Rebuilding a 95’ gl1500 I - weird one

[tnwebwise]

I forgot to wire the 55 amp fusible circuit and got the bike going as a test prior to checking the gauges and lights. Bike runs great. I add the circuit in and it runs very rough. So I take the fuses out related to that circuit using the tech manuals and add the fuses in one at a time to see if I can find the issue. Fuse 8… causes a rough idle and backfiring. And below the carb and in front of of it and above 1000 rpm it makes a whirring almost like a fan, or a bad bearing fan from a computer, basically louder fan then it should be. The radiator fans are wired but not in place and they are not on. With the fuse off/out the whirring is not there and bike runs great. Fuse 8 installed runs for crap and backfires and a fan like noise over 1000 rpm. Fuse 8 in the book and label is meters, tail and position. Why does this fuse cause rough running, backfires on deceleration and weird whirring noise.

I’m befuddled.

I rebuilt carbs and replaced vac lines, temp sensors and filters along the rear rebuild. Didn’t split the case. Runs great with no fuse 8.

Ideas?!?

[Rambozo]

The 55 amp is from the alternator. Just a guess, but I bet your battery is low, and the alternator has its tongue out trying to charge it back up. Keep the revs up or charge the battery and see how it behaves then.

[tnwebwise]

New battery on a noco smart charger, the 55 amps is a line from battery to fuse on right to alternator to fuse bank for many things. Alternator puts out 14.3.

[Rambozo]

Just a thought, since an alternator can whine when working hard. But that would be fuse 11 not 8. Can you track down the location of the noise? Can you measure the current draw with and without fuse 8?

[tnwebwise]

Got an amp meter and will check tonight - I think the noise over 1000 rpm (whirring like noise) is coming from the Air Shot Valve as the only other part there is the thermostat.

Ref: https://app.screencast.com/HaV2YlbSuicV ... Hq0JS11n2M

Also, does the exhaust to engine connection need a washer or gasket between them?

[WingsandThings]

There are copper crush gaskets between the heads and the exhaust headers.
Ideally they should be replaced whenever the headers are reinstalled. I think you can probably reuse them provided they are in decent condition.
If you don't see any when you remove the header, check to see that they are not still on the head.

https://www.ebay.ca/itm/191689211331?ha ... R4DgpvW2Yg