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My first street bike resto/rebuild Suzuki GT380

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Finally rebuilding a vintage street bike. 1975 Suzuki GT380 2 stroke tripple. Will be putting the pipes on tomorrow and then breaking her in. Went with the blue powder on the rims just f something different as the chrome finish was not great.

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I have the stock pipes. They are still in nice condtition, the baffles have been cleaned and repacked. I have a rare set of Piper 3-1 on my GT550 and thought about switching to those but I like the look of the originals

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Looks great! I actually like the Blue rims...something a little different

I just pulled my '73 out of full time service for a freshen up. Its been doing commuting duty for a few years now and its been about 15 years since it was last apart. Can't beat the quality.

My biggest struggle is pipes, 2 of my 3 headers got spiral fractures just behind the boss that slides into the exhaust port. I had to get an extra collar welded on the outside to seal and stiffen them up. I would love to get a 3-1 but they are pricey and I have to say the 3-4 exhaust is one of the sexiest around:busted:

I love this little bike. You can drive it all-out-all-the-time and not really have to worry about big speeding tickets :lol:

Great work! let us know how she rides

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WAY NICE!!!

Started a road bike restore myself a few weeks back,67 yamaha 250 twin,(one year only model)Note:the multi year bikes are a little easier to find parts.. It's in MANY boxes now,report soon to follow..

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Thats sounds nice Scale, sure it will be beautiful like your others. Questions about the GT380. Took it out today for the first ride...20 miles. I dont believe my battery is charging? I started to lose lights, horn, turn signals etc. Where is a good place to start checking with this? What does the voltage regulator do? What does the rectifier do? If I charge the battery it holds in the garage while bench checking the lights, could the battery still be bad?? Thanks everyone.

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Thats sounds nice Scale, sure it will be beautiful like your others. Questions about the GT380. Took it out today for the first ride...20 miles. I dont believe my battery is charging? I started to lose lights, horn, turn signals etc. Where is a good place to start checking with this? What does the voltage regulator do? What does the rectifier do? If I charge the battery it holds in the garage while bench checking the lights, could the battery still be bad?? Thanks everyone.

Hummmm,not real familar of the GT,does it have a generator brush system? Or a magnet\stator system? If it's the latter, check the two wires with the common color (maybe yellow)for AC volts,they will go to a rec\retifier then out as a (maybe)black and white wire check for DC power there. Maybe post up some pics of the elect stuff,i'll figure it out from there:thumbsup:

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Okay, here are some pics of what my alternator system looks like. This is NOT from my 75 GT380, mine is actually cleaner and looks brand new, but same part. I have replaced and checked with 2 other used voltage regulators and rectifiers and those did not show the correct reading either. Unlikely that 3 regulator/rectifiers are all bad, more likely I have something else going on. I also do not believe my alternator is faulty. Part is in far too nice of condition and the bike only has 4900 miles...practically still new.

I checked my reading on the full charge battery-13.5 volts, when I run the bike at 5000rpm I read 12.3 volts on the battery. My research has shown the reading should be 13.5-14.5 when at 5000rpm. However all 3 regulator/rectifiers had similiar low readings?

My battery during charging with the 6amp charger would show charger needle about 7 amps when first connected, then fully charged would show around 3-4 amps. Never getting much lower. I had the battery checked at local autoparts store and at 75% charge and 200 cold crank amps, the battery showed faulty? My new battery when filled with fluid and hooked to charger gets a charger gauge reading of 2-3 amps and after about 8 hours charging, the reading is down to approx 1 amp. Does this mean anything???

Is it possible that the 6amp charger will charge my old battery but the bike will not charge during running because it is not designed to put out enough amps that the "bad" battery is requiring??? Any ideas??? Thanks!

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Ahhh,yes it very well could be the battery at issue. Can you see into the battery from the side? Is it white anywhere? (Sulfated).What about an "old style" load tester test (toaster) what does it show? Now about the windings.. the stator should show no ohms to ground from the yellow wires and have some from wire to wire.The rotor the same but on the area where the brushes ride.

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Ahhh,yes it very well could be the battery at issue. Can you see into the battery from the side? Is it white anywhere? (Sulfated).What about an "old style" load tester test (toaster) what does it show? Now about the windings.. the stator should show no ohms to ground from the yellow wires and have some from wire to wire.The rotor the same but on the area where the brushes ride.

Thanks again for all your help Scale! :) I had to turn in the old battery when I bought the new one. I dont rememeber seeing any white. Was slightly low on fluid during the build but I topped off with distilled water prior to the 20 mile ride. I plan to install the new battery today as it should be full charge by now. Will then check it with the meter again to see if any change. Can I meter check the alternator with it on the bike? Can I check the "yellow to ground" and "wire to wire" from the plug? or do I need to pull and check inside? Below is a pic of my multimeter. Which black feed do I use? The middle "Com" or the left? What OHM setting do I dial too? I am a newborn on these streetbike builds :lol:

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Just FYI my Electrical skills have always been questionable, I'm no expert!

For checking the battery, you want to use the black in the 'com' and have it on VAC (20) to check the voltage and black in the '10A' with the dial set to '10A' to check the amperage on the battery (with bike running)

I know that on this bike the headlight can be a problem. I seem to remember it was an issue for us to get a bulb that worked well and did not drain the battery down super quick.

There is a clymers manual for this sucker, do you have a copy? It should go over the list of what/how to check

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Part is in far too nice of condition and the bike only has 4900 miles...practically still new.

36 years is a long time for electrical to sit for. I have seen pieces that look 100% perfect still in NOS bags fail because of break down over time. I'm not saying thats what your problem is, just saying that you can't rule it out because it looks nice.

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You can "back probe" the yellow wires set on vac 200 while still conncted With the probes connected to com and ohm\volt. on the meter.Yellow to yellow.

Then do a dcv20 check at the battery.

Very important,,,Newly painted frame..make sure the motor mounts and ground cables are cleaned of paint so the motor can ground through.

The 10amp setting is very handy..but the battery must be disconnected while running with the probe leads still on the battery and one other on the cable.(running through meter)

The 10 amp setting is only used with the grey "10amp" where the probe goes.

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Very important,,,Newly painted frame..make sure the motor mounts and ground cables are cleaned of paint so the motor can ground through.

Good call...I had this issue before (90% broken grounding lead, not paint) but it manifests problems in all kinds of weird ways. Good thing to check

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Thanks everyone for the compliments and the help. Glad you guys agree with the rim color, it is cool. The grounds, from what I can tell are okay. The motor and coils are grounded from coil pack to top of motor. Then a battery ground to the box and into the frame. There is a ground off the Voltage Regulator to battery box bolt. If the battery was not grounded, there would be no power correct??? If the Coil Pack was not grounded it would not spark correct?? I will check the Vontage Regulator ground again as this is most related to my problem. Ran it today with the new battery and ran awesome, I did not check the voltage though. Hope to tomorrow.

Thanks

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