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Suz GT185 wacky electrix, thinking voltage reg?

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  • #846395

      So ive got this gorgeous GT185 ive put a lot of work into recently. Got it repaired, plated, everything and have been riding it for a bit. For the most part everything was perfect, but today i was coming up a hill at about 3 k rpms in 4th gear and it started to slow and lose power till it died. Pulled over, kicked it over and found that it would only start if i had the throttle partially open. I had to hold the thing at about 6k rpm all the way home or it would die, which it did like 3 times:(. If i pulled in the clutch or shifted gears or anything that dropped the rpm below like 4 k it would die…and im almost 100 pcent sure it was from lack of spark.

      So…i know how these old dc dynamos work…they are setup to not charge unless the rpms are high, like open road high right? But i think this is something more.

      Other things to consider…whenever i start the bike i had to rev it up for a min or two finding that the charge light would illuminate and flicker if my rpm dropped below like 2k. Generally this wouldnt happen while stopped at a light unless i was stuck for 5 minutes…once again i thought this to be part of the old dynamo way of charging…but now if i dont keep revving it within a few seconds the charge light comes on, and shortly after it dies. So this is obviously electrical…but do you think it.may be that the undercharge setting on the voltage regulator is too high? Eg…it wont charge till the alternators putting out like 14 v rather than like 12.5? Or does it sound like the battery? Because obviously the battery should be able to maintain for a few minute on its own without being charged? Idk im stumped. Dynamo recently got new c brushes, tested, everything checked out. Also battery is a wet cell and is about a month old…it was fully drained a couple times a few weeks ago by accident when the charging system was up and running.

      Other questions…if it is the voltage reg, will any old voltage regulator do for this bike? Secondly…will one of those 3 pound sealed.20ah batts do for a new battery since this is a small bike? I wont use it to crank…just for plugs and lights, ect. Thanks…sorry about bad spelling, in a rush.

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    • #850164

        Good to see that you’ve replaced the carbon brushes, but there’s a bit more to check. I’m not an elecrical expert, so I lifted this advice from another site. I’ve edited the text slightly and underlined the sections which I think might be most important to you. Hope this info helps.

        [i]”The armature should be tested on what is called a “growler” first. This will determine if any of the winding is shorted out. If it is shorted out, then the armature will need to be re-wound. The next test is a ‘bar to bar’ check with an ohmmeter. This is a check for shorts between the commutator bars. If this also checks out OK, then the commutator can be turned. This is done in a lathe. The mica between the bars should also be undercut the same depth as the width of the mica. The mica is also removed from the sides of the bars in the undercut slots. The edges of the bars are then chamfered slightly and the commutator is then burnished.

        Bearings should be replaced and new brushes installed. The brushes should also be ‘seated’ to conform to the diameter of the commutator. This is done by placing sandpaper around the diameter of the commutator (one layer with no overlap) while it is installed in the generator housing. Then the brushes are installed and the armature is spun by hand a few revolutions. This will sand the face of the brushes to conform to the diameter of the commutator. The sandpaper is then removed. The generator can then be installed.


        It is VERY important to polarize the generator before starting the engine after the generator has been worked on. Even if just the brushes have been swapped out. If this is not done, the armature and/or the regulator can burn up.”[/i]

        These sites have info on how to polarize DC charging systems: and

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