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Hot!20HP Single Cylinder Intek won't turn over

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4cycle
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2017/11/27 10:34:21 (permalink)
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20HP Single Cylinder Intek won't turn over

I have a 20HP Intek model 331777 that quit running.Now the starter groans when it cannot turn over engine.I can barely turn flywheel by hand to get to non compression stroke and get starter to turn engine over.It will only pop once doing this.I did get it to run after blocking off intake with my hand,but noticed the exhaust was coming out the intake!I removed valve cover and it seemed the exhaust valve rocker arm stud came loose from the head.I think it was loose enough to not let the exhaust valve open.I also noticed the intake pushrod is very bent,could be from trying to open intake valve with full compression?
I ordered new pushrod and pushrod guide.I am planning to use red threadlock or high temp thread lock on the rocker arm studs when I re-install them.I did not see a measurement to set the valve gap at in the Briggs manual.
I am wondering if this motor is supposed to have the decompression on the cam,I did not see the bump opening on one of the valves when turning it over with the valves opening and closing normal.

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    AVB
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    Re: 20HP Single Cylinder Intek won't turn over 2017/11/27 11:04:57 (permalink)
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    Hmmm, doesn't sound good at all.
     
    First the camshaft does have ACR and it on the exhaust valve of this engine. Now the 793880 camshaft does have ACR failures so if your not the bump on the exhaust then camshaft would need replacing.
     
    Second that pivot stud needs to be Loctite in place and torque to specs.
     
    Third with the intake push rod being bent suspect that the valve itself has move and is now preventing the intake spring fully compressing as needed; therefore, bending the push rod.
     
    Intake Valve.003-.005 in (.08-.13 mm)Exhaust Valve
    .005-.007 in (.13-.18 mm)
    post edited by AVB - 2017/11/27 11:06:18
    4cycle
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    Re: 20HP Single Cylinder Intek won't turn over 2017/11/27 17:23:37 (permalink)
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    Thanks for your help AVB,I checked a few things and have taken off the rocker arms and intake valve spring.The valve moves in and out freely and when holding it and spinning,seems to meet the valve seat evenly,so I do not think it is bent.I could have bent the push rod by turning the flywheel backward by hand?
    I checked for the decompression valve working by inserting a push rod and turning over by hand.I only felt the normal movement of the tappets without the extra bump.Does the motor need to be turned over with the starter to get the decompression valve working?I looked at the parts diagram and it looks like the decompression valve is next to the camshaft gear that is next to the lobe for the intake valve?
    AVB
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    Re: 20HP Single Cylinder Intek won't turn over 2017/11/27 17:43:25 (permalink)
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    I see my thinking is ahead of my typing again sorry. You need to check the intake valve guide since that the side that has the bent push rod. Left the word "guide" out. It is out of place then it is a new head time. These valve guides are non replaceable.
     
    As for the ACR is on the exhaust of this cam. And no the engine does not need turn with starter. Once the engine reach near idle speed the ACR swing out and disables itself. Until does reach this speed it will bump the valve.
    4cycle
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    Re: 20HP Single Cylinder Intek won't turn over 2017/11/28 10:46:02 (permalink)
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    Thanks for you help again AVB,I am just taking this repair one step at a time,so any help is appreciated,just waiting for parts now anyway.I will check the intake valve guide that I can see from the top of the head.I see it has a valve stem seal on it.They can get damaged or come loose after being pressed into head when new?
    Thanks for explaining the ACR,it makes more sense being near the exhaust valve lobe of cam.
    If things look like I will damage anything,I am planning to install new push rod and guide,set valve clearance and turn it over.I will check again for the ACR working,I am thinking it must have been running when the rocker arm stud came loose,so it must have ran even with the ACR not working.
    The motor is still on the 10yr old Craftsman riding mower so I will check this before having to take it off.
    4cycle
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    Re: 20HP Single Cylinder Intek won't turn over 2017/12/05 13:04:33 (permalink)
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    Well Jacks Small Engine got my order to me just in time.I was able to put things back together yesterday when we had a record 50 degree day,today winter started here,with 0 degree windchill.Some parts were back ordered,they must have shipped order within hours of getting parts and even used USPS priority two day shipping,forcing postal workers to stop reading the newspaper.
    I installed new push rod and rod holder,rocker arms and set valve stem gap.Turned over engine by hand,everything seemed to be working,but still no bump opening of exhaust valve.I sprayed a shot of starting fluid in the intake,I have the fuel line disconected and carb bowl empty.Engine fired rite up for a second or two,good news!!I could not help trying to run engine so I installed valve cover and added oil to crank case.I attached fuel line and added fuel to tank.
    Turned over engine,everything seemed normal,engine fired rite up and ran great.I guess the decompression valve on the cam is still not working but it is running so good I do not want to take it off mower and take it apart.The only thing I noticed when it is running is a slight chirping sound,could be the intake valve stem was damaged slightly when push rod was bent.I did not mention one of the two valve keeper inserts was missing when I first removed valve cover,could be the cause of the bent pushrod and possible damage to the valve stem.
    Mikel1
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    Re: 20HP Single Cylinder Intek won't turn over 2017/12/16 19:32:02 (permalink)
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    Some models of intek acr is on intake valve. You can hear a slight pop back thru carb when starting. However there is very little movement on valve on the acr actuation.
    4cycle
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    Re: 20HP Single Cylinder Intek won't turn over 2017/12/18 15:32:50 (permalink)
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    Thanks for the info Mikel1,it does look like the acr mechanism is on the bottom of the engine,attached to the cam,the intake valve is on the bottom also.And I think you are correct that the cylinder pressure does get released out the intake.I had plugged the intake with steel wool wrapped in plastic to keep water out when I was degreasing the engine,when waiting for parts.I was trying to get it clean before having to split the case.After the parts came and I was cranking engine,after installing rocker arms,new push rod and valve cover gasket.The steel wool and plastic,that I forgot about (Doh!) came shooting out the intake.
    After that the engine started rite up and seems to really run good.I did not see much of a bump on the rocker arm for the acr when turning engine over,I could feel something at the push rod just after valve closed.I will listen at the intake when turning engine over for a chirp,or the pop as you described.Hopefully then I would not need to split the case to replace acr,be good to mow this spring,and this post will help others.
    4cycle
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    Re: 20HP Single Cylinder Intek won't turn over 2018/07/02 20:53:46 (permalink)
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    Just a past due update on the B&S 20HP engine.This spring I put gas in tank (I always drain all gas before storing for winter),it started rite up and I pulled it in garage to install engine cover.I installed mower deck and was mowing same day.I think part of the problem with not wanting to turn over was battery voltage.I also think that changing the oil had something to do with it turning over easier now.
    After my good luck I acquired two similar engines,B&S 21HP single cylinder.One has a hole in side of case near starter (decompression lever broke off cam and was floating around engine till it was pushed out the side),the other had the counterbalance weight come off inside engine.
    I will post about these engines as I am working on them.
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