how can you tell if you have a 4 stroke or a 2?

eric2524

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Jul 24, 2008
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2
How can you tell if you have a 4 stroke or a 2 stroke? I have a used yamaha 130 etxg from 88 used. No manual and was wondering if it was a 4 or 2. Any help?

Eric
 

eric2524

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Jul 24, 2008
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Re: how can you tell if you have a 4 stroke or a 2?

If it has 4 spark plugs does that mean it has 4 cylinder and is a 4 cycle or can it be a 4 cylinder 2 cycle? Kinda confused.
 

JB

Honorary Moderator Emeritus
Joined
Mar 25, 2001
Messages
45,907
Re: how can you tell if you have a 4 stroke or a 2?

Your question scares the devil out of me, eric.

Your engine is a 2 stroke. Numbers of cylinders and spark plugs is irrelevant.

Invest in a factory Owners Manual so you have a basic understanding of how your engine works.
 

Evinrude Boater

Lieutenant Junior Grade
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Jul 6, 2004
Messages
1,144
Re: how can you tell if you have a 4 stroke or a 2?

And for goodness sake buy some TC-W3 outboard motor oil and mix it properly with your gas.
 

Skinkutter

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Jul 24, 2008
Messages
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Re: how can you tell if you have a 4 stroke or a 2?

You should call the dealer where you got the motor and ask THEM. J.K. If you put oil in the gas or a reservoir it is a 2 stroke. but there werent too many 4 strokes in 88 anyhow.
 

eli_lilly

Chief Petty Officer
Joined
Dec 22, 2005
Messages
435
Re: how can you tell if you have a 4 stroke or a 2?

If you run it on the muffs and you can hear it from four blocks away, it's a 2 stroke. To verify, look back towards your house, from four blocks away, for the billowing cloud of blue smoke.

-E
 

SKEETR

Chief Petty Officer
Joined
May 3, 2008
Messages
430
Re: how can you tell if you have a 4 stroke or a 2?

I was gonna say to look on the deck or rear storage hatches for colorful stains.
 

jay_merrill

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Joined
Dec 5, 2007
Messages
5,653
Re: how can you tell if you have a 4 stroke or a 2?

Eric, as mentioned, the number of cylinders and/or spark plugs has nothing to do with whether a motor is 2-stroke or 4-stroke.

A 4-stroke motor (sometimes also called a 4-cycle motor) has 4 distinct compnents to each power pulse. Those are the intake stroke, the compression stroke, the power stroke and the exhaust stroke. All of these involve the piston moving up an down in the cylinder. On the intake stroke, the intake valve is opened and, as the piston moves forward, into the cylinder bore, fuel/air mixture is pulled into the cylinder. As the cylinder begins to move backwards, toward the cylinder head (compression stroke), the intake valve is closed and the fuel/air mixture is compressed. At a certain number of "degrees before top dead center," the spark plug fires and the piston is forced forward by the expanding gases. This is the power stroke. The final phase in the sequence is the exhaust stroke, when the piston moves back towards the cylinder head again, this time with the exhaust valve open. In a 4-2troke motor, the spark plug fires every other time the piston reaches a certain point in the "upstroke."

In a 2-stroke engine, the intake stroke and the compression stroke are combined and the power stroke and exhaust stroke are combiined. There are no valves in the motor, which has intake and exhaust ports cut into the sides of the cylinders instead. In this type of motor, the spark plug fires every time the piston reaches a certain point in the "upstroke."

One of the easiest ways to tell the difference between the two motors is to just listen to them. 2-stroke motors usually sound louder and have a higher pitch sound than the 4-strokes do. You may also be able to tell by the size of the motor - for a given horesepower rating, 4-stroke engines tend to be larger and heavier. This is due to the added parts associated with the valve train in the 4-stroke.

As was mentioned, you might do well to buy an engine service manual for your motor. I also recommend reading a bit about basic outboard motor design. The more you know about outboard motors in general, and your motor specifically, the easier it will be to operate it correctly.
 
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