[Spring Brook Rider]

Ok. This is probably a simple question for most of you motor heads but I'm still in elementary school when it comes to mechanics so here goes. What does it mean when an engine smokes only at start up. Runs clean all the time otherwise. uses little or no oil and runs like a banshee? 650 C with only 7000 miles.

 

[achille]

Sounds like valve guides,but only 7K miles?



How much is "very little" consumption?



Sometimes it's hard to see smoking in bright daylight,more obvious at night with headlights behind.



Abused during break-in possibly?

 

[LRCXed]

The valve guide seals could have dried out too. Especially since it has obviously sat for most of it's life.

 

[achille]

Pay me no attention SBR, I always overlook the seemingly obvious!

I'd say LRCXed has probably pegged it.

 

[Shep]

Ditto to what Larry says.The engine is too low a mileage IMHO for the actual guides to have worn,but it is possible.I'd go for the Valve stem seals.They come in the same Top-end head gasket kits so aren't usually worth buying separate and then I'd do a full top-end de-coke/Valve regrind at the same time,might as well as you will have to release the valves anyway.

It is possible to replace the seals with the valves still in but it's very tricky and not worth the risk IMHO.If it's not using much oil I'd leave it until you want to say do a cam-chain renewal and do a ,"Full" service or some other major work so long as the oil looks ok?

If you know a local mechanic who has experience of in-bike/engine stem renewal you could go that way but I wouldn't trust the procedure under normal circumstances and then there's the cost.



Pre-emptive oil and coolant changes and keep the tappets set well and ride it IMHO so long as there's no unusual engine noises

My 10 penn'th.

 

[Reg in Bristol]

What colour smoke?



If its Blue and smells oily see previous answers

If its Black or grey and smells like gas, it may be a result of a rich mixture

or too much choke.

If its white and dissipates quickly its condensation and quite

common when temps drop and/or its wet out

 

[nolavox]

What colour smoke?



If its Blue and smells oily see previous answers

If its Black or grey and smells like gas, it may be a result of a rich mixture

or too much choke.

If its white and dissipates quickly its condensation and quite

common when temps drop and/or its wet out

The voice of reason. I think you are spot on Reg.



We have high humidity here and if I run a motor without bringing it up to operating temps, it will condense moisture, this will also lead to some premature rust out. Most of the cars here are dripping smokey water from the exhaust first thing in the morning. Certainly knowing what kind of smoke is going to narrow the possibilities.



I'd also like to add that this IS a HONDA... I read a thread yesterday from a member who apparently had run his bike for a year without checking the oil... bone dry, and it still tried to run. I would diagnose it... and then probably not fix it, unless it was looking like a progressive catastrophe in the valve train. I have also found on my CX, that it will go rich and smoke if the emmission control stuff is not clean and breathing.



If it's not using or burning up oil, I'd just keep an eye on the oil level... and ride on!

 

[achille]

Did all engines come factory equipped with stem seals?



I've only dissected one ' 78 motor and there were no seals.



Of course I know that's not definitive........

 

[Shep]

Did all engines come factory equipped with stem seals?



I've only dissected one ' 78 motor and there were no seals.



Of course I know that's not definitive........

All the engines are supposed to have Valve stem seals.



Also to OP a clogged air filter can cause these symptoms as well.Renew if age not known IMHO.

 

[Spring Brook Rider]

Thanks guys. Oil comsumption is about nil. It's just the first few seconds of start up. Smoke is blue and smells like oil. I'll just keep ridin and not worry about it. When I bought it this spring from a lady in duluth I couldn't even squeeze the clutch lever. Spent a lot of time dinking with it and had my mechanic friend who knows all these older critters give it a complete going over. Nothing was major and it's my favorite steed. It sucks that it's gettin cold out now for ridin but I guess that's what warm baths are for. ya'll take care.