Output Voltages in gt250

All to do with wiring, charging or just trying to figure out whats gone wrong.

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Steve250
Still in the Driveway
Posts: 5
Joined: Sun Jan 13, 2019 9:43 am
Country: United Kingdom
Suzuki 2-Strokes: GT250B

Output Voltages in gt250

Post by Steve250 »

Hi all, been reading through this great forum and hope someone can help. Im just in the process of rebuilding my GT250B. Crank has been redone, new standard exhausts, and its got a replacement rectifier. ( https://www.discountbikespares.co.uk/pr ... 0-pattern/" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false; )
I bought the rectifier used, so dont know its specifications, or if its working right. My issue is, when I started the bike up, and put the lights on, the headlight bulb blew when I revved the engine. Checking voltages across the battery, Im getting about 13 volts at idle, rising to 13.8 volts at 5000 rpm. With the lights switched on, the voltage goes up to 15.8 volts. And that is without a bulb in now.

Do you agree thats too high and my rectifier assembly isnt working? Or could it be a simple connection problem?
I cant find any details regarding output, but do know it puts out more voltage with the lights on.
By the way, Im getting a serious misfire when its warmed up, and the points are sparking like crazy in the right side, indicating a bad condenser. Not related, im sure, but just another hurdle to getting it back on the road.
Any help or advice welcome.
karl pa
To the on ramp
Posts: 490
Joined: Sat Sep 05, 2015 3:14 pm
Country: us
Suzuki 2-Strokes: GT
Location: southeast pa

Re: Output Voltages in gt250

Post by karl pa »

Welcome to the forum, 15.8 volts with lights on is fairly normal for these with original voltage regulators, the regulators were tied to the ac part of the charging system and didn't do a real good job of controlling the voltage. Many, including myself have went to modern rectifier/regulator combo that do a much better job of controlling voltage. Early 250s didn't have regulators on them, they used the battery as the regulator. I would think your rectifier is fine, the problem lies in the regulator.
76 GT185
77 GT250
77 GT380
76 GT500
73 GT550
73 GT750
74 GT750
71 T250 scrambler
75 T500 cafe
Steve250
Still in the Driveway
Posts: 5
Joined: Sun Jan 13, 2019 9:43 am
Country: United Kingdom
Suzuki 2-Strokes: GT250B

Re: Output Voltages in gt250

Post by Steve250 »

Hi and thanks for the response. The thing is, apart from the battery, there is no voltage regulator fitted to UK bikes. Wiring diagrams suggest there is, but they are not included and mine never had one. Should that modern rectifier I listed in my previous post regulate my voltage?
There is something in a Suzuki service bulletin for GT250 saying check neutral bulb and high beam warning lamps, that they are fitted and of correct rating, if blown headlight bulbs are an issue. Hardly going to reduce your voltage much is it? :wth: :lol:
karl pa
To the on ramp
Posts: 490
Joined: Sat Sep 05, 2015 3:14 pm
Country: us
Suzuki 2-Strokes: GT
Location: southeast pa

Re: Output Voltages in gt250

Post by karl pa »

The rectifier you posted or any rectifier, only changes ac voltage to dc voltage, none will regulate voltage, the only way to keep voltage in check is to install a regulator, but the only thing I found to work is a modern rectifier/regulator combo. Somewhere I seen a post that a company makes them that plugs into wire harness that doesn't require cutting harness for GT250 and T500.
76 GT185
77 GT250
77 GT380
76 GT500
73 GT550
73 GT750
74 GT750
71 T250 scrambler
75 T500 cafe
Steve250
Still in the Driveway
Posts: 5
Joined: Sun Jan 13, 2019 9:43 am
Country: United Kingdom
Suzuki 2-Strokes: GT250B

Re: Output Voltages in gt250

Post by Steve250 »

Thanks Karl. Do you think I could fit a genuine regulator from an earlier model? My bike does have the wire with connector still attached to plug it in
.
karl pa
To the on ramp
Posts: 490
Joined: Sat Sep 05, 2015 3:14 pm
Country: us
Suzuki 2-Strokes: GT
Location: southeast pa

Re: Output Voltages in gt250

Post by karl pa »

Yes you can plug an original regulator into the harness, but I don't think you will have much luck. On my GT250B, the voltage was the same with the regulator plugged in or not. Also the original regulators are obsolete, so you will likely pay more for one than a modern rec/reg combo, they are around 50 dollars. I tried different regulators, even from snowmobile, but finally gave in and went with a combo from tympanium, but I had to modify the wiring harness to install.
15.8 volts is not extremely high if you use a conventional battery and keep it filled, the benefit to keeping the voltage below 14.2 volts is that you can use a sealed battery, anything above that will cook the battery dry.
76 GT185
77 GT250
77 GT380
76 GT500
73 GT550
73 GT750
74 GT750
71 T250 scrambler
75 T500 cafe
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