79' Special smokes out of left exhaust....badly

[jrm000kc]

My wife noticed this the day I picked it up long ago but it went away. Fairly certain it's oil smoke. Only does it if it sits for longer than a couple of days. Could it be a worn valve guide letting oil seep down into one of the cylinders once the engine cools off and sits? If I run it everyday, no smoke.

If it is a valve guide, how hard are they to fix? Guy at work said "don't worry about it" considering the age of the bike and how it's not a constant problem.

[Mathh]

Valve stem seals gone bad, change them all. You could change them without removing the head but you do need to remove the cams and lifter mechanisms. Must be described in this or the UK forum somewhere ..

[TopCatGr58]

It can be difficult to do with the head still on. You have to remove the valve springs/keepers to be able to get to the seals. Then there's nothing to hold the valves in/up in the head. Folks posted about a technique of using compressed air to pressurize the chamber with a fitting for the spark plug. OR stuffing a bunch of rope into the spark plug hole to apply pressure against the valves to keep them up.

Unless you have major engine problems, it might be best to just leave it as is. You might try some of that seal conditioner in the oil additive to try to help soften the seals. YMMV.

T.C.

[skids]

It is hard enough to do with the head off the engine!

[Mathh]

It can be difficult to do with the head still on. You have to remove the valve springs/keepers to be able to get to the seals. Then there's nothing to hold the valves in/up in the head. Folks posted about a technique of using compressed air to pressurize the chamber with a fitting for the spark plug. OR stuffing a bunch of rope into the spark plug hole to apply pressure against the valves to keep them up.

Unless you have major engine problems, it might be best to just leave it as is. You might try some of that seal conditioner in the oil additive to try to help soften the seals. YMMV.

T.C.

I used u piece of welding rod that I bent to keep the valve in place. Not too difficult but a pair of additional hands will help for sure.

[BA80]

Mine does the same thing James. After sitting a few days or weeks it'll smoke out the left side for a while.

It's because when you park it on the side stand all the oil left in the top end runs to the left side (gravity works) and seeps through the old seals a bit. It really isn't an issue during riding season for me. Bike still only uses about 1 quart between oil changes, unless I'm mean to it.

If you do change the seals on the bike, the air pressure trick works well. Just be sure the piston on the cylinder you're working on is at TDC and locked some way because when air pressure is applied it will force the piston down if you don't. You want to keep the piston up so that if somehow you drop the valve it doesn't go all the way down in the cylinder. Then you would have a serious issue.

[jrm000kc]

Okay thanks for the confirmation. What type of seals are they brass? I think I'll try the additive for now as it's not really burning any oil. (Sometimes it does use a little but that depends on how many stoplights.)

I read some people have used a flat head screwdriver, welding rod, whatever to hold the valve in. Couldn't you use one of those extendable magnet 'picker upper' deals if the valve dropped into the cylinder? If I ever get around to changing them might as well check the valves.

Thought I finally had all the kinks worked out but something this old there will always be a minor issue.

[Mathh]

Okay thanks for the confirmation. What type of seals are they brass? I think I'll try the additive for now as it's not really burning any oil. (Sometimes it does use a little but that depends on how many stoplights.)

I read some people have used a flat head screwdriver, welding rod, whatever to hold the valve in. Couldn't you use one of those extendable magnet 'picker upper' deals if the valve dropped into the cylinder? If I ever get around to changing them might as well check the valves.

Thought I finally had all the kinks worked out but something this old there will always be a minor issue.

The seal is shoved over the top of the brass guide and is made of silicon, nylon, teflon, viton and so on. The magnetic picker will not work if you mean to hold it up on top of the valve.. You first have to carefully slide the seal over the top of the valve without tearing it up. Be sure to lubricate the stem and seal well. Then slide the seal down and “click“ it over the top of the valve guide.

[skids]

I used u piece of welding rod that I bent to keep the valve in place. Not too difficult but a pair of additional hands will help for sure.

Curious. So you turn the crank to open the valve, put welding rod between the vlave and the seat through the sparkplug hole, and continue to rotate the crank to rotate the cam lob off of the lifter bucket???

[TopCatGr58]

Skids,

To replace the valve seals, you have to get the lifters off. To do that, you have to remove the cams. With both cams out, and all of the spark plugs out, there' s no compression to fight, and all the valves are retracted into the head with the springs, so you can use a long wooden dowel to determine TDC for that cylinder. Then you position the bent welding rod through the spark plug hole around and up against the valve. Then you will need a special rig to bolt to the head to allow you to compress the springs to remove the keepers and get the springs off while the rod holds the valve UP. Then pull the seal, replace, and then reinstall the springs/keepers, and then reset the crank to #1 TDC, and then install the cams with the dots up, and then ensure valve timing before buttoning up.

T.C.

[skids]

Skids,

To replace the valve seals, you have to get the lifters off. To do that, you have to remove the cams. With both cams out, and all of the spark plugs out, there' s no compression to fight, and all the valves are retracted into the head with the springs, so you can use a long wooden dowel to determine TDC for that cylinder. Then you position the bent welding rod through the spark plug hole around and up against the valve. Then you will need a special rig to bolt to the head to allow you to compress the springs to remove the keepers and get the springs off while the rod holds the valve UP. Then pull the seal, replace, and then reinstall the springs/keepers, and then reset the crank to #1 TDC, and then install the cams with the dots up, and then ensure valve timing before buttoning up.

T.C.

You make is sound easy. Thanks for the description. No typical valve spring compressor needed. No new head gasket needed. BTW, I am not doing this presently, I just couldn't visualize how it worked - now I can.