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Stihl BG 86 won't start

Started by JohnG28, May 10, 2012, 12:40:20 PM

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Al_Smith

I'm not sure if Stihl uses automatic advance type coils on the blowers or not .They did on some of the older saws namely 042 and 048 .Those would occasional fail but usually they would not advance .

FWIW you can actually get most two cycle to run without even a carb on them .A little squirt of fuel in the intake you might get 5 seconds of run .About the only way it could get out of time is if it sheared a key in the flywheel .

Now I don't have a BG 86 to look at but I do a BG 85 .I'll take a peek at a blown engine I have in the shed to see how the impulse line hooks up .If that thing came loose it absolutetly won't pump fuel .Even if it didn't though the prime should have gotten a putt or two out of it I should think .

Al_Smith

Well that idea is null and void at least on a BG 85 because it doesn't use an external impulse line .It's possible but not likely that the impulse could be blocked some how though .

What that model has is two lines coming from the fuel tank .Because the carb has a primer button a supply line plus a return line .

Clam77

Well.. it's been giving you fits since your first post about it in may... whatever's wrong with it ya best figure it out soon cuz fall is RIGHT around the corner..    8)
Andy

Stihl 009, 028, 038, 041, MS362
Mac 1-40, 3-25

JohnG28

Clam, Ill admit I haven't kept at it all this time, but still haven't figured it out. The oncoming fall sure made me start thinking about it it though. As for the engine, it has no impulse line either, internal also. I had the manifold off and hit all passages with compressed air. Gaskets are good and no blockage I can see of impulse or any other passage. This is a strato engine so has multiple intake passages, but they are fine. Fuel lines are fine, primer work fine. I'll check the flywheel again tomorrow, maybe I missed something. Don't have a tach to check the rpm when cranking, but there's still spark, that I know. >:( >:(
Stihl MS361, 460 & 200T, Jonsered 490, Jonsereds 90, Husky 350 & 142, Homelite XL and Super XL

Al_Smith


JohnG28

I didn't realize it myself until I looked at the manifold close, then did a little research. Only figured this myself recently, sorry I didn't include when I figured that out.
Stihl MS361, 460 & 200T, Jonsered 490, Jonsereds 90, Husky 350 & 142, Homelite XL and Super XL

Al_Smith

I kinda figured it had the impulse on the manifold after I looked at my junk BG 85 engine .

About the only thing I can say is refering to that engine design my buddys 441 saw became a pain in the buttocks to start after a while .Almost sounds like the thing is sucking the fresh air portion for the blow down cycle but not taking a suction through the carb so it isn't getting any fuel into the cylinder .

That's just a guess as I've never worked on that engine design .

JohnG28

Thanks for the continued assistance Al, and all the help from everyone else as well. That almost sounds like what I seem to be getting, but I finally bit the bullet today and took it to the shop. I've had enough and need it soon, so I guess I'll see what they say. I'll let you all know what they find. Thanks again for all the help. Either way I have learned some so no total loss.
Stihl MS361, 460 & 200T, Jonsered 490, Jonsereds 90, Husky 350 & 142, Homelite XL and Super XL

Clam77

Quote from: Al_Smith on September 20, 2012, 08:01:30 PM
I kinda figured it had the impulse on the manifold after I looked at my junk BG 85 engine .

About the only thing I can say is refering to that engine design my buddys 441 saw became a pain in the buttocks to start after a while .Almost sounds like the thing is sucking the fresh air portion for the blow down cycle but not taking a suction through the carb so it isn't getting any fuel into the cylinder .

That's just a guess as I've never worked on that engine design .

I can only think of 3 things why it wouldn't suck through the carb.... and each one gets drastically worse..   :D
Andy

Stihl 009, 028, 038, 041, MS362
Mac 1-40, 3-25

joe_indi

Quote from: JohnG28 on September 19, 2012, 12:26:20 PM
At the same time it's also spinning the nut and washer off the impeller side now, just as it's almost starting. I can pull on it all day and that nut won't loosen, but soon as it wants to start it spins off. Now I'm thinking this could be that the timing is off slightly, causing it to fire just a little too soon?
Seems like the ignition timing is way off so that the engine is firing in the reverse direction.That could get the impeller nut to loosen.
I am sure once more that the culprit is the ignition timing.
Like I have already said, a spark alone will not start that engine, the spark has to be at the correct time.

Joe

JohnG28

I'm sure you're right Joe. I don't seem to be able to figure out why myself though, but I'll hopefully know a little more soon. Thanks for your help.
Stihl MS361, 460 & 200T, Jonsered 490, Jonsereds 90, Husky 350 & 142, Homelite XL and Super XL

JohnG28

Well I finally got an answer to my problems today! The thing has been in the shop for 6 weeks now and I've been a little pithed to not hear anything despite a couple calls. I do trust this shop and I'm glad I did now. Turns out there was a bad crank bearing. This would explain it dying at WOT, as well as why nothing else worked. Even better, they submitted it to Stihl and they are covering it despite the machine being two years old and long out of warranty. Not happy to wait so long but happy with the outcome. I almost questioned Stihl over this but they definitely made up for it. ;D
Stihl MS361, 460 & 200T, Jonsered 490, Jonsereds 90, Husky 350 & 142, Homelite XL and Super XL

Al_Smith

Well that would make sense because a sloppy crank bearing would wipe out the seal .Which BTW is the cause of many Stihl Ms 200T's dying on the vine .

What doesn't make sense is a failure for no older than what it is .

JohnG28

I agree, it makes no sense to me either. I didn't get close to tearing it down that far, wouldn't have even considered a seal or bearing. Thing can't have 20 hrs on it. Either way I am happy that Stihl is making it right. I'll be keeping that in mind on my 200t too, wasn't any slop when it was tore down couple months ago. BTW Al, you were right about them 200s, sweet little saws. Easy to see why they're so popular. Thanks all that helped me along with this undertaking.
Stihl MS361, 460 & 200T, Jonsered 490, Jonsereds 90, Husky 350 & 142, Homelite XL and Super XL

Al_Smith

I suppose one slips through cracks now and again .Stihl does make a quality product though .I'm sure it shocked them about as much as you to see a premature bearing failure .

JohnG28

So I left my blower in the shop over the winter, don't have much use for it through the winter months, plus I actually sort of forgot about it with busy weeks. Anyway, I talked to the shop couple days ago, turns out not only were the crank bearings shot buy so is the crank. She was spinning in a nice oblong pattern. That would explain the impeller side bolt coming off when cranking. They sort of forgot about it too it sounds like, but I didn't pry either so I guess no big deal. Sounds like I may get either a new unit or (preferably) credit to trade up for another model.
Stihl MS361, 460 & 200T, Jonsered 490, Jonsereds 90, Husky 350 & 142, Homelite XL and Super XL

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