# Craftsman Briggs & Stratton: No Start, and now 50-60% Power



## Colt Hero (Apr 23, 2007)

Two-year old 21" Craftsman "675 Series", "Multi-Cut" Push Mower with 6.75HP Briggs and Stratton Engine. Model # 917-388450. Paid less then $200 new April 2008. Rip-cord start. No electric start. Also no oil filter, no gas filter, not even a primer bulb. No throttle control. No carbeurator adjustments.

Currently, it is only running at what sounds like about 50-60% power - just enough to cut the grass with a sharp blade, but that's it.

A little history: 

First of all, gas has NEVER been left in this mower across seasons. I always run residual gas out – but I also have never used any of those storage conditioners (Stabil?)

This mower cuts my yard (1/4 acre), but it also cuts a land lot I own (1/2 acre). The first season (spring 2008), I was cutting some high grass around a pine tree at the lot when the mower struck a brick hidden in the grass. The brick shattered, but not before it stopped the mower dead in its tracks. The mower DID re-start that same day (after waiting a while, IIRC) and it went on to cut the rest of that season OK, but there was now a "clinking" noise when pulling the ripcord that I didn't remember hearing when the mower was brand new (and maybe it was a little harder to start now, too). 

2nd season, mower cut fine again, but I could sense a slight lessening of power (based on engine sound). Clinking noise with the ripcord pull continued and starting seemed a little harder (although it always started). 

This season, after changing the oil, sharpening the blade, cleaning the air filter and spark plug, the mower would not start AT ALL (for the first cut of the season) unless I dunked the spark plug in fuel and quickly inserted it - then the engine MIGHT start, but would always immediately stop. So I removed the carbeurator and sprayed it liberally with carb cleaner. I also checked the flywheel key (although the mower DID cut last season), because of the brick two seasons ago. Looked OK – flush and square. Putting the nut back on, I wasn’t sure what the torque was – so I looked up the numbers on my previous Scotts B&S engine repair manual. It gave two numbers (based on model): 60 ft-lbs or 100 ft-lbs. I had read on the web someone recommending 125 ft-lbs, so I went with 100. But I couldn’t get the torque wrench to click at this setting. I think this torque was too much because pulling the rip-cord resulted in the cord failing to retract, plus lots of noise from the flywheel. So I backed the nut off and started re-torquing until I couldn’t get the wrench to click anymore – which resulted in 60 ft-lbs. Now, the engine runs (and sounds smooth enough), but it’s only running at 50-60% power!

Is an improper torque on the flywheel nut causing this lack of power, or do I have other problems? You might say the engine has lost compression, but it ran at probably 90% power on the last cut last season. All that has changed THIS season is the new spark plug, the torque on the flywheel nut, and the carb cleaner in the carbeurator.


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## glenjudy (Aug 26, 2006)

I'm curious when you say 'no primer bulb'.
These units have primer bulbs on the plastic air filter back plate that affixs to front of carb.

Did you only remove the carb and spray the outside of it, or did you dis-assemble the carb and spray clean?

Two things peculiar to the model is; 1) the bowl nut is the main jet and the orifices need to be thoroughly cleaned, they are small and I need to wear my glasses to see them all, 2) you often need to put two gaskets between the air filter backplate and the front of the carb for the primer bulb to work. (if the backplate was removed)
HTH


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## Colt Hero (Apr 23, 2007)

No - no primer bulb. There's a circular plastic "blank" where the primer bulb WOULD be if it had one. This mower is "primerless, easy start" - which I didn't like when I bought it (because my Scotts 6.5 HP B&S HAD a primer bulb and it makes starting easier), but I bought it anyway because I needed a new mower quickly and I had a $40 store credit to use. Wasn't a bad deal - I think I paid $160 after the smoke cleared for 6.75 HP engine, bagger, high-back wheels, but not motorized. Never started as easily as my Scotts, though (which was a 1/4 pull - maybe).

I took the pot off the bottom of the carb and sprayed into every orifice I could see with the carb OFF the mower. This carb is weird - it doesn't appear to come apart, except for the pot at the bottom. It really looks like one piece - no screws anywhere (and no adjustment capability, either). Cleaning the carb, I believe, was my main problem (even though it LOOKED pretty clean) because after pulling the rip cord about 100 times initially, the carb looked pretty dry (gas WAS flowing from the tank out the hose when I disassembled, so it wasn't a tank issue). I probably shouldn't have touched the flywheel since the mower ran last season, but I was curious with the non-starting that maybe the key had finally failed. Now I'm wondering if 60 ft-lbs is correct on that nut (although the engine SOUNDS OK - just low rpms). 

The gasket between the carb and the back of the air filter box is currently ripped. It got this way from manipulating the carb in my hands. When I put the air filter box back on, I just made sure the screw went through the gasket hole (which is still intact) and the tear (just below the left-side hole) was upright as the filter housing was tightened up against it. This couldn't be causing much of an issue, could it?


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## edward spens (Aug 5, 2007)

I had a guy that gave me one of these low com. machine, had to change the head gasket. Had to do this each year


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## geogrubb (Jul 28, 2006)

You have a partially sheared flywheel key, remove the flywheel, replace the key, turn the flywheel counter-clockwise against the key before you start tightening the flywheel nut as the force from hitting the brick will have distorted the flywheel some, tighten to flywheel nut to torque spec 60lb wait 5min then pound on the socket holding the flywheel nut and torque again, repeat again until the torque is set without change. Put it back together and you should be good to go. To lock the engine to remove the flywheel, remove the sparkplug, insert a screwdriver, angled slightly, and turn the engine until it is at the bottom of the stroke, fill the cylinder with a small rope, like pull start rope, as much as will feed easily, turn the engine and the engine is stopped, when finished back it off a little and remove the rope. Have a good one. Geo


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## Colt Hero (Apr 23, 2007)

How do you know the key is partially sheared? Right now, after removing the nut, the key is flush and square in it's bore immediately under the nut. It's located slightly off the center line of the pull holes and embossed arrows pointing to them. At first I thought this might be the problem, but that's the way it is (I think). 

I'm not sure I follow you on a couple of things:

1.) "Repeat until the torque is set without change": I'm torqueing to 60 ft-lbs each time, or am I changing the torque setting each time?

2.) "fill the cylinder with a small rope, like pull start rope, as much as will feed easily": Where? - Through the spark plug hole?? I was putting the handle of my breaker bar into the fins of the flywheel to keep it from moving, but this is tricky because I had to hold the breaker bar with my left hand while turning the torque wrench with my right. Not ideal. My B&S CD-ROM manual said to use a strap wrench, but I doubt that would be any better than my method.


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## RKDOC (Jun 20, 2006)

Putting a bar between the fins you have a very high chance of breaking the fins. Then you have to replace the flywheel. Placing the rope in the spark plug hole works very well. The strap wrench works well also.


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## dj722000 (Oct 29, 2008)

First off, when you use a pry bar or any means to wedge the flywheel from moving, your putting alot of pressure on one or two fins. This is a big no no as you can and will break a fin and your mower wont run or you wont want to be around it if it does run. (Shrapnell when the flywheel explodes from out of balance) A strap wrench is very effective as it puts pressure on all fins. As far as putting pull rope cord (Shoestring, whatever fits) into the cylider, GEO means to put it through the spark plug hole and leave a little bit out. Turn engine over until it stops. This will be firm enough to get your torque value.

As far as tapping on the flywheel nut, torque the nut to 60, wait 5 mins, tap on the socket while it is on the nut, leave torque wrench at 60 and it may turn a little before clicking again. All your doing is making the flywheel slide further down the shaft under pressure from hitting the socket, obviously you will have to torque it as the nut loosened a little from the flywheel sliding further onto the shaft.

But I agree, it sounds like something is wrong with the timing.


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## geogrubb (Jul 28, 2006)

Colt Hero;
Check the flywheel key pictures below, the first photo shows what looks like a good key from the top, which is what you see while looking down at the flywheel, however, look at what actually happened when the flywheel was removed in the second photo. Have a good one. Geo

Looks good here!









OOOOPS!


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## Colt Hero (Apr 23, 2007)

I'm logged in but I can't see the photos. There's a box with an "X" in it, but nothing happens when I click on it.

Regarding the breaker bar in the flywheel vanes - I didn't like it, either. It DID occur to me that something could break as I was torqueing the nut down.

String in the spark plug hole doesn't seem like it would work, but I'll try that (or get the strap wrench).

How about a carbeurator problem? Is it possible it's just not getting enough gas? Could it be the float inside (or the valve the float controls)? Maybe run some cleaner through it first before tearing into the flywheel? I know it COULD be the flywheel, but the mower ran last year on it's last cut without incident. Between now and then it's just been sitting.


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## geogrubb (Jul 28, 2006)

Colt Hero said:


> I'm logged in but I can't see the photos. There's a box with an "X" in it, but nothing happens when I click on it.
> 
> Regarding the breaker bar in the flywheel vanes - I didn't like it, either. It DID occur to me that something could break as I was torqueing the nut down.
> 
> ...


Try these links maybe they will show for you. Have a good one. Geo


Looks good here!
http://i190.photobucket.com/albums/z120/geogrubb/Flowers003-1.jpg

OOOOPS!
http://i190.photobucket.com/albums/z120/geogrubb/Flowers004.jpg


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## Colt Hero (Apr 23, 2007)

Couldn't see the pics at work earlier today, but they showed up fine from home. I've seen that happen at work before - but logging in usually fixes is. Anyway, thanks for the links to make sure.

The key on my mower is not that shape (I don't think). From the top it just looks like a square - the lower part shown in the first pictuer (not a "T" shape). But I'll look at it again. Maybe I missed the other part of it.

I won't be able to open the mower up again until at least Friday. Maybe I can post some pictures...


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## XXX#40 (May 12, 2007)

Take the (Walboro) carb back off and buy a needle and seat set, clean and blow out the carb again and re-install.


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## geogrubb (Jul 28, 2006)

Colt Hero said:


> Couldn't see the pics at work earlier today, but they showed up fine from home. I've seen that happen at work before - but logging in usually fixes is. Anyway, thanks for the links to make sure.
> 
> The key on my mower is not that shape (I don't think). From the top it just looks like a square - the lower part shown in the first pictuer (not a "T" shape). But I'll look at it again. Maybe I missed the other part of it.
> 
> I won't be able to open the mower up again until at least Friday. Maybe I can post some pictures...


That key is from a Tecumseh and is just for reference to show how deceptive they can be without removing the flywheel. Have a good one. Geo


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## rick-l (Sep 16, 2009)

Colt Hero said:


> I also checked the flywheel key (although the mower DID cut last season), because of the brick two seasons ago. Looked OK – flush and square.


What does flush and square mean? Flush as in sheared off? Does the key protrude and still locate the flywheel on the crankshaft?

Did you poke some strands of copper wire through the float bowl nut metering holes?


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## Colt Hero (Apr 23, 2007)

Looking at the linkage that runs from the rear of the mower (handle side) toward the front to the carb's engine-side butterfly, as the mower is running this linkage is constantly pushing and pulling this butterfly back and forth (definitely not right). If I push on the linkage (toward the handle end), to force it to a position (which pushes a horizontal metal rod on a pivot that goes into the back of the engine), I can get the engine to rev up to where I think it should be, but there's a constant resistance to get it back to where it "wants" to be. As far as the black plastic "arm" that runs across the top of the engine (and controls the outer butterfly on the carb) - when running, it is fully outward toward the spark plug or front end of the mower. If I pull it inward, the engine doesn't seem to like it. This appears to be working properly (I guess).

Now for the pictures ... never done this before ...

CAN'T GET PHOTOBUCKET TO WORK! FOR SOME REASON, CAN'T SEE THE STUPID LOGIN CODE (AND THE AUDIO CODE IS SO GARBLED IT'S UNINTELLIGIBLE). TURNED POP-UP BLOCKER OFF, MADE SURE ACTIVEX ENABLED, GOT THE LATEST IE LOADED, DON'T KNOW WHY THAT WON'T WORK. I'll try again later. 

Anyway, 

Rick-I: "Flush and Square" means after the flywheel nut is removed, the key is immediately below it, snug against the nut's bottom side, flush with the surface of the flywheel and square in shape in its bore (not shattered or splintered). The key cannot protrude upward because the nut is above it. And since it is apparently pristine in its bore, it must locate the flywheel, right?

And no - I didn't poke any wires through the float bowl metering holes - but that's a good idea that I could try (although I really think the problem is with the governor right now). All I did was spray the heck out of it, forcing fluid through any orifice I could see (and they're pretty tiny orifices).

XXX#40 - what is a "needle and seat set"? The white plastic "toilet seat" float pivots on a 3/4" long metal "bar" and pushes/pulls what looks like what you might be referring to as the "needle". Reminds me of a miniture version of those weights that swing on a line and make designs in sand at the Science Museum. What would the "seat" be?

If I have a problem with the governor, is that going to require more dismantling of the engine to repair?


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