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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28
votes
2answers
21k 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. - ...
19
votes
1answer
7k views

What is happening when a two-stroke engine is said to be “four-stroking”?

Many years ago, I was involved in a hobby of building and flying model aircraft. The aircraft used alcohol-fueled 2-stroke engines with glow plug ignitions. When these engines ran rich (and always at ...
15
votes
6answers
14k 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-...
12
votes
1answer
2k views

Does the air screw only affect the pilot jet?

I have a 2 stroke motorcycle, it's Kawasaki KR150. When I try to do some jetting on its carburetor (it's Keihin PWL26), I saw that there's an air screw. So now I've been wondering about this air ...
11
votes
4answers
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 ...
11
votes
1answer
2k 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 ...
9
votes
5answers
15k views

What are the problems in building 2 stroke engines with a large displacement?

I understand (from preliminary research) that when engine gets bigger, with a higher displacement that it is practically not possible to have a two stroke engine. What are the implications in ...
9
votes
2answers
622 views

Carb. Rebuild or Adjustment?

Just put a rebuilt 2 stroke and brand new Mikuni SBN carburetor in my jet boat. Got her running no problem the first couple times, now it seems I can't get any gas into the carburetor from the primer ...
8
votes
4answers
8k views

Is it okay to run aviation fuel (100 low-lead) in a dirt bike?

I'm wondering if it will be okay to run 100 octane low-lead aviation fuel in my 2007 RM250 motocross bike (two-stroke). Half of the people I've asked say yes, while the other half say no. Will it be ...
8
votes
1answer
2k views

Two-stroke dirt bike piston running into spark plug

Recently, I submitted a post on here regarding a broken ground electrode on the spark plug of my 2005 Suzuki RM125: Bottom piece of spark plug broke off in motorcycle engine Well, I found out what ...
7
votes
2answers
2k views

Two-Stroke Diesel Engine - Do they use forced induction on them?

As I have indicated before, I'm very diesel ignorant. I just know the basics, very basics. In a two-stroke diesel engine using forced induction seems necessary but at the same time I see challenges. ...
7
votes
2answers
183 views

Honda R8X-S heat seize

I've got a Honda R8X that heat seizes when I'm riding it when it goes over 40mph. The lad I got it off said he had it re-bored and that it was run in. Will I need to re-bore this again or is there ...
7
votes
1answer
3k views

Two-Stroke vs. Four-Stroke Diesel Engines - What is most commonly used in heavy vehicles?

I am not well versed in diesel engines. To prove my point, I've learned in the last month that a two-stroke diesel engine actually exists. My Question. What kind of diesel engine (four-stroke or ...
5
votes
2answers
8k views

No compression on my two stroke

I was recently riding racing my Honda 250R (1986) (informally), and, all of a sudden, the engine quit completely. I tried letting out the clutch in second gear (push starting) with my momentum, but ...
4
votes
1answer
2k views

Old gas in 2 cycle engine

I have a 2 stroked engine that sat for over 2 years. I drained the gas and can get it to turn over when I put starter fluid in the carb. it is blowing out a water substance from the muffler and cuts ...
4
votes
2answers
3k views

Single Cylinder 2 stroke bike with twin exhaust, will it need two chambered exhausts?

I am asking specifically about Yezdi (not in production anymore) 250/350cc motorcycles. Yezdi RoadKing was a 250cc single cylinder two stroke with twin exhaust. If upgrading to a calculated chambered ...
4
votes
2answers
130 views

If an engine starts does that mean compression is fine?

I am looking at buying a second hand 2-stroke engine. I have seen a lot online about checking compression before buying used engines. I don't have a compression tester, but will buy one if necessary. ...
4
votes
3answers
7k views

Two-stroke engine won't start - water in gas?

I realize this isn't a car question. There doesn't seem to be an appropriate Exchange for it, so I'm trying it here. I have a two-stroke engine (for a rototiller), and it worked more-or-less well ...
4
votes
1answer
68 views

Snowblower - 2 cycle oil without stabilizer

I'm not sure if this is the correct forum for this question. I have some 40:1 mixed gas (for my snowblower) that is about 6 month old with no stabilizer added. I haven't t tried it yet but should ...
4
votes
2answers
2k views

Adjust carburettor without hi-speed adjustment

I've got a Walbro WA226 with no hi-speed adjustment screw. Unfortunately, it seems that the issue is in the high-speed jet. Adjusting the low screw can set me up so long as the throttle is at full, ...
3
votes
4answers
3k views

Derbi Senda 50cc - Low Compression, will not run properly

I have a Derbi Senda SM 50 2005 plate. It has a good spark, however, it's not reading any compression. It's had a new top end and gaskets! What could be wrong? Sometimes it starts when you bump ...
3
votes
1answer
4k 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 ...
3
votes
2answers
145 views

Diagnosing a boat that wont start

Having some problems with my '92 Boston Whaler Rage jet-boat again.... See this post for all relevant boat info: Starting a 2 stroke jet boat after several years Ok, so I did basic troubleshooting, ...
3
votes
1answer
276 views

JLO Rockwell 2F600

I have an old hovercraft that uses a small aircraft engine in the front to power both the lift and forward propulsion. I was hoping to find any kind of manual or literature on the engine itself. The ...
3
votes
1answer
2k views

Small two-stroke engine runs poor

I have a borrowed cultivator (Echo TC-2100), and having hard time running it. It looks fairly new, and in good condition, but was possibly poorly stored and was not winterized. At first I could not ...
3
votes
0answers
82 views

Weed Wacker Not Running Properly

I have a Remington weed wacker that is ~2 years old. It worked great for the first 2 or 3 months but then I could not get it to work properly. I have tried new gas, new plug, adjusting the idle on ...
3
votes
0answers
125 views

Jet Boat, Cavitation or Misfire?

My jet boat is making a 'putting' noise when trying to accelerate. You can find all details regarding my boat here: My Boat Info The noise seems to happen in the mid-rpm range; 4,000 - 4,800 RPMS, ...
2
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5answers
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?
2
votes
3answers
1k views

Oil sump for 2 stroke vehicles

I do not know if there is any oil sump for a 2 stroke vehicle and basically it is mixed along with the gasoline. Why is that so in a 2 stroke vehicle. And can we have an oil reservoir or a sump of oil ...
2
votes
1answer
378 views

Is an exhaust mute bad for 2 stroke engines? [closed]

Will an exhaust baffle have any bad effects on a 2 stroke engine if it's used all of the time?
2
votes
2answers
20k views

What is the difference between a 2T oil and a 20-40 oil

I know a 2T oil is used in 2stroke bikes and its sometimes added with the fuel too. And a 20-40 oil also known as the engine oil is used to reduce the wear tear in the engine. I'm looking for a ...
2
votes
1answer
107 views

Two-stroke engine seizing at full throttle

I have an odd problem with a 50 cc air-cooled two-stroke scooter engine that keeps locking up at full throttle, then freeing up again. I just bought the bike second hand with a new belt needed ...
2
votes
2answers
4k views

Too much smoke in my 2 stroke

I have a 2004 Cagiva Raptor 125 and for the last week it's been letting out smoke a bit too hard: I have had the bike for a year and a half now. I did an engine rebuild as soon as I got it because ...
2
votes
5answers
710 views

2 Stroke engine magneto ignition system

I've got a 2 stroke 1 cylinder engine and its ignition system doesn't seem to work. I'm having problems with my magneto ignition system and I need help connecting everything up. I think I've ...
2
votes
1answer
682 views

2 Stroke making choking sound on full throttle after carb replacement

I have a Yamaha RX 135 which is a 2 stroke bike, and I have replaced it's carburetor , Previously it was stock 26mm round slide mikuni carb , and its been replaced with 30mm Flat slide mikuni. After ...
2
votes
1answer
3k views

String trimmer revving too high at WOT?

Someone gave me a 52cc string trimmer for free because they say it wasn't working. We would only get it started by dropping a few drops of fuel into the cylinder, and it would idle quite high for a ...
2
votes
1answer
115 views

How to clean a muffler from the inside?

I want to clean the muffler (final exhaust pipe) of my motorcycle (2004 Cagiva Raptor 125). It is a 2 stroke engine so a bit of oil has sort of... sedimented on the inside of it. How am i supposed to ...
1
vote
1answer
3k views

50cc Two Stroke Scooter/Motorcycle - Idle and start issues

This is my first motor-vehicle ever, a Simson s50 from 1976. Things seem to be running fine, but there are two problems I need to figure out: 1) The engine dies unless rev'ed constantly - eg at a ...
1
vote
1answer
63 views

How fast a 2 stroke engine wears, how much fuel it consumes(compared to a 4-stroke engine) and how to properly mix fuel with oil [closed]

I want to buy a 2 stroke engine to build a minibike. I am 15 years old and i never owned a 2 stroke engine before. I know they wear faster and consume more fuel than a 4 stroke engine. But how fast ...
1
vote
1answer
47 views

This seemed a good spot for engine-stuff, so: What are some ways that *may* lead to greater power in a chainsaw?

This seemed the best area to ask since it's not a tool question so much as an engine question, I use a high-end premade fuel and always have a sharp or sharp-ish chain, am just hoping to learn the ...
1
vote
0answers
87 views

Johnson 9.9 2 stroke wont idle anymore

I have a 1999 Johnson two-stroke 9 hp outboard motor. I have a 10 foot pelican that I put it on but the other day I almost flipped the boat after making a sharp turn, water got all in the boat about ...
1
vote
0answers
82 views

1997 Mercury 9.9 HP 2-Stroke starting issue

I've been banging my head on a starting issue with the outboard motor mentioned in the subject line (it's a manual pull-start). Problem is that when I pull it over, it doesn't sound/feel like it even ...
1
vote
0answers
2k views

2 cycle engine has spark and new carb won't start [closed]

I have a 49cc 2cycle engine that I replaced the carb on. It has fresh gas and appears to have a spark. I can't get it to fire even if I put some starter fluid in the air intake. It seems to have ...
0
votes
1answer
16 views

Primer bulb not drawing fuel

I had an old 21cc two stroke weedwacker engine that I had lying around and was trying to rebuild it for use in a possible hobby project. It sat with gas for a very long time so I disassembled the ...
0
votes
1answer
18 views

Craftsman Leaf Blower wont start, ignition coil failure?

In a previous question I asked about repairing a carb for my leaf blower and the repair didnt hold so I bought a new one. Replaced fuel filter and fuel lines, also replaced the carb gasket. I seem to ...
0
votes
1answer
40 views

Turn push/pull motion into up/down?

I don't know if this is the right place to ask, but I have an RC 2 stroke engine with a choke with an arm that requires up/down motion to open/close. The problem is I can't place a servo below, so I ...
0
votes
1answer
37 views

Two stroke engine stalls during incle

Sir I have 1967 two stroke Harley Davidson golf cart. It runs great on level ground but when I try to go up a incline hill it wants to stall and it only makes it up the hill using the choke. I changed ...
0
votes
1answer
2k views

2 stroke scooter won't rev under load

Just put a big bore kit on a Yamaha Jog (50cc to 70cc) and am getting ~115psi compression. It will reach full rpm on the stand but on the road it won't pass mid throttle and makes a hollow/rattling ...
0
votes
1answer
25 views

1966 Suzuki K11 Oil Change

Got a old suzuki that's running and working just fine. I got the fuel ratio for the bike which is 20:1 this a two-stroke. What I'm trying to figure out is the oil for the bike. Normally do 10w30 or ...
0
votes
0answers
29 views

Boring Engine Cylinders

I owned 1978 YAMAHA 175 Enduro (2 stroke) and i had to bore the engine cylinder and now i am using 1.00 piston in it.But i noticed that it's not speeding up above 80,when it reaches 80 it's like ...