Why are 2-stroke engines so consistantly unreliable

[BurnitBlue]

I once had a mercury 6 hp that behaved itself and started every time on a short pull, and always ran smoothly. That was the one and only engine that gave me no problem. I have also had two brand new engines a Johnson 3 or 4 hp. and a Tohatsu 4 hp. Also a used Yamaha 8 hp that gave absolutely no trouble for a year then suddenly at various times over a three year period all three became difficult to start until half an hour of pulling on the starter cord then ran rough. I am getting My IFboat ready to launch this year (been in my garden for the last 5 years) and I need to get these engines working. Along with two 50 cc mopeds and a chain saw that will not start I am beginning to wonder if it is the Swedish climate. I look after the engines and use good clean fuel and oil at the correct ratio. I have no idea at all what the heck I am doing wrong.

I have had many cars (4 stroke of course) and a few diesel engines on my bigger boats with absolutely no problem. So I wonder if there is something intrinsically about a 2-stroke small engine that I don't know about and in my ignorance I am killing the engines. Right now I have seven 2-stroke engines that will not work (all the above mentioned except the Mercury).

The only small engine I have that works is a 4-stroke lawn mower so it is definitely problems confined to the 2.strokes. Help please.

Edit; I have been sailing my Moody in Greece for 5 years but I need to get the IF moving because of the unknown Brexit implications.

 

[john_morris_uk]

Have you tried using Aspen fuel if you only run the engines occasionally?

 

[Praxinoscope]

Strangely enough the best fun I have had with a car was in my old SAAB GT750 a three cylinder two stroke engine. Used to go like the clappers, never let me down, until I pole-axed it, but have to admit fuel consumption could be a bit horrendous.
Most of my old Seagull engines have been reliably good starters and runners, but I have a small two stroke Yamaha that is driving me mad at the moment.

 

[fredrussell]

2 stroke engines are the spawn of the devil. I have a 4 stroke Yamaha 8hp and it is the most profoundly reliable and smooth running piece of wonderment in the whole history of engineering. I love it more than the boat it pushes along, and that’s saying something!

 

[earlybird]

Two-strokes are very good as long as every parameter is in good order, primarily:-
Cylinder compression,
Crankcase compression,
Ignition timing,
Mixture setting,
Fresh fuel.
All simple things but get any one wrong and they can be a real PITA.
Four strokes will start and plod along in a much worse state of tune.
Dunno why.

 

[lw395]

Two-strokes are very good as long as every parameter is in good order, primarily:-
Cylinder compression,
Crankcase compression,
Ignition timing,
Mixture setting,
Fresh fuel.
Get any one wrong and they can be a real PITA.
Four strokes will start and plod along in a much worse state of tune.
Dunno why.

You forgot the plug.
Two strokes are sensitive to spark plugs.
IMHO NGK are generally the best for 2Ts.
It has to be exactly the right number and in good nick.
Water droplets in the carb seems to be the most common thing I find when a small engine won't start.

 

[BurnitBlue]

Have you tried using Aspen fuel if you only run the engines occasionally?

I will have to look up on google what Aspen fuel is. I am not sure how a sentient engine knows how often it gets run It is a piece of metal. The last trip I made was 6 years ago when I went from Sweden into the European canals and only got as far as Berlin after a solid 6 hours a day usage. I take you point though that it could be accumulated fuel oil solidifying in the carburettor but certainly not on that occasion. I took both the Johnson and the Tohatsu and despite new plugs I had to cut the trip short. Totally confused. Thank you I will go to google and get back to the forum.

 

[BurnitBlue]

Ok I have looked up Aspen fuel which seems to be a fuel more suitable for 2-strokes. I will buy some while I am trying to get the engines working again, then I will have to switch back to petrol because it seems very expensive to use for my long distance canal escape run. Thanks for the tip.

IW395. Honestly I have a bucket full of plugs. Both the Johnson and the Tohatsu need a special plug because nothing but the correct plug will work. The Yamaha 8 hp will use a standard plug obtained anywhere.

I know about water in the carb and at first I thought that was the only logical reason for all my engines giving me trouble. I could take the carbs of blindfold before I bought the Moody. Talking of Moody, I have just remembered that is yet another 2-stroke (a tiny thing 2 or 3 hp with no gear shift) which worked when I bought the boat for a month or two. It is now a useless thing hanging on the stern rail bracket. So that makes eight of the things.

 

[CAPTAIN FANTASTIC]

I can not get on with two stroke engines. I threw overboard a Seagull outboard many years ago, its somewhere by the Wash if anyone is interested ��. I only use four stroke outboards which are much more reliable and no issue with having to mix petrol and oil. The garden chainshaws are two stroke but i also have an electric chainshaw for when the two stroke play-up��

 

[Norman_E]

A lot of the problems starting small 2 strokes are because people leave fuel in them. If fuel is left in the carburettor the petrol evaporates leaving the oil behind. The result of that is too much oil in the mix next time the owner attempts to start it, resulting in an oiled up spark plug. You will have far fewer problems with two stroke engines if you always turn off the fuel (or drain the tank) and run the engine dry before putting it away.

 

[Spyro]

A lot of the problems starting small 2 strokes are because people leave fuel in them. If fuel is left in the carburettor the petrol evaporates leaving the oil behind. The result of that is too much oil in the mix next time the owner attempts to start it, resulting in an oiled up spark plug. You will have far fewer problems with two stroke engines if you always turn off the fuel (or drain the tank) and run the engine dry before putting it away.

I've got a Johnson 3.5 which is about 17 years old. It runs and starts almost every time but the only time it hasn't it has been a problem with a gummed up carb through lack of use or water in the fuel. When it's in regular use it never gives any problem

 

[pvb]

I've had 2-stroke chainsaws, strimmers and hedgecutters for years. They've always started easily, even after the winter, and I never drain the fuel out for storage.

 

[BurnitBlue]

Well I certainly do not get on with 2-strokes either. I did not buy a 4-stroke because they are too heavy for an IFboat among other reasons. I honestly do not expect an answer from the forum but one never knows. I cannot shake the feeling that it must be something I am doing wrong. Also at the back of my mind I have a feeling about something called a reed switch which sits in the crankcase doing god knows what, (sorry John). As it is a part of a 2-stroke that is not present on a 4-stroke I have doubts about simply because I cannot find out what it does. Other thoughts have been the formulation of fuel in Sweden but I don't think that could be the cause. Maybe enhanced coke build up because it is colder here than most other places outside Canada.

 

[JumbleDuck]

This is a two-stroke.

 

[pagoda]

With any internal combustion engine, fresh fuel helps dramatically. If yours is over 6 months old, sitting in a tank, consider replacing it. Clean your plug and try again?

 

[BurnitBlue]

It seems that all suggestions and advice concern the carbs and or fuel. There must be something in that. I read somewhere that crowd suggestions are often more accurate than individual expert opinions.

I will go with fuel and carbs and concentrate on all the tiny holes and tunnels in the casting. I must admit that in the past I have just cleaned the bowls a much as I could. I was warned against poking wires in the jets and tunnels as they are easy to damage. I also recall, someone on YBW in a long gone thread some years ago saying that very thin copper wire can be poked in the channels (tunnels) with no damage. Is that true or is that bad advice. BTW I have often soaked the whole carb in pure petrol, ie no 2-stroke oil, but that may not be as effective as I thought.

 

[LadyInBed]

My two aren't unreliable. I have a Suzi 2 and a Mariner 3.3, I use old fuel but always run the carb dry after use, I very seldom touch plug or points.
To start, full choke and throttle to start position, then 6 to 8 gentle pulls and they start - always.

 

[BurnitBlue]

This is a two-stroke.

Where? I can't see one. Or do you mean that massive grey thing? Or are those tiny little Japanese people or model lego dolls? No forget that, That is one massive two stroke.

 

[BurnitBlue]

My two aren't unreliable. I have a Suzi 2 and a Mariner 3.3, I use old fuel but always run the carb dry after use, I very seldom touch plug or points.
To start, full choke and throttle to start position, then 6 to 8 gentle pulls and they start - always.

This seems also to be a theme. So it must be fuel as it is the only thing a user supplies to a brand new engine. Incidentally all the engines worked when new so I had the starting sequence OK. Also even when I get them started they do not runsmoothe and often just stop when the throttle is moved.

 

[TSB240]

I can confirm using a few strands of thin copper wire will be fine for cleaning the jet or passageways in your two stroke carburetor. I raced two stroke karts for 10 years . I can assure you two strokes were way more reliable and easier to work on than four strokes. I continue our simple routine 1 Check for a healthy spark. 2 check for fuel in cylinder by turning over engine without plug and full choke but plug earthed. Look for fine spray from plug hole. Put plug in and engine will start half way through your first pull on a cord wrapped around a rear wheel in our karts! Always fresh fuel and that was with a 12 to 1 oil mix not 50 to 1. Works for all types of application of two stroke engines. Keep fuel clean and dry. You will be surprised how many people leave their top air vent open and allow moist air or water to be sucked into their fuel tank by heat expansion and cooling day night cycle.