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Engine Rebuild... OOOPSIE!


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#1 theck4291 OFFLINE  

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Posted September 21, 2016 - 11:22 AM

21b707 0453e1 is the engine I have in my MTD Yard Machine.

 

I took apart the engine, the piston was destroyed and the cylinder was scratched up, so I got the new piston, and have already rehoned the cylinder and it honestly seems pretty good.... HOWEVER, I do not know how to set the valves back up correctly... lets say I have the piston at its fully compressed point, what position should my camshaft be in? I forgot to take note of this and do not know how to put it back together properly!!!!! 

 

 

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#2 Bud W OFFLINE  

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Posted September 21, 2016 - 11:26 AM

The crank and cam should have timing alignment marks on them somewhere.


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#3 dthomp17 OFFLINE  

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Posted September 21, 2016 - 11:37 AM

The crank and cam should have timing alignment marks on them somewhere.

As long as you didn't remove either the camshaft or the crankshaft you should be OK and the valve timing shouldn't be effected. There should be a little dimple (or similar mark) on the camshaft and the crankshaft that need to be aligned when either is removed and re-installed to get the valve timing correct.

 

Do you know what caused this problem so it won't repeat in the future?



#4 WNYTractorTinkerer ONLINE  

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Posted September 21, 2016 - 12:15 PM

The crankshaft turns two times to the cam's single rotation.  Line the marks on the gears up if you removed the crank to hone (hope you did!)  Also wash the bore with soap & water to get all the grit from the hone out of the bore unless you like repeating the task..



#5 crittersf1 OFFLINE  

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Posted September 21, 2016 - 12:54 PM

Should've taken some :camera: :hitting_self_roller:



#6 boyscout862 ONLINE  

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Posted September 21, 2016 - 01:42 PM

Download the rebuilding manual from our Manuals Section. I hope that you pulled the engine and completely disassembled it. Every part should be thoroughly cleaned and oiled prior to assembly. If you only do a partial disassembly, there will be engine killing crap left in the engine. Good Luck, Rick

#7 EricFromPa OFFLINE  

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Posted September 21, 2016 - 02:50 PM

Just line up the 2 small marks.1 on the crank gear and 1 on the Cam gear and your good to go.

 

Connecting rod gets torqued to 175in lbs or 14.58ft lbs.

Head bolts get torqued down to 35ft lbs.I like to torque them to 30 and run it for a couple minutes till it warms up and Hot torque them to 35ft lbs.It fully seats and squishes the head gasket down to insure that it doesn't blow out.I did a bunch like this and none of them have ever blown a head gasket after doing a Hot Torque.

 

Set both valve lashes to .004-.006 I put mine dead on .005.

 

Pic of a 14.5hp briggs timing marks.13.5hp will have the same marks but may have a Plastic cam gear.

Untitled.jpg


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#8 propane1 ONLINE  

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Posted September 21, 2016 - 07:29 PM

Never heard of a hot torque. Do you then retorque after cool down. ?

Noel
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#9 EricFromPa OFFLINE  

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Posted September 21, 2016 - 08:19 PM

Retorque while the engine is still hot.It's the only way that I've found that will 99% cure the Head Gasket blowing problem on the OHV Vanguard and Intek Single cylinder engines.

No need to retorque when it cools.The laminated gasket will flatten and bolts will stretch a tiny bit when hot and pull the head tight when it cools.I don't think they thought about bolt stretch on the ohv briggs.Doesn't take much at all to blow the head gasket between the cylinder and push rod galley where the metal is maybe 1/4" thick and the gasket material is even thinner

 

Check this out.14.5hp vanguard VS 21hp Vanguard single cylinder.See how thick the material is between the cylinder the push rod galley?Fairly thick material on the 14.5hp but the 21 is alot thinner and the gasket is even thinner and No head bolts any where near that thin spot.

 

14.5hp 2013-10-13 14.00.53.jpg vs 21hp maxresdefault.jpg

 

 

I've done this to literally dozens of OHV briggs engines and not a single one of them ever blew another head gasket.

 

1st one I did it to is on a 1994 White LT15 with 42 deck.That was in either 98 or 99 that I replaced the Oil sump gasket and head gasket.Engine still runs good to this day but you can tell it's getting low on compression.Rings are getting worn.Still doesn't smoke and starts easy.It's been used every week since then and never had that issue again.

 

I do all the maintenance on it.Last time I had to do any major parts replacement was 3 years ago I rebuilt the spindles,replaced 3 idler pulleys,belts and new blades.2 years before that I replaced all 4 tires and flushed the transaxle.I do oil change,new plug a quick carb cleaning and go over everything every spring just before mowing season.


Edited by EricFromPa, September 21, 2016 - 08:21 PM.

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#10 Tecumseh power OFFLINE  

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Posted September 21, 2016 - 09:57 PM

That's a good way to rip the threads out of the block

#11 theck4291 OFFLINE  

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Posted September 22, 2016 - 06:53 PM

Hey guys I got it all cleaned out and put back together. Must have had a full inch of sludge in the oil pan. HOWEVER, like before, I messed up. Since I took no pics, I cannot remember how to reattach the contraption that controls the speed. What is it called? All I can think is throttle linkage plate. Ive already attached the linkage, but there is a spring that I am unsure of where to reattach. It's about half the diameter of a penny. Not very big. Also the part on the engine that moves back and forth may have gotten bent because it just doesn't feel right. Anyone tell me what it should look like, and how much it should go back and forth.... Already reattached the rod and spring between that part and the carburetor.

Thanks for the help!! Hoping to have it running tonight!!!!

#12 EricFromPa OFFLINE  

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Posted September 23, 2016 - 12:16 AM

That's a good way to rip the threads out of the block

 

Head is about 3/4" thick and bolts are about 3 1/2 inches long and threads are 2 1/2" long.You can feel the gasket pulling down tighter when ya hot torque.

 

Only reason I do a Hot torque on a vanguard or intek is because I've replaced them before and torqued to recommended specs and had them blow out again in a couple weeks to a couple months.

 

Briggs should of cast another head bolt boss at that location.Good engine with a rather bad design flaw.

 

The laminated gaskets they use are super soft also and once the engine gets hot from mowing the bolts stretch a bit and the gasket de-laminates and eventually blows out on all of them.

 

Like this gasket did.

 

Untitled.jpg

 

Marked the head gasket bolt holes.Other 2 holes are for dial pins.See how far away the bolts are from where the gasket blows?Gasket is also thinner there.

 

11111.jpg


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#13 EricFromPa OFFLINE  

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Posted September 23, 2016 - 12:23 AM

Here governor plate assembly.Decent video.Can't find any decent pics.

 



#14 theck4291 OFFLINE  

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Posted September 23, 2016 - 04:24 PM

GOT IT RUNNING!!!! then it stopped.... no vacuum on intake. So I readjusted the valves. .005 on both, with it set about 1/4" from top dead center... is that right? it is what I saw on the briggs and stratton website. 

 

After doing this it ran, NO SMOKE!!! for about 2 minutes, then started smoking, and stopped running. Couldn't start back up, checked the valves because I was getting compression from the intake instead of vacuum. Reset the engine to same top dead center(marked my flywheel where the magneto armature is) and the exhaust valve rocker arm was completely loose. Sooooo, I went to tighten it more and it snapped the rocker arm stud. Now, thankfully I am only about out $10 in parts, but why did it keep getting so loose, and why was oil getting into the cylinder again? Is the OHV cover supposed to fill with oil, because when I opened it oil kinda poured out. Was oil getting into the cylinder because the exhaust valve was not operating? Very confused here, thanks



#15 EricFromPa OFFLINE  

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Posted September 24, 2016 - 02:53 AM

Oooops

 

You can replace the stud easy enough if you can get the broken part out of the head.They do put Loctite on most of the rocker bolts.Had a couple that didn't have any on but they were the older 1st gen 14-15.5hp vanguards.

 

If you have to you can drill into the center of the broken bolt that's in the head and use an easy out to remove it.Guessing it snapped off at the threads flush with the block?Or did it snap just the top off and leave the bolt head?

 

It should be at TDC on the compression stroke when adjusting the valves.Piston at top dead centre on the compression stroke and both valves will be closed.

You was probably on the exhaust stroke when you adjusted your valves.Exhaust valve hangs open a tiny bit on the exhaust stroke and the intake valve opens instantly after the exhaust valve closes.Coil fires twice,once on compression and once on exhaust stroke on a single cylinder lawn mower engine.

 

Turn the engine over and you'll see that both rockers get loose at TDC on compression stroke and only the intake rocker will get loose at TDC on the exhaust stroke.

 

You can put a screw driver in the spark plug hole and (turn it over slowly "BY HAND") and feel when it's at TDC.Piston will push the screw driver out and you can feel when it's TDC.If intake and exhaust valve rockers are both loose set them Both to .005.Then turn it over by hand again till the piston comes back up.If exhaust rocker is tight and intake is slightly loose there then your good to go.

 

 

Tightening a rockers.

Hold the torx bit firmly (keep the torx bolt from turning) and tighten or loosen the jam nut.     

 

 

Yes there is supposed to be Oil in the rocker cover.

 

Free Advice lol

If you ever smell gas in the oil or notice the oil level is WAY to full replace your float needle in your carb ASAP.Float needle on the vanguard and inteks even though they look good will often start leaking and fill the entire crankcase with gas in a matter of a couple hours.Check your oil before you use it or put a fuel shut off on it as a precaution.If you run it with gas in the oil it will blow up very quickly.


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