Unexpected oil leak from GS450 head

[Arek]

Hi All,


Running my head into a wall here…


I have finished putting together a GS450 engine and found a leak coming from the head gasket. So I re-did the top, new gasket made sure the surfaces were clean and true, and I was also really careful with tightening the head nuts in a criss-cross pattern to the right torque specs. Although I haven’t given it the 2nd round of torque (will do so when I’m back from work).


Did a quick run up and down a short street (250 meters) and to my horror it still leaks!


I did a closer inspection and even though I find oil around the head gasket, I now see that the oil might very well be coming from something above the head gasket. Please see the image where the oil pools.


Where could that be coming from? The head nut seems dry and free from oil. Is there a channel there? What does that #4 bolt do? Could it be coming from that?

IMG_6223.jpg

[John Park]

I think the bolt seals the passageway from the stud cavity oil passage to the cam bearing and the valve buckets. If that isn't the source of the leak it could be a crack or porosity in the head. Unlike the roller bearing motors, the oil pressure is about 50 psi rather than 5 or whatever. There are oil jets that reduce the flow/pressure down at the base gasket level that you don't want to leave out.

I'll take a look at my spare head and see what it otherwise could be.

[John Park]

The bolt should have a rubberized washer under it. I can't see how that area would ever crack as there's nothing happening there. Swap the bolt and washer from the other side over and if the leak moves with it the bolt could be bent or the washer needs replacement. I think the one that goes on the cam chain locknut would be similar or the same.

[Arek]

The bolt should have a rubberized washer under it. I can't see how that area would ever crack as there's nothing happening there. Swap the bolt and washer from the other side over and if the leak moves with it the bolt could be bent or the washer needs replacement. I think the one that goes on the cam chain locknut would be similar or the same.

Aha! Then that could very well be the culprit! Yesterday I checked the bolt and it wasn't all the way tight. It had a full revolution more before it became tight. The washer also looks hard and almost white. Will check if tightening it helps and for now I think I have some nylon washers that could do the trick.

Will keep you posted.

[Arek]

OK, it wasn't the bolt as I put in a new washer and made sure it sits tight. Did another test ride up and down the street, and this is how it looks. Maybe there is a crack somewhere and I have missed it, or it wasn't 100% straight? I'm running out of ideas of where to check.

6.jpg

[bwringer]

You need to spot exactly where it's coming from the instant it starts to seep.

Clean and dry the engine thoroughly, then spray that whole area with a thick coat of cheap foot powder from a spray can. I assume you have people with itchy feet in Denmark...

Start the engine and watch. You should spot the leak point almost instantly as it wets the powder.

Let the engine cool and wash off the foot powder -- it's kinda stinky.

[Arek]

You need to spot exactly where it's coming from the instant it starts to seep.

Clean and dry the engine thoroughly, then spray that whole area with a thick coat of cheap foot powder from a spray can. I assume you have people with itchy feet in Denmark...

Start the engine and watch. You should spot the leak point almost instantly as it wets the powder.

Let the engine cool and wash off the foot powder -- it's kinda stinky.

We Danes do have itchy feet, so I'll collect some of that powder and give it a go.

[Arek]

You need to spot exactly where it's coming from the instant it starts to seep.

Clean and dry the engine thoroughly, then spray that whole area with a thick coat of cheap foot powder from a spray can. I assume you have people with itchy feet in Denmark...

Start the engine and watch. You should spot the leak point almost instantly as it wets the powder.

Let the engine cool and wash off the foot powder -- it's kinda stinky.

Alright, I'm getting closer. I might have found out what it could have been. The tach-drive was not tight and even though I tightened it there still is a drop coming off it. I could suspect that it was coming from here and the air-flow would then distribute the oil backwards making it look like it's coming from the head gasket or elsewhere. Will have to do some more driving up and down the street and check if that was it.

On the left picture the tach-drive with some oil on the bolt area, and on the right the head-gasket. Although the powder has become a bit moist, I suspect that being from oil residue from last time.
powder.jpg

[Grimly]

The rev-counter drive is a favourite leak spot.
A tiny little seal and an o-ring live inside it.
Be prepared to gasp in surprise at how much they cost for the size of them.
One tip; carefully examine the shaft of the drive for a wear ridge where the old seal (and road grit) wore a nasty ring in it. No new seal will last very long on a damaged shaft.

[fastbysuzuki]

Or get the whole taco assembly for £13

https://www.mandp.co.uk/products/suzuki-gs-gsx-late-70s-early-80s-tacho-drive-unit-467999-678288

[Grimly]

Or get the whole taco assembly for £13
https://www.mandp.co.uk/products/suz...-467999-678288

If they're in stock. I tried to buy one from them a couple of months ago (in stock, according to the page) and got an email telling me they were out of stock. Annoyingly, the page didn't change to show its real status.

[bwringer]

My instructions for handling the tach drive leak.

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

The Suzuki part numbers for the seal and seal band for your bike appear to be the same as in my instructions, but verify that before ordering. There may be some difference in Euro models I don't know about, but I'm 99.9% sure it's exactly the same on your bike.

[Arek]

The rev-counter drive is a favourite leak spot.
A tiny little seal and an o-ring live inside it.
Be prepared to gasp in surprise at how much they cost for the size of them.
One tip; carefully examine the shaft of the drive for a wear ridge where the old seal (and road grit) wore a nasty ring in it. No new seal will last very long on a damaged shaft.

Ahh blast! I just want the thing up and running now. I think I have a cap somewhere to blind of the Tach drive hole, so I'll start with that and will have to do without the Tach meter ;-)

[Grimly]

Ahh blast! I just want the thing up and running now. I think I have a cap somewhere to blind of the Tach drive hole, so I'll start with that and will have to do without the Tach meter ;-)

You can remove the guts of the tacho drive and fill it with silicone. Once it's set, give a wrap of Teflon tape around the outside where the external o-ring is, and put it back in. Guaranteed that leak will be gone.
If you discover the shaft is is good condition and you might want to re-instate the drive, just fill the external end with silicone, as it will be easier to clean out later.

[Arek]

My instructions for handling the tach drive leak.

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

The Suzuki part numbers for the seal and seal band for your bike appear to be the same as in my instructions, but verify that before ordering. There may be some difference in Euro models I don't know about, but I'm 99.9% sure it's exactly the same on your bike.

Great thanks 👍