stihl leaf blower won't start


Old 10-29-01, 04:50 AM
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I was given a Stihl BG75 leaf blower. I have no history of it, only that it won't start. I replaced the sparkplug, still wouldn't start. Seems to me when I was a kid and tinkered with small engines that I could crank the engine with spark plug unscrewed and see whether it was sparking or not. I tried that with this leaf blower and see no spark. Does this tell us anything or am I off in wackoland? (It does have gas.) Thanks.

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Old 10-29-01, 01:45 PM
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Hello and Welcome Rich to the Do-It-Yourself Web Site and my Small Engine forum.

Based on the information you posted, you have already begun the process of determining what may be the problem. NO SPARK. The question is where to start looking. Start with the simple things first.

It may be the kill switch or stop button, {{{whatever it is called on that machine}}} is grounded. Try jumping it with a jumper wire and see if the engine will start. You may have to totally remove the wire or wires to it and see if the engine starts.

If nothing happens, check for spark at the plug again. You may have to remove the starters housing cover and visually check the wires and magneto.

Regards and Good Luck,
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Old 10-29-01, 10:29 PM
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The plug must have the metal side of the plug
touching metal on the engine, with todays blowers
that is easier said than done. If you have done this
and still have no spark, follow the plug wire to
the coil, you will have to remove some covers, which
will take a T-27 torx head wrench. At the end of the plug wire is the coil, a black box beside the flywheel. There
will be a small wire plugged onto a terminal on the coil.
Unplug it, then test for spark. You may have to reassemble it slightly to use the rope to spin it. If you still have
nothing, call your local Stihl dealer and talk to him.
If the blower was sold after 1995, there is a lifetime
warranty on the ignition. If he is unwilling to help,
e-mail me back and I will look up the distributor for your
area. If you have spark, then the wire going to the kill
switch is grounding out on metal.
Let us know what you find out, as the leaves are falling
fast here!
Old 10-30-01, 06:45 AM
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OK, forget the no spark theory. Thanks to Fisher pointing out the spark plug has to be in contact with the engine metal to check for a spark, I know can see a spark.

So I turned my attention to the carburator. I sprayed it with the usual quick start stuff, and finally removed the carb, took it apart clean it as best I could, and put it all back together. Still won't start.

My neighbor Bud thinks there's no fuel getting to the spark plug because when we remove it after trying to start the engine, the sparkplug is bone dry. Could this be one of the those rare times Bud knows what he's talking about? (Hee Hee)

Just in case you guys don't have any other ideas for me, what do you think my odds are if I just go out and buy a new carburator?

Thanks for your help. This is a great Web site.

Old 10-30-01, 08:01 AM
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Save your money. Are you sure the spray stuff will
fire enough to run an engine? Spray a good dose either
in the plug hole, then crank. Or down the throat of the
carb with the air filter removed and see if it will run
for a few seconds. If it does then your problem is in
the carb/fuel area.
Let us know,
Old 11-01-01, 06:23 AM
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Well, heck, still nothing. I've sprayed quick start in the plug hole and in the carb and cranked until I'm blue in the face and it won't even start to start. Any other ideas?

Old 11-01-01, 06:30 AM
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Is the plug clean? Do you get a strong enough spark? It should be fat, blue and consistent. If it's not the problem is still in the ignition.

Try a new, gapped plug. Put some fluid in the chamber. As Fish mentioned, if it now runs on what's in the cylinder and then dies, the problem is lack of fuel.

It's gotta be one of these .
Old 11-01-01, 06:32 AM
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The only other thing I can think of is poor compression and that's why it doesn't start..

But, try the other things first!
Old 11-01-01, 04:30 PM
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Hey Rich

I revert back to my orginal suspicions.

It's the ignition switch....

If the engine fails to start even with quick start...

It's an ignition failure.

Most likely...the ignition switch.

Try jumping it or bypassing it totally.

Old 11-01-01, 05:57 PM
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Thanks for all the suggestions. I do have a brand new plug, but I did not gap it myself. Anyone know what the proper gap is for the Stihl BG75 sparkplug? I think I have a gapper somewhere in the garage.

I have no training or experience, but I do think Iíll return to my attention to the spark. I mean, Iíve sprayed enough quick start in there to blow up a small city and still nothing happens.

Day job keeps getting in the way, but I shall endeavor to persevere.

Thanks again,

Old 11-02-01, 10:25 AM
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Take off your muffler and look at the piston. If
the exhaust port is choked with carbon, take a
sharpened wooden stick and chip it out, try to not
get chunks of carbon above the piston. If it is clear
try to start without a muffler for a couple of seconds
If the piston has up and down scratches on it, then your
unit may just be burnt up. If you have spark, good clean
fuel and the piston looks fine, check and see if the
flywheel key may have been sheared. Letus know.
Old 11-02-01, 06:01 PM
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The exhaust port was pretty clean, and the piston doesn't have any scratches on it, at least on the side I can see.

How do I check to see if the flywheel pin is sheared? There is a nut-like thing on the shaft next to the flywheel, but I can't seem to loosen it. Is it loosenable?

I can't see how it could be an ignition problem. Worked in the dark tonight, as opposed to dim light, and the spark is fat, blue and consistent. I check the spark, it's fine, screw the plug back in with fuel in the crankcase and crank. Nothing.

I forgot to mention, the pull cord has been shortened a bit. My guess is six inches to a foot. Could that do it?

It's a bugger, eh?

Old 11-03-01, 01:28 PM
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The round wheel with the fins is the flywheel, and if
the key should get sheared, it will spark fine, but just
at the wrong time. It is a rare occurrance to have one
shear, and many flywheels have the key cast into the
flywheel. Other wise, I would dump out all of the fuel
and try to start it while holding the throttle open.
Pull it a good 20 or more times, if it sputters then
dies, then add fresh fuel mix and start over. If an engine
is flooded/flooding, you need to air it out before you can
get it to fire. Also I have seen old fuel so bad that it refuses to burn.
Good luck and let us know.
Old 11-03-01, 07:32 PM
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does this blower have a spark arrestor at the exhaust? I have seen many of these clog up with carbon, preventing it from starting. I can't say I ever saw a Stihl do it though.
Old 11-04-01, 11:40 AM
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Try this it might work.
Pour a small amount of 2stroke oil into the sparkplug hole, If the rings are bad and loosing compression this should raise the compression to start, Next grab a Can of Carb cleaner any brand as long as its flamable, Spray into the carb and pull a few times and see if it coughs sputters or still does nothing,
I have seen Starting fluid not fire in a small engine, Dont ask me why i have no idea but i have no more than turned around and grabed a Can of Carb cleaner and pull the cord and by the 3rd time it atleast spits, WD_40 wont start em anymore they changed the formula i've heard.

Old 11-07-01, 07:11 PM
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Well, shucks. Stihl no start.

Let's review:

1. By standard test, the spark is fat, blue and consistent.
2. I have become familiar enough with this machine to know with certainty the no-start is not caused by a malfunctioning kill switch or on/off switch.
3. I have cleaned the carb and tried every suggestion listed above, yet there is not so much as one cough from the engine when it is cranked repeatedly, even with quick start or carb cleaner in the carb and crank case.
4. Fish suggests the possibility of a sheared flywheel key. I don't know how to investigate that possibility, but I can say the piston goes up and down as the flywheel is turned.
5. I have drained the old fuel and replaced it, so bad fuel is not the problem.
6. There is compression. For instance, there is resistance when I pull the cord, and there is suction when I pull the cord with my thumb over the spark plug hole, etc. Is there enough compression? I don't know.

I appreciate this Web site and its particpants, and I will continue to try your suggestions as long as the keep coming. Many thanks.

Old 11-07-01, 10:07 PM
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Take off the muffler and try to start it, but don't
choke it or prime it. Pull it a bunch, if nothing still
take out the plug. If it looks wet, reinstall, dump
out the gas and keep pulling till you get it to hit.
Once you actually hear it hit, then we'll take it from
there. I am guessing that with a semi clogged muffler
and a lot of priming, it may be so flooded that it will take
a lot of drying out before it will hit. The flywheel key
it a possibilty, but let's try this first.
Old 11-09-01, 08:37 AM
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"Quick start stuff"

Guys, I have a similar problem and have heard of this "quick start stuff". Can you describe exactly what it is and exactly what it's called so I can look for it at my auto parts store? Thanks!
Old 11-09-01, 06:35 PM
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The stuff I have is actually called Instant Starting Fluid made by a company called Soldier Seal. Just look around by the spray solvents, grease cutters, carb cleaning sprays etc. and you'll find something. Note someone said a post or two ago he had better luck with carb cleaner. None of it has done me any good...

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