1983 Honda vf750f no power

Realized I made this post in the wrong area. Here's my dilemma:

So, I bought a 1983 Honda VF750F last year and was told it needed a battery and cleaning. I know it wasn't true but I'm having trouble getting power. Everything is stock except the starter relay. The one that it came with was modified to accept a blade style fuse. I bought another one and popped it in. It sparked and blew the fuse out. 3 fuses later the silicon rectifier started smoking. Replaced that. Even bought a Rick's motorsports rectifier but noticed it doesn't come with the blue wire in the middle, not sure what that's about. So yesterday I popped the old rectifier and the starter relay it came with. No power. Any suggestions?

 

buying a non-running bike with most part replacements NLA is big gamble, especially an old pos like that.


i suggest pullin out all fuses [except main 30 amp] and unplug the r/r and stator for testing. then add one fuse at a time until main fuse blows. also its important to do standard tests on stator to be sure its not shorted to ground. be sure the B and M posts on the solenoid are connected properly.

maybe our #1 electrical expert Ph.D, grum, has some wisdom frum down and under.

 

Yeah, in hindsight I should've picked up a running bike but it be like that. I will give it a while and see what happens. And yes, any suggestions are welcomed. Thanks!

 

A bit more clarity needed here!
So, you are blowing the 30amp Main correct? When you say the "Silicon Rectifier started smoking", are you talking about the Clutch Diode or the Regulator/Rectifier? What is this "blue wire in the middle" you talk about 750 drawings I have show no blue wire for the R/R or starter relay? Does the Fuse blow without Switching On the Ignition? Do you have a wiring diagram of your bike, if so can you scan and post it on this thread?

Blowing the Main Fuse 30amp means a short somewhere between the Fuse and the Ignition Switch, and generally that will be a short within the R/R assuming wiring is standard. Beyond the Ignition Switch, the lower amp fuses in the fuse box protect those circuits and will blow before the Main Fuse 30amp. Do as Squirrelman suggested unplug the R/R the fit a new fuse, does it still blow?

Post pictures of the Starter Relay and the 4P plug with its wiring.

 

Thanks Grum.

I will be posting pics as soon as I can. But as far as blowing fuses, I bought a replacement starter solenoid relay, plugged it into its corresponding posts (B/M) and went to plug the battery. Connect the positive and when I went to connect the negative it blew the fuse. After 3 the silicon rectifier (will also post pics) started smoking a joint. I think the one I got was just no good because I've heard aftermarket starter solenoid relays are a bit of a gamble. But I'll be posting pics of everything soon.

 

Starting from the top.
Rick's r/r

Stock r/r

Stater solenoid

Plug for stater solenoid

Silicon rectifier

Could get the wiring schematic to upload. I'll see what I can do.

 

Don't worry about the wiring diagram, I have a VFR705F wiring diagram not sure what year, but that won't matter.

Firstly do you have a multimeter and know how to use it, volts and ohms measurements?

Top two Pics.
The middle Blue wire you talk about I think is actually Black, if thats the case then that wire is a Voltage Sense wire and most likely only needed for the OEM R/R. The Rick's replacement probably doesn't need it, to state the obvious make sure the Ricks one matches up with the Red and Green wires on the bike harness.

Starter Relay looks a mess! Have a look at the attached pic. These non genuine Relays are available on e-bay cheap as chips. Just do a search on the OEM Part No. 35850-MB0-007. Might be worth fitting a new one as it neatly houses the Main Fuse as well.

What's vitally important with the connector to the Starter Relay is that the Green/Red wire and the Yellow/Red go to the spade terminals that are for the Relay Coil.
The other heavier Red wires need to go to the two spade terminals that the Main Fuse feeds.
So with an intact fuse measure the 12v that should be on two of the relay spade terminals MAKE SURE that the Red wires go to these terminals and NOT the Green/Red or Yellow/Red.
Check and verify this.
Also with the plug removed from the relay. Set multimeter to Buzzer mode or lowest Ohms range. Probe the Green/Red wire and Red wire within the plug, make sure you do NOT measure a short. Have a close look at the Red Circled area of your photo attached, does the Red wire have damaged insulation and could this be rubbing and shorting to the Green/Red wire?

I have a gut feeling that perhaps the Green/Red wire might be on the wrong terminal and seeing the 12v Fuse voltage, is there any chance the plug could be accidently fitted to the relay 180deg from the normal position? This would account for the short AND high current through the Silicon Rectifier/Clutch Diode then through the Neutral Swich to Ground. Placing your bike in gear and rechecking for the short might verify this, assuming your Diode hasn't blown open.

So as also suggested have you tried unpluging the R/R to see if the short dissappears? To save blowing up fuses you could have your Ohm meter probing the load side of the main fuse terminal (FUSE REMOVED and NOT the Voltage side) with the other lead to Ground if the short is there you should read zero ohms or the buzzer buzzing.

 

Yes I do have a multimeter and know how to use it. I will try checking for shorts. I'll be purchasing an OEM solenoid soon. Expensive but better safe than sorry. Right now I have two clutch diodes (not saying I'm trying to blow one up but just in case.)

The plug for the solenoid can't go in another way, yes I tried it by accident. As far as I know, the starter solenoid is the only funky thing the owner modified.

I'll run som tests and get back to you. I'll be running them with the solenoid I have so now. After I check it with the multimeter

 

Just one little note on replacing the starter solenoid. They are two styles for how the cables are routed on a bike. Note the "B" (for Battery) and the "M" (for Motor) on the original. Those can be opposite, and then the wire locations on the plug are also opposite. I have used opposites on bikes and just re-pinned the wires at the harness side connector to compensate (as Grum described above).

Note that the new eBay solenoid pictured above is an opposite of what the original is.

And I "modify" my old fusible link style solenoids the same way, connecting a blade style fuse holder using eyelet connectors.

 

I figured that the solenoid might have been an opposite. I was thinking of re pinning the connector cable. I have a wiring diagram to guide me. But definitely going to get an OEM solenoid eventually.

 

Quick update. I re pinned the connector to the solenoid. No power surge and the fuse is all good. No power still.

 

back to basics

try checking with ohmmeter for connection between positive battery terminal and terminals on the fuse block with key ON. meter should read near zero.

use a fat jumper wire beteween battery negative and clamp it on to footpeg bracket or engine mounting bolt for testing.