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B&S 675 Series Camshaft Problems? Overheat? What did I do?

#1

l008com

l008com

I want to keep this brief but I also want to give you the full backstory.
I need help assessing what happened to this machine, and what it's current condition is.

This is a Craftsman Yardvac with a B&S 675 engine. It was in my neighbors yard never being used for 15 years or so, and one day he gave it to me.
I drained the gas and the oil, refilled both, and more or less was able to start it right up.
While it was running, I noticed some sparks flying out. I though this was just leaves on the muffler that were burning. But it kept going and now I think it was leaves all up around the flywheel obstructing air flow.

So the machine was running and running well for maybe 15 minutes to a half hour or so. Then is sputtered a bit, then died out. Kind of like it was out of gas, but maybe a little more abrupt. Also it was not out of gas. When I tried to restart it, at first there was no resistance at all. The engine would spin freely like the valves were stuck open. After a little while, suddenly the compression was back but still no starting. Eventually I took the engine head off and confirmed that both valves were moving fully and properly seating. But what I didn't realize at first was that they timing of the valves was way off. Intake-Compression-Power-Exhaust, thats NOT the order the valves were opening and closing in! After a little research, I decided that there must have been way more junk up under the plastic engine cover than I realized, and I must have overheated the engine, causing the plastic camshaft to melt.
It made sense!

Tonight I finally got the engine off and took the engine block apart.
Here's where I could use some second and third opinions to what I'm seeing.

First off, much to my surprise, the camshaft looks perfect. I thought the lobes were going to be partially melted and distorted but they look perfect to me!
full-camshaft.jpg

But it turns out, the small plastic gear on the crankshaft, that turns the camshaft, that might be where the problem is. it has a plastic notch that fits in to a notch on the crankshaft, and it looks like it is completely melted and smooshed. With that gear on the crankshaft, you can spin the gear easily without spinning the crankshaft. At first, that seems like the obvious cause of all this. But if it can spin THAT freely, wouldn't the valves not be opening at all? And why would just that one plastic nub melt, but none of the rest of the plastic in there?
crankshaft-driver-gear.jpg

Back to that camshaft, I said it was perfect but actually there is one flaw. The tip of one of the lobes does appear to have a little bit of damage. Not much though, I don't think this is causing any problems. But I'm curious what would cause that. Super hot valve rod maybe? Or maybe just a stuck valve rod causing the plastic lobe to be the weakest link? I'm thinking that with everything else fixed, this isn't a problem?
camshaft-with-slightly-mangled-lobe.jpg

Now lets talk about the oil. I changed the oil right before I started it up, so it had at most half an hour on it. I believe it was 5w-30 either full synthetic or semi-synthetic. When I cracked the crank case open, the oil that leaked out was very grey. I expected it to either be gold still like new, or brown like it was burned. But grey, that suggests metal wear. But what metal would be wearing? I drained the bulk of the oil before I removed the engine, I don't remember it being discolored but its possible I just wasn't paying much attention to the oil's color then.
engine-inside.jpg

So whats your take on all this?
The simplest solution I can see is that there was too much crap around the flywheel, the engine overheated, that caused the tab on the crankshaft gear (timing gear?) to partially melt and slip, but then somehow grab again, so now the valves are opening and closing but out of timing by a mile. Meanwhile during overheating, one of the valves stuck temporarily but eventually loosened up and started working normally again.

Am I missing something? Or making incorrect assumptions I'm not seeing?
The one good thing here, is that this is a yardcvacuum. So its going to be seeing probably 5 hours of runtime at most, per year. So if I've set the engine down the path of premature failure, I'll still probably get a lot more years out of it until then.
Right now my plan is to replace that crankshaft gear (timing gear?), and of course the engine seals, put it all back together and hopefully that fixes everything. Unless we come to some different conclusions in this thread.

Also, side note. I have the model number of the whole machine itself (247.77013.0) but I cannot find a model number ANYWHERE on this motor. It has a decal that says 675 series, but no numbers. And I need a number to be able to look up engine parts. How can I figure out this ENGINE model number?


#2

StarTech

StarTech

According to SearPartsDirect it is a Briggs 126T02-0521-B1 but that is not 100%.

But that engine has four different gears listed. And I have never seen a plastic crank gear until now. I just don't many of that series engines.

Careful look at the shroud as the number should be on it although could be rust covered.


#3

l008com

l008com

Where are you seeing four different gears, I'm only seeing one?

HOWEVER the one timing gear I'm seeing does not look like my timing gear. So I'm thinking thats not the exact correct engine.


#4

StarTech

StarTech

1736578765659.png
1736578901610.png
But as I said we need make sure which engine you actually have as Sears does link the wrong engines at times.

I am going back to bed as my back has eased up.


#5

l008com

l008com

I'm back over there now, so I can look for a model number on the engine. However I've looked everywhere and can't find anything except some stickers on the fuel tank that don't appear to be model numbers. Any ideas where I can find a model number for the engine so i can order up somer parts?

After a closer examination, I do think that little timing gear is the whole problem. Although I'm not 100% sure what caused it to melt/sheer, it does look like replacing it should get this thing back to perfect running condition.


#6

l008com

l008com

Here are two exterior photos of the motor if that helps. No model labels to be found :/

motor-2-mini.jpg

Motor-1-mini.jpg


#7

StarTech

StarTech

Pull the Red plastic and at the trim over the muffler. I have the model, type, and datecode hidden by the plastic cover. BTW serial too old to be looked up.
1736721965699.png


#8

l008com

l008com

Ok I pulled the plastic cover off, the metal cover and this is the ONLY numbers I could find. They don't appear to be the right format though. I scoured the rest of the motor and couldn't find any other numbers anywhere.

Attachments





#9

ILENGINE

ILENGINE

l008com said:
Ok I pulled the plastic cover off, the metal cover and this is the ONLY numbers I could find. They don't appear to be the right format though. I scoured the rest of the motor and couldn't find any other numbers anywhere.
Click to expand...
Look at the metal cover. There is a metal flange that sticks out over the muffler. the model info is on that flat flange. You can see part of the model number sticking out from under the plastic cover in Star's picture. Looks like 128 of 12B


#10

StarTech

StarTech

It will probably take some steel wool or 200+ grit sandpaper to buff out the area, just don't get too aggressive.


#11

Tiger Small Engine

Tiger Small Engine

l008com said:
I want to keep this brief but I also want to give you the full backstory.
I need help assessing what happened to this machine, and what it's current condition is.

This is a Craftsman Yardvac with a B&S 675 engine. It was in my neighbors yard never being used for 15 years or so, and one day he gave it to me.
I drained the gas and the oil, refilled both, and more or less was able to start it right up.
While it was running, I noticed some sparks flying out. I though this was just leaves on the muffler that were burning. But it kept going and now I think it was leaves all up around the flywheel obstructing air flow.

So the machine was running and running well for maybe 15 minutes to a half hour or so. Then is sputtered a bit, then died out. Kind of like it was out of gas, but maybe a little more abrupt. Also it was not out of gas. When I tried to restart it, at first there was no resistance at all. The engine would spin freely like the valves were stuck open. After a little while, suddenly the compression was back but still no starting. Eventually I took the engine head off and confirmed that both valves were moving fully and properly seating. But what I didn't realize at first was that they timing of the valves was way off. Intake-Compression-Power-Exhaust, thats NOT the order the valves were opening and closing in! After a little research, I decided that there must have been way more junk up under the plastic engine cover than I realized, and I must have overheated the engine, causing the plastic camshaft to melt.
It made sense!

Tonight I finally got the engine off and took the engine block apart.
Here's where I could use some second and third opinions to what I'm seeing.

First off, much to my surprise, the camshaft looks perfect. I thought the lobes were going to be partially melted and distorted but they look perfect to me!
View attachment 70375

But it turns out, the small plastic gear on the crankshaft, that turns the camshaft, that might be where the problem is. it has a plastic notch that fits in to a notch on the crankshaft, and it looks like it is completely melted and smooshed. With that gear on the crankshaft, you can spin the gear easily without spinning the crankshaft. At first, that seems like the obvious cause of all this. But if it can spin THAT freely, wouldn't the valves not be opening at all? And why would just that one plastic nub melt, but none of the rest of the plastic in there?
View attachment 70376

Back to that camshaft, I said it was perfect but actually there is one flaw. The tip of one of the lobes does appear to have a little bit of damage. Not much though, I don't think this is causing any problems. But I'm curious what would cause that. Super hot valve rod maybe? Or maybe just a stuck valve rod causing the plastic lobe to be the weakest link? I'm thinking that with everything else fixed, this isn't a problem?
View attachment 70377

Now lets talk about the oil. I changed the oil right before I started it up, so it had at most half an hour on it. I believe it was 5w-30 either full synthetic or semi-synthetic. When I cracked the crank case open, the oil that leaked out was very grey. I expected it to either be gold still like new, or brown like it was burned. But grey, that suggests metal wear. But what metal would be wearing? I drained the bulk of the oil before I removed the engine, I don't remember it being discolored but its possible I just wasn't paying much attention to the oil's color then.
View attachment 70378

So whats your take on all this?
The simplest solution I can see is that there was too much crap around the flywheel, the engine overheated, that caused the tab on the crankshaft gear (timing gear?) to partially melt and slip, but then somehow grab again, so now the valves are opening and closing but out of timing by a mile. Meanwhile during overheating, one of the valves stuck temporarily but eventually loosened up and started working normally again.

Am I missing something? Or making incorrect assumptions I'm not seeing?
The one good thing here, is that this is a yardcvacuum. So its going to be seeing probably 5 hours of runtime at most, per year. So if I've set the engine down the path of premature failure, I'll still probably get a lot more years out of it until then.
Right now my plan is to replace that crankshaft gear (timing gear?), and of course the engine seals, put it all back together and hopefully that fixes everything. Unless we come to some different conclusions in this thread.

Also, side note. I have the model number of the whole machine itself (247.77013.0) but I cannot find a model number ANYWHERE on this motor. It has a decal that says 675 series, but no numbers. And I need a number to be able to look up engine parts. How can I figure out this ENGINE model number?
Click to expand...
If you pull the engine shroud and it is packed full of grass, dirt, and debris, then it may have overheated. If the cam is messed up, then replace it while you are in there, and it is cost effective. These engines are generally not worth spending a lot on. Finding the model, type, and code is pretty basic information that is needed.


#12

StarTech

StarTech

Considering this unit as manufacture in August of 2008 I am surprised those paper labels has survive to date.


#13

l008com

l008com

ILENGINE said:
Look at the metal cover. There is a metal flange that sticks out over the muffler. the model info is on that flat flange. You can see part of the model number sticking out from under the plastic cover in Star's picture. Looks like 128 of 12B
Click to expand...

Its not there. That whole metal cover that goes over the flywheel has zero characters imprinted anywhere.Then inside doesn't have any surface rust, and it makes it much more clear that theres nothing imprinted anywhere. This is truly a ghost motor.

Attachments







#14

l008com

l008com

StarTech said:
Considering this unit as manufacture in August of 2008 I am surprised those paper labels has survive to date.
Click to expand...

I have machines from the mid 90s that still have their printed labels on there. This is the first machine I've ever come across that had no marking anywhere at all.


#15

l008com

l008com

Tiger Small Engine said:
If you pull the engine shroud and it is packed full of grass, dirt, and debris, then it may have overheated. If the cam is messed up, then replace it while you are in there, and it is cost effective. These engines are generally not worth spending a lot on. Finding the model, type, and code is pretty basic information that is needed.
Click to expand...

The cam looks fine, but the timing gear had some damage. There was some debris around the air flow areas. Not enough that I would think it would cause it to overheat, but maybe it doesn't take as much as I thought. It's certainly worth replacing that timing gear and seeing though.
... IF i am ever able to find out the engine model number.


#16

ILENGINE

ILENGINE

l008com said:
Its not there. That whole metal cover that goes over the flywheel has zero characters imprinted anywhere.Then inside doesn't have any surface rust, and it makes it much more clear that theres nothing imprinted anywhere. This is truly a ghost motor.
Click to expand...
It may be my imagination but it looks like you second picture has numbers on that muffler shield. I can make out what looks like 126T0 and a 62 in the corner of the lighter area of rust and looks like a 0 to the left of your thumb.


#17

StarTech

StarTech

IL I see the image too of the numbers pn an enlarged image just going have buff the area. They not deeply embossed so lightly buff the area.


#18

l008com

l008com

Now I'm going to have to go look at it again. In the photo, now I am starting to feel like I see something super subtle. But in person, with my own eyes, it looked blank. And I spent a long time looking over that shield again and again, looking at every speck of it. One more close look I guess and we'll see.


#19

StarTech

StarTech

Okay let's do this and by the owners manual for the YARD VACUUM. IT has a part list for the 126T02 engine.

https://www.manualslib.com/download/474499/Craftsman-247-77013-0.html

It say use crank timing gear 790345 but depending on the date code is might be 794388


#20

VRR.DYNDNS>BIZ

VRR.DYNDNS>BIZ

StarTech said:
According to SearPartsDirect it is a Briggs 126T02-0521-B1 but that is not 100%.

But that engine has four different gears listed. And I have never seen a plastic crank gear until now. I just don't many of that series engines.

Careful look at the shroud as the number should be on it although could be rust covered.
Click to expand...
First, an excellent job of reporting the digest of failure. two key points: 1) The cool down may have refused the timing gear to spring the valves while exploring valve motion, usually without compression so motion would not be hindered by other than valve springs. 2) The cam gear also may have failed to maintain position on the cam plus the cost is minimal. Also the dark color indicated it was very hot. I strongly suggest it's replacement. If by now you do not have a good lead on the needed part numbers, repost:


#21

l008com

l008com

Finally! I have the number! To my plain eyes, there were no numbers imprinted on that sheet metal flywheel cover. But people insisted it was there. So I put a round wire brush on my drill and scoured it down to bare metal and wouldn't you know it, some barely visible numbers started to reveal themselves.

At that point, you could see them, but not well. So I got a few drops of white paint and smeared it all over the flap of metal. Then I wiped it off, and the paint stayed in the holes. The end result:

engine-number.jpg

FINALLY! I can order the parts I need and move on!


#22

StarTech

StarTech

So it turned out to be the engine I post back in post #2. According the date code it use the 797521 which replaced the 795755; unless, you a woodruff present. I can verify that the 797521 is a metal gear as it been laying in my inventory since 7/2014.

Appearly Briggs did try a plastic gear and had to supersede it to a metal due to failures.


#23

l008com

l008com

Yup thats the same number i came up with on the B&S site. That makes me wonder if mine failed due to overheating, or maybe it just failed, all on its own. Plastic can be brittle, but then again if its always soaked in oil and never sees ANY UV light at all, it probably won't get brittle too fast. It is tempting to replace the camshaft too just so I never have to open this thing up again. But I don't think I will, it should be fine.


#24

kbowley

kbowley

If it were me and I went through the trouble of tearing the engine down. I would replace the cam along with the gear. It isn't expensive and is worth the peace of mind.


#25

l008com

l008com

If this were a lawnmower or a snowblower I probably would. But it's a yard vacuum that probably runs for all of 3 hours per year. So I'm just going to cross my fingers and keep the old cam.


#26

ILENGINE

ILENGINE

l008com said:
Finally! I have the number! To my plain eyes, there were no numbers imprinted on that sheet metal flywheel cover. But people insisted it was there. So I put a round wire brush on my drill and scoured it down to bare metal and wouldn't you know it, some barely visible numbers started to reveal themselves.

At that point, you could see them, but not well. So I got a few drops of white paint and smeared it all over the flap of metal. Then I wiped it off, and the paint stayed in the holes. The end result:

View attachment 70406

FINALLY! I can order the parts I need and move on!
Click to expand...
That picture reminds me of another person that claimed there was no model number on his engine, and to prove it posted a perfect crystal clear picture of the model number. And he still didn't realize that he had taken a picture of and posted the model number.


#27

l008com

l008com

Lol, well in my defense, my model number was literally invisible before i sanded it and painted it :p


#28

StarTech

StarTech

l008com said:
Lol, well in my defense, my model number was literally invisible before i sanded it and painted it :p
Click to expand...
But we thought you were Superman with x-ray vision.:LOL:

Seriously this is what we have to deal with on a regular basis. Not as bad as those with missing decal stickers. These I tend to stamp model/spec into the crankcase if I work on the engine. It and my recording the info in the customer file has saved me many times.

Kawasaki an Kohler are two worst ones for missing or faded out decals.


#29

S

slomo

Must say the white paint is brilliant. I was worried when you said wire wheel. I would of tried a rust converter first, once I saw the numbers LOL. Or a brass bristled wheel. I use an oily red shop rag to highlight those numbers. That paint leaves zero guess work. Nice job.


#30

O

Oddjob

slomo said:
Must say the white paint is brilliant. I was worried when you said wire wheel. I would of tried a rust converter first, once I saw the numbers LOL. Or a brass bristled wheel. I use an oily red shop rag to highlight those numbers. That paint leaves zero guess work. Nice job.
Click to expand...
I collect and use old woodworking tools, so I have some experience bringing back serial numbers and etches on saw blades. I gulped when I read that Yardwork John had used a wire wheel. But have to admit, his finished product is fabulous! I would have used 300 grit wet/dry sandpaper on a flat sanding block with mineral spirits as a lubricant, and slowly and gently tried to rub just the corrosion away and not the numbers. Then if necessary, I use a piece of soft white chalk to highlight the numbers.


#31

B

bentrim

It has been many years ago, but I had a similar issue with a pressure washer. The customer stated it just quit. After taking the base pan off found the crank gear had sheared the "key" off and did not drive the cam. Talked with Briggs and they stated the gears failed especially on pressure washers. But don't remember the replacement but think it was metal.


#32

l008com

l008com

For those impressed with the "paint" technique, i got the idea from Adam Savage, the mythbuster. He used this technique to make new metal things look old and used - when making movie props in his previous life. And then more recently I've seen people use the same technique to highlight the sizes on their sockets and wrenches. Which is something I would LOVE to do, except I have so many sockets, no way am I taking the time to wipe paint on and off each one!


#33

H

Harwill

To achieve a result similar to paint without the mess use a white tire marker stick. Much easier to read numbers on sockets and such.


#34

l008com

l008com

I like the permanent-ness of paint though. And honestly i'm very tempted to do this to every tool I own that has sizing imprinted on it. BUT do I really want to spend all that time doing it? Mehhhhh. If I ever have a slow week, maybe ill do it.


#35

R

RevB

StarTech said:
It will probably take some steel wool or 200+ grit sandpaper to buff out the area, just don't get too aggressive.
Click to expand...
Are these stamped characters? If so the old pencil rubbing and paper tracing method might reveal your data....


#36

F

farmerdave1954

Be smart. Change the camshaft while you are in there. Take advantage of the experience on this forum and learn from other people's mistakes. Don't ask me how I know.


#37

B

Bud57

l008com said:
Ok I pulled the plastic cover off, the metal cover and this is the ONLY numbers I could find. They don't appear to be the right format though. I scoured the rest of the motor and couldn't find any other numbers anywhere.
Click to expand...
The engine number should be right on the flywheel cover right on the piece that is over the muffler you my need to use steel wool to remove the rust the numbers should be stamped there


#38

l008com

l008com

So I've replaced the timing gear and a few other things. But I haven't tested the motor yet, the machine is still all apart, its going to take me a few more hours to get it all reassembled and ready for a test.

I'm hoping everything goes great, and I get a bunch of years out of this machines.
But if I don't, and somehow the engine is dead, I was looking at replacement engines as my PLAN B. HF does have one vertical shaft engine, but the output shaft is totally different.
Thats likely going to be the case for every lawmower engine. Does that mean I'm out of luck for this thing? Is the only engine thats going to work, going to be the original motor?

The impeller on this yardvac is not keyed, It is tapered to match the shaft and you just crank it down real tight. Meanwhile, this is what the HF predator looks like: https://www.harborfreight.com/media...58f04aec81e7c5e0be4c56edf041/7/2/72851_W4.jpg


#39

StarTech

StarTech

Even the Briggs replacement engine doesn't have the taper crankshaft.


#40

l008com

l008com

So what do you do? Is there really no way to replace the motor if it was dead? Or would I have to try to transplant this one's crankshaft into a different motor?


#41

ILENGINE

ILENGINE

it looks like from briggs the 126T02-0521-B1 gets replaced with the 126L02-1005 but you have to transfer the flywheel from the original engine to the new engine and remove the 691921 rope starter and 694849 crankshaft from the replacement engine and install the 392259 rope starter and 694478 crankshaft. But it appears that the 126L02-1005 has been replace with the 104M02-0182-F1 So I don't know what the conversion would be for that engine


#42

l008com

l008com

Well then fingers crossed I really don't need a new engine! I suppose the best option if I did would be to buy the harbor freight engine and bring it to a machine shop and see if they could mill the shaft somehow to make it fit


#43

l008com

l008com

Update:

I fired the machine up today and it started pretty easily and seemed to run well. I let it run for about 15 minutes. It was very cold out today, about 32°. I had sprayed fogging oil in the cylinder so there was a normal big cloud of smoke at first, but that went away after a couple of minutes.

The machine seemed to run great, no problems. HOWEVER when I shut it off, it was smoking. Not from the exhaust, the thing was just oozing smoke. Like it was running hot. Is this normal? The only thermal control is the spinning flywheel and I'm 100% sure theres no crap jammed up there at this point. So on a cold day like this, the thing should be running ice cold.


What do you make of that? I don't recall ever seeing my lawnmower smoking like that after warming up


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