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Questions tagged [two-stroke]

A type of internal combustion engine where all of the cycles of combustion occur in one 360 rotation of the crankshaft.

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11 votes
4 answers
2k views

Starting a 2 stroke jet boat after several years

The parents in law gave me a jet boat, it hasn't been started in 5 years. The boat resided in NH on a trailer on their yard for 5 years, so it has seen freezing temperatures frequently. From what I ...
Calvin's user avatar
  • 489
31 votes
2 answers
30k views

Why do two-stroke engine exhaust pipes look so strange?

Two stroke gasoline engine exhaust pipes are shaped strange. They expand into a wide diameter and then shrink down to a very small diameter where the exhaust gasses emerge into the environment. - ...
DucatiKiller's user avatar
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1 vote
2 answers
2k views

Exhaust back-pressure Q on simple 2-stroke yard-equipment engines:

I am having trouble getting a precise answer- is back-pressure necessary on a little single-cylinder 40cc 2-stroke like a chainsaw or a blower? I ask because people frequently modify mufflers to ...
2-stroke-q's's user avatar
16 votes
6 answers
21k views

What makes two-stroke engines less fuel-efficient than four-strokes?

It is a commonly-held belief that two-stroke engines are less fuel-efficient than four-stroke engines, and some example BSFC figures appear to confirm this as well. But what is it that causes two-...
Zaid's user avatar
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11 votes
1 answer
4k views

Brake Specific Fuel Consumption of 2-stroke vs 4-stroke

How much fuel do various types of engines burn per power output? I'm especially interested in naturally aspirated piston engines, and comparing two-stroke to four-stroke. The wikipedia article gives ...
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3 votes
1 answer
5k views

Bottom piece of spark plug broke off in motorcycle engine

I was riding my 2005 RM125 dirt bike the other day when it bogged down all of a sudden. I noticed the spark plug had backed out of the head, thus causing the stall. I pulled the spark plug all the way ...
hgwhittle's user avatar
  • 519
2 votes
5 answers
2k views

Two-stroke vs four-stroke design

Besides the apparent differences in fuel-injection, ignition, and valve timing, are there any other differences in the design/build of two-stroke and four-stroke engines?
ManRow's user avatar
  • 303