OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Engines Questions On Victa Two Stroke Engines G4/LM carby repair/modifications

Here is a step by step detail of how to get a LM carby to work properly, G4 is at the end of this post, only difference is the cam modification, all other steps are the same

You will require a 6mm or 1/4 tap and two 25mm bolts (cut both of these to 18mm), 1 nut of whatever thread gauge you choose.
You also need a kill switch, this can be either a momentory contact switch or toggle switch, a little bit of electrical wire, lug and a connector

It requires a marker, hacksaw and 2 sockets to act as spacers to hold the cam steady in a vice, do not over tighten the vice as this will damage the cam








Thread this with a 6mm or 1/4 thread (whatever matches the bolt you have), cut this bolt to 17/18mm long

Total thickness of washers is approx 1.6mm



Thread this the same size as the kill switch hole




This is your new idle adjuster screw, this is the 2nd bolt you cut earlier to 18mm

You no longer use the factory kill switch, use the momentary contact switch as shown, just fit one lead to the frame and the other wire to the wire that comes through the side of the original kill switch, the other wire is just cut off.


Once you have everything re installed and the motor running, you then adjust the idle screw as shown above, to set the engine rpm start the engine, pull the throttle back to stop position and then adjust the idle screw to get the idle revs you require.

This is how to modify the G4 cam, all other steps from the LM carby modification are required

You will require 1 x 4mm or 5/32 screw and tap











Lifter / Spider height adjustment to the highest point on the cam and no further

Thanks for going to the trouble of doing this, this will keep Powertorques running for another 30 years.

Not only the Powertorques Tiger, all those full cranks fitted with the G4 carb

well done. that seems to be a major improvement.

Very interesting stuff ! Thankyou for sharing it.

That's certainly given us viewers a better idea of what you are talking about.
You have made a very clever ( in some ways) carby reach it's full potential.
Is it possible, just possible, that you have made it better than the G3 carburettor??

Mowerfreak, not sure if it is better than the G3 and it doesn't really matter, there is buckets more of the plastic carbs out there, if you do this mod correctly the carb is guaranteed to work and that is all that matters

It would be necessary to run some dynamometer tests with Exhaust Gas CO or O2 monitoring, to answer that one.

In any case, it's a moot point, as G3 carby spares are in the process of drying up - they have long been NLA from Victa, and at least one of the two major aftermarket OPE spares suppliers has now deleted most of them [GA Spares].

Many thanks for your superb how-to, Norm.

I hate to think how many Victa pumped out over decades, but you are right, , of we spread the gospel that these things can actually have their bugs removed, we would at least partially stem the rapid ( and I mean RAPID) disappearance of this Aussie iconic backyard noise.

Mowerfreak, one thing with this mod is the iconic backyard noise does not need to be so loud if the Powertorque is not revving its tits off mowing grass that is 1" high.
Gadge, my son is over from NZ and IT is his game so that is why it is clear, I just did the leg work

Hello NormK,
I will save this and do it on my new PT project. I just have to sort out my base. it a lot of sanding , but will get there soon..
thanks for your effort.
speedy

excellent work Norm,we can all save a two stroke now thank's to you..cheer's

Does this result in a first time every time starting experience or do you still need to work on getting a strong spark and good sparkplug for that to happen?
One think I remember with a near new Power torque was the ridiculous ease in starting.
You could do it with your teeth.

Coils on Powertorques rarely fail or give trouble and the carby has little control over the spark plug. If all the ducks line up they are usually a one pull start, unless the useless float needle is giving problems and I have little control over them because they are just expensive to buy,cheap Chinese junk and poorly made

Another mod I did on an LM today, because the owner wanted to retain the kill switch was to drill and tap through the kill switch ramp on the cam in the same manner as I did with the G4 cam and this then allowed me to adjust the kill switch position and prevent it from running up to the flat on the top of the ramp and becoming stuck which results in having to pull the carb apart to free it up again. So far it is working well

Getting back to the float needle problems I might have a crack with these and see how it works out. Getting the brass needles made they came back with a stupid price of $35 each. These are a bit better priced.
http://www.ebay.com.au/itm/252780607048?_trksid=p2060353.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT

Hello NormK,
Did the mod, works well, smooth power. I used a fine hacksaw and got a really smooth surfaces on the gray part...
speedy

Hi speedy, glad to hear it works well, problem is now that you have seen how well they work you would never go back to the original design

Yes, I will get my new pt going first then do the mod. I didn't put the kill switch in or the bolts... but the rest works well.
speedy

Thanks heaps for taking the time to complete this mod, photograph it and post it.

1: I will be applying it asap to my twin, which should sort one of it's problems once and for all.
2; Off to the "Green Shed" to see how many G4's I can score (attached to cheap mowers of course!)

On that, most municipalities have a Green Shed where folks donate unwanted/broken stuff.
Always plenty of mowers, some in surprisingly good order. Just got to be quick though because they are usually stored outside and the fuel cap is the first souvenir to be taken.

The next thing that you will find is the float needle, this horrible little part is responsible for the early demise of millions of Victas. The new float needles and primer caps solve this although I have had a couple of issues with them, price on them is an issue if you only want one or two. Do not waste your money buying the ebay ones with the plastic needle they will mess with your head

Hi Norm,
I have a couple of questions for you about your carby mod, if you could offer some answers that would be terrific. I have been thinking about doing this to a spare carb for some time, as I have a couple of machines I use regularly that I think are in overall pretty good shape (seals, viton tipped needle and seat, clear jet, good spark, good compression etc.) which I can never get to start first pull cold. They often start second pull, run perfectly and restart easily hot. I don�t run them out of fuel to stop them but use stabil in the mix. What is the starting procedure with the modded carby? Throttle to run, single prime then start etc? Or are they all different and once you find a procedure that works for that machine go with it? Can I do the cam mod and not do the idle control screw or kill wires portion of the mod? I know I could try this all myself but wondered if you had some ideas already.
Cheers,
John

Hi John, I usually start them on full throttle then back it off but I find they will usually start pretty much anywhere, but full throttle is the spot I prefer as it makes sure there is fuel going straight in. I usually give 2/3 primes. You don't have to do the idle screw, just means that if you pull the throttle back fully the motor will usually stop because it will idle down too low. The idle screw just means you can just crack open the poppet to allow it to idle. This can be played with by only fitting 2 washers under the cam, but this usually keeps the revs too high for my liking, when you are emptying the catcher etc. You can use the existing kill switch but I found them too problematic and this is probably because all the aftermarket kill switch rubbers are not fit for purpose, I was spending way too much time trying to get them to work only to have them play up. The most annoying thing with the whole setup is the lump on the cam that once the lifter goes over the top into the stop position it often becomes impossible for the throttle cable to fight the spring tension and get the lifter to rise back up over the hump. Cutting the hump off gets rid of this problem but then you need to put the washers under the cam to lift it up to the same height as to what was the top of the hump. If Victa had just kept the hump height all the way, none of this would be a problem and the kill switch setup would have probably worked fine. The big problem is the cable has to fight going back up over the hump, fighting the spring and break away from the kill switch rubber which can often jamb all at once.

Thanks Norm, love your work. I think I�ll give it a burl and see how I go, cheers.

I made the cuts on the cam today, easily done with a dremel. I have a couple of G4 idle adjust caps, might try one of those. Just need the washers under the cam and will twist it on and try

Hi jds303,
I should have done it that way instead of using my hacksaw. I still haven't completed one fully, as the machine I was going to try it on has other issues that need fixing first. I should get it done pretty soon.
What grinding head did you use. I have a couple of sets with assorted grinders, but never know which ones to use for a given task.

I've been trying to get my head around this fix for a while now and wondering how best to go about it. I know virtually nothing about Victa mowers. New territory for me! I am going to see if I can fix the old carby as it is before I start attempting any modifications. I have a bad habit of making mistakes that I can never "undo".