GT500 Oil Pump Cam Orientation

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Mike MPD
Still in the Driveway
Posts: 4
Joined: Mon Mar 23, 2020 12:13 pm
Country: USA
Suzuki 2-Strokes: 1976 GT500

GT500 Oil Pump Cam Orientation

Post by Mike MPD »

Just got done replacing my oil pump seals but Im not confident I have the cam oriented correctly when I reassembled.


As I have it now, when throttle is closed the cam (2) is not pushing on the plunger (4). As I move the control lever (1) I can then feel it push the plunger against the spring when its almost at full open. Is that correct, or do I have it 180 out? Should the cam be pushing against the plunger when the throttle is closed (control lever is at rest), and then relieve plunger spring pressure as the throttle is opened?

Hope my explanation made sense.

1975 Yamaha DT250
1976 Suzuki GT500
1976 Yamaha RD400
2008 Yamaha WR250R
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Posts: 28
Joined: Mon Dec 14, 2020 4:50 am
Country: United Kingdom
Suzuki 2-Strokes: 1966 T20

Re: GT500 Oil Pump Cam Orientation

Post by gammakeith »

Yes, that looks the same as the T20 I rebuilt so you have it 180 degrees out. In the absence of the cam, the spring loaded plunger moves up and down controlled by the end-face cam running against the end of the screw (3) and gives maximum output. The throttle operated cam restricts the plunger movement by pressing on the tip of it. Thus, at full throttle the cam should not be touching the end of the plunger. Conversely, at tickover the cam allows only a small movement of the plunger as it rotates. I suggest you do what I did, stare at diagrams and the pump in your hands until you understand how it works.

Its easy to test by spinning the pump in a drill chuck when its together.

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