OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Engines Questions On Victa Two Stroke Engines Victa PowerTorque - High Speed Adjustment

Hi All,
Lately I�ve been experiencing the same frustrating problem with most of the old 2-stroke victa with G4 carburettor that I�m fixing (most but not all though).
They idle perfectly fine, but when the throttle is pushed in RUN position the engine starts running way too fast. Although I was under the impression that the G4 carby has only two speeds, most of the time I can actually find a decent speed by setting the throttle in between the IDLE and RUN position. Is this normal?
I can�t believe that so many mowers have exactly the same problem and I start thinking that I�m doing something wrong.
Thank you in advance for your comments,
Max

Sorry, I meant to say LM carby..

Hey Maxgara,
No doubt Tomo or Joe will chime in here however I'll start with a few idea's for you. Joe and Tomo are more experienced with the Victa's.
1) Have you checked the diaphragm in the carby? This is done by sucking and blowing. Very little air should pass through the carby if it is sealed correctly when you blow on the governer hose. A stuffed diaphragm will make it rev hard.
2) Check the governor port is not blocked - blow compressed air through it. I usually like to remove the flywheel and thoroughly clean the area in question.
3) Replace both manifold O Rings (small and large)
3) A washer or 2 behind the throttle cam lowers the engine speed however be careful as it lowers the idle as well.
4) Check the bottom crankshaft bearing if none of the above work. It will more than likely be covered in oily guck which is an indication of an air leak. The bearings are fairly easy to replace without a press.
Hope that helps.

Jaffa

Engine speed on the old full crank engines can be adjusted from the cowl. If needed I can explain the process. Bigted from this forum taught me!

Hi Jaffa, thank you for your comments.
1) I checked the diaphragm and it seals well against the plastic body. However, I�ll try to see if a new one makes any difference. I had the same problem with both the black and green diaphragms and I don�t think this is the problem.
2) I cleaned the governor port but I�ll try again with carby cleaner and compressed air. Does the size of the vacuum hose change the engine speed? I was reading in the victa manual that in the Vortex models there is a restrictor in the carby end cap to reduce the engine speed. Not quite sure how the size of the pipe affects the level of vacuum in the carburettor though..
3) I�ve just ordered a new set of o-rings including the large one for the pull starter. The one I have look ok, but you never know..
4) I added a washer and it reduced quite a lot the idle speed. No effect whatsoever on the RUN speed though..
5) I�ll check this. I suppose I have look for oily gunk leaking out the crankcase.

Hey Max ,i wont add much to this Jaffa has got most of it spot on .
Normally this issue is vacuum related , however ive rarely found a bottom bearing at fault as its well protected by the flywheel.

The starter o- ring is a regular offender , even if it looks ok replace it if its slightly stretched or pinched it will cause trouble, there is also another oring on the starter shaft that is often forgotten.

Another thing to check is the springs either side of the diaphram check to make sure someone hasnt been in and messed with them , trimmed them ect , also that they are in their right positions , small spring on the cam side and large spring on the cap side.

I had issues with a g4/lm this week but on the older full crank engine i had to make a post for idea's from the other guys turned out i had a leaking top crank seal!
stick at it !
cheers tomo

Yeah mate. Throw it on. Been trying to find this info.

I am assuming you have everything in the carby adjusted properly. The most important thing to check is the diaphragm is sealing. I have detailed the procedure behind checking this above. The same process applies for power torque and full crank engines when it comes to diaphragms.

If the diaphragm is sealing you could try adjusting the governor port on the cowl. Start up the engine with the governor hose connected to its port on the cowl. Make sure the engine is at full speed and twist the governor port left or right and you will notice the revs will adjust accordingly. The little wheel you click the hose into turns both clockwise and anti-clockwise. Just find your sweet sounding midpoint.

Lastly if that doesn�t work check your top crankshaft seal. These engines start with top seals cracked however they rev way to hard because they are leaning out due to excess air entering the combustion chamber.

To check the seal remove the flywheel and dribble a little 2 stroke on the seal and then rotate the crankshaft to check for bubbles.

Bigted will no doubt be able to add additional detail if I have missed anything.

Please make sure you wear appropriate safety gear when making adjustments to running engines.

PS. These are great engines. I still get a fair few through to repair and they all end up being great runners for relatively very low cost.

Jaffa.

Sorry mate. Can you put pics up of the govenor port you speak of??

The part you are adjusting. Your explanation is good, just not sure where exactly you are doing the adjusting

For your reference I have circled the vacuum port. Just twist the black circle surrounding the governor hose either clockwise or anti clockwise and you should hear the rev's adjust accordingly. This must be done with the engine running at speed so you can hear the changes. The governor hose must remain connected to the vacuum port and carby during this process.

Let us know how you go!

Jaffa

Yeah makes sense now. For some stupid reason I thought you meant the black circle on the inside of the cover!! Which didn't make sense seeing as you said to have the engine running to adjust!!
I'll give it a go tomorrow

Nolan, I have a fix for these carbs now to give a low tick over to full revs with full control. If you want to post me the cam and end cap from your carb I will modify them for the cost of the return postage, from memory you are on the other side of Melb so posting it will be the best option

G'day Norm, are you able to describe what modification you make to the cam?

Hi Tiger, it is a bit complex as I have tried a few combinations and it also involves fitting an idle adjuster screw in the cap, but seeing you are in Melb it might be easier to show you, once modified they are great,with full throttle control. The thing that is killing me with these carbys at the moment is the float needles sticking up and not allowing fuel to flow.
Anyway just to give you an idea as to what I do to the cam is cut the lumps and bumps out of the cam so it can operate smoothly. The carby is a brilliant rugged design, except for the cam design with lumps, the bizare kill switch setup that often takes many goes to get it to work and the problems with the float needles sticking. Get past those problems and best carby ever designed

Norm, I've had the same sticking issues with the plastic needle. Only solution I've found is to give the needle a very light sand, light being the operative word. I use 400 wet and dry. You only need to take off just a minimal amount and the needle won't stick, go too far and that introduces other problems. I'm having some overrevving issues which I'll post about in a separate thread.

Tiger the over revving is an easy fix if you know how to do it. I have PM'd you