'85 700SC - Lightly smokes when warm

[torlok2002]

Had this 85 700SC for a few years and have been babying it. It now has just under 40,000 miles and I have noticed that it lightly burns oil when it reaches operating temps. There is not a lot of smoke and its mostly noticable in the headlights of another car at night. You can detect the light smell of burning oil.

I was wondering if anyone might have an idea of the most likely issue. I'm guessing it is in need of new Rings. I'm looking at tearing it down this winter and doing a rebuild. I have a decent amount of engine experience, but am no mechanic.


Also, is it safe to ride in the meantime? I've had it covered in the garage for the past few months until I had a chance to investigate.   Thanks!


lorez-killboy3 by torlok2002, on Flickr
Me on the Dragon last year.

[skramer360]

I would think it would be fine to ride. I would if it were mine. Just check the oil regularly and enjoy until rebuild time.

[ariwhiteboy]

I agree with skramer...if it's not that serious then there's no need to tear into it until the off season. (If you're one of those unfortunate souls who has an "off" season.  )

[torlok2002]

Great, Thanks!

I'm glad I found this site, as it's a great resource for a bike not many shops around here have much knowledge about. And OEM parts are a PITA to obtain. 


Anybody have experience with this issue so don't tear into things that don't need to be torn into? Any possibility the smoke could be something simpler than worn rings with the above symptoms? Is 40,000 due for a rebuild anyway?

Until winter... 

[ariwhiteboy]

Well most carbureted bikes smoke a little when warming, at least all mine have. That's from condensation in the exhaust though...if it's smoking when it's warm and continues to smoke it's probably rings. What color/odor is the smoke?

[torlok2002]

It does not really smoke until its been warmed really well and then continues as long as it's running. Certainly not condensation.

The smoke it probably a white to grey-ish, but it's faint enough that it's difficult to see. It's most evident at night at stoplights when a car is behind with it's headlights shining, and color is difficult to determine in this condition.

I don't know what to call the odor other than an oil smell, but extended trips will leave a slight odor on your clothes. No oil residue anywhere on the pipes, but you can tell they are dirtier than normal.



I think this winter the head will be pulled anyways as I want to change the spark plugs and one of them is cross-threaded  and stuck. So I'll be throwing in a Time-Sert kit at this time as well.

[gammer]

If you are diving into it this winter, then if it were me I'd at least get the cyls honed and install new rings. Also, install new valve seals. These are two area's where oil can leak through and burn.
The valve seals will come with a gasket kit, along with the head gasket and valve cover gasket that you will need for the rebuild.
If you are feeling really adventurous, you could also pull the bottom end apart and have a look at the bottom end bearings and perhaps install a new cam chain.

[HandsomeSteve]

Just chiming in to agree - definitely sounds like rings.  Just make sure you keep the oil topped off, it will burn more as time goes on.

[gammer]

p.s. If you pull the head off any notice any deep gouges or scratches going up and down on the cyl walls, then a honing will not be good enough. You will have to bore it out and go one (or two) sizes bigger for the pistons and rings...or purchase a used cyl that is in good shape and have it honed.

[torlok2002]

Thanks all. Sounds like I'll be pulling the top end apart when the weather gets colder.

I'll check the cylinder walls and do an inspection/hone. I've rebuilt a DOHC inline four on a small car a couple of years back so I should have a good idea of what I'm looking at. 

For now I'll be prudent about checking the oil, pull the riding gear back out, and hit some twisties 

[tomb raider]

Nice action shot, what part of the globe is home ?       Mine is looking a top end fix as well....  Gammer, I didn't know there was over size pistons for these bike ? 

[torlok2002]

Nice action shot, what part of the globe is home ?     

Indiana, but that photo is from Tail of the Dragon.

[LOKi]

  to the forum.

To everyone. What about the babying it part? Could the smoke be from carbon buildup on the valves and top of piston?

torlok2002, when you say "babying it" what do you mean? What RPM range do you cruse at? How high to you let her rip?

My thinking is if your always short shifting and never letter her get above say 4,000 RMP's then you could have a build up of carbon on the exhaust ports. When it heats up the carbon starts to smoke. Could this be the case?

[martian]

Indiana here as well - Fort Wayne to be exact.  Haven't made it down to the Dragon yet though - I'm jealous.

[gammer]

Good point Loki.
Its not hard to run a tank of SeaFoam though it to help clean the intake valves and top of the piston. And running the RPM higher.

[LOKi]

Could give the BG 44K a try.

http://www.bgprod.com/home.html

[torlok2002]

to the forum.

To everyone. What about the babying it part? Could the smoke be from carbon buildup on the valves and top of piston?

torlok2002, when you say "babying it" what do you mean? What RPM range do you cruse at? How high to you let her rip?

My thinking is if your always short shifting and never letter her get above say 4,000 RMP's then you could have a build up of carbon on the exhaust ports. When it heats up the carbon starts to smoke. Could this be the case?

Oh, yes I let 'er rip occasionally. I certainly let the RPM's climb in order to properly utilize this tool  

By Baby I just mean that I have been doing frequent oil changes, keeping her real clean, thorough winterization, always stored indoors under a cover, and never ignore any symptoms that might be cause for alarm (Which is why I haven't ridden for a couple of months).

I have to laugh at the screen name Loki because an old friend used to use that and he doesn't know anything about motorcycles, especially the nighthawk  

[edit]  I'll give the seafoam a try on the next ride.

[gammer]

Gammer, I didn't know there was over size pistons for these bike ? 

From Honda.
I checked with my dealer early last summer and they confirmed that both 1 size and 2 size over piston and ring sets were still avail from the parts warehouse.

[kidagain]

Because it is taking some time to smoke I would inspect your engine cases. Since the exhaust gets hot a small leak may be burining off. I have had this happen in the past.

[torlok2002]

Because it is taking some time to smoke I would inspect your engine cases. Since the exhaust gets hot a small leak may be burining off. I have had this happen in the past.

I'm guessing you are referring to oil dripping off of the cases onto the exhaust?

I'm certain this is not the case, as I just replaced the oilpan (lost the crush washer when changing oil and cracked it) last year and bottom of cases and oilpan are nice and clean. And the smoke is certainly coming from the tailpipes.

If this is not what you mean would you care to explain in more detail?

[torlok2002]

Did a ride a couple of weekends ago and compiled a little video. Love being back out on two wheels!