Why do most small V-twins smoke at start-up?

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Not sure why but every V-twin I have owned smaller being 16-24 HP seems to smoke for a few seconds at start-up and I have heard others say that is normal. What is the reason for this?
 
My guess is they have a little more clearance in the valve guide stems because of the heat that these engines run at. Hence a little blue smoke like the valve guide seal would be bad at start up.
 
Originally Posted by spk2000
Not sure why but every V-twin I have owned smaller being 16-24 HP seems to smoke for a few seconds at start-up and I have heard others say that is normal. What is the reason for this?

Are we talking about Outdoor Power Equipment V-Twin's?

Most of them are horizontal, oil lays against the back of the piston and creeps into the cylinder, and it smokes on startup.

If I parked my Cub Cadet w/ Kohler V-Twin with the nose downhill, and started it a few hours later, it would make quite a smoke show, for several seconds.

There are vertical V-Twins in the world of Outdoor Power Equipment... by some weird rule, they always cost much more. They are also more suitable for go-carts and such.
 
I have a horizontal vanguard 16hp in a cub cadet. This thing has over 1800 hours on it and has never puffed one hint of smoke from the exhaust. It could very well be a trait more common on the vertical shaft engines due to the higher possibility of oil being pooled in the cylinders and getting past the rings while sitting.

Is this a trait of the lower cost engines or are you guys with vertical shaft kohler commands, vanguard, kawasaki seeing this issue as well?

as an aside I also maintain a Kohler magnum 18 hp (flat head, vertical shaft, opposed cylinders) and I cant ever remember seeing a hint of smoke at startup either.
 
Interesting as I had a Briggs Vanguard 16 HP that smoked at cold start up as well. That was in a Barretto rototiller. Pretty nice machine I got off Ebay that used to be a rental. Very heavy similar to a Troy Bilt but much heavier. It had hydraulic drives for both wheels and tines. Tines could go forward or reverse. Normally I didn't like the reverse method as it bounced around more even though it weighed over 700 lbs. Hitting bricks or large rocks would bog motor no broken pins. Miss that old tiller.
 
Originally Posted by spk2000
Not sure why but every V-twin I have owned smaller being 16-24 HP seems to smoke for a few seconds at start-up and I have heard others say that is normal. What is the reason for this?

It's the same principal why radial aircraft engines smoke profusely at startup. (A V-Twin is just a pie cut section of a radial). Oil gets past the piston rings and valve guides of these engines when they sit, due to somewhat looser tolerances. (Especially the horizontal cylinder models). As was mentioned higher operating temps are a reason. On aircraft radials oil would run down into the bottom cylinders. And it would cause severe smoking at startup until those cylinders burned off all of that oil.

Some of these big 2 row radials would leak so bad, they had to manually pull the propellers through a few compression cycles of the engine, to assure they wouldn't hydraulic lock with oil if they engaged the starter. If that happened they had to pull a spark plug and drain the cylinder. Oil consumption on these engines was very high. I read an article on the Convair B-36 Bomber that said each of it's Wasp Major R-4360 Radial engines had a 100 gallon oil tank to supply it with lubricating oil. That's 600 gallons of oil total for all 6 engines.

V-Twin power equipment and motorcycles are just a much smaller version of such a beast. But the same basic principals apply. So a few puffs of white / blue smoke at startup is a normal feature of these engines.
 
^ I think I'd rather have a little smoke at startup instead of that burden or expense.

I'm JUST NOW thinking about replacing the over 10 year old air filter on my B&S v-twin 19 HP intek engine in a mower. I have brushed some sediment off and banged it to remove some dust yearly, over the > 20 year period where it's on air filter #2.

Valve lash adjustments really? I guess you can spend as much as you want to. I never needed to do anything to this engine over the 20+ years except tighten the flywheel bolts once, and of course, change the oil/filter with nothing special, any major brand 30wt.

No good reason to pay more for 5W-30 synthetic unless it's a snow blower or water cooled engine... which it might be!

Granted, my lower standards could be due to only mowing 1/2 acre in my climate, you could be putting on more hours per year, but even so, I don't see the justification to treat a mower like it's your first born child if others don't have problems spending a fraction as much time or money. Except, this is BITOG where maintenance has nothing to do with need and everything to do with excess.
 
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^If you keep your eyes peeled like me, you get paid to buy synthetics. Free oil is always a perfect candidate for a lawn mower, is it not?

Regardless, my 23HP Kawasaki FR691V never smokes, never needs the choke used, and never hesitates to fire up. But it's had 5W-30 synthetic since after the 8hr factory fill. After 3 full hard years of mowing 4 acres year-round, it still runs like brand new. But I maintain it like my car. It will get it's 2nd set of fuel filters, 3rd air filter, and 3rd set of plugs this July. It gets a light dose of Techron twice a year, applied the tank before the oil change, and gets WIX filters & E-0 gas. You reap what you sow
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Originally Posted by tony1679
^If you keep your eyes peeled like me, you get paid to buy synthetics. Free oil is always a perfect candidate for a lawn mower, is it not?

Regardless, my vertical 23HP Kawasaki FR691V never smokes, never needs the choke used, and never hesitates to fire up. But it's had 5W-30 synthetic since after the 8hr factory fill. After 3 full hard years of mowing 4 acres year-round, it still runs like brand new. But I maintain it like my car. It will get it's 2nd set of fuel filters, 3rd air filter, and 3rd set of plugs this July. It gets a light dose of Techron twice a year, applied the tank before the oil change, and gets WIX filters & E-0 gas. You reap what you sow
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How many hours are on it?
 
Originally Posted by NH73
How many hours are on it?
No counter unfortunately. My best guess (minimum) is 6 hours a week, March through October (8 months a year), for the last 3 years (this is year 4). So my math says 624 hours, and that's being a bit conservative. It probably has more hours than I say it does. So realistically somewhere between 650-750 hours.
 
My B&S 20 HP INTEK twin smokes maybe only once in 20 start ups. I found out if I let it idle down for ~ 30 seconds it does't smoke on startup. Ed
 
Depending on how they're parked and stored, my take on this is a lot of vertical shaft V-twins may be parked slightly nose-down, such that some crankcase oil works it's way into the combustion chambers. Thus the blue smokey start up. Most will puff a little bit of black smoke with choke use on cold starts.

Not to say they don't, but I haven't seen any horizontal shaft V-twins smoke on cold start.
 
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Originally Posted by tony1679
my 23HP Kawasaki FR691V never smokes, never needs the choke used,


Funny, I started up my Deere yesterday and today, with the same engine.

Smoked a lot for the first 4 seconds.

It's got 1 year of service on it. 43.5 hours.
 
Originally Posted by spk2000
Not sure why but every V-twin I have owned smaller being 16-24 HP seems to smoke for a few seconds at start-up and I have heard others say that is normal. What is the reason for this?

It is likely because everyone believes you have to put in a lighter oil than is recommended.
 
Originally Posted by bobdoo
Originally Posted by tony1679
my 23HP Kawasaki FR691V never smokes, never needs the choke used,


Funny, I started up my Deere yesterday and today, with the same engine.

Smoked a lot for the first 4 seconds.

It's got 1 year of service on it. 43.5 hours.

My 21 year old Kawasaki 501v smokes on start up infrequently, especially if parked a while on a slope then restarted. I noticed this the first summer I owned it and mentioned it to the dealer. He said not to worry about it and it will clear up after running a few minutes. I haven't and it does. I've never had to top off the oil and it runs as good as ever.
 
Originally Posted by Lubener
Originally Posted by spk2000
Not sure why but every V-twin I have owned smaller being 16-24 HP seems to smoke for a few seconds at start-up and I have heard others say that is normal. What is the reason for this?

It is likely because everyone believes you have to put in a lighter oil than is recommended.


I have a Kohler Command Commercial and I call it the "Smoking Kohler" It has almost 700 hours on it and smokes no more or less on some startups than when it was new. It has had decent maintenance done on it.

10W30 is what Is recommended and what I use.
 
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