Suzuki GS 450 help – runs rough?

3 Apr 2015 | Author: | Comments Off on Suzuki GS 450 help – runs rough?
Suzuki GS 450 L

Suzuki GS 450 help – runs rough?

Need help with my friend’s 1983 Suzuki GS 450.

He’d left the bike in his backyard for approximately 2 years as it had been running rough and breaking down on him. He hadn’t stabilized the gas so I figured a shot of carb cleaner in his air intake might do the trick, and it did. it fired right up (Tentative High Five #1) but was noticably underpowered. Put some Seafoam additive in the tank and test drove it a bit – some improvement but a broken clutch cable took us out of action for a week or so. (

Replaced the cable and took the bike for a test spin – it was clearly firing on only one piston. Took out the carb bowls and checked the main jets – the main jet on the left side was completely plugged. Cleaned and replaced. (On a side note, we eventually discovered the meaning of the PRI setting on the fuel petcock when the carbs overflowed with fuel and puked out the carb overflow hose underneath the bike.

That one had be stumped for a bit).

After replacing the carb bowls and filling them, the bike now ran on both cylinders. It immediately had a high idle but otherwise sounded good. (Tentative High Five #2) I adjusted the throttle cable and the idle control knob on the carbs to bring the idle back down. Seemed to be idling fine – she reaches high RPMs without issue.

Again, taking it for a test drive, the bike ran rough (occasional pop, powered in and out) and died pulling into the driveway and wouldn’t fire back up again. Again, the bike started well once it cooled down.

Kinda at my wits end with this one – I have no idea why she’d run well at cold idle but so poorly once she gets hot. Short of completely tearing out the carbs and cleaning them inside and out, could there be another issue I’m overlooking? The bike seems to start and idle fine when cold, its only when it’s put to work that it falters.


Additional Details

Thanks gents for your suggestions. Sorry forgot to mention that in the beginning, we flushed the gas tank (surprisingly clean for having sat mostly empty for two years – virtually no rust). I only removed the main jets (which were plugged) and made no adjustments to the mixture or float height.

Having removed the main jets to soak/clean, I filled the carb bowls with carb cleaner and loosely installed them on the bottoms of the carbs to give everything a soak, after which I drained, reassembled and the bike fired fine on both cylinders then.

We did experiment with the idle adjustment knob between the carbs, thinking the idle was simply set wrong.

Suzuki GS 450 L
Suzuki GS 450 L
Suzuki GS 450 L
Suzuki GS 450 L
Suzuki GS 450 L
Suzuki GS 450 L

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