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Would you buy a Two Stroke or a Four Stroke next time and why?

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Created by Bundeenabuoy 1 month ago, 6 Apr 2019
Jolene
979 posts
10 Apr 2019 5:28PM
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woko said..
Jolene said..

AUS126 said..


Bundeenabuoy said..



AUS126 said..
I use to not worry about putting too much oil in the fuel, until I saw the unburnt oil come out the exhaust and leave an oil slick. I now realise how polluting 2 strokes are, and would happily put up with a heavier and more complicated outboard. I can see why we are moving on.





Are you saying that oill was running out of the exhaust?









Yes, unburnt oil goes out exhaust. I now tend to mix closer to 70 :1 instead of 50:1. I've been told you can get away with 100:1. Wouldn't want to have a warranty claim though.




You might be getting away without seizing the engine mixing oil ratio leaner but in reality your just wearing the motor out faster.


The fuel oil ratio is also affected by the the carby air mix, for instance to get more revs out of a two stroke you can lean it off ( we all know how they go like clappers as the fuel runs out, that's owing to the leaning of of fuel air mix ) but of course leaning the air fuel mix to get more revs means less lubricating oil for the engine, that is unless you increase the oil to fuel ratio to compensate.
Proably has no bearing on the average outboard, but I've used this method to squeeze more go out of every 2/ I've ever owned since I was put onto that theory in the pits at Liverpool speed way as a lad, and all of my bikes, mowers, brushcutters, chainsaws easily lasted as long if not longer that the the equivalent unit in other hands.
Golden rule- dedicated container, oil 1st ie: no oil in the container, no fuel in the container ever !


Whilst technically correct, a lean air/ fuel mixture has very little influence on lubricating the motor. A lean motor will fail from temperature rise long before lack of lubrication.
2 stroke carbureted motors usually run fuel rich on the idle circuit to 3/4 throttle , as they run out of fuel, they pass through the optimum fuel ratio at which point they develop the most power, then as the fuel runs out they go lean and stop.
A 2 stroke motor will tend to lean off as its held wide open for a period of time {like the straight on a race track) so by choosing that optimum mixture that gives the highest rpm at full throttle, your playing with fire, This is why power jet carbys (a jet that dumps extra fuel at wide open/ high rpm) are used on hp engines
The richer the fuel/air ratio along with the correct spark plug( to remove critical heat from the engine) the cooler the engine will run

woko
NSW, 430 posts
10 Apr 2019 7:36PM
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Jolene said..

AUS126 said..


Bundeenabuoy said..



AUS126 said..
I use to not worry about putting too much oil in the fuel, until I saw the unburnt oil come out the exhaust and leave an oil slick. I now realise how polluting 2 strokes are, and would happily put up with a heavier and more complicated outboard. I can see why we are moving on.





Are you saying that oill was running out of the exhaust?









Yes, unburnt oil goes out exhaust. I now tend to mix closer to 70 :1 instead of 50:1. I've been told you can get away with 100:1. Wouldn't want to have a warranty claim though.



One part of the 2 cycle phase is the bit where the piston travels toward the bottom of the stroke compressing the airfuel mixture in the crankcase. This pressurised mixture is released into the cylinder via ports and some of it makes its way out through the exhaust port flushing the spent combustion gases out of the cylinder before the piston(on its way back up) closes off the exhaust.
Its perfectly natural to have an unburnt mixture in the exhaust.
On 2 stroke race engines , by designing an exhaust that utilizes sound and pressure waves created when the exhaust port cracks open, this unburnt mixture can be forced back into the cylinder (by sound/pressure waves), effectively raising the compression ratio which can result in a massive boost in power.


Well that's the most informative, no nonsense explanation of the expansion chamber I've ever heard !
Id assumed in my ignorance that the expanding gases worked not unlike a turbo and helped extract the spent fuel.
brilliant !

woko
NSW, 430 posts
10 Apr 2019 8:25PM
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Jolene said..

woko said..

Jolene said..


AUS126 said..



Bundeenabuoy said..




AUS126 said..
I use to not worry about putting too much oil in the fuel, until I saw the unburnt oil come out the exhaust and leave an oil slick. I now realise how polluting 2 strokes are, and would happily put up with a heavier and more complicated outboard. I can see why we are moving on.






Are you saying that oill was running out of the exhaust?










Yes, unburnt oil goes out exhaust. I now tend to mix closer to 70 :1 instead of 50:1. I've been told you can get away with 100:1. Wouldn't want to have a warranty claim though.





You might be getting away without seizing the engine mixing oil ratio leaner but in reality your just wearing the motor out faster.



The fuel oil ratio is also affected by the the carby air mix, for instance to get more revs out of a two stroke you can lean it off ( we all know how they go like clappers as the fuel runs out, that's owing to the leaning of of fuel air mix ) but of course leaning the air fuel mix to get more revs means less lubricating oil for the engine, that is unless you increase the oil to fuel ratio to compensate.
Proably has no bearing on the average outboard, but I've used this method to squeeze more go out of every 2/ I've ever owned since I was put onto that theory in the pits at Liverpool speed way as a lad, and all of my bikes, mowers, brushcutters, chainsaws easily lasted as long if not longer that the the equivalent unit in other hands.
Golden rule- dedicated container, oil 1st ie: no oil in the container, no fuel in the container ever !



Whilst technically correct, a lean air/ fuel mixture has very little influence on lubricating the motor. A lean motor will fail from temperature rise long before lack of lubrication.
2 stroke carbureted motors usually run fuel rich on the idle circuit to 3/4 throttle , as they run out of fuel, they pass through the optimum fuel ratio at which point they develop the most power, then as the fuel runs out they go lean and stop.
A 2 stroke motor will tend to lean off as its held wide open for a period of time {like the straight on a race track) so by choosing that optimum mixture that gives the highest rpm at full throttle, your playing with fire, This is why power jet carbys (a jet that dumps extra fuel at wide open/ high rpm) are used on hp engines
The richer the fuel/air ratio along with the correct spark plug( to remove critical heat from the engine) the cooler the engine will run


Again an excellent discription ! You obviously know your 2/s very well and I was proably very lucky not to destroy the more domestic machines and as for bikes Thers a fair chance that I was off the edge of the track before they got a chance to blow up !

Jolene
979 posts
10 Apr 2019 7:41PM
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woko said..

Again an excellent discription ! You obviously know your 2/s very well and I was proably very lucky not to destroy the more domestic machines and as for bikes Thers a fair chance that I was off the edge of the track before they got a chance to blow up !


I did my share of pushing the bike back to the pits and laying on the ground too. Just moved house and workshop recently and had a tough time throwing away all the broken 2 stroke engine parts memorabilia.
sorry for the thread hijack Bundeenabuoy but mention 2 strokes and I get all warm and fuzzy ,I see more magic in a 2 stroke than I see in a harry potter movie

Sectorsteve
NSW, 2002 posts
11 Apr 2019 5:26AM
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I was trying to find a 2 stroke to buy. they are illegal to sell from july. no new stock in oz, since last July.

we should see the great barrier reef replenish itself in no time with this new BS.

Bundeenabuoy
NSW, 465 posts
11 Apr 2019 7:31AM
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Jolene said..

woko said..

Again an excellent discription ! You obviously know your 2/s very well and I was proably very lucky not to destroy the more domestic machines and as for bikes Thers a fair chance that I was off the edge of the track before they got a chance to blow up !



I did my share of pushing the bike back to the pits and laying on the ground too. Just moved house and workshop recently and had a tough time throwing away all the broken 2 stroke engine parts memorabilia.
sorry for the thread hijack Bundeenabuoy but mention 2 strokes and I get all warm and fuzzy ,I see more magic in a 2 stroke than I see in a harry potter movie

I am always appreciative when someone adds something positive, informative, funny, interesting, or out of the box.
Cheers mate.

Ramona
NSW, 4887 posts
11 Apr 2019 8:16AM
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Sectorsteve said..
I was trying to find a 2 stroke to buy. they are illegal to sell from july. no new stock in oz, since last July.

we should see the great barrier reef replenish itself in no time with this new BS.


6hp Johnson available in Nowra. Not mine and I don't know the condition but should get 20 years or so out of it.

Bundeenabuoy
NSW, 465 posts
11 Apr 2019 10:52AM
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Sectorsteve said..
I was trying to find a 2 stroke to buy. they are illegal to sell from july. no new stock in oz, since last July.

we should see the great barrier reef replenish itself in no time with this new BS.


There is an 8hp mercury foresail on eBay for $830

Sectorsteve
NSW, 2002 posts
11 Apr 2019 2:28PM
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Thanks fellas. I ended up with Gaels Johnson 8hp in exchange for 11east coast charts. The engine works Well . If You're reading cazou . Fair winds north. He did a very fine job in that Triton. New boat.
I took my 8hp mercury to a marine mechanic in ft George's basin. Kept it for 2 weeks and said. " I can't get it going. . "
I spent 450 on a new cdi unit too. I will try taking it elsewhere. Moby marine I reckon

southace
QLD, 3997 posts
11 Apr 2019 3:21PM
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Where I'm currently working we have
8 X 60 hp Yamaha 4 strokes ,
4 X Honda 100hp 4 strokes ,
2 X 90hp 4 stroke suziki ......

3 of these motors are using oil quicker than you can put the oil in them. In fact one I brought back today with 4 hours on the clock was below half on the dipstick. It does appear to be a common problem when using them commercially , the smaller 4stroke personal outboards and Honda gensets mostly get gummy carbi problems which can be electro cleaned for about $80 at the local service centre.
Still far better technology now than the old 2 stroke outboards I feel.

UncleBob
NSW, 405 posts
11 Apr 2019 3:45PM
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Sectorsteve said..
I was trying to find a 2 stroke to buy. they are illegal to sell from july. no new stock in oz, since last July.

we should see the great barrier reef replenish itself in no time with this new BS.


I believe that it is only new 2 stroke motors that are affected, second hand motors are still ok to sell.

cazou34
NSW, 130 posts
11 Apr 2019 4:23PM
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Sectorsteve said..
Thanks fellas. I ended up with Gaels Johnson 8hp in exchange for 11east coast charts. The engine works Well . If You're reading cazou . Fair winds north. He did a very fine job in that Triton. New boat.
I took my 8hp mercury to a marine mechanic in ft George's basin. Kept it for 2 weeks and said. " I can't get it going. . "
I spent 450 on a new cdi unit too. I will try taking it elsewhere. Moby marine I reckon


Good to know

Purfler
NSW, 41 posts
11 Apr 2019 4:27PM
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UncleBob said..



Sectorsteve said..
I was trying to find a 2 stroke to buy. they are illegal to sell from july. no new stock in oz, since last July.

we should see the great barrier reef replenish itself in no time with this new BS.





I believe that it is only new 2 stroke motors that are affected, second hand motors are still ok to sell.




The authoritative source for information on this:

www.environment.gov.au/protection/emissions-standards/outdoor-power-equipment-and-marine-engines

Bundeenabuoy
NSW, 465 posts
11 Apr 2019 4:34PM
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cazou34 said..

Sectorsteve said..
Thanks fellas. I ended up with Gaels Johnson 8hp in exchange for 11east coast charts. The engine works Well . If You're reading cazou . Fair winds north. He did a very fine job in that Triton. New boat.
I took my 8hp mercury to a marine mechanic in ft George's basin. Kept it for 2 weeks and said. " I can't get it going. . "
I spent 450 on a new cdi unit too. I will try taking it elsewhere. Moby marine I reckon



Good to know


Better to keep than gold

UncleBob
NSW, 405 posts
11 Apr 2019 5:28PM
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Purfler said..

UncleBob said..




Sectorsteve said..
I was trying to find a 2 stroke to buy. they are illegal to sell from july. no new stock in oz, since last July.

we should see the great barrier reef replenish itself in no time with this new BS.






I believe that it is only new 2 stroke motors that are affected, second hand motors are still ok to sell.





The authoritative source for information on this:

www.environment.gov.au/protection/emissions-standards/outdoor-power-equipment-and-marine-engines


Thanks for the verification, not illegal to sell, just to import after 2020

Ramona
NSW, 4887 posts
11 Apr 2019 6:55PM
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Select to expand quote
Bundeenabuoy said..

cazou34 said..


Sectorsteve said..



Better to keep than gold


Buy up now! I have my future tender/workboat engines stored. The good long term 2 strokes like Evenrudes and Mercury's have already started to get more expensive. The ex Army 2 stroke 40's are good buying at the auctions but there is starting to be plenty of buyers.

Sectorsteve
NSW, 2002 posts
13 Apr 2019 5:20AM
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Select to expand quote
cazou34 said..

Sectorsteve said..
Thanks fellas. I ended up with Gaels Johnson 8hp in exchange for 11east coast charts. The engine works Well . If You're reading cazou . Fair winds north. He did a very fine job in that Triton. New boat.
I took my 8hp mercury to a marine mechanic in ft George's basin. Kept it for 2 weeks and said. " I can't get it going. . "
I spent 450 on a new cdi unit too. I will try taking it elsewhere. Moby marine I reckon



Good to know


I'm back in Australia and might be going up the coast soon too.
I worried that might happen !

BlueMoon
585 posts
13 Apr 2019 5:26AM
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Hi Jolene (or others) just trying to understand your post atthe top of this page more. You mention playing with fire if operating your 2stroke at full throttle, if I'm reading that right?
I always operate my 2 stroke garden equipment at full throttle, chainsaw, brushcutters, blowers etc. Then when turning them off, remove finger from throttle and turn them off straight away.
It has served me well in recent years and don't seem to choke up the exhausts this way.
Should i not be running the equipment at full throttle?
I obviously don't runthe 2 stroke out board wide open, but do give ita decent run occasionally.
Cheers

sirgallivant
NSW, 1418 posts
13 Apr 2019 6:39PM
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Jolene, did you ever work on reed valve or rotary valve two stroke?
The scavenger type was and is the common one today but few knows the mistery of a Trabant motor or the MZ race engine any more.
It used to be fun tuning them.

woko
NSW, 430 posts
13 Apr 2019 8:35PM
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Select to expand quote
BlueMoon said..
Hi Jolene (or others) just trying to understand your post atthe top of this page more. You mention playing with fire if operating your 2stroke at full throttle, if I'm reading that right?
I always operate my 2 stroke garden equipment at full throttle, chainsaw, brushcutters, blowers etc. Then when turning them off, remove finger from throttle and turn them off straight away.
It has served me well in recent years and don't seem to choke up the exhausts this way.
Should i not be running the equipment at full throttle?
I obviously don't runthe 2 stroke out board wide open, but do give ita decent run occasionally.
Cheers


Blue moon, you will be just fine runnin your gear wide open throttle, we got a bit side tracked in terms of performance tuning. Use recommend oil ratio and appropriate oil type and you will see years of reliable service, air filters on chainsaw especially let you know when they need cleaning, as they don't rev like they should. ( too rich fuel mix )
i would hazard a guess a huge percentage of 2/ failure is due to no oil in the fuel. And it's easy to avoid

Jolene
979 posts
14 Apr 2019 1:40PM
Thumbs Up

Select to expand quote
BlueMoon said..
Hi Jolene (or others) just trying to understand your post atthe top of this page more. You mention playing with fire if operating your 2stroke at full throttle, if I'm reading that right?
I always operate my 2 stroke garden equipment at full throttle, chainsaw, brushcutters, blowers etc. Then when turning them off, remove finger from throttle and turn them off straight away.
It has served me well in recent years and don't seem to choke up the exhausts this way.
Should i not be running the equipment at full throttle?
I obviously don't runthe 2 stroke out board wide open, but do give ita decent run occasionally.
Cheers



Hi Bluemoon.
There is nothing wrong with running a 2 stroke at full throttle if the fuel mixture is correct for the load the engine is carrying . If you tune the motor to run at specific load so that fuel mixture ideal, close to being lean and and max rpm, the motor should be fine,,, but if you increase the load and the time duration it stays at that load, the engine has a good possibility of going too lean and failing.

Examples of this would be a motocross bike tuned for motocross track where the throttle is mostly active around 1/2 to 3/4 throttle and only held pinned open for relatively short periods. This bike runs perfect on the track, However,,"Playing with fire" take the same bike to the beach or sand dunes where the soft sand or long straights of beach put a much higher load on the engine for longer durations. And you might be lucky to get 2km up the beach before you melt a hole through the piston. Rebuild the engine and now appropriately jet and tune the bike for high load of the beach and now the bike is unstoppable, you can ride it flat out all day.,,, but take it back to the mx track and you now find it lacking response, sluggish and your lap times are 5 sec slower.

Chainsaws and brush cutters are normally tuned to a point of max rpm and then the high speed screw is slightly opened a little more going rich, dropping the rpm slightly and creating a random miss in the firing. The over rich mixture now protects the engine for the normal load changes it encounters,, although with a change of cutter type on the brush cutter or bar and chain on the saw, the engine may require tune up attention ,
2 stroke glow engines are another type that require attention to tuning especially in model helicopters
2 stroke engines produce more heat, they fire every time the piston is at the top unlike a 4 stroke, This makes the fuel mixture more critical for cooling. If you have a look at an air cooled 2 stroke engine and an air cooled 4 stroke, the first thing you notice is the cooling fins on the barrel and the head are much larger on the 2 stroke.

Jolene
979 posts
14 Apr 2019 4:04PM
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Select to expand quote
sirgallivant said..
Jolene, did you ever work on reed valve or rotary valve two stroke?
The scavenger type was and is the common one today but few knows the mistery of a Trabant motor or the MZ race engine any more.
It used to be fun tuning them.



Mostly Yamaha engines, TZ 350s (Piston ported), RZ 250, 350 , 500 (Reed valve) YZ 125.250 MX
Mikuni, EI, lectron Keihin carburetors

Plus numerous others

PRD kart motors
and of course OS and Thunder tiger glow(rotary valve) motors for model aircraft and choppers
The only other rotary valve engines I had some involvement with was a Rotax in a Gyrocopter.and a Kawasaki KR 250

Tuned many chain saw and brush cutters. most have the adjustable high /low jet Walbro style carbs[



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"Would you buy a Two Stroke or a Four Stroke next time and why?" started by Bundeenabuoy