still burns oil after rebuild

[78caferacer]

During my restoration of a 78 GS1000E I installed new valve guide seals. It burns a lot of oil (yes, it's really oil, not an over-rich mixture) for the first five or so minutes, then is fine. I've got good compression (150+) in all four cylinders. Before I tear this thing down again, I sure would appreciate some advice. It's hard to believe it could be the rings. Wouldn't it continue to burn oil after warm-up if it was the rings. Help!!!

[DimitriT]

So this happens on all cylinders or is there one in particular? You can tell from fouling on the plugs.

You replaced valve seals with OEM? When you inserted the seals did you push them down over the guide with your thumb or did you tap them in with a socket. The reason I ask is that I've ruined a couple of seals by tapping them in. Now I just push them down until I feel them gently pop into the groove on the guides.

Are you getting oil in other places? Head gasket? airbox drain tube?

[reddirtrider]

Sounds like seals as the previous poster is alluding.

The symptoms you mention can happen if the seals on the left side of the bike leak. You turn it off, put it on the kick stand, and the bike will lean over far enough for oil to puddle around the lowest valve guide. It then leaks in and you have burning oil next time you start it up.

You're right in that it's not the rings.

[78caferacer]

Thanks, guys. It appears to be at least two cylinders that are oil-fouled. Not getting oil anywhere else. I did "gently" tap the seals into place with a socket. I've ordered 8 more seals from Z1 and will replace them all again and see what happens. Thanks for your help!

[focus frenzy]

you also have to factor in that it takes a good five minutes or so for the engine to warm up good and for the pistons to expand fully from heat and seal up good.

it also takes a good 1000 miles to fully seat in the rings, and these air cooled bikes do use oil, it is the nature of them.

was the cylinders checked for trueness all the way from top to bottom?

where they well inside specs?

I ask because the PO of my 1000G had done the top end and put in new pistons and rings and honed the cylinders but clearly didn't measure anything. it sucked oil down like a really rich two stroke so he walked away and it sat for years before he sold it.

I took it apart and the cylinders were worn 1mm over stock (100K miles)

[Road_Clam]

Thanks, guys. It appears to be at least two cylinders that are oil-fouled. Not getting oil anywhere else. I did "gently" tap the seals into place with a socket. I've ordered 8 more seals from Z1 and will replace them all again and see what happens. Thanks for your help!

I am experiencing a similar issue. My bike is sucking oil in the #3 cyl only. I thought for sure it was a bad intake valve seal. I tore down the whole top end, new gaskets, and new valve seals and my #3 cyl. STILL burns oil. I guess the only thing left is bad oil rings.

[focus frenzy]

I am experiencing a similar issue. My bike is sucking oil in the #3 cyl only. I thought for sure it was a bad intake valve seal. I tore down the whole top end, new gaskets, and new valve seals and my #3 cyl. STILL burns oil. I guess the only thing left is bad oil rings.

unfortunatly it happens, from what I have seen the oil rings loose their tension before the compression rings.

[reddirtrider]

I am experiencing a similar issue. My bike is sucking oil in the #3 cyl only. I thought for sure it was a bad intake valve seal. I tore down the whole top end, new gaskets, and new valve seals and my #3 cyl. STILL burns oil. I guess the only thing left is bad oil rings.

If your bike continues to burn oil excessively after start up, then it's very possible it's an oil control ring. If it stops after start up, it doesn't seem likely.

[Don-lo]

I took it apart and the cylinders were worn 1mm over stock (100K miles)

Wow, that's a lot.

Up here, I've heard that called a Texas overbore (running a bike without filters in dusty conditions)

[chef1366]

You need to check the ring end gap. If you already changed the valve stem seals don't chase your tail again. If you're going to take the top end off it's not that much harder to pull the cylinder and check everything out.

[focus frenzy]

Wow, that's a lot.

Up here, I've heard that called a Texas overbore (running a bike without filters in dusty conditions)

LOL! funny you should say that. it had a vintage K&N replacement type filter in it when I got it and it had no sign that it ever had a foam seal and there was a 3/8ths gap between the filter and the mating surface in the housing.