increased oil consumption and smoke on startup

[superawesome]

Hi,

my GS 1000 always used some oil, but it has increased a lot in the last weeks (maybe 300ml on 150 km). I also have white, lingering oil smoke at startup/revving that stops when the motor is warm (left exhaust).
Compression on all cylinders is good (roughly 140 psi) which hopefully rules out the piston rings. Checking the many oil smoke posts here I guess I need to change the valve stem seals.

I recently cleaned and rebuilt the carbs, reset the fuel and air screw (fuel is 7/8 out, air is 1.5 turns out on #2, #3 and #4 but two full turns on #1). Used carbtune and colortune to adjust (I guess the two turns on #1 opposed to the 1.5 on the others is because the fuel screw is slightly bent (see thread here)).

Since the oil consumption went up after the carb rebuild, could there be a correlation?
Before I had the Colortune I did ride with bench synced carbs for maybe 200 km, maybe that overheated and disintegrated one of the valve stem seals?

Could there be any other reason for the high oil consumption/smoke? I did check for a blocked breather unit by blowing in the breather tube, and had air coming out the oil filling hole.

Long story short, what could I check to make sure it is the valve stem seals? I did order new ones but it seems like a big job to replace them (wanna try without taking head off), so it would be nice to know for sure that it is not something else.

Thanks for your help
J?rgen

 

[superawesome]

some additional info (don't know if related):
- valve clearances have been adjusted prior to carb rebuild
- bike backfires, only at startup

 

[Nessism]

This thread may help...https://www.thegsresources.com/_forum/showthread.php?244545-Valve-seal-replacement

 

[Guest]

This thread may help...https://www.thegsresources.com/_forum/showthread.php?244545-Valve-seal-replacement

Yup, I agree with Ed. My old GS650L had the exact symptoms you describe: compression was good, valve clearances were in spec, smoke at startup that eventually went away, and increased oil consumption. It's 99% probable that the valve stem seals are the culprit.

 

[superawesome]

Okay, that sounds pretty reassuring. I did order new seals already, just picked them up from the dealership.
Rob's thread is great, thanks for pointing me at it. Just have to get some pvc pipe for the removal tool. Any idea what diameter? Shims are 29.5mm, so I'd guess a little less...

 

[Guest]

I used an oxygen sensor socket. Had the slot cut in it already and worked very well with my C-clamp.

 

[superawesome]

After successfully replacing three seals I found the valve guide was broken off on the fourth (cyl #3, exhaust side). I guess the head needs to come off to fix this.

Does anybody have a part I for the valve guide? I don't see it on the fiche...

 

[Guest]

I see you're in Switzerland so I checked cmsnl.com. Found part number 11115-45721, valve guide, GS1000EC, 1978 - 19 euro

 

[superawesome]

Right, it is listed on the "cylinder head" page. I looked at "Camshaft/valve" Thanks

 

[superawesome]

For the record, here is the broken off valve guide. The seals are in surprisingly good shape though, but I did not get to the left side yet (where I got the smoke at startup).


As I have to take off the cylinder head now, what else should I do while it is off? Is there a " top end rebuild guide" somewhere here (I wouldn't be surprised )?

 

[hannibal]

I used an oxygen sensor socket. Had the slot cut in it already and worked very well with my C-clamp.

Brilliant! I made the tool from PVC and by the end of my valve work, the PVC was bending and far less effective.