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stihl leaf blower troubles

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stihl leaf blower troubles

Postby plotthound » Sat Oct 20, 2018 3:19 pm

so a bud dropped his stihl br 420 leaf blower off to me to look at.would not run after about 2 minutes of use.i pulled the carb off and after about 3 hour I managed to get all the ports and passages clear with a piece of copper wire and a healthy dose of carb cleaner.put everything back together with a carb repair kit and got the sucker running.will run for a few minutes then it starts to smoke and then it stalls.will start up again with choke on then will continue to stall and smoke.as I type this I just thought of the vent hole in the fuel tank(duh) that I never checked.if its not a plugged vent hole is it time to throw a new carb on it?those little carbs are near impossible to clean.
thanks
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Re: stihl leaf blower troubles

Postby KE4AVB » Sat Oct 20, 2018 6:23 pm

If my IPL is correct you should have either a Walbro HD-28 of HD-29.

You should never wire probe a 2 cycle cube carburetor as you can damage the delicate check valves.

As for the stalling check the spark arrester in the muffler.
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Re: stihl leaf blower troubles

Postby Luffydog » Sat Oct 20, 2018 8:42 pm

The left over oil sticks to it and blocks the holes off. Also seen dirt dobbers fill them with mud as well. It will cut the power way down and most times will idle but not throttle up and if they do they don't have power and stall.
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Re: stihl leaf blower troubles

Postby plotthound » Sun Oct 21, 2018 6:16 am

gonna take another look at it today guys,hopefully its the fuel tank vent or the spark arrestor screen.how do you guys clean your carbs?in an ultrasonic cleaner or a chemical dunk? :?:
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Re: stihl leaf blower troubles

Postby Luffydog » Sun Oct 21, 2018 6:35 am

Yes for the most part. But most times you'll find that those carbs are pretty cheap just to replace. Then there are those that will cost more than a new blower.
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Re: stihl leaf blower troubles

Postby KE4AVB » Sun Oct 21, 2018 7:53 am

Ultrasonic only use here for these cubes as there are tiny rubber check valves inside these carbs that are not available for replacement most times. Dip cleaners can actually destroy these as if you read the label on dip cleaner it says for you to remove all rubber parts. I actually only use the UC for all my carburetor cleaning now and have since 2014. That is when I gave away my last can of dip cleaner and I haven't a can of spray cleaner in years either. I do clean the exterior of carbs before putting in UC with 2C fuel mix using my air power engine cleaning wand to remove excess dirt and oils

Please note Stihl has propriety agreement now with Zama on the carburetor that Stihl uses and probably has one in the works with Walbro now too making it nearly impossible to get these parts. I just ran into this with a FS-56 that I needed a RB-155 rebuild kit for and Stihl dealer here wanted 3X the price for the kit. This just like the Briggs forcing distributors that sell their parts not to carry any aftermarket parts for the Briggs engines such as air filter and carburetor kits. It same for new dealers as I found reading the dealer agreement when I was looking into becoming a dealer. I still am able to source these parts but is a lot more difficult now as I must buy direct, thru Amazon , or eBay.

And as Luffy said some are cheaper to replace then fool with the rebuild and others are more than the equipment is worth. Those that are costly, I usually rebuild if I am able to obtain the rebuild kit; otherwise, I just send the customer to the dealer which sells a new complete unit if I can't get the replacement carb reasonably priced.

My local JD Stihl dealer is now charging $100 per hour for labor so most of the equipment is simply tossed and replaced. I still get my parts through them but try to avoid ordering them as they hit me with a $20 shc charge if they order them through the Stihl warehouse.
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Re: stihl leaf blower troubles

Postby plotthound » Sun Oct 21, 2018 9:32 am

thanks for the advice guys,if I was charging 100 bux an hour I would have 800 bux plus parts into this piece of crap lol.i pulled the spark arrestor out and sure enough it was plugged solid so I cleaned it up good.started the blower but got the same results,will run for a few minutes the die.took the spark arrestor right out and got the same result,removed the fuel cap but that made no difference either.damn thing just runs for a few minutes and seems to smoke a lot then dies.i even dumped the fuel and put my own known 50:1 mixed gas and the same crap again.will call the stihl dealer on Monday and see what a carb is worth,also will check ebay and amazon.

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Re: stihl leaf blower troubles

Postby KE4AVB » Sun Oct 21, 2018 10:55 am

I don't see if you changed the spark plug or not but if you haven't and if the BR420 has the NGK BPMR7A. These are prone to failures. I have seen anything from completely shorting out, causing engine knocking, and even one that actually was cause dieseling. I have still got to try the Bosch USR7AC but they are the same 10mm plug design except the Bosch is a little shorter where the plug wire attaches.
Incorrect info posted...Sorry. Corrected info posted later in this thread.
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Re: stihl leaf blower troubles

Postby bgsengine » Sun Oct 21, 2018 11:53 am

KE4AVB wrote:I don't see if you changed the spark plug or not but if you haven't and if the BR420 has the NGK BPMR7A. CMR7H? These are prone to failures.

BPMR7A is a 14mm plug.....
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Re: stihl leaf blower troubles

Postby KE4AVB » Sun Oct 21, 2018 1:04 pm

My bad thanks for the catch BGS. Yes I was thinking of CMR6H and should not let my mine wonder like that. It should have dawn on me when I was thinking of the 10mm when other plug was a 14mm.

That what I get for not having my readers on. Then it is the Bosch WSR6F that is the replacement for the NGK.
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