G1 No Top end speeed, please help

[slonomo]

I'd say if it's hitting the 28 mph range then that's all she's got captain. If it's revving that high and still not getting to 20 mph, then I'd say it's a problem with the clutches. With stock size tires and engine the G1 will top out at about 30 mph. If you play with the jets it might squeak 32 mph. If you change the carb it can go up as high as 40 mph, but that's pushing the limits.

You might have a clutch that isn't fully shifting out. Put this thing up on jack stands and watch the clutches shift as you rev it up. If there is a broken or worn part preventing full shift, it will be visible.