OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Engines Questions On Victa Two Stroke Engines Victa 18 motor running erratic

Hi All

I have an old victa automatic frame and baseplate with a motor number 156156 over the number 4.

Firstly, is this known as a series 4 motor and were these motors originally used on the automatic frame?. There is no "Predicta" setup on the mower but the axle clamps have the slot to take the automatic flaps and there are 2 tapped holes either side of the baseplate.

I have managed to get the motor running after numerous pulls and I am still trying to work out choke and throttle settings to make starting easier. However, once the motor fires up it seems to be running a bit erratic with revs increasing and decreasing constantly and making little popping noises like small backfires. Reminds me of the Russian painter Spitzfartzandcoffs - sorry for that.

I have also noticed that there is some play in the crankshaft when I lift the flywheel. Would this up and down movement of the flywheel and crank signify wear in the bearings and seals or, is it something simpler. If it is a bearing problem, can a mug mechanic like myself fix this reasonably easily or is this a job for a specialist.

Could the movement in the crankshaft be contributing to the erratic running of the motor or is it more likely to be a timing issue?.

Sorry for the longwinded post but any help I can get would be greatly appreciated as I would like to get the motor running nicely before I start on the full restoration.

Pete

I would be suggesting that the bearings and seals are worn, after all they are probably 50 something years old. They can be bought fairly easily but I would reccomend that a workshop replaces them for you as the big end crank bearing requires some precision work to get it lined up straight again.

The speed variations you described sound like "hunting" - this is something governors do, nearly always because the mixture is too lean. What happens is that the engine cannot hold the speed the governor is calling for, and gradually slows down. When the speed error becomes large the governor slams the throttle open, which triggers acceleration enrichment, allowing the engine to carry the load and speed up to the governor setting. However as soon as it reaches the set speed, the throttle partly closes, the mixture goes lean again, and the speed sags again.

The cause of lean mixture with 2 strokes that have non-adjustable carburetors is nearly always an air leak into the intake pipe or crankcase, low fuel level in the float bowl, or an obstructed main jet. In this case you may have leaky crankshaft seals, which allows air to be sucked into the crankcase. This air has not passed through the carburetor, and therefore has no fuel mixed with it. This results in all of the mixture that goes into the cylinder being leaner than it should be.

Thanks fellas for the response to my question, I will have to see if it worth replacing the bearings and seals or whether it is cheaper in the long run to buy a reconditioned motor.

I would liked to have fixed this motor to keep the mower as original as possible but, it sounds like it is beyond my abilities.

Many thanks

Pete