OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Engines Questions On Victa Two Stroke Engines Starter pulls ok when no spark plug installed

In this post Pull start problem I posted that the pull cord would jerk and not pull cleanly. After stuffing around for hours on the starter mechanism and re-installing it, it has not improved. I then try it without a spark plug and it pulls easily, what gives?????

Tiger,

Question?

1. Is the blade plate on when you are trying to start the engine?

2. Is it two stroke or four stroke?

Answer these two questions and I will give you a possible answer to the problem.

Hi Bruce,

1. No, took blade plate off

2. 2 stroke.

then it will kick back , no blade plate = no flywheel , whack it back on n see what happens then

Scarey trying to start with blade plate off.

The Blade plate was on before and the pull cord behaved the same way. I took it off because the nut had rusted wasn't up tight against the blade plate so I thought it would be safer to take it off.

Good Move....Just curious.If the nut was rusted and not mating with the plate.was the plate lose? If so then this would still be the same as having no plate if its slipping feely,intermittent tight jerking with a pull back and give just after each compression stroke? The fact its better with no plug is a given..But if its tight still...hmmm...More info?But as Vc says Just put on another starter and check that way,but I doubt its that ....A Rotomo might be a better option for you they are great...start it by hand no worries!lols..Na Im just goofin keep us posted on what you find

Tiger,

Note that if you do not have the washer on the correct way (Nut side stamped on washer) it will not lock the blade plate in position (if put on incorrectly) even if you think it is tight it will not hold.

The blade plate is like a flywheel which balances the engine so if it is loose it throws the timing out.

If you take your time and think about what you are doing you will get the job done twice as quick than if you try to race it. If you are not sure then please ask (for your own safety) here because the moderators, who are a great bunch of guys are waiting to help every member if they can.

Since it doesnt "jam up" with the spark plug installed perhaps the decompression valve has either been replaced with a a spark plug or it could be jammed shut, The decompression balve is located ontop of the head, to find it you will need to remove the black cowling ontop of the motor. I dont have any pics on the computer to illustrate but if I get out the back in the next few days I will take a couple.

The nut wasn't holding because the shaft that it was on was a little worn but your advice on safety is appreciated.

Thanks Joe, I have the cowling off but couldn't see a decompression valve, have another look today.

It sort of looks like a mushroom shaped disc mounted in the top of the head, if it has failed in the past somone may have replaced it with a suitable bolt or an old spark plug...

Joe I think you have nailed it,
Well I have one here with the same symptoms ( jerky pull start )
I only just then swapped the decompressor for a known good one and now have a clean pull start.
Here is a picture:

Thanks to Joe and tiger, you guys have helped me solve this mower.

Here is an image of a stripped decompressor valve, I serviced the one I had on the yellow mower (but didnt test it).
Valve should close under suction.

I can't see it. Here's a photo taken from above, do I need to keep stripping it down?

Yes, keep stripping mate!
As Joe has said, take off the black cowling that you are now looking at, the decomp valve is the round thing on the top of the cylinder head above the spark plug.
Don't forget to post a pic of what's under the cowling.

the black cover is what joe meant by 'coweling' remove that too , 2 bolts/nuts on the head .2 small bolts on each side then you will see it . be carefull of the vaccum hose , it might break the SMALL connection on the carb ! be sure to remove it 1st from the gov' fitting on the coweling . just above the carb , a round looking jigger with a small hose from it to the carb'

Have taken cowling off and yes there is a decompressor unit there, what is the next step?
I don't have a spare decompressor unit to swap over but notice that the compression is good and the piston and cylinder bore look very clean.

I had a close look at your decompressor, hard to see, but does it have 3 small clips holding the top on? (like in my image above)
If so you can strip and clean it, put it back together, test it by placing a tube on top and sucking on it to see if the valve closes.

If it is a sealed one, then you will need to get another one off a wreck or buy one.

I have seen a few of these with a spark plug blocking the decompessors port and the hose that used to go it, blocked off.

You could put an old spark plug in the port, block off the hose and try your engine to see if it works.

Should work provided you have fuel, air, spark, compression and good seals.

It does have 3 clips but there is dirt surrounding them making them hard to see. I'll have a go at taking it apart, I can only assume that it doesn't work or that it's dirty.

Yep, clean it up like you are a surgeon, lay it out in sequence mate, so you get it back together in the right order.

Point to note: keep control of that small spring, if it springs off onto the floor it can be very hard to find, even with a magnet, just ask me.

Hi again Mark, gave the decompressor a quick clean, put it back on, same result ie starter jerks. When the decompressor was off and the hole uncovered, the starter did not jerk.

I tried putting a spark plug into the decompressor hole and blocked off the hose that was connected to it with some cleaning towel, the starter jerked again and mower did not start. The muffler is a little rusty around the mouth but is up against the engine. Is there anything else I can try, the piston and engine bore are smooth and in otherwise good condition.

tiger,

So with decompressor removed and and a spark plug inserted into the decompressor valves port.
You still have a jerky pull on the start rope.

What you are feeling now, is the normal compression of the engine.

Remember the valve is there for an effortless start.

When stripping and cleaning the decompressor, make sure the diaphragm is sealing against the metal plates that sandwich it, the plates mating surfaces need to be smooth and clean.

Mark, with the decompressor removed and spark plug inserted I see no difference to when the decompressor was inserted, I'll keep trying but this is getting frustrating.

Alright, so no difference.
I am afraid that things dont aways go your way when fault finding mowers.

From this distance I cant feel this jerking action of the pull starter.

Let me tell you that with a spark plug blocking the decompressors port there should be quite a lot of resistance when pulling the starter cord and it will be jerky when pulled slowly.

Now with a seviceable decompessor in, it should be easy to pull the starter cord.

tiger, have you tested the valve closes under suction?

I couldn't take the decompressor apart but cleaned what I could with the air compressor, if I blow on the decompressor nozzle the valve is activated so it seems to be working. If the decompressor is not on the mower it pulls easily, as soon as that port is closed, the pull starter is hard to pull.

Just about ready to pull this apart for spare parts, if anyone in Melbourne reckons they can fix it, it's yours.

Mark could you elaborate on what you mean by closing under suction?

Tiger, if it has two sharp compressions per revolution, and if they are the same whether the decompressor is fitted or is replaced with a second spark plug, the decompressor valve is not working. That could be because the valve is defective, or because the correct signal is not reaching its activation port. The engine should start and run perfectly with the decompressor not working, it will just be hard on your arm, and on the starter mechanism.

I can't pull the starter cord more than about 6 to 8 inches no matter whether the decompressor or spark plug is in. Are there any other explanations or things i can rule out?

Tiger, if you where located in Brisbane I would invite you round and we could both fix your mower and have a yarn.

Place a piece of pipe on the valve as below.

Then suck on the hose, the valve should close, see closed valve below.

I use a clean pipe for this, I dont put petrol in my mouth.

I certainly wouldnt tell you how to feel or act, but I try not to let a mower defeat me, it is just a hunk of metal.
When I hit a dead end, I put it aside and come back to it later.

Thanks Mark and I would definitely take you up on your offer, who knows might even drive up to Brisbane but don't think the car would make it.

Appreciate your support but I've spent a few hours on this machine and feel I haven't got anywhere. Your photos are great and really make the forum a superb resource for many people.

If the decompressor is really to blame here I know someone who has a later Victa but I think there decompressor is sealed, wonder if they're interchangeable? Could try and put there's on mine.