GT 380 Regulator

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Woodpecker
Posts: 25
Joined: Tue Oct 29, 2019 12:11 pm
Location: Rainham Kent

GT 380 Regulator

Post by Woodpecker »

Advice please! Some backgruond information about my 1972 GT380. After restoring some "other makes" I bought the suzuki as a total wreck from the sister of the previous owner who had unfortunatly died. She had no documentation but confirmed her brother owned the bike for many years but when it went wrong just left and apparantly bought another bike. So I estimate it was abandoned about 30 years ago and having completely rebuild ever part the problem was a failed gearbox needle bearing damaging the counter shaft resulting in oil seal failure. Now all sorted and ready to ride when good old HMRC and DVL sort out a new plate.
Back to the problem which I think is the regulator. There is no charge to the battery, I am getting a low a/c voltage of 10.5V from the alternator. At about 1500rpm the control voltage to the alternator rotor is about 6v and increased revs don't make any difference. I have adjusted the regulator screw but it makes no difference.
In an attempt to check the regulator I bypassed it by connecting the green and and orange wires and had 16v on the battery! I don't want to go down the solid state combined rectifier route or shell out £100+ for a new regulator this is a budget restoration which cost to date make me unwilling to add up. So the first question Have I identified the problem or going in the wrong direction?
The second question can these be repaired there does not seem to be much in them! I could get a replacement from Ebay for about £30 and give it a try.
Thanks Stu
barney01
Posts: 3118
Joined: Wed Sep 26, 2012 7:33 pm
Location: Prestatyn.Wales

Re: GT 380 Regulator

Post by barney01 »

First thing to do is remove and clean all connections between the generator and the battery. Many problems in charging the battery are caused by dirty connections and earths. Use contact cleaner and make sure connections are good.
There are two types of regulator early ones(should be on your J) have a removable cover so you can adjust it. Look here to see how to do it
http://www.3cyl.com/mraxl/gt/manuals/gt ... 550-49.htm
Is the battery fully charged and in good condition?
There are modern solid state reg/recs available for your bike i.e. Electrex rr77 but the are not adjustable. Many people swear by them but be aware that due to the age of your loom, in particular the battery sensor wire, sometimes they overcharge the battery.
NO SMOKE .......NO POKE
Woodpecker
Posts: 25
Joined: Tue Oct 29, 2019 12:11 pm
Location: Rainham Kent

Re: GT 380 Regulator

Post by Woodpecker »

Thanks Barney yes I have checked and cleaned all the connections and yes I have an early one and tried to adjust it so i think its shot!So does any one know how to mend it or do I go to ebay? I would like to keep it as it was the loom is old and I notice a 2v voltage drop when the ignition is on. The battery is new.
barney01
Posts: 3118
Joined: Wed Sep 26, 2012 7:33 pm
Location: Prestatyn.Wales

Re: GT 380 Regulator

Post by barney01 »

So did you open it by taking off the cover? Sometimes a good clean will suffice. Just to confirm your earth connections to the frame are good too.
Failing all that they are quite robust so get another off ebay. Its a shame you cant borrow one to try first.
NO SMOKE .......NO POKE
Woodpecker
Posts: 25
Joined: Tue Oct 29, 2019 12:11 pm
Location: Rainham Kent

Re: GT 380 Regulator

Post by Woodpecker »

Hi Barney
Yes I did remove the cover and cleaned all connections and all the earths. I have given the regulator to my brother in law who is an electronics man to find out why its not working. These seem very basic bits of kit and someone should be able to repair them. All that said a replacement arrived today from Twowheel spares and although dirty and neglected 13.48v at 1500 rpm and 14.5v at 3500rpm.
All I need now is a new plate from DVLA and a dry road.
Many thanks for all your help.
Stu
barney01
Posts: 3118
Joined: Wed Sep 26, 2012 7:33 pm
Location: Prestatyn.Wales

Re: GT 380 Regulator

Post by barney01 »

Result. Yes they are simple which is why i prefer them to the sealed modern ones :D
NO SMOKE .......NO POKE
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