Craftsman BackPack Leaf Blower No Spark

welchs101

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i am in no rush or anything using this as a learning exercise really. so i was thinking of ordering a carb kit and trying this out. but i kinda wondering if this is really going to work. when i took the carb apart the pieces looked ok to me.......the diaphragms looked ok....(as far as i could tell but my experience in these matters not good). gaskets looked ok not great but ok......just wondering if a kit is really going to help......i have a feeling i missed something.
 

bertsmobile1

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Cube carbs are pressure vessels
So "looks OK" does not cut the mustard
They must really be pressure tested & vacuum tested
The fuel tank & fuel cap and tank breather ( where fitted ) must also be tested.
If you don't know what new looks & feels like then you can not make a visual assesment of your old diaphragms & gaskets.
So you are just urinating into the wind .
If you really want to lear then search Joe Pace, two stroke carburettor diagnosis on you tube .
When I finally came across his series of tutorials it made a massive difference to my cube carb work.
I now only pull apart about 1/3 of the carbs that I used to because I find the faults are usually in the cap or tank and rarely in the carb itself.
The exception to thi is one where old fuel has been allowed to evaporate in the carb in which case it is a bin job .
Once opened it is nearly impossible to reseal them air tight using the old gaskets so it is SOP to fit new diaphragms & gaskets if a carb is opened .
Star has already sent yo a link to the service manual and on the same web site Walbro have about 1/2 dozen 3 minute service videos.
 

StarTech

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My experiences are different as I seldom find tank venting to be the problem.

But from the previous images first I noticed a fuel pump diaphragm order problem. Second the fuel pump pumping flaps are deformed. And third the metering diaphragm looks like it is stiffen. On some engines it doesn't take whole lot of stiffening to cause problems.

As far as to kit or not it is gamble either way. Luckily these kits are fairly reasonable to try vs an OEM carburetor. I usually repair at least 98% of the ones I do. Of there will unrepairable carbs at times like the ready start versions.
 

bertsmobile1

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When I did the months hand over from the previous owner I had little experience with cube carbs as I always tip the fuel out of my hand held devices and run them dry.
Thus my 30 year old gear was working perfectly ( or so I thought ) so I had no reason to pull them apart.
He showed me to clean down the engine pull the carbs off , replace the diaphragms & gaskets reassemble then do the checking that should have been done first if the tool did not run properly.
Now I work according to the proceedure shown by Joe Pace, starting with the cap & tank and many times all the tool really needed was the fuel line pulled 1/4 out further to re-establish the seal between the fuel line & tank on throw aways or a new grommet on quality tools or with the GX 25 /35's the cap vent cleaned
While it is nice to have a customer come back with a "thank you it runs better now than it did when new " in reality most just want it to start & run & the less that costs them the better
So $ 30 for replacing the old hard fuel line is better than $ 80 for a full rebuild & replacement of all service parts.
 

StarTech

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Bert, this is where experience is key when working on these machines. An experienced person can easily diagnose a problem without tearing things apart indiscriminately looking for cause when it might simply be a broken fuel line. When I first started working on 2 cycle handhelds it would take most of a day to get them running where now it usually takes around an hour. I actually learn on a whole full size pickup truck bed full of another shop's discarded handhelds. I manage to get 3/4 of them working and sold.
 

welchs101

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sorry for not replying sooner.........been sick with covid...actually still kinda sick. i just did not want you guys to think i had stopped reading or gave up on this blower......
 

bertsmobile1

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Bert, this is where experience is key when working on these machines. An experienced person can easily diagnose a problem without tearing things apart indiscriminately looking for cause when it might simply be a broken fuel line. When I first started working on 2 cycle handhelds it would take most of a day to get them running where now it usually takes around an hour. I actually learn on a whole full size pickup truck bed full of another shop's discarded handhelds. I manage to get 3/4 of them working and sold.
Nothing I like more than getting something I have never seen before & working out why it failed then how to fix it .
Then there are silly things I should have understood like the fuel pumps push fuel & air into the tank not suck fuel out of the tank as liquids push better than they pull .
However I can be just as lazy as the next man so doing what my predecessor showed me without thinking through what was happening was of course the easiest way to go .
As you know, once you know & understand how cube carbs work then you can fix just about any on them, if they are fixable
 

bertsmobile1

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sorry for not replying sooner.........been sick with covid...actually still kinda sick. i just did not want you guys to think i had stopped reading or gave up on this blower......
No need for appologies
Nothing here is compulsory.
Sorry to hear you got the virus & hope you get a full recovery.
Some of my customers took month to get over the first variant and some are still not 100% more than a year latter.
Touch wood I have managed to avoid it so far but the way our government is managing ( or not rather not managing ) the outbreak it is just a matter of time.
Apparently the economy & dividends to shareholders is more important than peoples health .
 
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