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

sounds like a blocked exhaust??

have you got the diaphragm on the right way? Don't know that it would cause THAT problem but Iv'e had heaps brought to me for repair after the owner "Hasn't touched it" and the diaphragm has been on upside down. It's an easy thing to do if you rush the install without thinking about it...

Your problem is the fact that the carby is a bitsa. The The parts from the G4 and LM are not interchangeable. The only interchangeable parts are the primer face.
The poppet valve must be set to "C" facing the fuel inlet hole. The "seat" of the valve has 3 distinct steps around the perimeter of it. The different heights determine how much its going to rev. The only domestic machine that doesn't use setting C is the vortex as it has a bigger heavier blade carrier and hence need to rev less.
Are the 2 governor springs in the right place? The longer one goes in last between the diaphragm and the end cap. It also might be too light, and not pushing the valve open enough.

phew !

Different strokes for different folks.

See the link below. Good explanation of the G4 and LM carby. depends on the needs/specifications of the engine.

https://www.outdoorking-forum.com.au/pages/Victa/Carby%20Information/Late%20Model/Victa%20G4%20Carby.pdf

Thanks,
Pete

Thx Big Ted - I'll have another look at the poppett - at first inspection it seemed symetrical in all regards so I thought its position in the carby body as irrelevent despite the numerous letters moulded into it. If indeed the seat is stepped then incorect positioning would certainly make a difference. .... You may have hit the nail on the head! But i still would have thought that shifting the position of the idle adjusting screw would have had some impact on the engine speed?

One last thought after reading the posts is the positioning of the boss of the diaphragm boss - With it facing upwards towards the big spring it will certainly cause a higher loading on the diaphragm that in turn will force the popett to a greater opening and incraese engine speed so I have something else to think about! ..... Conversel,I did read the attachment you kindly sent and I notice that the instrcution was to install the diaphragm with the boss facing downwards - ie. Against the smaller spring but this would unload the diaphragm and reduce poppett opening and re4sulting in an lower engine speed so buggered if i know??????

- Think I'll despatch the mongrul plastic carby heap of sh#it to the shizenhouse and try and find an OLD amal and fit it on!

- BUMPS

I'm sorry Bigted ,but I have to strongly disagree.The only internal parts that were not the same was the diaphragms.Shown below,and the main Jet.Tha carby had a different part number due to the spray tube being installed which can not be removed once in.

This is the G4 with diaphragm and clip.

This is what the LM setup was.Although they are different they can be changed over with one another and work.I myself have done this.
Also every other part is the same and have the exact same part number on them (for the parts that have part numbers on them that is).
This also depends on which poppet value you have as there was (From my knowledge) three different types some don't need anything done.Like the black has the same surface all around it,and no letters on it.
On 100% of the G4's they had a different face which was grey in colour and some not all used a remote primer as there was no primer bulb on the front of the face.
I really think that Bumps carby isn't a G4 as they really didn't have a big run and currently they are hard to find.I know as I've been trying to find more as I have some in the collection with LM carbys and they should have G4's.
Apart from from if he has G4 parts mixed with LM's except for those mentioned it won't make a rats behind of difference.It's all the same.

OK Bumps here's some questions nobody has asked.
What is the mower your trying to get running?
What type of engine is it?
Can you post some pictures for us?

Hello all Contributors

From a historical perspective the original design intention with the G4 was
to make a prime-less carby. It wasn't a success.

My understanding is that there is significant difference in the G4/LM.
Interchangeability between the two is something I can't answer.

Here is a good technical description taken from these forums.
It may be of some help here:-

One paragraph in the ahe attachment that Cyber-Jack kindly provided is qite interesting.
It states that the "newvwhite plastic poppett valve that has a small spigot and some lettering one of which is marked "C" must not be used as replacement for the original bleck poppett valve" (that had no markings.

.... It seems that Victa stuffed around with the LM carburette and made several design changes over the years? I think that I have unwittingly stripped down 4-carburettas and mixed up the parts never imaginging that there could be small but important changes within the mouldings and the internals..... A trp for the in-experianced!

Please also note that in desperation, I acted on the recommendation to change the muffler. When I did this I looked inside the export prt and discovered broken bottom piston ring. I've now sripped off the cylinder and found the bottom ring was broken in tw0 places with one fracture being right on the exhaust port. Top ring and cylinder bore was OK........ I'm now wondering if a broken bottom ring could cause my engine symptoms:
- Erratic up and down engine speed at wide open throttle position
- Unable to idle
- Little if any control of engine speed using throttle lever
I still have concerned with by "Bitza" carby as someone has called it but could the root cause be the broken ring???? ..... Your thoughts please gentlemen.

- BUMPS

Dear Ihatewetsocks,

I can confirm that the diaphragm was correctly installed.
Thx for the suggestion
- BUMPS

All,

One additional thing I should have metioned regarding the poppett is that I has a choice of two - unmarked black poppett or the newer style white poppett with the lettering and the short spigot on the moulding. For no real reason I chose to install the black poppett. If the engine still doesn't run properly after fixing the broken ring issue, should I change the balck poppett for the new white poppett and installing it as described on the earlier posts - Letter "C" facing the carby spray hole???

One other matter that may be important - all the carburettas that I stripped to produce one "good" on had the large diameter clip that secured the diaphragm. I noticed on the parts diagram that cyba-jack provided that one view showed a small circlip as the means for securing the diaghragm. Given that the 4- carburettas that I stripped all used the same large diaghragm, could this mean that all carbys were in fact the same model?


THX - BUMPS

That's why I wanted to to squirt some areostart down your air filter tube as I really thought you were not experiencing carby issues.There not the sort of problems you have with these carby's unless the accelerator isn't connected.I was trying to get to that but I guess in this occasion you just got bombarded with to much information and was taking note of every one.Don't worry it does happen especially when you have three people helping and three different views,but I guess that's what happens on open forums.

Stick with the black poppet value the white one is the older one and the black one should be fine to use.
The cir-clip ones were from the G4 carbys only,the LM's didn't have them.As was shown ealier
Heres another look.
Top two G4's (Of which I'm fairly sure you don't have).
Bottom two LM (which most likely your would be).




If you could post some pictures of what you do have,then that way instead of chatting about the differences we could help with what you do have.

so the powertorque didnt have the small clip ? and the ones i have pulled down here have all been changed i guess . early to late ones too . seems they use either or but enough , good luck with it mate , hope it works out well

I guess it's like everything vccomm use up all the old parts first before using the new ones.
My documents show from a Technical bulletin that the LM was introduced in November 1978.
So I'm guessing that the older bits could still have been used,after all from a business scene it would be silly just to throw out parts that can still be used.This is making me want to count how many G4's I need and ask if anybody has any.I should as I know I'm short on them.

OK well due to this particular topic I decided that I'd better have a look at what G4's and LM's I have and what are some of the differences.Just before I go any further I think somewhere above I have made the wrong statement.I think I said that the earlier G4's had the white poppet values and the LM's had the black.Sorry I think that is around the wrong way.Not sure why I wrote that but I did.
Now vccomm yes I found also that a lot of my G4's had had other updated parts put them I guess due to work being made by a Victa dealer and I too found other diaphragms changed to the newer ones but I still stand by what I've as I have documents that state this and the changes that were done by Victa.
Here is some pictures to help with the things that were different.
Caps.G4 left LM right.

Main Jet G4 left LM right.

Diaphragms G4 left LM right.

The same here,G4 left LM right.

Poppet valves as far as I know there was only three types.If anyone really wants to see the shape difference between let me know I have other pictures to show the difference.

Bottom side I hope you can all see the letters we were talking about earlier.



All in all I had fun checking the changes and seeing how many of each carby I have.Now to work out how many I really need for my collection.

Just re enforces the fact that the first step is ALWAYS know the condition of your engine FIRST

I agree I always make sure engine is worth my time to start with. However when I first started I did the same just jumped in and then found problems. I guess it's how we learn.

Excellent photo Blumbly but one quick question:
Are the three poppetts all the the same length?
....... I'm trying to acertain if one type was specically made to suit the idle adjuster screw on the caby cap? ie. Given that my adjuster has no affect on engine speed it may be possible that the screw is not contacting the poppett and forcing it down to either limit or increase the idle speed?

Are there any comments as to whether a bottom broken ring could cause spasmotic engine operation under no load conditions??? I'm going to replace the rings of course but I thougtht I'd ask the question.

Thx- BUMPS

Yes the poppet valves are the same length they just have different groves and step ups. Expect the black one is just all round and a smooth surface. They all will work with the idle adjustment screw. Just have to make sure the large spring is in place.
Yes broken ring or rings will cause what your problem is. I've found that with 2 strokes they will run with broken rings ,but just have problems like you've found.
I had one of my Twins run and run well it just didn't seem right. I thought it was a vacuum leak or a decompression valve problem. I found (when I pulled it apart to restore it) that one cylinder had two broken rings and a chunk out of the piston,but it still run ok.
So yes that will be your problem.