82 GS300L - Right-Side Drop Outs, Bogs, Stalls

[fbody_mike]

I'm guessing to use the gn250 box you will need two, one for each coil as the gn250 is a single cylinder.
Take a look at the gs500e from say 1993, it's a 7 pin and the 500 is a parallel twin like your 300. Except your 300 is a higher revving 4 valve per pot, the advance curve may be different but maybe it won't matter. The mounting points and box size even look the same for the 300 and 500.

[philmotion]

Hey Mike,

Thanks - good info on the GN. The 500 sounds like an easier place to start. Amazed at how much you guys know drilling down into this level of detail. Will start looking and see if I have any luck.

I'm guessing to use the gn250 box you will need two, one for each coil as the gn250 is a single cylinder.
Take a look at the gs500e from say 1993, it's a 7 pin and the 500 is a parallel twin like your 300. Except your 300 is a higher revving 4 valve per pot, the advance curve may be different but maybe it won't matter. The mounting points and box size even look the same for the 300 and 500.

[jborum]

Long story short, rewiring a GS250 ignitor box is probably going to be the most natural fit for your GS300. This newly manufactured one for $200 uses a plug that looks similar to the GS450, but they're a small company that builds to order and they can put a connector on that mates with your GS300 wire harness. I found their customer service slow but otherwise very good.

https://www.regulatorrectifier.com/catalog/1980-1981-suzuki-gs-250-gs250-cdi-unit

I own a GS300, and I also had an ignitor box that failed. They are impossible to find because this bike was only made from '82-'84, and for some reason they have a different connector and slightly different timing specs than almost all of the other Suzukis of that era. The box and the connector are both unique. I attempted to open and repair the ignitor, but since it was sealed with resin and gravel it was a lost cause. I understand some are sealed only with resin that can be dissolved, but this one is not like that.

I found an original in a junkyard in Florida, but they wanted $300 for 40-year-old electronics that are also about to fail. No thanks.

The GS250 solution above is not what I did. I used their GS450 ignitor box instead because the timing numbers looked more precisely matched. However, to make it work I also ended up needing to install the advance governor from a GS450, slot the signal generator mounts to create a timing adjustment, and fiddle with it somewhat blindly. The timing marks are no longer relevant, so all I could watch was the RPM readout on my timing light. I think that the GS250 ignitor would not require all that extra trouble, and the mechanic at my local motorcycle shop has the same suspicion.

Here's an attempted visual comparison between the pin configuration of the 300 & 450. I suspect the 250 has the same pinout configuration as the 450, but confirm that. The guys at Regulator Rectifier will need the pin configuration in order to put the correct connector on.

GS300 ignitor box, male pins on box

	(connector	clip)
Signal Generator L (G/W)	Signal Generator R (Br)	Signal Generator Common (B/Bl)	EMPTY
Ignition Coil L (W)	Ground (B/W)	Ignition Coil Common (O/W)	Ignition Coil R (Y/B)

GS450 ignitor connector, pigtail with female pins

	Ignition Coil Common (O/W)	Signal Generator L (G/W)	Signal Generator R (Br)
(connector clip)
	Ignition Coil L (W)	Ignition Coil R (Y/B)	Signal Generator Common (B/W)

Loose ground wire (B)

A better visual I made in Word:
Suzuki-GS300-GS450-ignitor-pin-configuration.jpg

Below are some timing specs from similar-era Suzukis to show why I settled on the ignitor from the 250 or 450 as the best potential replacements.

Separate footnote: I also had low voltage at my coils that was problematic, so make sure you have plenty of juice there.

Best of luck!


Ignition comparisons:

1982 GS300
Ignition type: Transistorized
Ignition timing: 15º BTDC below 1650rpm and 40º BTDC above 4500rpm
Ignitor # of pins: 7, one 2x4 plug
Signal generator resistance: 200-280Ω


1982 GS450
Ignition type: Transistorized
Ignition timing: 15º BTDC below 1650rpm and 40º BTDC above 4500rpm (transistors)
(from 1982 GS450GA Suzukimatic owner’s manual)

10º BTDC below 1650rpm and 40º BTDC above 3500rpm

(very close - from Clymer 77-87 manual for GS400, 425, 450)

Ignitor # of pins: Six pins plus ground wire
Signal generator resistance: 60-80Ω (not problematic)


1983 GS250FW
Ignition type: Points or Transistorized
Ignition timing: 20º BTDC below 1650rpm and 35º BTDC above 3500rpm (points)
20º BTDC below 1650rpm and 40º BTDC above 3500rpm (transistors)
Ignitor # of pins:
Signal generator resistance: 250-500Ω


Others


1977-1987 GS400 (Clymer manual, probably US)
Ignition type: Points or Transistorized
Ignition timing: 10º BTDC below 1500rpm and 40º BTDC above 3600rpm (transistors)
Ignitor # of pins:
Signal generator resistance: 250-500Ω


1981 GSX400 (Canada, France, Germany) (more sporty bike)
Ignition type: Points or Transistorized
Ignition timing: 20º BTDC below 1650rpm and 35º BTDC above 3500rpm (points)
20º BTDC below 1650rpm and 40º BTDC above 3500rpm (transistors)
Ignitor # of pins:
Signal generator resistance: 250-500Ω


1990-2006 GS500E
Ignition type: Fully Transistorized
Ignition timing: 12º BTDC at 1200rpm and 40º BTDC at 4000rpm
5º BTDC at 1200rpm and 40º BTDC at 4000rpm (CA model only)
Ignitor # of pins: 8, 2 plugs
Signal generator resistance: 250-420Ω


1983 GS550
Ignition type: Transistorized
Ignition timing: 11º BTDC below 1650rpm and 31º BTDC above 3000rpm
Ignitor # of pins: 8, 2 plugs
Signal generator resistance: 250-500Ω


1990 GS650
Ignition type: Transistorized
Ignition timing: 10º BTDC below 1650rpm and 40º BTDC above 3500rpm
Ignitor # of pins: 6 pins plus ground wire
Signal generator resistance:

[jborum]

The gs250 has a mechanical advance, and the gs300 has electronic advance. So no, it won't work unless you get the entire signal generator from the gs250 and who knows if the crankshaft shaft ends and covers are the same.

This is not correct. The Suzuki service manual for the 1982 GS300 is actually just an addendum to the 1982 GS250 service manual. Both have the same transistorized ignition system.

On my 1982 GS300 I can see the advance springs stretching as RPM increases, so it's a mechanical advance.

On 1983 and later models, the ignition system incorporates an electronic advance circuit and mechanical weights are no longer used.

1979 and earlier models used a breaker point system instead.

[Gorminrider]

What a detailed post! good work! for someone looking at replacement options... (but need niggling say that the post 1980-1986 "GSX 400 twin" has never had points unless you have some info I don't.)