Question about 2 stroke running.

nitroscope8

New Member
May 26, 2008
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Long Island, New York
In browsing through other threads I commonly read people talking about their 2 stroke acting as a 4 stroke while cruising and 2 stroke when accelerating. Ok...what does this mean? If it's a 2 stroke, how does this thing 4 stroke? The SLIGHTEST Idea I can come up with is that this pertains to a different in pitch from the engine because It sounds more of a pop pop pop when cruising but more of a brrrrrrrrrr when accelerating, but I can be way off. Any insight?
 

Bikeguy Joe

Godfather of Motorized Bicycles
Jan 8, 2008
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up north now
That was probably me talking about the 2 stroke/4 stroke thing.

What happens is the engine not under load has too rich a mixture and fires every other cycle, like a four stroke engine. Most modern 2 strokes will run in a 2 stroke all the time, but our ancient piston ported engines will (when properly set up) break between a two cycle and a four cycle.

When just right, these engine break between a two stroke and a four stroke as they run in cruise mode, the slightest extra pull causing the engine to break into a full rich two stroke cycle.
 

Skyliner70cc

Member
Mar 8, 2008
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4 stroking a two stroke means the mixture is so rich that it fires 1/2 as often as it should. 4 stroking is not recommended because it'll foul the plug and may cause rings to stick plus it will never allow engine to hit its normal operating temperature.
 

Bikeguy Joe

Godfather of Motorized Bicycles
Jan 8, 2008
11,843
236
63
up north now
Yes, but when set up right, these engines do four stroke when not loaded.

I changed my carb settings a dozen times an every time I got it to run in a two stroke across the range, there was less power and the engine ran hot.
 

nitroscope8

New Member
May 26, 2008
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Long Island, New York
Seems like mine is running well then. I had to adjust the carb clip because it was going through fuel faster than it should, but now it runs great and the plug is a light gray color with oily carbon everywhere else...which I assume is good and normal for 32:1 mix.