OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Engines Questions On Victa Two Stroke Engines Change rings on a 125cc victa 2 stroke

Amendment: I have discovered that this motor is a 160cc

Hello
I am about to change rings on a 125cc 2 stroke engine off a victa utility.
The reason I am doing this is because it was blowing alot of smoke.
I havnt done this before and am treading carefully.
I have read through some of the threads and have half a clue.
At this stage I want to be sure I get the order of the rings right and the gaps in the right location.
Any help would be much appreciated.
Thanks
Mark

Mark, the first question is whether you actually need to replace the rings. Smoke from a 2 stroke depends mainly on how much oil you put in the fuel, and how much old carbon has built up in the exhaust port and muffler. To find out whether you need to replace the rings, first pull off the spark plug lead, then pull the starter cord and feel the amount of resistance. Then remove the spark plug, put a spoonful of engine oil into the cylinder through the spark plug hole, reinstall the spark plug without connecting it, and pull the starter cord again. If the resistance (that is, compression) has increased quite a lot, you need new rings.

If you do need new rings, remove the muffler and look at the side of the piston through the exhaust port. If it is scored, you need a new piston as well. If it is not scored you probably don't need to replace it unless the ring grooves are damaged.

Replacing the rings can be done several ways, depending on the engine design. Usually you remove the cylinder head, then remove the cylinder from the crankcase by sliding it over the piston. You can then remove the old piston rings by flexing them gently without breaking them, until they just slip over the top of the piston. This is practice for putting the new ones on without breaking them. Note which way up the rings go and which is which. Next break one of the old rings, and grind the end of it square to the sides of the ring, to make it into a ring groove scraper. Scrape the carbon out of the ring grooves, keeping the scraper square to the sides of the groove and ensuring you do not remove any metal. It is a bit tricky getting right up to the pegs in the ring grooves that prevent the rings from moving around the piston. Just take your time and be careful. When the piston is clean, you put the new rings on. For low-tension rings like a Victa has, you gently open them by the two free ends until they will just barely slide over the top of the piston to reach the grooves. Of course you have to put the bottom ring on first. They can only go on one way up because of the shape of the ring groove peg, but the top and bottom rings may be different from each other so put the correct bottom ring on first, then the top ring. "Time" each ring rotationally before you expand it and slide it on, so the ring groove coincides with the position of the peg: do not put it on in the wrong position then try to move it around the piston over the peg after it is in the groove. Oil the piston and the rings/grooves. To slide the cylinder down over the piston you have to compress the rings. With these weak little rings you can do it with your fingers, one ring at a time. If you can't, you need to cut a thin piece of steel or aluminium sheet to use as a ring compressor, with a piece of tie wire to squeeze it down to the required diameter. If you use a compressor, when the cylinder has passed over both rings, cut the tie wire, straighten out the metal sheet, and take it off the connecting rod. Then you can bolt the cylinder to the crankcase and put the cylinder head back on.

Thanks for the reply Grumpy. I tried to upload a photo.
Smoke from exhaust was excessive.
1.fuel mix 25:1 and fresh
2.yes, muffler was choked up at outlet----clean now
Will put engine oil in cylinder and test and check for scoring.

Let me get to it and I will let you know how I get on.
Thanks much
Mark

OK Mark. Pity I didn't reply before you took the head off.

Hello again
How does this piston look?

It looks pretty good - those scratches seem to be superficial. How was the compression?

I didnt put it back together to test the compression Grumpy.
Yes, I couldnt feel any scratches with my fingernail.

I have measured the piston at 61mm approx, across the crown.
Is this a 160cc motor then?
If so then I will have to edit the text in all the posts

I have purchased 2 sets of rings (125cc & 160cc)
each kit has a grey,black & wavey coiled up ring. Im not sure why they are different colours and what the wavey one is for.
To date, I have struggled to tell the difference between the 2 sized motors.

The 160 cc Powertorque is 61.5 mm bore, 54 mm stroke. If your stroke is 54 mm it's 160 cc - same bore and stroke means same capacity, regardless of construction.

It might help if you post pictures of the rings.

Yes this is a 160cc, I was told it was a 125cc when I bought it.
Now I have noticed a wave type ring under the bottom ring(closest to piston skirt)
Just have to find out which ring goes in the top groove (crown end) grey or black.
They are the same size.

The wavy thing is a ring expander: it increases the contact pressure between the lower ring and the cylinder bore, to scrape oil off the bore. This makes the lower ring function partly as an oil ring. With an expander under it I doubt you can compress the ring with your fingers - you are likely to need to make a sheet metal ring compressor.

Check whether the rings are exactly the same width. Then see if they are exactly the same depth (one needs to have room under it for the expander). If they are the same dimensions, you'll need to find out which is which from instructions or from someone who knows.

Grumpy, thanks for you words today

They have helped me no end and given me a bit of confidence to go forward.
I have also learnt alot, I love this forum.

I must have far too much time on my hands.
Stroke 53.975mm and piston diameter 61.493mm (figures off spec sheet)
(I measured close to these)
Volume of a cylinder = Area of base x height
A = pi x r2 = 3.14 x 30.7465 squared = 2969.9
2969.9 x 54.975 = 163270 cubed
163270 divide by 1000 to get cm cubed
=163.27 cm cubed (close to 160cc)

That is what happens, Mark. I can recall a car manufacturer developing an engine of 201.24 cubic inches, but the styling department rejected "201" because they felt it wouldn't look good on a badge, so for many years it was called the 202. A bit of poetic license is traditional.

The grey ring ended up being the compession ring or top ring.
I got these into the cylinder carefully using my fingers.
I rinsed inside the crankcase out with 2 stroke fuel.
Motor is assembled and seems to make all the right noises when I turn it over.
Plastic carby took up alot of my time.
Work tomorrow, so have to put it aside to start it another time.

Have you checked the crankshaft seals? Much easier now than after you put it back on the base.

It is just a matter of trickling a little fuel on each seal with it on top and the crankshaft vertical. If the fuel vanishes, you need a new seal.

If the crankshaft bearings have no slack at all, the seals are probably OK, but this is a good time to check them.

Wish i had logged in a bit earlier.

125cc has nuts where the base of the cyl goes onto the crank case.
160cc has the long studs.

The 125's were long gone by the time the external coil and side pull came about.

I dont see a module so im tipping that still has the points in it. If they are due for replacement it is almost if not cheaper to buy a power torque module and use it in place of the points.

Antiseize on the thread of the centre bolt for the pull start is a good idea too.



The motor was on a utility??? Is it an alloy base one??
There are no spacer collars on the crankcase studs so if it was on a steel base the blades would be eating some serious dirt.



Were the rings worn away to nothing???


Cheers, Bob.

G'day Bob
I am a sparky and really shouldnt be playing inside an engine, but I am drawn to mowers and am keen to learn.
I have 2 x super 24's for my block, plus a victa utility, all with these types of motors on them.
I found them to work great. They all support my steel bonnet Cox ride on that I restored.
I mow the slopes with the 2 strokes.

In answer to your questions:
1. This machine has an electronic ingnition module.
2. It was on a steel based one that has seen better days.
3. Yes spacers where used.
4. The rings? to me they still looked OK?

Thanks for the info on 125cc vs 160cc, this has been a mystery to me for some time, now I have more of a clue.

There seems to be alot of these engines around on mowers that have seen their day, I would like to bring some of them back from the dead and reincarnate them onto my super 24's or utility.

Grumpy,I have checked the shaft seals with fuel, they seem OK.
Cheers

Sounds like it's time to put it back together then, mark. Please keep us posted - especially on whether the compression feels different after installing the new rings.

Mark, perhaps you should have pluged up the decompressor hole with an old spark plug and tried that.


Never mind, you know what youve got now and its not bank breaking.



I hear what you are saying. I like buying the old full cranks. They are a good thing. I fix up the good ones, some get 4 stroke or Power torque motors on them, then the motors get sorted and put on utilitys or alloy bases with dead motors. Ive fixed up a couple and put them on Super 24's.


I sold a full crank the other day to a couple of american lassies. An orange one. Carb clean out and away it went, new filter and plug and a fresh pair of blades for good measure.
Ive another in the back shed thats got a fair bit of surface rust, its the $100 special to entice an up sell, if only they knew i had it out the front testing it, i set it on eat dirt and i couldnt push it fast enough to get it to stall out.


I have a sabre thats nothing special, all the shine is gone, but its complete, nothing broken, im going to have a hard time parting with it.



Could have been a real curly one this one, had i got the carb back on and put fresh fuel in it. I spotted it by pure accident when i was checking spark while doing the pins on the carb.

Well, the cylinder head looks broken. How were the piston and connecting rod?

All good.

Pulled the rings off the piston, washed it. Put the rings back on.

The head and cyl cleaned up and put it back together.


Started first pull and runs sweet.

Lesson being, dont leave a mower lying about with out a spark plug in it if you live in an area infested with european wasps.


Bob.

Hello, please see an update.
Have reassembled an old base that I nearly took to the tip, this is all Ive got to mount the engine on to test it.
I had dramas getting the throttle cable into the plastic carby (I'm sure there is an easy way).
When I first tried to start it, compression felt good. wouldnt start though.
Stripped carby, realised the fuel bowl was upside down.
Anyway just thought I would share my teething problems.
Engine is now running, it sounds fine and is smoke free.
My Victa utility is up at the block, looks like I have an engine to put on it.
Next I will load test this engine, I will let you know how that goes.


Can I start a new thread? I would like to rebuild a 4 stroke engine now, I have two here that start and run, but stop as soon as I load the cutting disc.

Mark, you should always start a new thread for a new topic. Your engine rebuild should go in the forum for that engine type (probably Briggs and Stratton Engines, by the sound of it).

We'll keep this thread open until you report on your tests on the Victa 2 stroke engine.

G'day
I have now cut some grass to load test the engine, It chuffs out smoke whilst underload only.(At full revs)
I have cleaned out the muffler best I can, could this be the issue now?
Thanks
Mark

Was there a build-up of carbon in the muffler when you started the project?

A well-tuned engine, either two or four stroke, has hot enough exhaust to burn carbon out of the muffler when it is running under load. If the carbon is bad enough it might even burn a bit at light load or a fast idle. So, if you still have carbon in the muffler, and you have the right oil to petrol ratio, chances are it will put out blue smoke when you load it up, until the carbon is burned away - which means the first one or two times you mow the lawn.

If the muffler is clean and you have the right amount of oil in the fuel, the exhaust will only smoke heavily if the mixture is too rich. I suggest you watch the exhaust until you've mowed the lawn twice, and if it still smokes then, you need to check the carburetor, and re-check to be sure you have the correct amount of oil in the fuel. However from what you've said it sounds as if you probably just didn't get all of the carbon out when you cleaned the muffler. I would normally rely on burning most of it out, unless it was very heavily built-up and partly clogged.

Please let us know whether it continues to smoke. If it clears up by itself, I'll close the thread.

Report
There is only so much grass to mower around here.
Smoking from exhaust is clearing up, still smoking though.(under load)
I feel confident it will clear up with further use.
I have removed the wire from the muffler and cleaned up inside.
Mark

Thanks Mark, it sounds as if it is just a clearing exercise on the muffler. If the compression, mixture and spark are right, it can't form new carbon deposits, just burn old ones. I agree though that once the grass is short, you can't put a load on the engine and the exhaust won't be hot enough to burn some of the deposits in the muffler. Please let us know how the situation evolves. I think there are plenty of people who want to know more about the process of recovering a carboned-up engine.

Hmmm thats strange. Its got 8" wheels on the back and 7" wheels on the front. Usually they are 6" front wheels.


If your Utility chassis has the side ways facing motor you will have to flip the carb again.


Good job on getting it rebuilt.

Cheers, Bob.