OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Engines Questions On Victa Two Stroke Engines Victa Silver Streak 2 Stroke, Spark, fuel, no fire

Hi all,
I have an old 160cc 2 stroke. The type with the oblong exhaust, not the tear drop one.

I cant get it to start! I have cleaned out the carb. I can see that the poppet moves up and down freely, and moves with the throttle cable. It has a blue spark when i test it. I'm using a brand new plug. Champion CJ9. All fuel line and breather pipes are new and clean. The fuel is new and clean. I've cleaned the whole mower so it looks like new. I can see that fuel is getting in to the carb float chamber, the carb needle and gause is clean and block free.

I cant get it to start. When i remove the spark plug, the spark is blue, and i can see vapours puffing out of the spark plug hole when i pull the start cord. The compression seems good, when i have the throttle on stop position i can hear the engine sucking through the air filter housing.

It was running perfectly before this! I can't work out what the issue is. I've tried leaving it for a couple of days and still no luck. I've tried starting it without the air filter without success.

Can anyone point me in the right direction please? I've ran out of ideas and need some expertise.

Cheers,
Trev.

I suggest you squirt a small amount of fuel either through the air intake or through the spark plug hole, then try again to start it. If it starts and runs for a couple of seconds then stops, the problem is fuel (carburetor, or induction air leak). If it doesn't start, the problem is spark, compression, or port blockage. Tell us which, and hopefully we can help you get further.

Hi Grumpy,
Many thanks for the reply. I put a small amount of fuel into the spark plug hole, replaced the spark plug and it didn't fire.

Interestingly it did fire a tiny bit when i had the carb removed and i pulled the starter cord.

Thanks,
Trevor

If it won't fire with fuel in the cylinder, you have insufficient spark or compression, or the spark is happening at the wrong time. You might learn a bit more by removing the muffler and checking the exhaust port is clear (leave the muffler off), replacing the decompressor with a spark plug, and trying the fuel-in-the-plughole trick again. You should be able to feel the compression - both crankcase and cylinder compressions - quite strongly then. If you can, and it doesn't fire, there is something subtly wrong with your ignition.

Grumpy got it in one, Take the muffler off and check the condition of the piston by looking in the exhaust port.

Thanks guys, I took off the cylinder head and cylinder. There was a bit of coke build up in the exhaust port, I've cleaned that off, high pressure hosed the parts, cleaned with a cloth then put the engine back together.

There seems to be compression twice on a revolution of the engine, so I think the compression in crank case and cylinder is fine.

I think its looking like an ignition problem, i've regapped the E-Core, the spark is there and is blue. Like you said perhaps it is firing at the wrong time. How do I adjust this? Is it something to do with the electronic ignition module?

I really appreciate your help so far. it's great to be learning.

In theory the ignition timing can't be changed, since it is set by the magnet on the flywheel and the flywheel is on a key that locks it to the crankshaft. On the very old engines with breaker points you could vary the timing a few degrees by using the wrong point gap: increased gap advanced the ignition, and reduced gap retarded it. However many breaker-point engines had slots in the point set so the timing could be adjusted.

One point needs to be clarified: did you check the spark with the spark plug connected, or did you hold the plug lead close to the cylinder head and let it spark from the lead to the head? If you have a defective spark plug, or much too small a plug gap, that could be the problem.

Joe suggested that you inspect the side of the piston through the exhaust port, in case it is scored. Scored pistons do not control the ports properly, giving the effect of incorrect valve timing. I suggested that you try to start the engine without the muffler fitted, in case the muffler is choked or has a loose baffle. Did you try both of those things?

Hi Grumpy,
I had a quick look at the piston whilst i had the cylinder head and block off last night. My novice eyes didn't see any scoring, there was rather a lot of coke build up on the top of the piston and in the exhaust port but that was it. I've cleaned the exhaust port but not the piston head.

I had the same thought as you regarding the spark plug, i tested the spark by resting it against the cylinder head and pulling the starter rope.

I forgot to say, I had the engine running perfectly until i turned it on its side to clean off the grass from underneath to tighten the blade nutes. After this it wouldn't start. That was 2 weeks ago! Since then i'll recap what i've done;

1. Cleaned and rebuilt the carb, checking the needle and float, the fuel intake needle, diaphram, also checking the popit moves correctly when moving the throttle cable. Also i've checked there is a seal when sucking on the governing breather pipe.

2. I've replaced the spark plug and all breather and fuel pipes with new pipe.

3. I've checked fuel is getting into the float chamber and up to the injection needle.

4. I've taken off the cylinder head & block, cleaned the exhaust port, inlet port, and put back together.

Last night the starter rope broke, so i will replace that, then i will try starting it with the exhaust removed like you said.

I'm really glad of the advice, i am stuck you see, the engine seems to have spark, fuel and the air intake pipe is free and clear.

I'll let you know when i've fixed the starter rope and tried to start it with the exhaust off.

Cheers,
Trev

That extra information is useful. In theory, if the behaviour of the machine changes suddenly, something must have happened to it that caused the change. There is one thing we know about that changed: an old, coked-up engine was turned on its side, then suddenly stopped running. The muffler probably had a large amount of carbon in it, and turning the mower on its side may have caused it to shift. You may have a blocked muffler. I was recommending that you remove the muffler just in the interest of completeness, and because a blocked muffler seemed to fit the symptoms. From what you have now said, it also fits the circumstances. At a minimum, it needs to be disproved as a possibility before you go further.

You were right! I removed the muffler and pulled it to see if it would start, but i didn't have the fuel tank attached, so it was only going to start with the small amount of fuel in the float chamber. It did start breafly, so i put it back together with the fuel tank attached leaving off the muffler. The engine would then fire a few times and die. Then eventually wouldn't fire much at all.

You;ve helped me make significant improvements i'd say. Thanks! Would you think that i now need to get new head and block gaskets, as i didn't replace them on monday when i took the head and block off the engine. Is it possible this is the cause of the engine not running properly now?

I've checked and there is still fuel and spark getting to the engine. There is also vapours coming out of the exhaust port when i pull the starter cord.

Cheers,
Trev

It is difficult to say at this point, but you need to be certain that those gaskets are not leaking: it won't run properly if either of them leaks. You might try the fuel-into-the-air intake or into the spark plug hole trick again. If it runs better when you do that, than it does when you supply the fuel through the carburetor, then there is either a fuel system/carburetor fault or an intake leak. If it doesn't run when you do that, it may (emphasis, may) be the head gasket.

Usually a gasket has to leak very badly to cause it to not run at all. Sometimes when you reassemble an engine the cylinder or cylinder head jams on the studs and doesn't sit properly on the mating surface. That kind of problem can cause a complete non-start or almost non-start. A guess: perhaps your original problem was the coked muffler closed off the outward flow from the exhaust port, but your investigation has caused a problem in the gaskets, the fuel tank/fuel line, the carburetor, or the spark plug. Example: there might now be crud blocking the fuel tank filter, where it wasn't before. Or, if your fuel tank filter isn't working, a fresh supply of crud might have moved down into the carburetor needle and seat. Another example: as you said, there might now be a major leak in a gasket. A third example: when you reassembled the carburetor, you may have got something wrong (especially if it's a Victa plastic carburetor: it takes a near miracle for a new player to get one of those working after reassembling it).

Hence my suggestion that you try the fuel-in-the-plughole trick again. If it fires up decently but briefly, look at the fuel system, carburetor, and intake pipe/crankcase sealing. If it doesn't, you may have a fairly serious head gasket problem.

Don't feel badly about the possibility that you've caused a problem or two when you worked on the engine: most of us do when we first try to do these things, especially if we don't have a reliable mentor who is physically there and looking over what we do. I had the good fortune to have a father who was both experienced and helpful. When you have to learn by a boot-strap process, it is tough going at first.

AS this sound to me like a full crank engine it may well be worth checking out the crankshaft seals also, tey would probably be well over 20 years old and made of rubber. Leaking seals can cause irratic running.

Hi guys,
I've finally got it running like a dream! Thanks for all of your help. I really appreciate you taking the time to help me.

I tried the trick of putting petrol directly into the inlet port. The mower wouldn't fire. So I decided to look at the spark again. Again I saw a spark, i tested it a few more times and i noticed that the spark was only really happening at the fastest turn of the pull. So took the HT Leed out of the plug cover, then held it close to the engine block. I noticed I could get a spark at really low rovolutions of the engine that way. The spark plug is brand new! So i regapped it to a small gap of 0.02mm. Then i noticed i was getting a spark much more consistantly. Happy days. The engine start and ran on the first pull of the starter rope!

I've tried it several times since and the mower is starting and running like a dream!

In the end i've;
1. Replaced the HT lead, which had an intermittent break
2. Replaced the spark plug
3. Regapped the plug
4. Cleaned out the exhaust ports

A combination of these has my mower running!

Thanks again guys, you've been a great help.

It sounds as if your new replacement spark plug had an internal short or breakdown in the center insulator. I think that is fairly unusual, though not unheard of. In the old days it was routine to check whether the ignition system would spark strongly across a sizable gap between the end of the plug lead and the cylinder head. A brand new magneto would often spark half an inch or a bit more than that. You should be sure to use the correct plug gap: if your "new" plug won't fire strongly across a 0.030" gap, throw it away - the basic Briggs & Stratton magneto service test requirement is double that.

Your broken HT lead probably didn't matter - it just sparks across the gap inside the lead as well as the gap in the spark plug. However it slowly burns the copper away on both sides of the break in the lead, so the lead fails eventually when the gap inside it becomes huge, so it's best to replace defective parts even if the engine is running satisfactorily.

Incidentally on multi-cylinder engines with Kettering (coil, capacitor and breaker points) ignition it used to be a standard mechanic's trick to identify and "cure" oiled plugs by running the engine and pulling off each plug lead in turn until you found out which one made no difference to the way the engine ran. Then you held that plug lead a quarter of an inch away from the spark plug electrode. The increased gap increased the firing voltage to a very high level, and burned through the oil fouling in the plug. After about five or ten seconds it would be running on all cylinders and you could put the lead back on the spark plug. I've used that trick myself - it works wondrously well, and is very useful when you're a long way from home when you foul a plug. (Most of us were way too cheap to buy new parts when you could get the old ones working again.)

I'll close this thread.