Main Fuse blows when the bike is hot.

[STN]

So the main fuse, 30amp blows when the bike gets hot. It doesn't short when I disconnect the VR so I'm guessing its the VR. But do you guys have any suggestions, I'm just about hitting my head on the garage door.

[DonTZ125]

I'm not sure what the question is - the fuse blows when the bike is hot, but not when the VRR is unplugged. Ergo, the VRR has died, but fortunately the main fuse is (for once!) doing its job and protecting the rest of the bike.

Replace the VRR with the upgraded model.

Shameless plug - I build an adaptor harness that makes changing from the old 4-pin VRR to the new 6-pin VRR the work of minutes. viewtopic.php?f=76&t=8325

[STN]

Well I hate to say it but I do have the new VR. The engine and electronics are of 1998 600 stock. But a bad VR would cause the main fuse to blow when it gets hot? Then it seems to work fine when she cools down, and I've replaced the fuse.

[DonTZ125]

Depends what exactly has gone wrong. It's not inconceivable that you have something in the VRR wirepath that is frayed and melting out the insulation. The VRR does get hot, and semiconductors (especially dying ones) do very odd things as they warm up. There's a fair bit of current flowing there; if you suddenly get a short from a hot pin to ground, it's gonna draw a LOT more than 30A.

Try swapping out a known good one, if possible. If the problem goes away, it was the VRR. If the problem persists, it's in the wiring.

[yamaha_george]

Don,
the fact the fuse goes when HOT is definitely electronics rather than plain wire issues in my book

[STN]

Just the man I was hoping might chime in? I agree with Don, it could be the wiring, but I doubt it, it looks fairly solid. But what do you think YG?

[yamaha_george]

Just the man I was hoping might chime in? I agree with Don, it could be the wiring, but I doubt it, it looks fairly solid. But what do you think YG?

STN,
At this point I would have my meter out and making resistance/volt tests on the Volt Regulator AND the black box PLUS the actual HT coils.
had a case a few years back that would blow the fuse when the HT coils got hot and were breaking down under load (NOT on an FZR by the way)

[STN]

Well I just rode it 7 miles in the rain after letting it warm up completely for about 10 minutes. I also ground down the frame a bit to allow for some new metal to get in contact with that ground that hooks to the VR. It seemed to work fine (but it always does, till it blows), so now I wait for another 110 degree day and see if its the VR overheating and causing the fuse to blow. Or I might just take this time to add a slim fit computer cpu fan to the outside and see if that helps. I

[yamaha_george]

STN,
could also use thermal compound to help the heat path from VR to mounting plate

[STN]

Sorry to bring up this old craptastic thread, but I think I've got it fixed now. While the VR gets super hot, I think the short may have been because of the wiring, or maybe because I took off the Exup directly out of the cdi. In any case she seems to be doing great, now before I go off to college again I'm getting her ready for a years worth of torture. I've just the adjustable shock mount and the front fork seals to finish. And maybe adjust the valves.
In any case, thank you gentlemen.

[yamaha_george]

STN,
good to hear you have a positive result and the work is going forward, if you get stuck you know where to yelll.........

[DonTZ125]

The VRR should not get "super hot"; double check your ground path, including the ground wire from the battery to the frame.

[CJD]

So the main fuse, 30amp blows when the bike gets hot. It doesn't short when I disconnect the VR so I'm guessing its the VR. But do you guys have any suggestions, I'm just about hitting my head on the garage door.

You Sir answered your own question, everything has a life span.

While the VR gets super hot, I think the short may have been because of the wiring,

How far can you push your bike when your Faulty VRR decides to let you down again? Trust nothing. replace your failing VRR