Suspected stuck piston rings

[Adrian GilesParticipant @adriangiles39248]

I’ve used carb cleaner aerosol as an indicator for years, if your engine coughs and starts on carb cleaner, you know that the basic engine setup is ok. It’s then down to either ignition or fuel.

[I.M. OUTAHEREParticipant @i-m-outahere]

Bryan , the reason why you have not recieved a lot of replies stating that they used X chemical to fee up stuck rings and it worked perfectly is probably because it would not be a conventional repair or cure to the problem .

You have no way of knowing " how " stuck they are and what is causing them to stick – is it old dried up oil ? Possibly , is it varnish build up ? Possibly or is it carbon build up ? Once again possibly or are the rings broken ? Possibly and no amount of soaking with any chemical known to man will fix that !

The reason i recommended a leakdown test is to definately confirm what is leaking before you go tipping stuff down the injector hole which may or may not work anyway . Anything that can disolve what ever is causing the stuck rings will remove all of the oil film between the cylinder and piston which could cause scoring on start up until the oil works its way back in there . If you were worried about using a starter spray because it washes away the lubricant , wouldn't you be more worried about what you use to try to free up the rings ? Long before i would even consider using something to disolve the gunk would take the head off and slowly warm the piston up with an lpg blowtorch , just hot enough so if i spit on it the spit starts to sizzle . You could then try some hot ATF ( yes hot ! Warm it up in a tin with the blowtorch applied to the bottom of the tin until it starts to smoke ) in there and let it soak overnight . At least that way you are using something with a lubricant not a solvent or corrosive .

You mentioned in your pm that the engine probably stopped at TDC – this is unlikely but not impossible , with the mass of the flywheel and generator rotor it would tick past tdc and keep rotating until it hit the next major resistance – the compression stroke , it would have bounced back a little -maybe back far enough to hit the bottom of the power stroke and could have stopped anywhere in-between , in-between those two extremes both valves have opening and closing events where the valve springs are compressed . This was a real problem with engines like briggs and stratton that had little short mufflers as the exhaust valve would sit there open and condensation would set in rusting the valve face and seat especiall if stored over winter like this -if i only had a dollar for every time i have seen that !

[Phil WhitleyParticipant @philwhitley94135]

even with stuck rings, which is very doubtfull on an engine with so few hours on it, it should at least cough a bit with easy start, and give a few puffs of smoke from the exhaust. If it is not doing this, then there is no compression whatever, Ie for one reason or another, the valves are not seating, the head is not fully down etc etc.. Check the tappet clearances, watch the motion of the valves as they open and close, more to the point, take the injector out and check the compression, even if it is only with a thumb over the hole. If there is any compression whatever, it should give at least a smoky cough with easy start!

[Howard LewisParticipant @howardlewis46836]

Really stupid question: The decompressor is not stuck?

On a similar single cylinder diesel, that would not start, one of the valves was found to have stuck, holding the valve off its seat. Removing the head, and cleaning the valve stem to remove the carbon build up, freed it and solved the problem.

Howard

[Nigel McBurney 1Participant @nigelmcburney1]

Could your problems be due to the bio additives in the fuel, the additives are causing lots of problems particularly if the percentage exceeds 5 % the fuel goes "off" after a relatively short time, and the bio coming from natural sources causes bacterial growths ,a friend has a David Brown diesel tractor and the mesh filter in the line from the lift pump to the injection pup gets blocked with a black messy gunge. I would for a start drain the WHOLE system a, and fill with new fresh diesel. For an engine with 100 hours it should not be worn, as the exhaust seat was corroded possibly due to the valve being left open in a marine environment and may have corroded the rings. I would have thought that a loss of 20 % compression would not cause too many problems, my very old Lister LT 1 diesel was well worn as it was in my cement mixer but it would start with one winding the handle and two others rotating the drum. Personally I would strip the engine why potentially ruin a near new engine, it may be difficult but a 400 cc engine is not that big.

[Howard LewisParticipant @howardlewis46836]

Bryan,

You have a couple of PMs

Howard

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