GS1000G Oil Leak - oil pressure sender unit?

[Johno]

I have an oil leak at the rear of my engine block and it appears to be coming from the oil pressure sender unit located directly under the auto cam chain tensioner and carbs.

Has anyone had a similar issue and can the oil seal and sealing washers on the unit be replaced without having to remove the carbs?

From looking at the parts diagram the oil leak could be a failure of the pressure switch o ring part # 16448-45000 and or the sealing washers part# 09168-06023.

Attached is a parts diagram the relevant parts are 38 and 40.

Any advice would be appreciated.

[Dogma]

The carbs should come off and go back on pretty easily. If not, you probably need new intake rubber anyway. An maybe a general re-sealing of the whole intake system. If you haven't already, it probably needs it.

The tensioner may be leaking, and that could look like something from the gallery. I'd want to get a good look. Instructions for the tensioner rebuild can be found on Brian's site.

I'm not sure if the gallery cover with the pressure safety switch can be removed with the carbs in. I've never needed to try, since I'm so comfortable yanking the carbs. It's not the wrestling match it is on so many other bikes.

[Nessism]

The sensor plate will come off without removing the carbs. There is an O-ring in a groove on the plate, and the sensor itself has an O-ring. Leakage is quite rare on these parts but you never know. Leaks from the cam chain tensioner, which is in the same area, is far more common.

[Johno]

Thanks for your thoughts and advice guys.

I've just degreased and pressure washed the motor and will go for a ride this afternoon.

I will be checking the shims soon so will check that things are torqued down correctly.

The only options for the oil leak appear to be the head and base gaskets, cam chain tensioner or the oil pressure sender unit.

I'll try and eliminate each possibility.

[Rich82GS750TZ]

Have that whole area clean and dry, then spray it all with a coating of powdered foot spray. Start it up and see where the powder gets wet first.

[Johno]

Thanks Rich. Good suggestion.

[bwringer]

This is almost always just the usual leak from the cam chain tensioner.

Dale posted the link to my rebuild instructions:

https://www.bwringer.com/gs/camchaintens.html

The o-rings for the oil pressure switch are cheap and easy to replace, so why not? But these usually don't leak.

And while you're in the neighborhood and ordering OEM stuff, another universal leak point is the o-ring around the nose of the starter. It's always hardened and cracked after three or four decades, and is also quite easy to replace.

[Johno]

And while you're in the neighborhood and ordering OEM stuff, another universal leak point is the o-ring around the nose of the starter. It's always hardened and cracked after three or four decades, and is also quite easy to replace.

After degreasing the engine and drying it, I gave the bike a good run and and am almost 99% sure it is leaking from the oil pressure sender.

bwringer could you clarify the "nose of the starter"?

Thanks Johno

[bwringer]

After degreasing the engine and drying it, I gave the bike a good run and and am almost 99% sure it is leaking from the oil pressure sender.

bwringer could you clarify the "nose of the starter"?

Thanks Johno

When you pull the starter out, the nose of the starter protrudes into the engine case and is sealed with an o-ring. This o-ring leaks on every GS after about 20-30 years.

The o-ring is #8 on this diagram:

https://www.onlinecycleparts.com/oemparts/a/suz/50d40337f8700230d8b4ea21/starting-motor

You can see the o-ring in this photo of a GS1000 starter from Stockers Starters:

https://www.stockers.com/index.php?dt=SS-16

Oil from this leak will not appear around the oil pressure sender; it will appear on the bottom of the engine, coming from the Mystery Hole. The Mystery Hole is a drain hole in the cases that keeps water from building up in the starter cavity. It's common for new owners chasing a starter o-ring leak to spot the Mystery Hole and panic because OMFGWTFBBQ there's a GIANT HOLE in my ENGINE and OIL is coming OUT!

This is a piece of blue tubing stuck into the Mystery Hole on a junk engine to show where it is and what it does. Do NOT plug your mystery hole...

From the top, with the starter removed:



From the bottom:

[Johno]

Thanks bwringer for your very detailed response and explanation.

I expect I have both issues.