2 Stroke carburetor needs some tuning

[Brandon1023]

Well the easy stuff is over for my chainsaw (The carb cleaning, buying new diaphragm etc..) and now it's time to get it tuned. After gallons of sweat, and much frustration, the engine is firing, and running for maybe 3 seconds. It will pick up in speed, maintain the speed for 1 second, and then die. I just can't remember if this indicates a lean or rich condition. I know it's simple and there's people who have no problems with 2 stroke repair. I for one, am not one of those people.

Yes, it's getting fuel, yes it's got a strong spark, yes the gas is new. No, I didn't measure exactly how much oil. I put about 1 1/2 caps in a 1 liter gatorade bottle along with regular gas.

Thanks for any help.

 

[Nodroz]

Check your spark plug for reading. This will tell you if running rich or lean. Is the compression still good?

 

[sexyvicta]

if it runs better with some choke then that will tell you if its lean.

tune the high speed first when the engine is warm. with the saw at wot, richen it until the revs drop/its starts fourstroking then lean it off until just before that point. Then tune the low speed. set it just rich enough that it will idle and make transition to high speed without hesitation etc. You may need to adjust high speed slightly to get it to do that

thats what i do anyway and it works.

edit: theres probably lots of videos on youtube about this. watch a couple to get an idea of how to do it

 

[Brandon1023]

ive seen how to do it, and ive done it with a couple other 2 strokes. theyre just not something i usually mess with. anyway, it doesnt start on idle, so i cant really get the engine hot. i forgot which one youre supposed to start with. i adjusted the idle speed screw a bit, but its just slightly open enough.

edit- check the spark plug for reading? you mean to see if the cylinder is flooded?


ALSO i cant help but feel that some of the starting process in a 2 stroke depends on the pull. seems like the sharper you pull, the better chance of a good fire. probably has to do with the voltage from the coil.

 

[Russ2251]

It will pick up in speed, maintain the speed for 1 second, and then die. I just can't remember if this indicates a lean or rich condition.

Simple one word answer... Lean.
Clockwise = lean
Anticlockwise = rich
No different from a 4 cycle.

 

[FatCat]

The first place you should start is getting and accurate fuel mix. If you tune it to run off this mix in the Gatorade bottle it won't run the same when you put a proper gas/oil mix in. (unless you had a lucky guess) You would just be chasing your tail. Remember on a 2 stroke getting the right oil mix is very important. It's what lubricates the engine. A chainsaw may not be so finicky but not knowing your gas/oil mix on any 2 stroke is just asking for trouble. Mix up some fresh gas and start from there. Do you have a service manual for this saw? If so I'd jump back to stock settings on the carb. That's always a good starting point and then tune to your liking. Hope you get her figured out. Good luck

 

[Brandon1023]

thanks for the replies. i mixed a new batch of 20 oz of fuel and 1 tbsp of 2 stroke oil. i find it hard to believe you need such little oil in a 2 stroke. it will start up on choke without too much problem and then it dies a few seconds later. it will run longer when i put my finger over the small hole in the choke plate, and dies again.

ive started at 1 1/4 and worked my way to 2 out. is it possible that the carb is STILL dirty? it doesnt make one effort to start up on half or no choke, and this either indicates a lean condition (which i dont think, since i gave it 2 turns out), or a dirty circuit. i guess ill give the carb another ****n soak.

 

[Russ2251]

Lean, lean, lean.
Check that fuel is freely flowing at carb nipple.
Check diaphragm.
If it has a primer bulb, make sure it is supple along with connected fuel lines.
Some carbs have very fine mesh screen that must be clear of any debris.
And most importantly... NO AIR LEAKS PERMITTED!!!

 

[sexyvicta]

yeh what russ said. I think you're probably wasting your time trying to tune it out with the carb. There will be a leak(air), a blockage(fuel) or a faulty diaphragm.

edit: if you can get it to start and idle for a bit with full choke but wont do anything else it usualy indicates the diaphragm is faulty. In my experience anyway

 

[Brandon1023]

really? coulda sworn its a new diaphragm, but i have a spare, so ill install it tmw and further troubleshoot it.