Help with adjusting leafblower to run right

[JHZR2]

Hi,

my parents have a crafstman leaf blower that was purchased in about 1996. It has been used, but not terribly heavily, because it only ran once in a while.

They bought it at one of their houses, which was at sea level. They took it to their place in the mountains (its only 800-1000ft above sea level though) after the first year, and it never ran right. It was never taken back to sea level to see how it ran, but it was taken to sears for warranty repair, which kept it from running right still.

The probem was that typically it took 50+ pulls to get started. The engine doesnt have a primer bulb, and Im sure that doesnt help, but we have a LOT of other 2-stroke equioment, and this doesnt seem to be an issue with those other pieces that dont have primers.

Well, I went away to college, and they could get it running sometimes, so I guess they never bothered with it much. however, Im at home for the holidays, and we were using it for moving some leaves today.

We pulled it and it started suprisingly well. It took a few pulls, but it had been run dry and had been sitting a while. OK, great...

But the problem was, it wouldnt run if shoke was less than 1/2. It seemed to run best at somewhere between 1/2 and 2/3 choke, but at full throttle, it still wasnt very happy, and this was obvious - it didnt make anywhere near the power that my echo 210 blower/sucker does. Now sure, my echo is a lot newer, and it is an echo, but this thing has never run right.

So, given the situation that it takes a few too many pulls to start, it will only run if choke is 1/2 or higher, and it is lacking power, how should I start to attach carb adjustments? Everything else 'tune-wise' is in perfect order, so Id like to try to adjust the carb.

Any suggestions how to best start and execute?

Thanks!

JMH

 

[Jim 5]

I had similar trouble with a homelite line trimmer that started acting up seemingly for no reason. I had just mixed some fresh gas and some ~5 yr old homelite 2 stroke oil.

Just to rule out bad oil, I dumped the mix in the tank of my truck and mixed up a new batch with some new Stihl 2 stroke oil and new gas.

All my problems were solved. I'm sure you've already tried, but if there's a chance your 2 stroke oil or the gas isn't fresh, that's going to cause similar symptoms if my experience means anything.

If you've ruled out bad gas/oil, then it could be a carb issue. My new Stihl blower has detailed instructions for adjusting the main jet. It's clockwise to lean out the mixture (on a stihl). One tip they gave was that the factory setting was something like 2.5 rotations counterclockwise after the main-jet screw was fully screwed in to the stop. You could baseline your adjusting screw by counting exactly how many turns in it takes to bottom out (so you'll be able to restore the factory setting). Then you could start experimenting.

So it seems like if it runs OK choked, then your blower is liking a richer mixture. If you can identify which screw is for the main jet (there's usually two - one for the main carb circuit and one for the idle circuit), then you could try to richen the main circuit likely by turning the main-screw counter clockwise until it hits its sweet spot.

If you've baselined each screw by counting how many turns from bottoming out, you can always restore it to the way it is now....even though that's not great.

Can't hurt anything to experiment a little. Just use gradual stages and work only one circuit at a time so you can tell which change to which screw caused the improvement or worsening of performance.

Good luck and tell us how this works out for you!

 

[Jim 5]

One other point of which I'm sure you're aware (I'll admit that it took me more years than I'm willing to say just to figure this out)

To start a two stroke small engine:

- full choke - 1/2 throttle (prime once now if bulb is full, assuming you've got a primer bulb),

- pull until you feel the engine almost fire (this can be a few pops or as subtle as the last bit of the pull being a little easier) If you keep on pulling at full choke after this step, you'll flood it and be pulling for 50 times,

- next go half choke - 1/2 or more throttle

- pull until the engine starts (it will run but kind of roughly),

- run like this for about 30 seconds to a minute revving the engine and then switch over to no choke......you should have full power now.

This procedure works on my homelite line trimmer, and on my stihls.

On my stihl's (MS250 Chainsaw, BG85 Blower) detecting the firing (and it's an almost imperceptible - like a 5-10% power stroke) on the full choke mode was really tricky at first....and that's the key. With my stihls, if I think maybe I perceived that it maybe fired on full choke...then I switch to half choke right away. It will start on the next pull for me at that point.

The first time I tried to start my new Stihl chainsaw it was a 50 puller...I was screwing up at the full choke stage (not detecting that tiny little start/stumble), keeping pulling at full choke and flooding it as a result. It's possible that since the engine started out dry, you didn't have this same flooding trouble this time. Or it's bad gas/oil. Or your carb is set too lean. You mentioned its tune otherwise was OK and you are presumably getting good spark when you should.

Sorry for the long narrative, since I'm sure I'm telling you something you already know...however, I'm denser than most and it took me a surprising amount of time to figure this out.

 

[flatlandtacoma]

If it won't run without choke and won't run at full throttle, it is too lean. Try richening the needles and make sure there aren't any torn/dry gaskets or cracked fuel line sucking in air.

 

[punisher]

There is a more than even chance you have a hardened diaphragm,pinhole leak in a fuel line letting in air or a gasket leak in the carb. The problem is once you get the mix needles all out of whack compensating for a bad part then it can be misery getting the carb set up properly after it is fixed properly.

If you are set on adjusting the mix, lightly bottom out each mix needle recording the number of turns it takes to do that. This will give you a baseline to go back to.