GT250 oil pump sticking

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MarkH
On the street
Posts: 23
Joined: Mon Aug 10, 2015 8:43 am
Country: US
Suzuki 2-Strokes: 75 Suzuki GT250, 74 Kawasaki H2

GT250 oil pump sticking

Post by 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
http://www.machinesofman.com

75 Suzuki GT250, 74 Kawasaki H2 750, 82 Suzuki RM 125, 00 Kawasaki KX 250, 15 Honda CB1000R
GTandcbr
Yeah Man, the Interstate
Posts: 590
Joined: Tue Mar 10, 2015 12:35 pm
Country: WALES
Suzuki 2-Strokes: suzuki gt 550j
Location: Wales

Re: GT250 oil pump sticking

Post by 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
98 carb Blackbird and GT550j
MarkH
On the street
Posts: 23
Joined: Mon Aug 10, 2015 8:43 am
Country: US
Suzuki 2-Strokes: 75 Suzuki GT250, 74 Kawasaki H2

Re: GT250 oil pump sticking

Post by 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! :clap:

Mark
http://www.machinesofman.com

75 Suzuki GT250, 74 Kawasaki H2 750, 82 Suzuki RM 125, 00 Kawasaki KX 250, 15 Honda CB1000R
Craig380
Expert racer
Posts: 1250
Joined: Mon Dec 01, 2008 2:52 am
Location: Manchester, UK

Re: GT250 oil pump sticking

Post by 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;
1976 GT380 - wounded by me, and sold on
2006 SV650S - killed by a patch of diesel and a kerb in Feb 2019
2017 SV650 AL7 - naked and unashamed
MarkH
On the street
Posts: 23
Joined: Mon Aug 10, 2015 8:43 am
Country: US
Suzuki 2-Strokes: 75 Suzuki GT250, 74 Kawasaki H2

Re: GT250 oil pump sticking

Post by 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.
http://www.machinesofman.com

75 Suzuki GT250, 74 Kawasaki H2 750, 82 Suzuki RM 125, 00 Kawasaki KX 250, 15 Honda CB1000R
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