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Old Mar 02, 2005, 03:05 AM
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Hard starting 2 stroke... need help!

Hey guys,
i've got an old Eager Beaver by McCulloch 2 Stroke whipper snipper engine. The only problem is that it's a real PITA to get started. Hardly ever starts just by pulling the starter. But when it does start it runs fine. Has a smooth idle and good throttle response. It also starts real easy once it's hot. Any ideas how to fix this problem I've taken the whole engine including carby apart and cleaned it and it all looks pretty good to me. I'd really like to get this thing started more easy. Cheers.
Alex
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Old Mar 02, 2005, 08:31 AM
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Hi Alex- Hows the compression on that thing? Jim
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Old Mar 02, 2005, 09:10 AM
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Adelaide, South Australia
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I'll take a guess that your spark is getting weak. I had a similar problem once with a Robin brush cutter and after trying everything including new rings (although the old ones still looked fine) I ended up with the only thing left being the spark. I had what seemed to be a good spark holding the lead close to the cylinder and also when connected to the spark plug out of the engine (this being the very first thing I checked anyway). Eventually I checked it with two plugs in series, one outside the engine and the other installed. This simulated the way auto plugs used to be checked in a chamber of compressed air. No spark! Hot air offers less resistance to a spark which might explain why you can start yours when hot.
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Old Mar 02, 2005, 10:28 AM
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Quote:
Originally Posted by Regecide
Hey guys,
I'd really like to get this thing started more easy. Cheers.
Alex
Ether--AKA Motor starting fluid.

Kurt
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Old Mar 02, 2005, 12:22 PM
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East Anglia, UK
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You know, I had a 4-stroke mower like that. Woudl never start cold after a few years.

I took it in to get it servuiced, and they regoround teh valves and it was no better.

Latsd year, about 6 years after its 'service' the pull cord got tangled up. and I had to dismantle half the mower to clear it.

I was busy greasing up teh slides and oilinmg teh moving bits when I noticed that the choke wasn't working at all.....the throttle cable had been knocked back a bit so full throttle which was suposed to be choke as well, wasn't.

Tell you what, I moved it back, and the damned thing started first time.

IF comression and valves are good - and there isn;t much valving in the average 2-stroke anyway, chances are it needs more fuel when cold.
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Old Mar 02, 2005, 03:11 PM
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The 4 things an engine needs to do to run properly: Suck, Squeeze, Bang, and Fart!
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Old Mar 02, 2005, 03:34 PM
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Mark- I've never thought of it quite like that, but that's a pretty good description of a 4 cycle engine, but his is a 2 cycle. As far as ignition is concerned, I'd bet that it's capacitor discharge so there's not much you can do about it other than changing the plug. Jim
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Old Mar 02, 2005, 04:15 PM
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Yep, if the fuel supply is good all you need to do is get it wet and it's will fire. My big petrol burning airplane engines need to be choked untill fuel drips before they will start.

Have you noticed that the new little trimmers and leaf blowers come equiped with a primming bubble?

Wiz
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Old Mar 03, 2005, 06:20 PM
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As far as I can tell compression seems to be fine. There could probably be a bit more though. I've checked the plug outside the cylinder and there is def. a spark. I might jsut go grab a new one. They aren't that expensive.
I think the problem I'm having is that not enough fuel gets in when I'm trying to start it. I've removed the plug, squirted some fuel in and it starts no worries.

Also, what is ether and how does it get used when starting the engine?
Oh yeah, there are no valves to speak off whatsoever.


Alex
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Old Mar 03, 2005, 09:40 PM
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Quote:
Originally Posted by Regecide
.......I think the problem I'm having is that not enough fuel gets in when I'm trying to start it. I've removed the plug, squirted some fuel in and it starts no worries........

Alex

It could still be related to compression. The squirt of gas could be helping to seal the rings in the cylinder, and give you better compression. I would check the compression before the squirt of gas, and then again after.

Dave
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Old Mar 04, 2005, 06:23 AM
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Lake Macquarie, Aust.
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Get some aerostart but it's also marketed also as "START YA BAS.... " (true name!)

They are ether based, and you just squirt in in the intake for a second or so, and it'll start first pull . If an engine with spark won't start with it, it'll never run!

A couple of 2 stroke facts for you guys.

2 strokes do indeed suck, squeeze, bang and, er, blow , they just do it differently.

Valves are used in them, reed, or rotary disc for the inlet, but aren't compulsory as you can use the piston skirt itself to close the inlet. Most of your whipper snipper/mower type 2 strokes use the latter "piston ported" as it's cheap and as they generally run at fixed RPM they are timed to suit that RPM.

They can also be used on the exhaust ports, guillotine or rotary valve to adjust the height (timing) and also the area of the exhaust port to help broaden the power curve.

Too much oil when premixed, does not make a "safer" mix as you are only displacing the fuel itself, so you can still seize from overheating due to a lean burn. The engine will be plenty oiled as you take it aprt to fix it though

I threw that last one in as I hear the opposite every now and again in my trade, and it annoys me


I'd say the problem is worn rings/low compression:

What happens when initially starting a 2 stroke with leaking rings is when the piston is going up it creates a low in the crankcase drawing air and fuel into it. If the rings aren't sealing (or the crank seals are worn, or a leaking barrel gasket, or the crankase itself) not all of the "mixture" in the crankcase that will end up being burnt in the cylinder has come from the carburettor, meaning a weak or lean mixture. Combine that with the fact you need a richer mixture anyway when cold you now have one stubborn possesed whipper snipper!!

When it gets real bad you'll find that it will struggle when hot too.

You find that by pouring some fuel into the cylinder helps because you have just turned on the "choke" the old fashioned way.
Oil will have a similar effect when poured into the cylinder as it helps the rings seal.


assuming you have the choke circuit clean I'd say this is your problem. These engines have so few parts, but ALL of them need to pull their weight for gardening bliss to occur!

Just get some of the ether based products as fishnut first said, and forget about the stupid thing!



Cheers
Paul

Edit: Try to pull the cord as fast as you can and don't let it stop between pulls may help. Get that thing spinning fast!
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Old Mar 04, 2005, 06:37 PM
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Quote:
Originally Posted by gouch

Edit: Try to pull the cord as fast as you can and don't let it stop between pulls may help. Get that thing spinning fast!

Thanks, I tried that lol and it felt like I'd done a solid session at the gym
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Old Mar 04, 2005, 06:44 PM
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Originally Posted by gouch

Edit: Try to pull the cord as fast as you can and don't let it stop between pulls may help. Get that thing spinning fast!

Thanks, I tried that lol and it felt like I'd done a solid session at the gym
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Old Mar 09, 2005, 07:30 PM
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2 Cycle

Another thing to check is the exhaust ports to make sure thet they are not filled up with carbon from all the oil that is ran throught the engine over the years. Remove the muffler if there is one and look at the holes. If they are plugged take a knife and open them up.

Mowman
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Old Mar 12, 2005, 10:06 PM
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The first thing to check on a used 2 cycle engines that wont start well is the piston condition.
I used to work in a saw shop and would watch people spend hours chasing down problems with the carb, ignition ect.., only to find that the piston was scored( junk). It does not matter how small, if its scored, its no good. I would say most of the damage I would see on 2 cycle engines was piston scoring from running too little or no oil in the fuel.
Pull off your muffler , look in the exhast port and slowly pull the starter cord. You will see any scoring if its there.
When ever I work on any 2 cycle engine I go in this order:
Check the piston
the exhast for blockage
the compresion
the ignition and fuel
I find if I go in this order I waste the least amount of time and money.
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