Valve seals - intake only?

[toomanybikes]

My '81 definitely has smoke on start up, which I expect is due to leaking valve seals. The lazy part of me is thinking about only replacing the intake seals under the assumption that exhaust seals don't contribute to any oil entering the cylinders and causing the smoke.

Does that sound right to the forum experts?
Is there another reason to change the exhaust valve seals?

I'm familiar with the process and have done it before, but the exhaust seals and collets are slightly harder to change than the intakes since they tilt downwards under most normal maintenance positions. I've heard some people lay the bikes on their side to make it easier, but I don't think I want to do that

[CYBORG]

If I had determined I had a bad valve seal, I would change them all. They all have been exposed to the same heat, same wear and tear, etc. Something to the saying, "do it right or do it twice".

[redglbx]

In my experience (???) Goldwings sometimes tend to smoke on startup, not all and not all the time but it’s kind of the nature of a flat engine. Does it clear up and run clean ? Then I would ask does it smoke on decel which is a sign of bad valve seals ? If so then I defer to Cyborgs comments above , change them all !

If it doesn’t smoke on decel and you don’t have to regularly add oil to the sump then it’s possibly just normal G-Wing ! Or it could be bad rings or an overly rich carbs…

As an example my 76 that I bought new has sometimes smoked since new, sometimes it doesn’t,,, sitting for a long time particularly on its side stand encourages start-up smoking.. but my 76 which has been sitting in my shop for about 4-5 years now due to a chuffing out the exhaust and me having major back surgery making me unable to work on its center stand, but over the past few months I have been able to spend time on it and starting it many times is a bit of a crap shoot,most of the time it just starts clean and runs,,, occaisionally it smokes the shop over. It’s a GL !

Anyway, at this point on your bike I would do a couple of things ,, do a compression test and see what you have, the actual number has some importance but it’s more important that all 4 are similar. I would also do a leakdown test which should give you an idea of the health of your cylinders. And since you’re doing all this and you should have all the spark plugs out and the throttle held wide open, so inspect all the plugs and look for anything abnormal, they should all look the same .

My 76 from new had 135-145psi cranking compression until I milled .040in off the heads and advanced the cams, both increased the cranking compression which is now around 195psi.. imho,, Honda’s specs on all this is quite confusing at best, so again in my opinion it’s more important that they are all similar..

If all of the above checks out then I would prescribe the RaT method,,”fill it up , ride until empty & repeat, enjoy” … also if you don’t know when the last time the belts were changed (5-10yrs max) change your belts..let us know what you find, I hope all this helps..

[CYBORG]

Also check the oil level. Bike on center stand, not on the upper mark, but between the marks. Over filled can cause smoking as well. Especially if parked on the side stand

[redglbx]

Cyborg, good advice ! I forgot about that ! I used to fill to the top mark or slightly above and yes it smoked more often !

[toomanybikes]

Thanks all for the info. More info ...
1. Smokes on startup, then clears after 30 seconds or so
2. Oil level currently about 1/3 from the bottom of the sight glass. Don't recall the original fill level, but it would not have been above the sight glass.
3. Compression check from Jul'24 had #1-3 at 140+ and #4 at 130
4. Belts replaced Jul'24.
5. Don't know about smoke on decel. I'll check that next time a get a chance to ride it.
6. I'll check spark plugs.

[redglbx]

Too, has this bike been sitting for a while ? I suspect that it’s fine and needs the RAT technique applied,, ride till empty,,,refill and repeat !

Basically just ride it and enjoy it ! The compression I would call ok, and if it’s been sitting a while they tend to smoke for a while until things reseat ,,, keep an eye on the oil level,,, , one thing that just popped into the brain is do you have the crankcase vent hose hooked up to the air cleaner ? My 76 will use a serious amount of oil if I disconnect mine and use absolutely none if it is hooked up.. Also might be worthwhile to service the oil separation can on the RH backside of the motor, make sure the separator media is good ( you can use a piece of the green foam available at auto parts stores that they have for the aircleaner PCV valve separator. Just make sure it’s breathable… you can blow through it..

[toomanybikes]

Too, has this bike been sitting for a while ? I suspect that it’s fine and needs the RAT technique applied,, ride till empty,,,refill and repeat !

Basically just ride it and enjoy it ! The compression I would call ok, and if it’s been sitting a while they tend to smoke for a while until things reseat ,,, keep an eye on the oil level,,, , one thing that just popped into the brain is do you have the crankcase vent hose hooked up to the air cleaner ? My 76 will use a serious amount of oil if I disconnect mine and use absolutely none if it is hooked up.. Also might be worthwhile to service the oil separation can on the RH backside of the motor, make sure the separator media is good ( you can use a piece of the green foam available at auto parts stores that they have for the aircleaner PCV valve separator. Just make sure it’s breathable… you can blow through it..

It sat for several years, but I've ridden it about 400 miles since it became roadworthy maybe 6 months ago. It is still smoking on startup. The crankcase vent is connected to the airbox.

I didn't do anything to the separation cannister, so i'll have a look there.

[redglbx]

Too, it may just be the normal GL start-up smoking deal , quite frankly I’d check your canister, mine had the foam separation media just falling apart and had a lot of dead bugs in it, I sealed it up so there’s no vacuum leaks and past that I’d check to see if it smokes on decel (valve seals) and just monitor the oil level, if it’s all good then just ride it and enjoy it.

[toomanybikes]

Too, it may just be the normal GL start-up smoking deal , quite frankly I’d check your canister, mine had the foam separation media just falling apart and had a lot of dead bugs in it, I sealed it up so there’s no vacuum leaks and past that I’d check to see if it smokes on decel (valve seals) and just monitor the oil level, if it’s all good then just ride it and enjoy it.

Maybe I'm missing something. Do you have an image the cannister and separation media? I found and emptied the overflow cannister above the swing arm and behind the starter clutch area (which was full), but there is no foam media, just a plastic container.

PXL_20251114_132013049.jpg

Are you talking about the oil separator screen on the lower right side of the engine, tucked in behind the frame rail?

PXL_20251114_134130275.jpg

[Sidecar Bob]

See below. A pinpoint sized drop of oil in a combustion chamber can produce a huge cloud of smoke. If you start with the oil level halfway between the too low and overfilled lines and it doesn't use oil don't worry about it.

Smoke-On-Startup-Service-Bulletin.jpg

[redglbx]

Bob,

Too, I made a mistake , I went back & reread thus and realized this is an 81 which doesn’t have the same breather/separation can that the 75-77’s do ,, not rebuildable on yours ,,the only thing you can do is just make sure all the lines are hooked up to keep a negative pressure in the crankcase. And don’t overfill things..

[toomanybikes]

Bob,

Too, I made a mistake , I went back & reread thus and realized this is an 81 which doesn’t have the same breather/separation can that the 75-77’s do ,, not rebuildable on yours ,,the only thing you can do is just make sure all the lines are hooked up to keep a negative pressure in the crankcase. And don’t overfill things..

OK, then the last thing I'll check is if any smoke happens on decel.

I'm not overly concerned about the smoke, just lining up maintenance projects for the winter. If I don't need to mess wit hthe valve seals, that's one less thing on the list.

[toomanybikes]

UPDATE - Downhill test yesterday yielded no smoke on decel. I'll leave the valves seals alone.

Interestingly, part of the smoke tendencies is due to the boxer/flat engine, which make sense, but the BMW boxers I've owned don't have the same tendency. They were years 1998 through 2010, so maybe they are just not old enough.

[redglbx]

Too, good news ,, I guess just ride it and enjoy it ! On the BMW’s , I often wondered the same thing but I think it’s because the sump on the beemers is much deeper than on the wings which puts the oil level a lot lower than the bottom of the cylinders, there’s a lot of motor below the bottom of the cylinders whereas the wings have the oil level not all that far below the cylinders. Which I think is why parking on the side stand promotes the start-up smoking, the beemers don’t seem to have that problem, plus they have a pretty easy to use center stand where the Wings are a bit of a hassle to use which promotes the side stand use..

Anyway that’s my .02 on all that,,, so just ride your wing and enjoy it !