Blowing white smoke

[200mph]

A picture of the old and new seals along with the valve guide or boss where the seal fits would really go a long way in communicating the situation.

Some valve seals come with a plastic condom that fits over the valve stem to prevent valve seal lip failure/damage when going over the valve lock groove(s).

 

[Bonaro]

OK..Let’s think about HOW they work: Oil splashes around inside the valve cover and gets all over the valve stems. The valve going up/dn introduces oil down the inside of the guide and burns up inside the cylinder. When the engine is shut-down... oil slides down the stem and enters the cylinder and creates a lot of smoke on startup. Both are to be avoided.

IF.... IF... the seal is snug against the valve stem.... the entire seal (if not snapped down onto the guide) will reciprocate up/dn along with the valve stem. The “hat” will prevent oil from splashing onto the valve stem and also prevent oil from running down the stem ... thereby preventing oil from getting into the cylinder.
(Even if they are not snapped down or friction-fit onto the guide...as long as the rubber seal is against the stem.)

Do not bastardize the design of the part. IF...IF you have the proper part it should work properly. IMO

The only thing bastardized here is Kubotas design flaws and vague shop manuals. I found new seals, $5 each plus the ride, be here in twp days. Gonna put the new ones on by hand after I mike out the depth to ensure I dont seat them to deep and cut them again. I have Friday off so I would expect it to run by Friday afternoon barring any other fubars

 

[Bonaro]

A picture of the old and new seals along with the valve guide or boss where the seal fits would really go a long way in communicating the situation.

Some valve seals come with a plastic condom that fits over the valve stem to prevent valve seal lip failure/damage.

I think I understand the situation but I will try to get some decent pics tonight

 

[200mph]

Thanks for considering.

It many not help you, but those who might follow in your footsteps years down the road.

Good luck and hope the rest of assembly goes smoothly for you.

 

[Bonaro]

Here are a few pics of the new and old seal installed side by side. Old seal is all rubber, new one is steel jacketed. The grove on the guide seems to be about .040 lower than the lip on the new seal so it doesnt snap in. However, it does fit very snug. The replacement seals will be here tomorrow. Gonna press them on by hand and run it

 

[200mph]

Thanks for the pictures.

With respect to the groove in the head. Is there a difference in position between the old and new head? ie: would the valve seals engage the groove on the old head?

Perhaps there are other seals available that would allow the retaining bump inside the valve seal to engage the groove.

Good luck.

 

[Bonaro]

Thanks for the pictures.

With respect to the groove in the head. Is there a difference in position between the old and new head? ie: would the valve seals engage the groove on the old head?

Perhaps there are other seals available that would allow the retaining bump inside the valve seal to engage the groove.

Good luck.

The Grove on the guide seems the same between old and new. The seals are different. I have looks and only find one choice for a seal

 

[Bonaro]

New (genuine Kubota) valve seals installed. They all snapped in with a satisfying click. I think my first set were aftermarket knockoffs.
Head is all assembled and ready to install after a quick samich

 

[GeoHorn]

New (genuine Kubota) valve seals installed. They all snapped in with a satisfying click. I think my first set were aftermarket knockoffs.
Head is all assembled and ready to install after a quick samich

Can you post pics of the genuine vs the knock-offs?

 

[Bonaro]

Can you post pics of the genuine vs the knock-offs?

I already trashed them. The groves on the ID were slightly different than the OEM