4 - stroke Piston rings

[Spaniard_King]

Does any one here know if any 4 stroke manufacturers pin there piston rings??

For all the people who are gunna ask.. it stops the rings from moving around the piston.

regards

Garry

[FNQCairns]

I do doubt it on a 4st sort of goes against the theory of how rings work in a 4st but things have a habit of moving on. I wonder if high output 4 st road bikes have pins?

Did you find a strange score in a bore?

cheers

fnq

[FNQCairns]

I do doubt it on a 4st sort of goes against the theory of how rings work in a 4st but things have a habit of moving on. I wonder if high output 4 st road bikes have pins?

Did you find a strange score in a bore?

cheers

fnq

[Spaniard_King]

FNQ,

If they don't pin them and the engine is left trimed down where do you thing the oil on the bore would run to ;) I believe this is a fault of the 4 stroke and the main reason why some 4 strokes will blow smoke from new :o.

Bassically any 4 stroke that happens to have the ring "gaps" at the botom of the bore will leak oil into the combustion chamber if the engine is left trimmed down for any length of time.

what do you recon??

Garry

[The_Walrus]

Hi Garry,

I don't follow your last post.

How can the oil leak past the rings given that the oil sits under the cylinbers?

On occasions, I've left my yammy 25/4 trimed in to the max for a couple of weeks and have not notices any smoking. Mind you for in between trips storage, I usually make certain the outboard is level.

The only time I've had some smoke was after a service when the oils was overfilled. I took out 100 mls before the oil level was bach within the marks on the dip stick.

Luc

[noluck]

far as i know rings should move around and no one pins tham
all so on alfa romeo or subaru # car #motor is side ways and #some endgins are #with dray samp and pistons #hanging down
and rings are not pined
i hope this help
cheers no_luck

[Spaniard_King]

Hi Garry,

I don't follow your last post.

How can the oil leak past the rings given that the oil sits under the cylinbers?

On occasions, I've left my yammy 25/4 trimed in to the max for a couple of weeks and have not notices any smoking. #Mind you for in between trips storage, I usually make certain the outboard is level.

The only time I've had some smoke was after a service when the oils was overfilled. #I took out 100 mls before the oil level was bach within the marks on the dip stick.

Luc
Luc,

outboard pistons run Horizontal, car engines run vertical. So the oil falls away from the rings in a car..it cant do this in an outboard unless it is trimmed up in a transport postiion.

Garry

[rajawolf]

Garry ,
Now u have me thinking and I have to know....I might go pull my honda mower apart now and see.

[The_Walrus]

Thanks Gary

So used to car type engines, I forgot that outboards run horizontal ::)

Luc

[FNQCairns]

Hi Garry you could be right I guess it may do some pooling below from the skirt, but it will need to pass the oil/helper/compression ring before it can get into the chamber.

I know nothing of these engines specifically but based on older but comparable engines I would guess and combined with your theory what is happening is the outboard probably uses relatively high performance, rattle when cold, thin ringed pistons because of the sustained high rpms they need to run at. These really do not do the job until at operating temp, then combine this the standard spec 'too thin' oils the manufacturers recommend so that their fuel consumption figures impress the political Greenies worldwide and - there you go!

A person could also throw into the mix an mineral oil that is at half life and has lost a portion of it's property's (too thin from day one) and we have a cold start smokin engine!

All just guesses, and they say there is no need to decarbon these 4st engines, I would be running a ring free or something if it were mine.

cheers fnq

[rajawolf]

FNQCairns and other people,

I have seen many posts from #USA forums about decarboning of 2 stroke outboard motors, they advise what to use in the states, but do you know what product we can buy in Australia, that can be used to decarbon a 2stroke outboard motor...it has been bugging me for ages.

Sorry to hijack the thread Garry.....

Cheers,

Tony

[rajawolf]

FNQCairns,

You have a cake and candle in your profile..is it your birthday today?

If so Happy Birthday mate!!!!!!!!!! [smiley=laola.gif]

[FNQCairns]

Thanks Rajawolf seems only last week I was only half this age hope the next 20ish go slower!

IMO that stuff is a saviour in a can for injected and premix engines, I have seen a couple of dealer declared 'needs to be torn down' engines show an almost clean bill of health after a really good soaking with this stuff.

I have used the Johnson brand, cannot say it is any better or worse than the other dealer stuff out there.
We do not have deep creep or sea foam out here yet at least not the last time I checked.
Also IMO all other things being equal regular use of this stuff will double the lifetime hours on an injected or premix power head.

cheers fnq

[Spaniard_King]

FNQ,

It all comes back to pinning the rings in there desired position, I know the 2 strokes had a problem with this due to heat (they kept wanting to fall out ::) ) But I think heat should not be too much of a problem in a 4 stroke.

The Johnson/Evinrude Product for de carbonizing is called "Engine Tunner"

cheers

Garry

[FNQCairns]

Yeah typically if the rings line up in a 4st then blowby will increase but oil usage does not as a rule, the oil ring/scraper deals with that aspect, it's not usually a big deal. Need some horizontally opposed car engine techs to fill in the gaps.

If the engine was in a car and was designed for a less athletic life I would assume the problem would never arise due to the design of the piston and rings to suit that application.
I have heard the Yamaha's do the smoky start thing but had not heard of the others having the same problem, but I dont really take much notice either.

You could be onto something Garry but the only non invasive way I can suggest to investigate is to do a leakdown test on the suspected cylinder/s to check for a line up if a line up will show well enough this way and then check that it also owns the dirty-est new plug after 5 seconds of a smokie startup. Then wait 20 engine hours and do it again.

Dont really want to go pinning 4st rings, it's nice to have them traveling around the bore equalising wear/thrust etc

The question is just too hard hard for this little black duck :-/.

cheers fnq

[dfox]

Garry, i understand what your saying, have you had smoke come from a cold start on the honda's?
Our old honda 90 never experienced any smoke , and none of our yammies ever had. Im only submising but an upright (vertical) cylinder would have all (most) of its oil run back to the sump, but a horizontal setup would have a small amount sit in the cylinder. This in fact may aid in lubricating a cold start until oil pressure starts forcing oil out of the conrods onto the cylinder walls. FNQ has given a theory on how its maybe possiable to get oil past the rings,and to have the gaps and oil sit at the bottom to allow this seems plausable? But if this was the case many motor bikes would experience the same, and seeing honda yamaha and suzuki are quite familar with horizontal engines in there bikes id find it hard to believe that this would occur...foxy

[Spaniard_King]

dfox,

was a topic of conversation at a recent dealer seminar I went to. and it was not confinned to any one brand. It only needs 1 cylinder to have the rings lined up near the bottom and you get a smoker :o A hell of a job just to move the rings around a piston :-[

It's not a wide spread problem owners are reluctant to own up to having a 4 stroke smoker :o

Garry

[The_Walrus]

Rajawolf,

Re carbon built up, I use the fuel supplement from ProMa Systems in all my engines, car, boat, mower and wiper sniper.

The oldest engine (10 years) is the mower (4stroke). Like all mower it's had a hard life (ie very little maintenance). It smokes a little on startup but apart from that works very vell. Last time I took the top off. I didn't notice any carbon built up.

It may be worth a try !!!

Luc

[rajawolf]

Thanks guys ..I will try some of the products you mentioned.

Tony