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Briggs 28Q700 - Flywheel issues....


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08-28-12, 04:32 AM   #1  
Briggs 28Q700 - Flywheel issues....



Apologies for not having the exact type #.....however my problems are 'general'.
Older snapper lawn tractor 155LTH 42BBV (15.5hp B&S horizontal engine),.....solenoid and starter died. Diagnosed with meter.
Replaced starter and solenoid. Now passes proper current..etc.

Ring gear (plastic) had a LOT of teeth missing so I am attempting to replace it with the new aluminum gear.

Issues:

1 - Cannot get flywheel off. Used puller, broke bolts,...used puller some more. Used knock tool hitting it with hammer with prybar underneath..etc. Currently I am spraying it daily with PB Blaster and hoping for some magic to happen.

2 - And this is where my memory is sketchy. I feel like I was previously able to rotate the flywheel by hand endlessly,...meaning 360deg....720deg....it would continue to rotate.
NOW...it seems to rotate only about 350 +/- degrees before it 'hits' something. I can feel/hear compression...etc. The plug is still in,....but this definately is like a 'clunk' when it reaches its rotational limit.....I can rotate back and forth no problem....but simply not endlessly.
I am not sure if this is normal. Something tells me this is bad.

I have not 'beaten' on the flywheel or crank with a 10lb hammer at all....in fact I have been very careful not to use the 'hammer' approach much at all and haven't hit the flywheel itself with anything other than a rubber mallet (and not that hard either).

Any insight? Advice? Thoughts?

Thanks!

 
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08-28-12, 10:54 AM   #2  
Are the bolts from the puller in to deep??

 
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08-28-12, 12:14 PM   #3  
Abolutely,...in all the way.
The crappy steel bolts though were no match for the torque I applied,...

I might get some grade 8 bolts...and try that. Somethin tells me though that this will take more than simply torque on a puller. Even with a 3 foot bar...

 
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08-28-12, 04:39 PM   #4  
That is the reason the flywheel won't turn, the bolts are in to far,,,or am I lost??

 
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08-28-12, 06:46 PM   #5  
If the bolts are in too far, they will hit things on top of the engine, thus your problem of not turning 360 degrees.

To gt the flywheel off, put a lot of pressure on the puller and give the flywheel a sharp blow from a regular hammer. Not so hard as to break it, but to give it a good shocking blow. A rubber mallet will only make it giggle.


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08-28-12, 08:29 PM   #6  
If he hit's the flywheel the magnets will come loose and they will need to be expoyed back on. Look dude when you get a steady amout of pressure on the flywheel puller (I use a harmonic balancer pulley) hit the center bolt that is applying pressure to the top of crankshaft, one good whack and it will come loose and you may have to apply more pressure on it, whack it again and it should come loose, but don't hit the flywheel itself. Good luck.

 
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08-29-12, 12:00 AM   #7  
That's precisely why I said don't hit it so hard that you break something. Briggs recommends that you not hit the flywheel, so I'm not going to argue it too hard, but I am telling the OP how to get a stubborn flywheel off. Done it many times. As always, check for damage just in case. Never had it make magnets come off.


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08-29-12, 06:35 AM   #8  
Just trying to help Cheese.

 
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08-29-12, 07:40 AM   #9  
THANKS!

So....taking your advice,...and 1 whack! And it popped right off.
There were no thrown magnets,....I cleaned it up....put on the new ring gear...put it back on....and....no joy.
Here is what it is doing:

1 - Starter motor 'tries' to start it,....but only briefly...it spins up, engages the ring gear and rotates the engine maybe 1-1.5 turns before stopping,...essentially acting like it only has enough 'oomph' to turn it a little bit. note:* I kept starter motor gear that came with starter...I did not replace with starter motor gear that came with ring gear. They have same #of teeth,...I will say though that they are slightly different in 'tooth shape'.....not sure if that could be source of issue? Doubt it.
- With meter, the wire to starter is supplying 12.5v when attempting to start. So solenoid is good.
- Battery has fresh charge and shows 12.5v as well......after awhile of trying to start it...battery was at 11.9v

2 - After the initial attempts (maybe 4-5times) of trying to start it,...eventually the starter would engage the ring gear but wouldnt turn the flywheel at all.......

3 - When the flywheel would turn, in the initial attempts to start....the engine made NO sound like it was trying to combust or start.
- New plug
- New fuel filter


So...I guess now I need to start going down the long list of diagnosing the whole spark,fuel,compression thing. A lot to learn,....will be spending a good bit of time on google today!
I know good info exists on testing spark,....carbs...etc..etc.

One thing I read about was trying to start the mower without the plug in and see if it rotates the flywheel. I am not sure what doing this proves,......thoughts?

Any other, overall thoughts? Tips or tricks?
FYI - The mower came with the house, and was definitely not maintained well. It ran fine for a few months,....then this all sorta happened at once. Wouldnt start....solenoid/starter motor followed quickly.

Note: Someone suggested valve lash as a very likely culprit....

 
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08-29-12, 10:59 AM   #10  
Yes, adjust the valves. The clearance is too much, disabling the compression release.


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08-29-12, 11:07 AM   #11  
If you will adjust valves when piston is on Top dead center you will have this one fixed. Adjust both valves to .005 thousands of an inch it will engauge the compression release and it will crank fine. Good luck.

 
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08-29-12, 11:19 AM   #12  
Actually the piston needs to be set just past TDC (a quarter inch to be exact) in order to get the proper adjustment setting. If it is set on TDC, the compression release mechanism can be in the way.

Briggs says this at their site:
Servicing the valves | Frequently Asked Questions | Customer Support | Briggs & Stratton


"Release the brake spring. Then, turn the flywheel to close both valves.

Insert a narrow screwdriver into the spark plug hole and touch the piston. Turn the flywheel clockwise past top dead center until the piston has moved down 1/4". Use the screwdriver to gauge the piston's range of motion (image F)
. PLEASE NOTE: This procedure must be performed for each cylinder on V-Twin engines.

Check the valve clearance by placing a feeler gauge between the valve head and the rocker arm (image G)
. Clearances differ for the two valves and typically range from .002 - .004" to .005 - .007". Valve clearance specifications for your engine series are available by viewing our Engine Specifications Chart (PDF).

Adjust the clearances as required by turning the rocker screw. Once adjustments are completed, tighten the rocker nut.

Install the valve cover, using new gaskets, as required, and make sure the cover is secure."


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08-29-12, 11:39 AM   #13  
Interesting.
Got it.

Wanna hear something funny? I'm going to actually have to look at which direction the FW normally rotates,......if I am going off top dead center I do not want to be rotating the wheel the wrong way and end up slightly BEFORE top dead center!
noob.

Thx again guys! Maybe tonight she will run! Had great luck so far with your help.

 
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08-29-12, 01:02 PM   #14  
Looking down at the top of the engine, the flywheel normally rotates clockwise. Take the valve cover off and rotate the engine by hand. You will come to a point where both valves "rock". In other words, one opens and the other closes and there is one tiny spot in between where if you rock the engine one way, one opens, and if you rock it a little the other way, the other opens. This is top dead center but on the wrong stroke. I make a mark on the flywheel and shroud so that they are pointing at each other at this very spot. Then turn the flywheel another 360 degrees until those marks line up again. That will be TDC. Rotate the engine another 1/16th of a turn or so and you'll be at the right spot to adjust the valves. This is something I've developed after working on these for years and beats removing the plug and trying to determine the exact position of the piston.


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08-29-12, 01:26 PM   #15  
Great technique!
Thanks!

Im out for the day,....will report back tomorrow with results

Thanks!

 
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08-30-12, 08:51 AM   #16  
We have succes!

Well guys! It works now!
The valves were definately off.
Fires right up and runs like a champ!
Amazing help! No way could I have done this without everyones help!

Now....when first running (it has always done this for the 3 months weve had it)......for about 3-5 minutes the exhaust emits dark smoke.
Any thoughts here? Is there some sort of fuel additive cleaner or such that will hellp clean stuff out?
Carb cleaner?

I guess I want to continue working on this mower and bring it back up to as a good as shape as possible! Fluids and proper lubing I got sorted. But for 'helping out' the engine?.....Any advice appreciated!

 
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08-30-12, 10:10 AM   #17  
The black smoke for several minutes is from the choke sticking. Look at the carb where a looped wire goes to the throttle control. When you push the throttle lever up to the choke area, this looped wire pushes the choke on. When you pull back to un-choke it, the wire linkage should come with it. If not, that's the problem. To fix it, take the 2 bolts at the intake out and let the carb drop.. tug it out of the air filter housing. Remove the plastic elbow at the end of the carb. Use a pair of pliers to pull the choke plate out of the carb. Note how the spring is positioned at the top of the choke shaft so you can remember how to put it back, then pull the choke shaft up out of the carb. Take the spring with it. Now scrape the sides of the choke shaft with a razor blade from top to bottom. This will remove tiny shavings of plastic. Do this all the way around until the shaft fits and turns freely in the carb, then put it back together. Make sure the spring is in place so that it holds the choke open. 10 minute job when you're familiar with it.


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08-30-12, 04:22 PM   #18  
? Houston! We have a problem .

I should not have spoke too soon after only running the mower a few minutes last night. (After valve job)

Things are NOT well.

Tonight:
-Put in new air filter....put shrouds back on....

Fired it up. The starter had trouble cranking,...it engaged....and spun....but very hesitantly....Upon re-tries it started. But had to crank awhile!!

*Note: When starting you must have the brake depressed.

When it would 'catch' and start running....it ran rough....10-30seconds...when I took my foot off the brake it died.,....and backfired a big spark Started realizing it would die everytime after I let off the brake.

On more start attempts I noticed that keeping the key in the "start" position while waiting for the engine to catch....with the starter running: The + wire on the bat was smoking and melting the rubber sleeve around the + terminal

Finally I decided to start it, keep my foot on the brake (since for SOME reason taking my foot off the brake causes the engine to stop)....so I ran it like that for awhile (maybe 1 minute)...before I noticed an orange glow "pulsing", "emitting" from the muffler.
SO I shut it down immediately. The muffler area was HOT....TOO HOT.

So I am at a loss.
- Something is up with the safety switch on the foot brake. I put in a new solenoid. There were 2 fin clips....blue wire and white wire. I did not think it mattered which wire went to which fin....maybe it does?

- Could I have screwed up the valve adjusment?

- Again, the starter motor has trouble turning the flywheel....it DOES,...but only have several start attempts.

- Pulled plug....nothing crazy...looked fine.

- Brand new hi amp cold crank battery. New starter motor. New ring gear. New solenoid. New ignition switch. New fuel filter. New air filter. New plug. Checked and gapped properly.

Thoughts?...Im too far in to take this to a shop!....

 
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08-30-12, 07:28 PM   #19  
The valve adjustment could be the problem, but if you had the flywheel off, go back to it and make sure the flywheel key and flywheel/crank slots are all in alignment. the latter would account for the hard starting and the hot muffler = advanced timing. If the valve adjustment was off that alone would account for the hard starting, but not the hot muffler.

The problem with the dieing/foot brake could be a seat safety switch.

 
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08-30-12, 09:11 PM   #20  
The flywheel key would also cause the hot muffler by throwing the timing off, causing combustion to be while the exhaust valve is partially open. If you didn't tighten it very tight or if you put oil or grease on it, it is probably sheared.

The pedal problem is probably because the seat switch connector isn't pushed on tight enough. The smoking wire sounds like it may be a poor connection at the battery cable or you just cranked too long.


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08-31-12, 05:19 PM   #21  
Addressing things 1 at a time today.

- fywheel is seated, key is in place. (new key from re-install).
- Checked valve clearance....it was off
- reset clearance. SAME issue....didnt want to turn flywheel easily at all
- Pulled plug. Flywheel spins like a bat outta hell no problem.
- Plug back in....doesnt want to spin...it will eventually,...but not easy at all....spins 1/5th turn...stops....buzzes...etc.

- Checked valves again and noticed something:
2 valves....upper and lower. 1 side of rocker has the ROD that goes into the engine...that rod pushes back and forth controlling the valve....(I don't know the right terminology for these parts....:-(

The top valve rod is tight...and moves the valve properly open and shut..etc. All the way through the stroke it is firm and controlled in motion.

The BOTTOM valve rod is controlled and tight as the piston rises to TDC,...but THEN it completely releases and is floppy, the valve is floppy, you can easily push the rod in/out through the whole decompression part of the stroke back and forth with your fingers...and the valve ofcourse flaps in the wind! flaps open 1/4" easy.....just "floppy"....
THIS DOES NOT seem proper? Is the rod broke?.....or more likely is there something wrong with the cam?

 
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08-31-12, 06:28 PM   #22  
Cam pushes push rod which pushes rocker which pushes valve. Valve is held in tension by the valve spring.

You're saying on the top valve you only have a clearance (space) between the rocker and the top of the valve at the adjustment point = 1/4 in past TDC and this is normal.

The bottom valve you have normal contact between the push rod and the rocker until the engine just passes TDC. Then you have excess clearance between the rocker and the top of the valve? And you have adjusted/readjusted that valve to specs at 1/4 in past TDC. If that is the case and you have proper adjustment at that rotation of the crankshaft, you could have a valve sticking or a flat cam or a broken valve spring.

Another possibility is the adjustment nut isn't holding and the adjustment is off.

 
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08-31-12, 07:45 PM   #23  
Top valve = proper clearance at 1/4" (downstroke of piston) past TDC per B&S manual.
Top valve rocker and rod operate properly through full cycle. The rod is always 'solid and connected'...operating the rocker accordingly.

Bottom valve rod is solid during the downstroke of the piston and operates rocker accordingly.
Bottom valve rod suddeny is EXTREMELY loose on the compression part of the cyle. You can grab it with your fingers easily and pull and push it in and out.
It is connected to the rocker properly....BUT since it is sooo loose the rocker then rocks sloppily..easily opening more than 1/4" of gap between rocker and top of valve!

BOTH rocker nuts are properly secure and not loose.

The slop in the bottom rocker is 100% due to the very large amount of "play" and "looseness" in the rod. This looseness again though is only present on the upstroke of the piston towards TDC. Once it hits TDC and the piston starts downward the rod becomes solid again. At 180degrees from TDC it suddenly has TONS of slop again....

 
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08-31-12, 07:49 PM   #24  
Those push rods sit in a little pocket on the cam rider. See if maybe yours is out of the pocket.

 
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08-31-12, 09:46 PM   #25  
This is with you rotating the engine clockwise as viewed from the top? This doesn't make sense... there isn't anything on the cam that would cause this even if it wore out and still allow it to run at the same time. Does the valve open and close as much as the other valve?


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09-01-12, 05:32 AM   #26  
Sorry Cheese....I wish I knew better how to describe this.

But to respond to you: yes.

Question: On the valve rod that pushes the rocker up and down.....should you be able to simple grab that rod with your fingers and push/pull it in and out causing the rocker to rock and the valve to open/close?

On my lower valve,....for 1/2 the cycle of flywheel rotation you CAN simply pull that rod in/out no problem. Of course, since that rod is loose you can also simply rock the rocker by hand easily! And rock it a very large amount!

On my upper valve....at no point during the flywheel rotation cycle can you move that rod, or rocker by hand. It is "controlled" by the inside of the engine or something (noob way to describe it...I know).....it is not loose,...and you cannot grab the rod and slide it in and out of the engine at all.


When rotating the flywheel by hand, CCW the valves do both open and close in a cycle....yes. They "visually" to my very uneducated eye....appear to be functioning fine. But with the incredible amount of slop in the lower....surely this must be tied to my issue?

And setting the valve clearance on both EXACTLY as described in the Briggs manual......still gives me a hard start....will not turn the FW easily at all!.

Pull the plug and it spins it like a top.

So considering valve clearance is set correct.
Considering that mechanically there is nothing preventing the starter from spinning the flywheel (as proven with plug out).

Something must be going on "inside the engine" ? And this weird lower valve loose rod situation surely cant be proper?

 
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09-01-12, 06:03 AM   #27  
If you can move the valve itself that freely you don't have enough spring tension = bad valve spring. Without the rocker contacting the valve stem at all can you work the valve up and down by hand?

A bad valve spring would account for the extra flop you're describing since the spring wouldn't be adequate to pull the rocker/rod down against the cam on the down side as it allows the valve to close.

 
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09-01-12, 10:02 AM   #28  
Correct, sounds like a broken valve spring. Also, you said, "When rotating the flywheel by hand, CCW the valves do both open and close in a cycle....yes". It is important that we are clear about clockwise and counter-clockwise. Doing the adjustments after finding your spot after TDC rotating the engine CCW will result in incorrectly adjusted valves.


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09-01-12, 05:38 PM   #29  
Cheese - My bad...I do indeed mean clockwise,...like a clock. NOT Counter Clock wise.

I think I might follow you. I feel like an idiot though not knowing the terminology.

We have the push rod which comes out of the block and is attached to end (A) of the rocker.

At the other end of the rocker end (B) it is NOT attached to anything but instead pushes against this little springy thing. This cylinderical unit is not actually attached to the rocker at all,...and it is here that we use the feeler gauge to check clearance.

In my noob brain,....the valve is at end (B).

So I am saying that the pushrod at end (A)....is what I can simply use my fingers to pull in and out freely. There is no spring attached to it....unless it is inside the block?

This ability of this rod to move in and out...thereby rocking the rocker very easily, and sloppily....allows the rocker to pull FAR away from end (B).

When you say 'valve spring'....the only spring I see is the one wrapped around the cylindrical object that comes in contect with end (B) of the rocker.
I do not see how this spring has anything to do with the tension or solidity of the pushrod coming out of the block and attached to the rocker at end (A).

If in fact,...we are somehow talking about the springy thing at end (B) ....that seems to be potentially easy to replace?

 
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09-01-12, 05:59 PM   #30  
The springy thing at end (B) doesn't hold end (B) up with enough tension to keep the rocker forced tight against the end of the push rod as it moves in/out. It's that springy thing that is likely broken and collapsed to the point of not functioning properly.

The purpose of the spring on end (B) is to close the valve. What you see is the valve stem with the spring attached to it. The valve stem is where you measure the adjustment to set the valve lash.

You have valve lash (clearance) to give the valve sufficient room to fully close as it expands and contracts. You find this in a solid lifted valve setup. In an automotive design the valve clearance is often "0" since a hydraulic lifter is used. The hydraulic system compensates for the varying length of the valve stem due to heat variances in the metal stem.

 
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09-01-12, 08:34 PM   #31  
The cylindrical piece is the valve spring. The valve stem is the metal piece running through the center of the spring. This spring is what keeps the rocker arm pushed tight to the pushrod. When the cam in the engine lets the pushrod go back in towards the engine, the spring on the valve rocks the rocler arm back toward the pushrod, pushing the pushrod back down. I don't believe I have ever seen one broken on one of these engines in all my years working on them, but there's a first time for everything. What I don't get is that there is only one little spot in the entire rotation of the engine through all 4 cycles that allows the pushrod to be loose. A broken spring causing too much clearance would cause this on more than just one occasion throughout the full cycle of the engine.

I tend to think something else is going on here, but I can't yet imagine what. Do both the valves still have the little caps on them? (they are tappets) The rocker arm stud isn't loose is it? Can you post pictures or a video of the setup and the condition of the valves and rocker arms in different stages of the engine stroke?


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09-02-12, 05:36 AM   #32  
Valves in small engines really don't have a lot of travel so the stress isn't nearly as great as in automotive applications, especially in with high lift cams in performance applications. You wouldn't have near the breakage.

But, with what you're describing as the excess clearance part of the cam rotation, apparently it's the closing of the valve that's the issue. Whether that problem is attributed to a weak/broken spring or possibly a valve sticking or something in the cam rider is the question.

As a rule most mechanical fixes fall into something normal. Not too much comes from off planet.

 
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