What else can I look at....................

[WoodMann]

As many of you know, I took in a stray chainsaw a few months back. I took the bar and chain off to begin restoration and today I primed the cylinder with premix just for fire over a few times, but for the life of me this thing will not start. Air filter looks OK, I even removed it for test starting. I've cleaned the plug and held a nail in the coil lead feeling for a shock- OK. Anyone got any other advise what to look at or do? Thanks....................

 

[taxidermist]

Advice....... dont hold the nail when you pul it over next time and you wont get shocked........LOL ......as far as help.... what kind of saw? and we will start there.


Rob

 

[woodconvert]

Are you sure it's getting fuel?. Got compression??...if you've got those two and fire you should have boom. No fuel, no boom. Low compression, some boom. Does it not pop or smoke at all like it's trying?. Did it set with fuel in it for a long time???. The carb could be goobered up with old fuel or debris. Have you cleaned the carb?.

Were it me i'd make sure the carb was clean and functioning properly and go from there.

And as a side note, instead of using a nail or other object to check for spark...use the spark plug. That way you eliminate the possibility of the plug being bad.

 

[sapratt]

One thing you could try is a small shot of ether. One quick shot in the carb then try starting it.
If it fires then you know its the carb. If it doesn't start then its probably the cylinder or plug.

 

[brad068]

As many of you know, I took in a stray chainsaw a few months back. I took the bar and chain off to begin restoration and today I primed the cylinder with premix just for fire over a few times, but for the life of me this thing will not start. Air filter looks OK, I even removed it for test starting. I've cleaned the plug and held a nail in the coil lead feeling for a shock- OK. Anyone got any other advise what to look at or do? Thanks....................

Don't use a nail. Use the plug and make sure that the plug is grounded out to a metallic part of the engine and pull it over. Even if you got a little shock it might not be enough volts to jump the gap of the plug.

Is the piston OK. What did the original plug look like? You probably don't have a compression tester so if you can, look into the spark plug hole and see what the cylinder and the top of the piston look like. The cylinder wall should be shiny and so might the top of the piston if not covered in carbon. If you see any metallic like dull aluminum or nicks in the top of the piston you might as well forget it!

If it looks good this is where a leak-down test could be valuable. A 2 cycle engine needs to be able to hold pressure on both sides of the piston. You can have all the spark and compression in the world in the combustion chamber but if there is a air leak in the crankcase the engine will not run. It might pop and fart but it won't start. Most common are the crankshaft seals, vacuum line and the intake spigot/gasket.

 

[eba1225]

Woodmann,

Sounds like you may have one or two or probably more problems which you need to dismiss. My Stihl 028 which I received for free looked like it had good spark, but the shop said it was weak and prpbably the carb is shoot too. Well I found a replacement coil, installed it and away I went runs ok, but now I do believe that I have a carb issue as it has no power.

Keep plugging away at it until you eliminate all the problems. If you can afford it take it to a shop for an evaluation, my evaluation cost me $35, well worth the $$.

Erik

 

[WoodMann]

Thanks guys, I'll keep trying this and that and keep ya'll posted. The plug had a light coat of carbon on it that I cleaned off, I'm thinking of trying a new plug. I don't wanna pout too much into the saw though, y'know..............

 

[Gooserider]

As a very rough compression test, you should be able to pick the saw up by the starter rope... It might then *slowly* pull the rope out, but you should definitely feel serious compression, even with a little saw.

I would also second the SHORT test using a can of ether starter spray, which would at least give some indication that compression and spark are OK...

If you can start it on ether, then it's a pretty safe bet that the electrics are OK, and that compression is tolerable, leaving the problem focus on the carb and the rubber bits. If you have compression, and it won't start on ether, look at electrics, if you don't have compression, check the piston and cylinder.

Gooserider

 

[brad068]

The only things I uses ether for is starting diesel tractors in -20F weather and my spud gun. It will pop and fart on ether but like I said before if there is an air leak in the crankcase it will not run. Its not fuel injected so when you spray ether into it and it sounds like its going to run it gives you a false since that the engine is ok. This problem is far less common that a carb issue, but keep it in the back of your mind.

 

[Gooserider]

Agreed, and I would emphatically NOT use ether as a routine starting fuel, nor do I like it as a primary diagnostic... I would reccomend it as a thing to use only in a situation like this where trying to determine which system is at fault, AFTER having checked out the obvious candidates...

However I'm not talking about getting a "pop & fart" out of the engine - I'm saying you should be able to start and RUN for 5-10 seconds on the ether - there is a BIG difference between "trying" or "almost" starting, and actually running for more than one or two revolutions...

NOTE - this is VERY hard on the engine, as the ether quickly removes the oil residue from the bearings, and especially the piston rings and cylinder - however a few seconds of running only shouldn't be a real problem. (I've also seen people do this trick alternating ether and WD-40 to keep the engine running longer. It's a cute trick, but not much point to it...)

Gooserider

 

[brad068]

Thats why I say "in diesel tractors when really cold or a spud gun". There is really no point to keep an engine running on ether if the fuel system isn't working right. When and if the engine (2 cycle) starts and runs on ether with a leak in the crankcase, it will continue because you are forcing the combustible fuel into the crankcase and cylinder and you may think that you still have a carb problem when really there's not. I've fixed a few snowmobiles over the years that have burned up a cylinder because a crank seal went bad and the other cylinder pulls it along. It still gets fuel to the combustion chamber but at a very lean amount and eventually burns up the piston. Most people don't notice the decrease in power and just keep on riding.

More common though, it is a gummed up carb that restricts the main jet and leans out the fuel mix and burns up the piston. Because if the pilot is plugged it won't idle right and that is noticed right away.

 

[WoodMann]

THanks guys- but remember I primed the cylinder directly to see if it would fire, thus bypassing the carb...............