[PhildoBaggins]

I have a 79 Yamaha XS400

Im having a couple electrical issues.

1. the electrical starter doesnt turn over. When i try and start it the relay just clickes. Would this be due to the starter points are worn causing a bad connection?


2. The battery is weak when i try and start it has a really hard time (Crank start) but when i put the battery on charge the battery will start right up. Is that due to a weak battery or am i looking at more here??

 

[UngaWunga]

1 is caused by 2. Get a new battery, and check your charging system to see if it is actually charging your battery.

 

[PhildoBaggins]

I ended up charging up the battery and it seems to be fine. The start will turn over but as soon as it does it makes a funky noise like its jumping off track on the chain.

I started the bike and tested the battery to see if it was charging. There was no charge on the battery what so ever. So Im guessing thats the AC Generator. I tested my regulator (solid State) for resistants and there was none at all. I happen to have an elctro magnetic one so i switch it out to see if there was a difference. And no there wasn't.

So now what happens when i crank it up thee bike runs good at the first couple minutes of start up then when it gets warmed up it really starts to bogg down and back fired.

Anyone have ideas for me to look at? Seems like a mess at this point.

 

[snorkelfork]

this would be a good time to refer to the faq area at the " how to diagnose why your bike is shit" section that xander has to date failed to write...

...connoisseur of slack...

 

[xander450]

Fine. FINE. But you're screwed now because I'm in no position to pull parts off of bikes to take pictures for the faq... that's going to have to be your job.

What format do you figure this ought to be in?

A

 

[PhildoBaggins]

HAHA!! Yeah it would be a good time to refer to that section.

Basically im just going to check the wiring on the AC Generator and assume the carbs are fine since they were just completely rebuilt.

Any pointers about dealing with the AC Generator?

 

[xander450]

Yeah. Don't bother with it until you have a battery that holds charge.

If you don't have a bunch of lights on, your bike should idle for a good hour just on a charged battery (not that I'd recommend you do that to an air-cooled bike). If it's crapping out within a couple minutes, your charging system has nothing to do with it (except to the extent that the lack of a charging system may have killed your battery).

Btw, automotive batteries rarely recover from total discharge, so if that is where you were at you can pretty much assume it's done for and buy a new one.

You're going to need your bike running to test the charging system.

A

 

[PhildoBaggins]

Well come to find out im having two seperate problems.


The carbs are crapping out after the bike warms up after a few mins. It almost feels like its too much gas getting to the bike kinda bogged down. idle is fine.

The charging system is a completely different problem i just discovered so im going to have a look at the leads on the AC GEN and see what i can find out.

 

[xander450]

What gives you that impression? Not that there's any reason to think you're wrong - but why do you think carbs?

Here's why I ask. Let's say your battery was crap and you start your bike. At idle the charging system isn't doing anything - doesn't kick in until 3.5K or so, and doesn't get good until the 4.5-5k range. SO, you're running entirely off your battery. As the charge diminishes, your spark gets weaker and skips some cycles. Unburned gas collects on your plugs, which quickly foul.

Not that that scenario is what's happening, but it's very plausible.

A

 

[PhildoBaggins]

Well that completely makes sense.

Here is why i think its two seperate problems. I recently had my carbs rebuilt and the guy was suppose to make them run a little richer since im going to pod filters instead of the stock breather boxes. When i crack it up with the battery fully charged (I tested it) it was idle and purr like a wet dream. As i let it sit for a couple minutes and start to increase the throttle it will start to pop and act extremely bogged down. And at that point it doesnt even want to stay running unless i really give it gas. Kinda seems like the jet needle is runnning to rich.

The charging system however i found out is not working. I did replace the solid state regulator after i tested it for resistances and it didnt have any at. I put in an older elctromagnetic regulator that did have the allowed resistance. And I still dont know if the rectifier is good or since i dont have any charge at all coming to the battery.

It sounds like a mess but im going to adjust the jet needle and see if i get a different result.

Also I check the battery out and all the cells are full of fluid so thats why i kinda ruled it out.

What do you think?

 

[xander450]

Just eliminate your battery. You don't even have to replace it - just hook up the charger while the battery is attached and run your bike with the charger pumping voltage into the system. That way we can eliminate the battery.

If your problems continue, pull your plugs and have a look. Also, find out HOW your guy adjusted your carbs. Did he change the idle or main jets? Replace jet needle, or adjust it? Crank the idle mixture screw toward the wet side? ...because if we don't know how he made it rich, it'll be harder to fix.

A

 

[PhildoBaggins]

well here is the funny thing.

The bike is running perfect now. Here is what i did:

1. adjusted to the jet needles to 2 they were at 3 and 4 so im guess that was one of the big problems.

2.The charging issues I ended up taking everything off on that side and checking the wires and it all checked out ok. I ended up switching back to the solid state regulator and for some reason it all worked. the battery starting charging and it all checked out ok.

Here is a strange question Is there a different between a solid state vs electro magnetic regulator in regards to the resistance? I test the solid state and there was none at all when i tested the electro magnetic one they was the allowed amount. So it makes no sense to me.