After months of working on my 1980 Suzuki GSX400E, I finally got it running and idling steady, and it rides great. But there’s one issue I can’t figure out—it won’t rev past 7,000 RPM, whether it’s under load or just revving in neutral.
Here’s what I’ve done:
• Set the ignition contacts to spec,
• Adjusted the valves,
• Installed new carb diaphragms,
• Synced the carbs and cleaned all jets,
• Replaced all O-rings on the intake boots, carbs, and throttle shaft seals,
• Running the stock air filter.
The bike is in great shape now except for this RPM issue.
Electrical Specs:
Battery Voltage:
• Key Off: 12.61V
• Key On: 12.04V
• Idle (1500 RPM): 15.04V
• 2500 RPM: 15.2V
• 5000 RPM: 14.9V
Voltage Drops:
• Lead Drop: 0.22V
• Negative Drop: 0.11V
Coil Resistance:
• Primary: 4.0 ohms
• Secondary: 40.8 ohms
Stator:
• Between Stator Wires: 1.4 ohms
• Stator to Ground: 0 ohms
• R/R Diode Test: 0.924V
I’m wondering if the electrical system might be the culprit, especially since I’m seeing 15.2V at 2500 RPM and 15.04V at 1500 RPM. Could this overcharging be what’s limiting my RPMs, or is there something else I’m missing?
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