S650G smoking. Valve stem seals?

[Bl8tant]

We have a late model (1980ish) S650G with only 550 hours on it. My grandfather bought it new, and he maintained it fairly well. Last year it started smoking a little bit (mainly when accelerating from idle). Now it's smoking more, and I want to get it fixed before things go too far. It starts easy, idles great, runs great. But it will belch (blue)smoke when you accelerate from idle. Then it smokes slightly while running at working RPMs. The tractor sat idle for several years when my grandfather was ill. After he passed, we started using it again. Prior to that, it had several other "sitting" spells (up to a year at a time).

So I'm thinking that the valve stem seals deteriorated due to sitting so much over the years. Can I still buy just the seals ? I have the service manual, and think I can do the seals without pulling the head (use compressed air to hold valves in place). What do you guys think ?

Any idea on cost of the seals ????

Thanks for any help/suggestions !

 

[Ilikeurtractor]

Valve seals should be pretty cheap (I'd expect to pay less than $30 for a set assuming a 4-cylinder engine). Hard to tell if valve seals are the culprit though, but would be a cheap place to start and you should, in theory, be able to replace them w/o pulling the head. If compressed air doesn't hold enough, you might be able to get away with putting the piston at TDC for the cylinder you're working on and then pushing the valves down until they hit the piston and then continuing to compress the springs to allow removal of the spring retainers assuming the valves steams are in-line and parallel to the piston travel. I haven't actually tried this, but something you might want to think about. I can't say I have a great way for pushing down the springs, but some engines are small enough that it might not take a tremendous amount of force. I know on a diesel the clearances between the valve face and piston crown are small enough to make this feasible, not sure about on your gasoline engine though.

I think they may actually make spring compressors that work without needing access to the combustion chamber too (looks like they require compressed air on the cylinder as you mentioned). The Lisle 16750 Valve Spring Compressor works with that method.

 

[skylarkguy]

another trick i have heard of for changing stem seals is to feed a bunch of small diameter rope into the cylinder through the spark plug hole. This fills it up and won't let the valve drop in once the retainer is released. Never tried it but sounds good at least.

 

[Ilikeurtractor]

Anything that might save the cost (and hassle) of a head gasket (and some are quite expensive) would be worth trying. Thanks for the tip.

 

[Bl8tant]

FYI - I use the rope trick for removing the clutch/flywheel on chainsaws,weedeaters,etc. Feed the rope into the plug hole until "full". Then turn engine to TDC. It will keep the engine from turning while you loosen (or tighten) fasteners.

Where would you guys recommend getting seals ???

 

[Johnp33]

You can buy a valve spring compressor LYLE they work great, you collapse the spring, and with the plugs out turn the motor gently if the valve is pushed up enough to get the spring out then you are good to go if not the rope trick works great, do not loose the end, turn the motor untill it pushes the valve up, then you are good to go. YOU MUST COVER the keepers with a rag you will have to hit the top cap to break it loose, the two keepers will fly.
Most times, the valve seals come with the head gasket installation Kit, ask you dealer if they are sold separately.
When the valve spring is collapsed see if the valve guides are worn, I suspect the seals stuck and slid up, do both the exhaust and intake while you are at it.
If you have access to a bore scope and the pistons have a ring around the outside it is the rings.
If it puffs smoke then pull the exhaust manifold, and then you will know which cylinder.

 

[Bl8tant]

John,

If I read your post correctly, then you agree that valve stem seals could be the problem ? Given the low hours on the tractor, I sure hope that's all it is. I'd be really bummed to put her out to pasture over a "worn" engine. Despite it's age, it's in nice shape and everything works great....just looks like a mosquito fogger when running.