Why are 2-stroke engines so consistantly unreliable

[BurnitBlue]

Thanks for all the tips. The consensus that fuel is the likely problem with 2-strokes is firming up. Two products I have not heard of before is Carb Cleaner and an ultrasonic cleaner. I will look into them, with eight engines to get going I need all the time saving tips I can get.

I have started with the Yamaha 8. Testing will be a problem because of the weather so I am considering rigging up a bracket and water bin in the basement. Initially all I need is to start the engine for a few seconds just to see if it starts easy. I am aware of co2 so just a few seconds on then off then a few seconds again will tell me that three-quarters of the problem has been solved (or not).

Actually I am quite surprised at the number of posters who get good trouble free service from their outboards.

 

[JumbleDuck]

One thing I forgot to add is that I am very careful about getting my 100:1 fuel mix right.
A 35mm film container filled to brim with 2T oil is 300ml, that is mixed with three 1ltr milk bottles of unleaded.
I always give it a good shake before topping up the tank.

That is (a) a very big film container and (b) 10:1.

 

[LadyInBed]

I can only say that I've never had a problem with old fuel or old plugs.
If the mix is right the plugs dont oil up. Yes, plugs fail, but not too often. In 30+ years I've had about three plugs fail and one set of points that needed burnishing and regapping.
I am thinking that failing / difficult to start is mainly caused by fuel left in the carb bowl for a week or so after previous use.

 

[doug748]

....
Cleaning fouled spark plugs.......just doesn't seem to work these days, I don't know if its something to do with the petrol, maybe the ethanol? I find if I have a duff plug that they soon stop working again when cleaned, so always replace them these days, after all it is normally only a few pounds.

Certainly a school of thought:

https://www.triumphrat.net/vintage-technical-tips-and-tricks/202549-tip-on-spark-plugs.html


FWIW, OP. I have had few problems with 2 stroke outboards over the years and none with plug fouling.
The problems are usually fuel supply, as the others have said, though I did have one Mercury where the power pack failed and it never went again. That was on an IF Boat. My Evinrude 6hp was perfect for the job till stolen but I can't blame the motor for that :nonchalance:

 

[Pavalijo]

I have a 1988 Yamaha 2 str 4hp.

When I first got it (previous freshwater minimal use by a "fettler" so good nick generally) I used a 75:1 mix (I had read some mixed opinions online). Thus worked fine until one day I was pootling upriver on tickover watching something - when the engine stalled and wouldn't start. Taking the plug out and cleaning it restored it to usual reliability.
I always turn the fuel shut off at the end of each day's use to run the carb dry. I have never run it in seawater for more than a few days before flushing fresh water through after an outboard engineer said that the thermostat and channels around it can salt up and that freshwater flushing is important.

 

[Boo2]

I like my nice, lightweight, reliable two strokes...

Draining carbs after use is important if motor is used infrequently - petrol evaporates and oil is left to gunge up the carb internals. Stripping the carb and using an ultrasonic bath seems the best way of dealing with this...

What solvent would you use in the US bath, Lodesman ? Just plain water ?

Edit: Just seen that Allendale sell a US specific carb cleaner, see here.

Boo2

 

[lw395]

Thanks for all the tips. The consensus that fuel is the likely problem with 2-strokes is firming up. Two products I have not heard of before is Carb Cleaner and an ultrasonic cleaner. I will look into them, with eight engines to get going I need all the time saving tips I can get.

I have started with the Yamaha 8. Testing will be a problem because of the weather so I am considering rigging up a bracket and water bin in the basement. Initially all I need is to start the engine for a few seconds just to see if it starts easy. I am aware of co2 so just a few seconds on then off then a few seconds again will tell me that three-quarters of the problem has been solved (or not).

Actually I am quite surprised at the number of posters who get good trouble free service from their outboards.

Repeatedly running a stroker for a few seconds is a sure way to oil the plugs.

 

[TQA]

100 to 1 is insufficient oil for a long life.

Tohatsu tried it for a while and returned to 50 to 1.

 

[macd]

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.

I suspect you're actually referring to a reed valve assembly, which is essentially a one-way valve which allows extended port timings without risk of blow-back through the carburettor. The 'reeds', usually of flexible GRP sheet (but can also be of steel), are mounted on a small cage in the inlet tract. Simple, effective and no cause for concern. Untold thousands have done sterling service on motorcycle engines with much higher specific output that tender-pushing stinkwheels.

The cage and its reeds are usually easily removed. Even the most cursory inspection will reveal how they work.

This is a two-stroke.

Impressive, Jumble. I've always had a soft spot for these: https://en.wikipedia.org/wiki/Napier_Deltic
Check out the animated schematic.

P.S. Two-stroke IC engines were invented by a Scot, which may colour your (and my) view of them. It's not recorded whether Mr Clerk was sober at the time, which may colour the view of others

 

[Pavalijo]

100 to 1 is insufficient oil for a long life.

Tohatsu tried it for a while and returned to 50 to 1.

That is probably what I read when I went for 75:1. Maybe I should stick with that as a compromise but make sure I don't run at low revs for any length of time.

 

[johnalison]

I have in the past encountered stale-fuel problems. I had a Suzuki 2.2 and was running it on the previous year's fuel but it kept on stopping after a minute or so. New fuel cured the problem. When I used to dinghy to and from my mooring I became quite adept at knowing how far from my destination I should shut off the fuel and leave myself only a few seconds' worth to burn off.

 

[CJU]

If you want to use non ethanol fuels Esso Synergy Supreme apparently doesn’t contain any. I always use it in my bikes as they unfortunately don’t get used enough and I can’t be bothered to keep draining the tanks.
Quote:
‘The majority of unleaded 95 Octane petrol sold in the UK contains up to 5% ethanol as required under the Government's Renewable Transport Fuels Obligation (RTFO). ... Esso super unleaded petrol (Synergy Supreme+ Unleaded 97) is ethanol free (except in Devon, Cornwall, the Teesside area and Scotland).
Fuels Frequently Asked Questions | Esso
https://www.esso.co.uk › fuels-faqs’

 

[fergie_mac66]

I've had "issues" with a few 2Ts over the decades. Many of the issues are common with the 4T issues I've also had, apart from the fact that 2Ts can suffer from oiling-up of the spark plug/s which is much less of a problem with 4Ts. It tends to mean that if a 2T is being a bit of a bugger to start, perhaps due to a poor battery, poor electrical connections, poor fuel flow etc. then the 2T will oil-up with repeated attempts to start it which means that you then have another reason why it won't start. :ambivalence:


Richard

if your plug oils up in a 2 stroke then the plug needs to be one number hotter which burns the oil off.if the engine is run at lower revs use one stop hotter plug, if its always run at high revs you might even need one stop cooler the hotter the plug thequicker it needs replacement. link here to plug temps
https://www.google.co.uk/imgres?img...hUKEwjZybics5PgAhXDrHEKHcM0Dn8Q9QEwAHoECAYQBg

 

[fergie_mac66]

smaller outboards also can be given a starting issue if they are too deep in water,Small boat , man at back dips the engine in too deep and even small back pressure causes more difficult starting . The hotter plug is also easier to start.

 

[JumbleDuck]

Impressive, Jumble. I've always had a soft spot for these: https://en.wikipedia.org/wiki/Napier_Deltic
Check out the animated schematic.)

Deltics are fantastic. I have seen, but cannot now find, a video of a model one running. On the other hand, in my search I found this

By the way, people might like to know that from a thermodynamic point of view what defines a diesel is not compression ignition, but combustion at nominally constant pressure, which basically means a much slower burn than an Otto cycle engine which burns at constant volume. The easiest way to get a slow burn is to squirt fuel in as a sort of flame thrower, rather than have a cylinder full of mixture go off, hence compression ignition tends to follow for convenience.

 

[Kinsale373]

After 20 years I'm on my 2nd Tohatsu 3.5 The first required a rebuild after 10 seasons back and forth to a mooring still works well an starts easily. I have used less than 5 plugs over the years!. The trick with 2 strokes is to shut off the petrol supply and let the fuel burn out of the cab if you are not using it for more than a few days. Othewise the fuel may oil the plugs. After laying up for the winter (with fuel removed from the tank) remove the plug and spay a little lube into the cyclnder to free up the piston before starting.
If you do have a slow start after a long lay up , remove the plug, heat with a blow torch or gas ring and re insert hot. Never fails!
They are great tough light engines and easy to repair.

Fire them up in a small bucket of water after a long lay up. Slip the split pin and remove the prop and they will fit into a small bucket. Sort out any issues before you are down at the boat.

Kinsale 373

 

[lw395]

After 20 years I'm on my 2nd Tohatsu 3.5 The first required a rebuild after 10 seasons back and forth to a mooring still works well an starts easily. I have used less than 5 plugs over the years!. ....3

I don't get through a lot of plugs myself either.
But when conned into looking at other people's 2 strokes, new plugs often work wonders. It's the second thing to try after checking the carb is free of dirt and water. Since my mooring is a fair distance from where I launch, my outboards always get a decent run to heat the plug properly. Also I've always had small motors that see a decent amount of 'over half throttle'. People shuffling about with 8HP motors at low throttle will often have more trouble.
Years ago, I did a lot of miles on 2T bikes. I found that some plugs would have short lives, but sometimes you got a good plug that just kept clean. I'd advise carrying a spare plug and a plug spanner.

 

[LadyInBed]

100 to 1 is insufficient oil for a long life.

Tohatsu tried it for a while and returned to 50 to 1.

I bought the Suzi 2 2nd hand in 87 so it's been going 30+ years on 100:1 what do you call long life?
Maybe Tohatsu recommend 50:1, but Suzi book says 100:1

 

[Graham376]

I bought the Suzi 2 2nd hand in 87 so it's been going 30+ years on 100:1 what do you call long life?
Maybe Tohatsu recommend 50:1, but Suzi book says 100:1

Yamaha specified 100:1 for the Malta as well. Mine ran for many years without problems using Quicksilver oil. As lw395 says above, constantly running around at low revs isn't good for any engine, they need a good blast every now and then.

 

[Heckler]

If it available to you I would recommend using Carb Cleaner, which is an aerosol spray of various aromatic solvents which are intended to dissolve the gums and varnishes inside the carburettors' delicate bits. In the UK it is best bought from motor factors rather than car accessory shops.
You still need to disassemble the carb to get at everything, but it is very satisfying to see the gunge dissolve and run off the parts leaving clean metal behind. Poking things into the jets might still be necessary but leaving the carb cleaner to soak means you don't need to poke so hard. A compressed air jet is also useful there, as are cocktail sticks to dig sludge out of corners.
My dinghy engine is a 1967 Seagull Featherweight and once woken up after the winter layup starts second pull for the rest of the season
Good luck

Carb cleaner, spawn of the devil! Snake oil! The reason being is that peeps wave it everywhere on the outside of the carb without stripping and think thats it
The only answer is a PROPER stripdown and some copper wire, judiciously used!
The main jet is easy to get at, everyone takes the bowl off and cleans that BUT the issue is with the pilot jets and internal passages that arent easy to get to.
The biggest prob today is the alcohol that the EU force fuel companies to put in petrol in the name of saving the planet! (5% the last I heard of) Sigh! it doesnt, can you imagine, the alcohol comes from fermenting food stuffs. All the peeps that are starving in the world and the wonderful tree hugger and bunny lover tribe say that fermenting foodstuff is good to produce alcohol to put the product in petrol is really good!
Anyway, alcohol absorbs water, so it absorbs water that ends up lying in your carb over the winter.
when the petrol and alcohol aevaporates, then small amounts of water are left which then corrodes your jets which are made of brass and leaves a nice blocking material on them! Your honda floatbowls which are made of steel rust away from this water and the aluminium float bowls on others react with the water to form a grey jelly like material which lies in the float bowl to block etc.
The answer, as I have said, is strip and MANUALLY clean the jets and passageways. Also drain the flaot bowl on a regular basis to get rid of alcohol absorbed water.