now is the battery not being charged reliably.

The battery died on me earlier this month so I went ahead and replaced it as it didn't look be matched for the bike. I got a wet one then filled and charged it. The bike was running great but the sensor would still be tripped occasionally. I wasn't able to start it earlier this week but did a roll start. I'm noticing that around 3k rpm the alternator kicks in and charges the battery (alarm goes off) but once it goes past that the charge drops a little causing the alarm to be tripped again.
I measure the battery once I got home and it read 12.48V, I put it on a trickle charge for a bit so it should start the bike later. I know the battery reads ~14.4V when the bike is running between 2-3k rpm.

Any suggestions on what's the culprit? I'm thinking regulator or alternator. I know I just measure the brush length (still gotta figure out where it's located) for the alternator but I'm not sure how to check/test the regulator.

 

You have all the symptoms of a non-charging system...that issue with the signals is very damning...just sounds like you don't have enough electrical power to make the relay cycle below 2500 rpm...

The alt (stator actually, on bikes) should start charging soon as you get off idle, so by 1200-1400 rpm or so you should see 13.5-14v at the battery.

12.48v surface charge after riding is pretty low. should be more like 12.85v with a new battery.

I'd say your reg/rec is probably on the way out, but you'd have to check the stator output at 1400 rpm or so compared to reg output to battery. If the stator is supplying the power but the battery is not being charged, the reg is not working right. But check all related connections first.

The stator on bikes usually supplies power to the reg by way of three identical wires (same color and size)...you need to leave the reg connected while testing or it can damage the stator, but put a test lead from a meter into where the wire comes into the reg plug and meter the output from each wire (20v DC scale)..each wire should be supplying 1/3 of total charging voltage, so at 1400 rpm or so you'd wanna see 4.5-4.7v or so (for a total of ~14v or better) from each.

If you have solid charge from the stator but it's running the battery down at the same time, you have your answer...the reg/rec is bad...

 

After I took it off the charger the battery reads 12.85V. I had suspected it was most likely the regulator, can you tell me where exactly it's located? I think it's right to the left of the battery wedged in a bit (I'll check the manual for the diagram).
I'll test it out tonight after I go for a ride, for some reason when it's cold the idle jumps a little.

 

I tried testing everything today and for the life of me I couldn't find the alternator/generator. Can you tell me where it's located on the body?

 

Alternator is in the big round case stacked on top of the motor, below the carbs on the left side.

I think your regulator is gonna be under the sidecover, below the seat on the left side. Will have a metal box with heat sink fins on it.

 

http://www.partforyamaha.com/pages/OemP ... ibrand=YAM

Here ya go...good place for looking up how things are put together....

hint, it's referred to as "generator" on there

And your reg is where I said. pull the left side cover off. If you're lucky enough to have a left side cover...mine came without...

 

The battery may be bad, like cell phone batteries, charging an incorrect battery life shorter.

 

Ah I see, Gotta pull the cover off to see the wires. I was pretty sure it was there but I didn't want to pull off the wrong cover (some have sealant and such).

I've got a parts catalog that I refer to, the annoying thing is it shows the generator assembly and doesn't reference the location of it. In the manual it even skips describing the location. I found the regulator but didn't go through testing it.




On a sidenote, I was changing the right-side foot peg and notice the bolt had been scraped/dented by the PO when he high-sided. After I took it off I couldn't get the nut to go back on, do you know the size of the bolt and nut? The thread on them is a bit mangled and won't line up right.

I believe the part number for the bolt is 90109-12651-00, according to the yamaha parts site it isn't available and I wasn't able to find it on my regional parts site The nut is 90185-12080-00.

 

Hi Ashex, You have the same bike as I do so here is what you need to know, on the left side( the kick stand side) the alternator is behind the round cover just under the carbs just behind the cylinders, there are three Allen bolts that hold the cover on, and it takes a 5mm Allen wrench.

When you remove this cover it will hang by some wires, on the inside of the cover you should see the Carbon brushes they press against 2 Copper rings, you want these Copper rings to be reasonably clean with no crap in the gap between the rings.

As the Carbon brushes wear, they give off a Carbon dust which will interfere with the power going to the Copper rings.
The purpose of these brushes is to turn the rotor into an electromagnet thereby causing A/C current electricity and that why they are called alternators. So as you can see, anything that interferes with the making of this electromagnet needs to be dealt with. Also check for oil leaks from behind the rotor, this will contribute to the gunk that can build up on the rotor.

 

Thanks for the advice, I opened up the alternator and found a good amount of carbon dust. I wiped it down with a clean terry cloth then closed it back up, here are a couple pics of how it was:



That's about as far as the good news goes. I started it up and the battery warning light went off so I assumed it was okay. I should have charged the battery all the way but for some reason didn't. I went for a ride to see if the battery warning light would flicker and interestingly it behaved opposite of how it was before, when the rpm went above 2k the light would occasionally go on, when it did the light was go off once it dropped down to 2k or so.

This is where the bad news happens, while I was on the highway I had to do a hard brake due to a couple cars stopped on the wrong side of the road, the bike died when this happened but I let the clutch out to get the engine rolling and kept going. Right after the bike started I could tell it was running rough so I turned around to head home. The bike died when I got off the highway but I started it up and got back on the highway to get home.
At this point I could feel the bike struggling, I was steady on the throttle and the rpm wasn't jumping around but I could definitely feel the bike losing power. I began losing speed no matter how hard I hit the throttle it wouldn't increase speed, I pulled off to the side of the highway when it died and wouldn't start again (lights came on, starter turned but the engine wouldn't).

Ended up pushing it to the next on-ramp then came back and pulled the battery. I have it on a trickle charger but I suspect it's not the battery due to how the bike behaved before it died, can anyone suggest what I should check when I head back tomorrow with the battery?

 

Bring a multi meter with and see if the battery voltage is 14.5 volts at 2500 rpm. If not you better find a trailer to haul your bike home.

MN

 

The problem is the bike isn't starting, I hooked my car straight to it and still couldn't get it to start. I've got the battery on a trickle charger at the moment, so if it starts with it tomorrow I'm bringing it straight home and getting a rectifier off a local XJBikes member tuesday.

 

Did you take a voltage measurement before you put the charger on? Not sure how dead the battery was from trying to crank your engine. Charged battery should be around 12.65 volts at rest.
Also did you polish those stator rings where the brushes ride? Also how far were the brushes from the wear lines?
Lastly you should check the alternator connector up under the tank to see if it's melted. Very common issue on these bikes.

MN

 

It sounds like you have a slipping "starter clutch", unlike Harley's or BMW's we don't have a "bendix" which throws the starter pinion into gear, we have what's known as a "Sprague clutch",( turn it one way and it's free, turn it the other way and it grabs) when the starter turns the gear on the end of the starter which is in constant mesh with an idler gear which meshes with the gear on the starter clutch, the clutch grabs and relays torque to the chain which drives the alternator, this chain is driven by the crank. When the engine starts turning on it's own power the starter clutch free wheels. The type of oil in the engine can affect how the starter clutch behaves, for example we don't run synthetic oils meant for cars, it can cause the very problem you have reported.

 

I checked and it was around 12.26V so way below what it should have been. I'm not sure that I polished but I did wipe it thoroughly, I'll check it again tomorrow if I can get the bike to start.

What should I do if I have a slipping "starter clutch", get a rebuild kit?

 

turns out I jumped the gun. I went back this morning with the battery and it still wouldn't start. It was low on gas but wouldn't start on reserve so I got a gallon and poured it in, after this the bike started up and I got home. So as my good doctor once said "It's just gas".

So for the reserve, would you say I need to replace the petcock or clean out the tank?

As for the charging, I finally spotted those three white wires hidden in a sleeve behind the air intake. I'll look at it tomorrow.

 

Picked up a rectifier and swapped it in, While putting it on I noticed a lone cable hiding behind the panel. Anyone know where it goes?

 

I believe that's a grounding strap. On mine if I recall from attaching my auxiallary outlet, that black wire is just attached to that nut that is in the picture just to the left of the wire. Undo that nut, put the loop around the bolt, and tighten the nut down on it. This could be a lot of your problem if your electrical system isn't grounded(although I think there are other grounds on the bike).

 

I installed the rectifier last week and secured that grounding strap, a quick test showed the voltage was increasing as expected with rpm. I've been riding it for about a week without any battery issues. I checked the voltage on the battery and it reads at 14.8V!

The battery sensor still isn't good and continues to set off the alarm, I'm thinking the resistor I installed is too large.