OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Engines Questions On Victa Two Stroke Engines Victa 160 Plastic carburettor

As Blumbly says Bumps, broken rings will cause running problems in a two stroke because they will cause a loss in compression. Depending on the sealing of the piston in the bore, the symtoms can vary often making it hard to work out, From what i understand, the biggest difference between the 125 and 160 motors was the hardness of the bore and the thickness of the pistons, this resulted in 125's still running , and often really well, with next to no rings left as the sealing was so good, where as the 160 barrel was a lot softer and piston much lighter resulting in wear that affected the running much earlier. combine that with worn crank seals etc, etc, it's mostly why it's the 160 that causes headaches.....

Also with a 2 stroke they (being the rings) have to suck (or have compression) on both the up and down strokes. As to pull the fuel air mix from the carby and through the crankcase to allow for the bottom end to be lubricated. Then pull the fuel mix into the combustion chamber. Where as 4 strokes only needed compression on the backwards stroke. Due to having a sump with oil to lubricant it's bottom end. So less work is needed by the rings in a 4 stroke.

Giday all,
Just a quick note to say thanks to everyone who assisted in this battle.
Case is now closed! .... Replaced the broken bottom ring (top one too but it was OK) and engine sprang into life. It now starts easily, idles beautifully and revs out ro full speed. I was really surprised with the problems that one bottom broken ring posed. Every issue I had with the engine pointed towards the carby but I was on the wrong tram. One suggestion however still puzzles me a little - I think it was Blumbly who suggested spaying Aerostart of "startyahbastard" into the air inlet to determine whether it was carby or "something else" .... I must query how spraying this compound into the engine would help diagnose the problem .... Could you please expand on this fault finding tool??
Anyway it was an interesting journey compunded by the may changes Victa had made to the G4 and LM carburetta ove the years and the uncertainty that exists when a novice strips several units and then mixes up all the parts and starts the reassembley based on using the best bits and the fact that every item mechnaically fitted together.... there were different length main springs, different caps, different poppetts, different diaphragms and even the cams that had subtle differences to their countour profiles(but they did have different part numbers moulded into the unit)and all the bodies "appeared to be the same but part numbers had eroded away so it was impossible to tell if they were in fact differenct from one another. I've attached a few photos to illustrate the differences. I've also added a photo of an Amal 361/1 that I fitted to a Victa 160 for use on my Grand Childs go-Cart .... It superior in every way to that heap of plastic shi#t that Victa produced. I did a lot of research on trying to locate another one but there as scarse as an honest politican ..... they were used on a number of mowers and stationary engines in the 60's msot notably the "Hurrican" Engine (manufactured in Sydney) but Amal (UK) originally supplied it to BSA for use on their 125 cc Bantam D1 motor bikes in the 1950'2 and early 60's. There is a huge cult following in the UK on restoring and even riding the old Bantams and the Amal 361/1 is highly sortafter and I can understand why ....it really fired up the Victa 160 and the gocart literally flys....... and such a simple robust design and manufacture! ...... Don't know why Victa didn't follow Hurricans lead and use them as well???
Anyway as I opened up with .... Case closed!

Well done Bumps and a great outcome, one of the best learning curves possible!!

Bumps I was just looking around and stumbled across this, I realized you had been struggling with this motor for a long time but I didn't think it was quite that long. Anyway we now know how to solve the LM carbs and can mix and match any parts from a dozen carbs and get them to work as a carby should work with a tick over idle and full control over whatever revs you need depending on how high the grass is you are mowing. Great carby once setup, but most things I have read about getting them to work is just folklore and myths