GT250 oil pump sticking

[MarkH]

Hi all,

So I have an issue with my 1975 GT 250. I happened to notice that my oil pump cable became disconnected (thankfully, no engine damage). Upon further inspection, the reason it disconnected was because my oil pump arm doesn't always return all the way (when letting off the throttle) from time-to-time (thus, the cable came unhooked). It seems to get stuck about 1/4 from resting, idle speed. The spring looks fine. I cleaned it up with some carb cleaner (thinking it was just a build up of some two-stroke oily residue). That didn't seem to help. The cable is moving freely. I did rebuild this bike 4 years ago.

Could it be that the nut is too tight (the nut that holds the oiling setting at the correct mark)? I haven't loosened it yet - I'm just throwing it out for other experienced guys.

I could see loosing it some, then adding thread-lock. But I'm not sure if that would help.

Any advice or ideas would be appreciated!

Mark

[GTandcbr]

It is worth mentioning that the oil pump only returns to the fully off position every 60 rotations of the crankshaft and most pumps are damaged by owners forcing them back. It's more likely you have a cable or clip issue that is causing the problem

[MarkH]

Ah, very interesting!!! I didn't know that! I'll test that to see if it returns when it's running.

I might just need to tighten/crimp the arm a bit so the cable barrel doesn't come undone.

Thanks for the info!

Mark

[Craig380]

The oil pump on my 380 used to do this too, and I asked about it on here about 15 years ago. H2Rick, who used to work at a Suzi dealership, told me that it was a known problem, and usually only happened when the engine was cold because the sealing o-rings in the pump would be a bit tight and sticky. When the engine is fully warmed up, the lever usually returns to the fully closed position.

See service bulletin #12 under 'General Index' at this link: http://www.oldjapanesebikes.com/mraxl_G ... ins/page-2" onclick="window.open(this.href);return false;

[MarkH]

Thanks for the info.

I was in a panic when I noticed my cable was detached - but I'm pretty sure it happened when the throttle was twisted while it was sitting in storage. After reattaching it - I started it the arm returned just fine. I'm a bit paranoid now, however. I was even thinking of either spot welding or jbwelding the cable-end barrel to the cable (as you can still remove the cable by moving the arm to max).

I'm gonna spin up another thread soon about the whole story (it involves this issue, a top end rebuild, etc). Truly a series of unfortunate events.