Holy Cow !!!

called the dealership today to see if they had a diode in stock and a price.

not in stock special order, 10 dollars plus tax!

does anyone know the details on this diode? the amps/watts/ ohms? so i can get one from radio shack?

 

$10 for the exact replacement is a hair steep but not to screaming outrageous. I'd offer a replacement suggestion but I don't know anything about your 400. Is there any print or embossing you can read off of the old diode?

 

no the diode fried its now all black

 

Diode from what?

 

Part Number 3h5-81980-00-00 Diode.

located in the wiring harness under the seat covered with a clear blue rubber sleeve


1982 xs400j maxim, Cleaned tank, cleaned carbs, new battery fully charged, New spark plugs tried to start it and POOF smoke under my rear end. I would like to know if anyone has crossed referenced the part
at radio shack

also no spark issues ,i want to change the spark plug wires and the coil wires, and regap the plugs and try again but at 10 + dollars a diode from the bike shop will become costly if i can not track down as to what caused the diode to fail in the first place. i have heard that the age of the diode could have caused this but i want a few diodes just incase the problem persists.

also i want to remove the airbox and replace it with K&N filters each protruding from the side where the covers go, will this affect how the bike runs? . yes i know the battery will be in the way but i plan on relocating it between the filters in a new designed battery holder.i put a new cheap radio shack fuse holder in it but it will be replaced by a MINI FUSE block or a circuit breaker system.

I have service manuals for just about every yamaha from the 80s b ut none have a trouble shooter flow chart that will help.

 

I dug deeper and found that the SIDE STAND RELAY is totally rusted inside and out . the starter circuit relay is slightly rusted.


Does the side stand relay stop spark if its not working or if the side stand is down?


It still cranks strong just no spark

 

i have always gotten a spark with the sidestand down.. so i don't think that would have an effect.. but with it rusted out.. i'm not sure about that..

question.. did you have it in gear?? if you have it in neutral, you can start it with the stand down, but if you have it in gear it won't start at all

 

If the bike is in neutral - no it won't stop spark

If the bike is in gear and the clutch lever is pulled in - no it won't stop spark

If the bike is in gear and the clutch lever is out - yes it will stop spark

 

Ok, sidestand relay should not stop spark if bike in neutral. On the other hand the sidestand realy sounds to be in poor condition.

I don't know where to find any XS wiring diagrams. That same diode is used on the sidestand circuit on the XJ750 Maxims, that's how I found it is still available from the dealer.

I wasn't sure it was used for the same thing on your XS though. Seems likely that the circuit is similar since you have a ruined sidestand relay too. Relay probably took the diode out.

On the XJ750 Maxim that diode appears to allow the low oil switch to kill the spark - while not having the sidestand trigger the oil light. In other words, you could replace the diode with a piece of wire and the system would function normally except having the sidestand down would turn the oil light on. I think, assuming the sidestand relay works similar to the 650 maxim (My factory 650 manual shows what's going on inside the relays, the XJ diagrams on the web do not).

It also appears that the way the system on the 750 works the same way as on the 650. The sidestand relay grounds the black wire on the TCI killing the spark. You can disable the system on the 650 by pulling the sidestand relay. I expect yours is the same way.

So, pull the sidestand relay and see if you get spark.

 

Oh, and if that diode does what I think it does one of THESE from RadioShack should do the trick. 2 for 59 cents.

 

Have to correct you on this.. If the bike is in gear, regardless of whether the clutch is in or out, if you put the sidestand down, it will kill the engine. It also will not crank in gear with the sidestand down, regardless of clutch.

I'll have to get out my manual and look that up.. The oil level switch definitely does NOT kill the engine in a XJ750J Maxim. I've had the warning come on when the level gets low and do something that makes the oil in the sump slosh forward, and the engine stays running. In fact, to me that sounds really dangerous. I know having the engine die is nowhere near as dangerous as having it seize, but its dangerous nonetheless. Imagine you're in the left lane of a freeway doing 75, someone does something stupid in front of you and you slam on the brakes, oil sloshes forward, oil light comes on, engine dies. By the time you've realized what happened, the engine is flooded and won't restart. You're slowing down rapidly, and now you can't make it across 4 lanes to the shoulder...........

 

I believe the diode is used in the starter circuit but not for sure on that .

I thank you on the information on that diode , it looks like its a 1 amp diode to protech against a 30 amp surge.

now to find out what the original diode specs are.

 

HMMMM. The wiring diagram has that diode tying the leg of the sidestand relay connected to the clutch switch into the oil light circuit. Perhaps it prevents cranking if the oil level is low.

 

The diode isn't to protect against a surge. It ties the low oil signal into the safety system somehow. Looks like the diode prevents the clutch switch operating the oil light. Of course, I'm looking at the 750 diagram.

It's specs are - lets electricity only flow one direction. Should only pass enough current to operate that little relay. 1 amp is plenty for that. Problem probably is that relay is shorted out resulting on too much current through the diode - cooking it. Get the relay taken care of first or you'll just cook the next diode (or something else).

That relay's function is to kill the spark if the bike is in gear and the sidestand is down. If it's buggered it may be killing the spark regardless. Yank it and see if you get your spark back.

 

Thank you again Micarl i will see if i can locate a new side stand relay and just for added measure i am replacing the starter ciruit relay as well .

i will not beable to do anything until next weekend. i will let you know what happens.

BTW a co worker has a 1986 XJ700 virago its sweet clean and running good. he made a comment he wanted a bigger bike , maybe an 1100 virago. he planned to save some money so he can buy one next spring. I asked what he wanted for the 700 and he said to me he would sell it for 1500. ( i could probably get it for 1200, flashing the cash , a dirty trick to do to a guy who is going to be a new daddy by xmas) I hope it works LOL

I have 120 dollars a pay check going to the bike fund now . I will have 1200 by xmas for sure , not only will I be working at my regular 7 to 4 job but i will be working at oceanspray for harvest for the months of october and november. maybe i will use the oceanspray money for the bike and pay him earlier

 

Has anyone tried the rad shack diodes for this? I have the same blown diode in my XS400K , actually, when I first got mine it had no diode, and was direct wired, which caused the neural light to be on in all gears.... I replaced it with a diode I had laying around, but it was probably less than 1 AMP , and it fried...
I may swing by and get a couple, will post results...

 

Ghost I got one ready to put on the bike today the 1N4001 RS diode, I plan on getting a few more just incase it fries again but i suspect the original fried due to age. will post my results ASAP

 

Hehe, I just picked up a pair...
Ran out of daylight tonight, will install tomorrow...

Oh, if you need any specifics on anything, drop me an email or pm, I do have a copy of the service manual

 

Something else is wrong tried starting it but the diode got real hot but didn't fry , so i stopped.

gonna give up on this and take it to the mechanic.

 

I would suggest a good rectifier type diode with at least a few amperes of capability. I don't know how much current you should have flowing through there but if I did, I could get you a good number for an appropriate diode. I know a 604 is good up to 6 amps, but that is the extent of my knowledge.