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Hello all.
I did a search to see if i could find anything.
I have a troy-bilt 21" push mower with a Briggs & Stratton 675engine model #126t02-0675-b2

I was mowing and hit something and the engine stopped. I tried to restart (pull start) and it turns but won't catch. I did some research and found a very common cause is the flywheel key shearing so I took it apart and checked. it looks fine. no marks or ridges or anything in it. Before removing the flywheel, and after draining the gas and unplugging the spark plug wire, i manually turned the flywheel. While doing so I watched the gap between the wheel and whatever that electrical part is (yes I am a complete noob but I can read and like to at least try before sending it in.) and saw no difference in the gap nor did I hear any scraping sound.

I had mowed the lawn out front the day before with no issues. The blade is balanced and there were no vibrations. I figured since I have it apart i'd change the oil and replace the plug and filters anyway. However, as the mower was working perfectly fine the day before I suspect there is more tot he issue then that. I even let the engine sit overnight before trying again in case I'd flooded the thing. No luck. soooo....not sure what to do at this point. I am going to probably do a complete tear-down anyway just to see what it looks like and If I need to, send it to a shop to put back together.

However, any ideas on what is preventing the starting?

Sincerely,
Jeff

Hello Jeff & WELCOME to LMF...

First thing to do, after checking the flywheel key, ...
See if you are having fuel problem... spray starter fluid into the carb, see if it starts up... :smile:KennyV

will do. I removed the engine from the frame and have it on some wood planks. I assume I should put the flywheel back on.

Off hand, if it is a fuel process why would it have worked the day before? do you suspect the jolt somehow snapped a fuel something?

Secondly. how do I start it without the pull starter?

I would say put everything back together before trying anything including putting the blade on and starter rope. How in the world can you try to start it when it is siting on wooden blocks all apart ?

no ideal. i mean i didn't know if i assembled the motor and fuel tank and mounted to a block of wood or something I could start it by, and I'm guessing here, trying to spin the flywheel real fast and see if it starts.

hsnopi said:

no ideal. i mean i didn't know if i assembled the motor and fuel tank and mounted to a block of wood or something I could start it by, and I'm guessing here, trying to spin the flywheel real fast and see if it starts.

Click to expand...

No ... that won't work...
You also must have the blade attached, as it is necessary & acts like a flywheel to give the engine the needed inertia to continue ...
Put it together and it will make looking for the problem MUCH easier... :smile:KennyV

listen to these guys.....and reassemble it...then we can troubleshoot in logical order:smile:

your armature air gap is .010-.014

hsnopi said:

no ideal. i mean i didn't know if i assembled the motor and fuel tank and mounted to a block of wood or something I could start it by, and I'm guessing here, trying to spin the flywheel real fast and see if it starts.

Click to expand...

Sure sounds like a good way to lose a finger or two if it started It sound like you had better be bringing this to someone who knows what they are doing before you hurt yourself. One finger will cost you more then the whole mower or the repair job.

I don't want to hurt anyones feeling on this forum and realy enjoy helping someone fix their mower and that is what this forum is all about. But some of the things I read on here the person just has no Idea what they are doing and it would be better to bring it somewhere to get it fixed right. This last person if was spinding a flywheel by hand to start it and it just fired once could get hurt.

i appreciate the concern and my feelings aren't hurt. you put that very tactfully. However, you will not that I asked before doing anything like that. I do understand these a re dangerous machines and not legos.

STATUS::
So I reassembled it, mounted it back to the frame, hooked up the starter cord, put on the blade, added oil, added gas then reconnected the sparkplug.

I pulled the starter cord slow a couple times to make sure it wasn't tight and to get a little fresh oil into the whole system. then I started it. I started but it seems to now be running slowly and has a slight vibration it didn't have before.

My thoughts...
-Timing is somehow still off. not sure how to fix this yet.
-Crankshaft is slightly bent though I can't see how unless it's at the lower end under the deck.

I checked the blade for balance and it's fine. No rotation on the horizontal.

So I suppose my next step is to check how to check timing and if it isn't that then I am guessing I bent a shaft.

Opinions?

reynoldston said:

I don't want to hurt anyones feeling on this forum and realy enjoy helping someone fix their mower and that is what this forum is all about. But some of the things I read on here the person just has no Idea what they are doing and it would be better to bring it somewhere to get it fixed right. This last person if was spinding a flywheel by hand to start it and it just fired once could get hurt.

Click to expand...

I'm sure most will not get their feelings hurt....
Sometimes jumping in head first is a big mistake... having the sense to ask questions Before jumping in... usually comes from experience... from making big mistakes...

A 3 hp engine can hurt you, even kill you. As the size increases that possibility also increases.... Somewhere along the line each person has to evaluate their personal level of knowledge and ability to recognize the dangers they expose themselves...

I not only remember hand crank engine days... I have a tractor with a crank & an electric starter, Every now and then I will use the hand crank, but I recall a lot of other folks with broken arms, so I also remember the correct way to use a hand crank.... That little bit of trivia is becoming lost with electric starters...

Some learn by asking questions... some by reflecting during convalescence, and some do not ever learn...

But your right.. .doing things may be more dangerous than they seem... I don't think anyone will actually get their feelings hurt by having that pointed out now and then... :smile:KennyV

hsnopi said:

....
-Crankshaft is slightly bent though I can't see how unless it's at the lower end under the deck.



Opinions?

Click to expand...

That is exactly where it will bend when you hit something with the blade...
To check if that's what happened... REMOVE the spark plug and rotate the blade while watching the distance in reference with the mower deck... if there is any variance... it's bent.!
If it is bent not a big problem, you can easily bend it back, post back with what you find... if needed I'll post a video from youtube on straightening a bent crank shaft... :smile:KennyV

i'll go give that a shot now. it's only a slight vibration. would that also account for the slow engine speed?

and thanks for the quick response

a lot of videos are saying the crank shaft can't be bent back. Can you post that link?

A slight vibration CAN interfere with the carb and governor.... not having the governor linkage properly hooked up is a more likely cause... :smile:KennyV

what did you hit anyways??

hsnopi said:

a lot of videos are saying the crank shaft can't be bent back. Can you post that link?

Click to expand...

Sure... Here it is...: ‪Brigg's $ Stratton bent crank repair redneck style‬‏ - YouTube

I completely agree with what this guy says... Not the most recommended method but, pay attention and if it wont work ... you will have to replace the crank... engine ... or mower...
:smile:KennyV

apparently i hit a stump I didn't know was there. I've since removed it.

So, I took a 2x4 and a nail. I unplugged the spark plug wire, tilted the mower over, removed the blade, lined up a nail tip, embedded int he board, with the center of the shaft. I then rotated the shaft and saw no variance in the position. However, I did notice the blade mount is messed up. the 2 knobs that center the blade are gone and the X in the center has 2 legs sheared off.

I remounted the blade and tried to start it. it was hard to start. finally started and still vibrated and ran slow. I will look into the governor linkage. I have an idea what that is but not positive. However, until I get a new blade mount I don't want to run the thing again. The idea of a blade shooting out from under the mower sounds distinctly bad. Sadly, the local Sears parts Direct is closed already.

i will say this is a single speed mower. Further, there was a plastic piece which acted as a lever.

ok i downloaded the freaking illustrated parts guide...
and of course it doesn't have that part.
ok found the part.

the Vane Air Autochoke system connects to the thermostat. However, it is an odd looking connection. it just kind of wraps around. It seems very loose so I am wondering if that might be it.

Illustrated Parts Lists | Repair Parts & Maintenance Products | Shop | Briggs & Stratton
part 291 and 1386

the governor is your throttle linkage control and maintains a certain rpm....driven by the cam gear...it could have been damaged so that your rpms wont rise and stabilize..

some videos.
it running
http://www.hsnopi.net/03.mp4 24mb

the shaft and blademount (sorry aout the quietness
http://www.hsnopi.net/04.mp4 31mb

the engine and vane autochoke and other linkages.
http://www.hsnopi.net/05.mp4 48mb

thanks.

awesome video quality!...i need to learn how to do that!:thumbsup:

a new blade hub mount may solve the vibration...if the blade's not flush and even....it can cause imbalance

ok, i will order one. gonna get a new air filter and plug while i'm at it.

This may shock you but i took those videos on my Smart Phone. Samsung Galaxy (At sprint, the fascinate in verizon and I forget the AT&T version)

far out!..i have the iphone 4....i have to experiment now:biggrin:

Jeff... Might I recommend you reduce your video file size... You do not need 23.5 meg for a 55 second video clip....
I'm not going to do the 431meg... I can go to netflix if I want to download half a gig of video...

I shoot video with my phone also... but I will edit and reduce the file size before posting...

Back to the mower, replace the blade adapter and check that the blase is true, not just balanced... KennyV

it's 43 megs. not 431. i apparently missed putting in a space between the name and the file size definition. if 41 is still tooo large lemme know and I can try to figure out how to reduce it and still be able to get any detail out of it.

since i was already messing with it i got the tuneup kit, which oddly seems cheaper than the parts individually, and ordered a new mount which will be in tomorrow.

so
i got a new spark plug, gapped it and put it in. drained the old oil, put in fresh, fresh fuel with stabilizer, new air filter, new mount adapter and remounted the blade, which i again checked for balance. now it won't start at all. Even after several pulls. soooooo....gonna have a friend help me check the new spark plug for a spark. if it has spark, which I suspect it does, not sure what to do next. i still need an answer on that autochoke vane in video 3 and make sure that is assembled correctly.

so, that leaves timing which as far as I know isn't even adjustable.

so i have discovered the vane autochoke is also referred to as a pneumatic governor. i still have YET to see how those two parts are connected. or rather, how they should be connected.

ok....you really needn't put fuel stabilizer in a mower unless you plan to park it for winter.....how much did you use?

i used what came int he kit. so that's good to know for next time.However, I figured out, through BRILLIANT deduction, why it wouldn't start. After the tune-up I forgot to reattach the spark plug wire. :confused2:

So, it is running, it just seems to be running slow now. I think that is a matter of the carb tuneup. it still seems to vibrate though.that might still be the timing.

where i cann buy a blade adapter for a BS 675 engine ? thanks