OutdoorKing Repair Forum Forums Collectors Corner Rotary Victa Corsair scored cylinder

G'day tiger,
there is scoring on the piston and top ring, I cant see if there is any in the bore.

I would replace the rings and reuse that piston. Make sure scored metal has not entered the ring groove.
(Give the scoring a light clean up)

Forum members have taught me in the past to, carefully remove the rings (they can snap)
Removing the old ones is practice for replacing the new ones.

Then clean carbon out of the ring grooves using a piece of old ring ground flat so that you can use the edge as a scrapper.
Try not to remove any metal.
The intent is to have a snug fitting ring that can move freely in its groove.

Things to notice: where the pins in the grooves are located to avoid the transfer ports, how the ring fits around the pin when compressed, thickness of rings.

If you have scoring in the bore you will get combustion gases passing past the rings.
Here are 6 blocks I stripped and honed today. They are in order one to six.
I was looking for good cylinders to use for rebuilds.
What I use, I'm not exactly sure of yet.

G'day Mark, there is some light scoring on the cylinder but not much. The top ring on the piston was stuck at the point where it must have overheated. I gently moved both rings and now they are both moving freely although the top one feels like it has grit underneath it. Tried 2 mower places today for new rings, both said they didn't have any and would have to get them in. Is there any point in trying the current rings once the groove has been cleaned up?
Appreciate the info on rings, I didn't think there was that much to them but you've saved me some grief. Notice that you said that you honed your cylinders, is it worthwhile me doing the same on my cylinder?

I think that since you have gone to the effort of pulling the piston out, you should do all you can to make the best engine out of what you have. You will be rewarded with and engine that starts easily and runs well.
You say the bore has light scoring, is it like any of my images above?
The first three blocks above will definately go to scrap metal.
I will use the bottom two.
The rings need to seal against the bore as it travels up and down.
Rings are available on ebay for a small amount.
I only hone the bore if I think it needs it.

I reckon mine resembles no. 4 the most. Not as good as 5 and 6 but a little better than the top 2. I hear what you're saying about the rings and I did try to get them yesterday. It's just that the mower is in parts everywhere and I'm eager to get this mower working again. I'll have a look at ebay and see what's around.

You can get the cylinders rebored and a kit (exchange) would start at a cost $99.86 (depending on cylinder type)and that includes the piston assembly and rings.

Thanks Bruce,
I certainly would like to have some rebored blocks with pistons to match.
I have always felt uncomfortable ditching a scored block.
I will put these aside for now then.

tiger I forgot to mention the rings are available at outdoor king, search victa rings and they will pop up.
We are working on similar machines at the moment, I have this one ready to assemble after lunch.

Hello again, just thought of something else to check: tiger look at the crown of your piston for any stampings.
like .20 or .40

This would mean your cylinder has been bored out oversize at some point & would have a piston to match.
If that is the case, then you must get the appropriate oversized rings.

Thanks Mark for your help, I have bits and pieces everywhere but not much room hence the need to get the thing back together quickly. Will check the piston for any markings. Does anyone have any guidelines for when an engine needs a re-bore, there's some discrepancy I've noticed about when you do one, someone here was saying that even with a scored cylinder that a Victa could still run?

Hello tiger, to answer you questions as best I can from what I know, yes your Victa would run with the scoring I have seen in your images, the issue is how long would it run for ( "longevity" or "life expectancy" )
I think every person has their own level of what is acceptable.

Thanks Mark. For the record I took the piston out and gently massaged the rings and now they move a lot more freely, cleaned what I could in the ring grooves. Re-assembled the whole thing and no cigar - did not want to start. If anything it feels as though there is less compression than when I started. Now I should say that the large o-ring underneath the starter mechanism is perished but I put it back in with a bit of grease, not sure how much this affects the compression. So it would appear that the rings are faulty but I've rung around and there is a mower shop that might have some in stock and is open.

I do have another engine for the powertorque series, very similar and from what I can see it has a cleaner cylinder bore but I couldn't get the crank pin off this one. A little more rusty than the Corsair but may have a go at swapping the engine over.

Thanks for letting us know what you did, there are alot of reasons for an engine not firing into life.
Some good reading on this site.
Try this thread:

https://www.outdoorking-forum.com.au/forum/ubbthreads.php?ubb=showflat&Number=31919&page=1

Just an update on where I'm at. I have changed the o-ring under the starter, the head gasket and tracked down some piston rings but they were taken out of another machine, the guy at the mower shop assured me that they'd be fine. So having done all this, the machine still does not fire up although the compression is very strong and noticeable.
What is troubling though is that when you pull on the starter, smoke appears, it appears to be coming from the decompressor area. Whipped off the muffler, can't see any piston damage but the smoke worries me, any ideas what's gone wrong?
Should add that I squirted a little petrol in the spark plug hole to see if it would start.

Hello tiger,
Seems like you have made some good progress.

The smoke seems to suggest it is trying to start.

I would see if it fires with a spark plug blocking the decompressor port.

If it fires, then you have a decompressor issue.

Also, if a 2 stroke is flooded with fuel, it wont start.
Remove the plug, clean it, pull the starter to drive excess fuel out, reassemble & try again.

G'day again Mark, you were right with the decompressor. Stuck an old spark plug in and it fired up. The decompressor is a sealed unit, I don't suppose they can be cleaned out/serviced can they? Changing the head gasket and o-ring underneath the starter all helped but no doubt changing the rings really did the job. Thank you again for your support.

With those decompressors, I clean around where the valve seats & put a small piece of wire through the tiny hole in the top where the hose connects.
Check the black plug on top, is it a tight fit & sealing.
Use a piece of hose to test that the valve closes with suction.
Then see if it works in an engine.
Yes, I dislike the fact that you cant strip and clean this type.
With the valve out, youll soon find out if you have a good starter rope.

Thanks Mark, gave it a clean with the decompressor and it seems to work better.
One thing though the fuel tank is a little loose under the cowling. It doesn't seem to affect performance but I like everything to be nice and tight but there are no screws/tabs/clips around that area. Are the fuel tanks suppose to be a little loose?

Yes the fuel tank just sits there, originally there was a big foam washer that went between the cowling and fuel tank around the fuel filler to hold it a litthe bit tighter but these days most of them have broken up and disappeared. I am unsure at present if the foam washer is available as a part.

Thanks Joe, I noticed that there are tabs on the fuel tank and I thought they would serve some purpose. Probably wouldn't be hard to fabricate some sort of foam washer, I just like everything to be nice and tight.