I made a silly mistake.

[Zero Gravity]

I was recently replacing a set of bent forks on my 1979 CB750K and decided to start the bike after completing the fork swap since it had been about a week since I'd started it.

The bike started perfectly and ran just fine until... A loose key on my keyring fell onto the fuse panel which I had stupidly left the cover off of. There was spark and the bike immediately shut off.

Now nothing happens at all when I put the key in the ignition and turn it to the "ON" position. The bike had no electrical problems before this and none of the fuses in the fuse panel appear have blown after I saw sparks. I have tested each fuse for continuity with my multimeter and each one tests positive.

I am totally at a loss for where to start probing.

When it comes to mechanical issues, I'm pretty handy but electrical stuff intimidates me quite a bit. Any wisdom would be greatly appreciated.

 

[899ccs]

You took out the 30 Amp main fuse behind the left side cover

 

[SenseAmidMadness]

Yep, there's a big ol' 30 amp fuse on your starter relay under the side cover, and another smaller one on that relay too. That's most likely the one you popped. The relay controls power distribution off the battery positive terminal.

 

[Zero Gravity]

Thanks so much guys, I will check that out when I get home today!

It does look like the OEM main fuses are pretty spendy for what it is (a strip of fusible metal). Is there any reason not to wire in a standard automotive type 30a fuse between the contacts?

 

[750_cafe]

Thanks so much guys, I will check that out when I get home today!

It does look like the OEM main fuses are pretty spendy for what it is (a strip of fusible metal). Is there any reason not to wire in a standard automotive type 30a fuse between the contacts?

I got one of the 30 amp automotive fuse housing and wired each end into it just for shi*s and gigs to see if it would work got the 30A automotive fuse, plugged it in and long behold it did in fact work. Everything works as it’s supposed to, maybe even a little better, and now I no longer need special fuses! I suggest it if you are looking to do so cause these bikes tend to burn the main fuse.

 

[jasonscb750build]

I got one of the 30 amp automotive fuse housing and wired each end into it just for shi*s and gigs to see if it would work got the 30A automotive fuse, plugged it in and long behold it did in fact work. Everything works as it’s supposed to, maybe even a little better, and now I no longer need special fuses! I suggest it if you are looking to do so cause these bikes tend to burn the main fuse.

I blew mine last night chasing neutral/ oil power/ ground issues.

Did you just crimp ring terminals to the ends and attach at the screw posts?

 

[750_cafe]

I blew mine last night chasing neutral/ oil power/ ground issues.

Did you just crimp ring terminals to the ends and attach at the screw posts?

Yes, it was pretty easy, the only complicated part was mounting the fuse housing some where. I just ended up using electrical tape and wrapping it around the housing along with the solenoid. Hope this helps!!

 

[jasonscb750build]

Yes, it was pretty easy, the only complicated part was mounting the fuse housing some where. I just ended up using electrical tape and wrapping it around the housing along with the solenoid. Hope this helps!!

Considering the factory metal type seem to be a special order thing, this helps tremendously. Cheers brother.

 

[mrtwowheel]

I blew mine last night chasing neutral/ oil power/ ground issues.

Did you just crimp ring terminals to the ends and attach at the screw posts?

Whatever ring terminals you use, A 30 amp circuit terminal should be crimped and soldered. If I have to use a connector from downtown I cut the plastic insulator off, crimp, solder. shrink wrap.

 

[Zero Gravity]

Well, I stopped by a friend's motorcycle shop and he had a bunch of OE ribbon style 30a fuses. He gave me a handful.

Got home, took off the side cover and opened up the little hatch on the starter solenoid. Sure enough, it was blown (and there was even a spare ). Replaced the popped one - and the spare - and the bike started right up.

I will switch out the ribbon style for a blade style when I run out of the ones my friend gave me. The wiring on the bike is totally stock and seems to be in good condition (and I now know to be SURE to put the fuse cover back on before putting my keys in the ignition!!), so here's to hoping that's a long time from now.

Thanks for the advice, everyone!

Now to back to fixing everything that was damaged when I put it in a ditch....

After replacing the forks, handlebars, and clutch perch/lever I've noticed the bars still feel a little tweaked while riding. I'm guessing the triple tree is slightly twisted so I'll be swapping it out for another I've got and taking the opportunity to put in fresh steering bearings. While the forks are off again, they'll get rebuilt with new seals and progressive springs.

Unfortunately, it seems there are also at least two hairline fractures in the oil pan so that will also be replaced. Is there anything else I should do while I've got it off?

The front rim is also definitely a little bent. Rather than trying to take the bend out with spoke adjustments, I will also use this as an opportunity to replace the rims with a set of gold ones I have.

By the time I'm done breaking things on this bike, it'll practically be brand new hahaha. I've named the bike Spiff (like the spaceman) but maybe Theseus would've been more appropriate.

 

[Zero Gravity]

Here are a few pictures of the bike. I got it back in October. 27k miles for $1300. Not too bad and definitely worth dumping a little more into.

I spend the last month getting it ready for a long road trip and decided I'd take it to a shop to take care of putting on new tires, chain/sprockets, and rear brake shoes to make some progress while I was at work. It was a shop I don't normally use (my friend's shop was closed for the month while he was recovering from a heart attack). Unfortunately this other shop put their least experienced mechanic on the bike and he forgot to put a cotter pin back when reassembling the rear brake... which promptly disassembled itself while I was riding a day later and locked up.

I canceled my trip and ordered parts. Since I wouldn't be doing more than a few miles a day while commuting, I figured I'd free up the rear brake and ride it gently while parts shipped. That turned out to be a bad decision and I overshot a turn on the way home one night about three days later (on the very same turn the brake had locked up on, in fact).

Towed the bike home and got to ordering more parts...

As bummed as I am to have crashed it, I'm trying to focus on the silver (gold?) lining of being able to rebuild it better than it was.

I'll likely be posting a lot more as I tear further into this bike.

Thanks again for being such a valuable resource!

 

[brettp]

Do you store it outdoors? If so, that makes me sad.

The if the oil pan is aluminum (or at least nonferrous) try using aluminum brazing rods. It is stronger than the aluminum and will close them up nicely and you can grind them down smooth. Note, I tried using them on a side cover but they didn't work well for me. But I'm new to them, also.

 

[Zero Gravity]

Do you store it outdoors? If so, that makes me sad.

The if the oil pan is aluminum (or at least nonferrous) try using aluminum brazing rods. It is stronger than the aluminum and will close them up nicely and you can grind them down smooth. Note, I tried using them on a side cover but they didn't work well for me. But I'm new to them, also.

I do and use a bike cover when it's wet. I live on gravel roads in Oregon, so that's why it's always dirty. I rent and don't have a garage, that makes me sad. Can't have it all, I suppose.

In addition to hairline fractures, one of the cooling fins broke off so I'm just going to replace it with an intact piece. So far I've been taking the "buy another and refurbish the old one" approach when fixing this bike so I'm left with a pile of spares and am not shit out of luck if something goes wrong down the road.

At any rate used oil pan on eBay is literally $30. I'll consider brazing the old one after I swap it out.