Inspecting for Sticky Rings?

[RudiGreyling]

Hi Guys,

I've been hearing about the inspection for sticky rings through the exhaust manifold. My 503 has done 400 hours, so I want to inspect the rings, as part of the 100hr checks. I am not keen to pull the top at this stage, so i want to check via the exhaust ports.

What exactly does one do and what do you have to look out for?

Thanks in advance,
Regards
Rudi

[RudiGreyling]

Anybody out there???? :D

I'd like to do it this weekend, and have had no responses yet.
Don't you guys check for sticky rings on your 2 strokes?

Thanks
Rudi

[Morph]

I'm doing a 503/586 course this weekend and then I will be able to give you an answer. I would have thought other guys could have helped you by now. Why don't you give Niren a call at Aviation Engines

[Aviation Engines]

With exh manifold removed, you will be able to view the piston walls and rings through the port.

Remove one sprak plug on each cylinder to make turning the crankshaft easier.

You want to push on the rings to ensure that they are not stuck inthe ring grooves on the piston.

Inspect the piston walls for any signs of siezure.

Check the deposits on the piston crown. If it's more than 1mm thick, you will have to remove the cylinder heads and cylinders and carry out a decoke.

If the deposits have traces of a yellow/orange colour, this is a sign of lean running or detonation. All 2-stroke oils contain an element that when burnt at very high temperatures it results in yellow/orange coloured deposits.

Another sign of detonation is the build up of tiny melt droplets around the spark plug electrode.

Typical causes of detonation are:

Incorrectly calibrated carbs causing lean mixtures
low octane fuel
incorrect heat range spark plugs

Hope this helps.

Regards
Niren

[kb]

Niren, are there any signes to look out for before I pick up my set of spanner's, and the "gentle-persuader" (aka 5 Pound hammer). and start taking the motor apart. should I be looking for something (excess smoke) or listening for something that does not sound right?

[RudiGreyling]

OK, the info came a little late, but this is what I observed. Comments Please?

I took of the exhaust manifold, and took out both plugs, to get enough light to see good.

1) I inspected the walls of the piston through the exhuast port while moving it up and down and it looked clean, no scratches, no scuffing...must be good!
2) I tried to move the rings with my fingers, but there is almost no space to do this, and very difficult to see anything, with your fingers in the exhaust port. I could not feel any movement either, read a difficult tasks. So I don't know if I failed or passed this test...
3) Inspected the piston top through the spark plug holes, I had almost no deposits on the crown, very little and less than 50% of the area was covered in a thin layer of black carbon +/- 0.1mm thick, the rest of the 50% of the crown was completely clean and a muddy brown colour.

Comments from the guru's please!

Regards
Rudi

[Aviation Engines]

First to answer kb's question: I assume you're asking about signs of detonation -

1. While operating in the high range (5800 - 6500 rpm) you may feel a slight flat spot/jerk, this may be accompanied by a spike in the EGT readings if you have gauges to measure this.

2. Melt droplets around the spark plug electrode, they look like tiny ball bearing. You may also see traces of grey on the electrode.

Ideally the spark plugs should burn a light to dark brown at all times. Excessive idle times would result in a dark brown/black colour and long operating times inthe high range will be a lighter brown. In my experience this is the same for most oils, the colour may vary depending on the type of oil used.

Hope that answers your question.

[Aviation Engines]

to Greylingr

Before we jump to tearing the engine apart, try using something blunt, you want to be ale to push onthe ring adn ti return with a slight spring action, the movement is less than 1mm. DO NOT DAMAGE the ring in any way, be careful!

If there is absolutely no movement, get your tool box out and more importantly, the relevant manuals, a very "touchy" point for me, NEVER WORK ON YOUR ENGINE WITHOUT THE RELEVANT MANUALS!

......AND A GOOD TORQUE WRENCH.

Remove the cylinder heads, cylinders.
Cover the crankcase with some rags to prevent any dirt getting into the crankcase.
If the rings are stuck, try pulling them open from the open ends, hopefully you can remove them without breaking.
Severe sticking does require breaking them. new rings..........
DO NOT over-stress the rings, this will create cracks which you may not detect.
If they are stuck badly you could immerse the piston and rings in some Acetone for a while, it may help to loosen them.
If the ring grooves are severly coked, you could use a piece of an old broken ring to clean it out.
Quite often the bit of fine water paper folded to fit snugly into the groove will do the job.
If you have been able to remve te rings without breaking them, insert them in the cylinder and push down with the piston or suitable object so that they go squarely into the cylinder about 20-30 mm from the top.
Using a feeler gauge, measure the end gap.
Maximum allowed is 1mm. If you measure more than 0.5mm replace the rings with new ones.

Re-install rings, if old ones, remember same cylinder they came off. I would always recommend a very ligt home of the cylinder, but not always necessary.

New gaskets, base and head.
Torque is 22Nm, inner screw first and work outwards in a cross pattern.

DO NOT torque the screws holding the cowl down to the distance screws more than 22Nm, rather torque to 20Nm.

During assembly remember to use 2-stroke oil on all components.

There goes your weekend....................

[Cali]

WOW thanks Niren

And here I thought this was a job for a Gynecologist

[Wart]

Thanks for the info Niren. Again we must be grateful that we have the experts available here to give us guidance and tips to ensure that we fly safe.

Thanks.

[RudiGreyling]

Hi Niren,

Thanks for the detailed reply, very good information!

I will try and move the rings with the next checkup in 25 Hrs, with blunt object like a old screw driver. Unfortunatley everything is back together already, so it will wait till then.

Is there any relation between a clean piston top and sticky rings?

My reasoning is that since my piston top is pretty clean at this stage I hope my rings will be clean as well..(or at least last till my next 25 hr inspection. ) I don't want to go tearing a good engine apart yet.

Regards
Rudi

[Aviation Engines]

Is there any relation between a clean piston top and sticky rings?
Not necessarily, I've seen pistons with excessive deposits on the piston crown, but no sticking rings and vice-versa.

There are many factors at play here such as:
Type of oil used
Ratio of oil to fuel
Carb calibrations
Wear on the pistons, rings and cylinder

I agree don't go opening the engine unless you have good reason to do so. Leave it till your next 25hr inspection.

[Leprachaun]

Hi guys, firstly thanks to Niren and Rotax for the service provided- great when you have backup from a supplier.
If you have not done it yet my suggestion would be to get somone who has done it before to assist you - otherwise practise on juniors scooter , if something goes wrong it wont kill ya - these are simple two stroke engines, but you must know what you are doing - I have a DVD available on the 503 - tools needed , how to strip , what sequence , etc and how to check (rotax approved of course ) , those who are interested can contact me - Dont bugger up a good engine if you dont know what you are doing- gotta call this week from a fellar who wanted to know how to remove the needle bearings from the "sump " of a 582 , he decided to decoke and pulled out the gudgeon pin, but forgot about them needle rollers, now a quick decoke becomes a trip to JHB -
Fly straight ,fly high,and last of all fly safe ,Leprachaun