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Old 03-29-2011, 10:17 PM   post #1 of 17
Dave M
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Default Briggs OHV valve adjustment

I picked-up a nice looking White 1500 LT a couple months back, with the beginnings of a disassembled motor (just the tins and the ignition pick-up coil had been removed) and was told by the PO that it "wouldn't start". After some basic reassembly, I could see that it wouldn't turn over, much like a weak battery. But, the motor was free and it would spin without the spark plug installed. I thought it might be a valve adjustment issue, and as it turned-out, was a little deeper than that. It had a pretty badly bent exhaust valve push rod, and a destroyed push rod (plastic) guide. Recently, I thought I saw a pretty good video on MTF about adjusting the valves on a Briggs. I can't seem to find it using the search function, though. Can anybody give me the procedure and clearances to adjust the valves on this motor?
Model number on the motor is 28s777-1142-E1. Thanks for any help.
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Old 03-29-2011, 10:42 PM   post #2 of 17
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Default Re: Briggs OHV valve adjustment

Set the piston at tdc then a 1/4 " below and adjust the exhaust at .005 and intake at .007...use a torx and hold center nut and loosen the outer nut and use a feeler gauge to correct adjustment with torx then hold torx and tighten the outer nut on both...run engine then check clearence again....that is how i do it...
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Old 03-29-2011, 11:42 PM   post #3 of 17
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Default Re: Briggs OHV valve adjustment

Your series engine, 280000 Series OHV single cylinder, the valve clearances are as follows..

Intake - 0.03"-0.05"
Exhaust - 0.05"-0.07"


How to Adjust Briggs & Stratton Overhead Valves

  1. Turn the flywheel to close both valves.
  2. 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. PLEASE NOTE: This procedure must be performed for each cylinder on V-Twin engines.
  3. Check the valve clearance by placing a feeler gauge between the valve head and the rocker arm. Clearances differ for the two valves and typically range from .002 - .004" to .005 - .007". Use the correct clearances for your model engine.
  4. Adjust the clearances as required by turning the rocker screw. Once adjustments are completed, tighten the rocker nut.
  5. Install the valve cover, using new gaskets, as required, and make sure the cover is secure.
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Old 03-29-2011, 11:46 PM   post #4 of 17
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Default Re: Briggs OHV valve adjustment

Great, thanks for the quick responses.
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Old 03-30-2011, 06:57 AM   post #5 of 17
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Default Re: Briggs OHV valve adjustment

http://www.youtube.com/watch?v=0cWoEk5Guos

http://www.youtube.com/watch?v=PbYbSKN4CxI
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Old 03-30-2011, 10:23 AM   post #6 of 17
Dave M
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Default Re: Briggs OHV valve adjustment

RamHD, thanks for the PM and the spec chart. That has a bunch of great info, all of which I need. Shryp, you hit the nail on the head. That was the video I was looking for. Thanks again for all the help.
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Old 03-31-2011, 12:18 AM   post #7 of 17
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Default Re: Briggs OHV valve adjustment

Ummh, doncha think it might be worth it to figure out why the pushrod bent? Two things I can think of are: 1) over-revving the engine to where the valve hits the piston and stuff gets bent, or 2) a sticking valve. I would check how freely the exhaust valve moves in the guide, and also check that the guide has not started to push out of the head. I understand that some like to migrate to where the rubber valve stem seal gets smushed between the guide and the valve spring retainer as the guide has moved. Unless you know none of the above apply, that is.
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Old 03-31-2011, 10:18 AM   post #8 of 17
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Default Re: Briggs OHV valve adjustment

"I understand that some like to migrate to where the rubber valve stem seal gets smushed between the guide and the valve spring retainer as the guide has moved."

There will be no seal on the exhaust valve however the guide may have worked up with the valve retainer hitting it. Guide should not extend more than 1/8" above the head casting.

Since exhaust valve push rods do not bend for no reason, as said above, finding the cause is very important.

Walt Conner
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Old 03-31-2011, 11:25 PM   post #9 of 17
Dave M
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Default Re: Briggs OHV valve adjustment

I agree. Push rods bend for a reason. I'm not real familiar with this OHV motor-at least not as familiar as I'm about to become. This is the aluminum push rod that bent, which I believe is the exhaust side. I'll check for a sticky valve for sure. As far as over-revving, that could have happened with the PO, can't really say. There is a plate mounted below the tappets that has two square holes in it, that in-turn have two plastic pushrod guides mounted in those square holes. One of the plastic guides has been obliterated by whatever happened.
Can I see the valve guides from inside the pushrod chamber, or do I need to pull the head?
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Old 04-01-2011, 10:05 AM   post #10 of 17
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Default Re: Briggs OHV valve adjustment

missing some zeros I think, should be .003-.005 and .005-.007

Quote:
Originally Posted by RamHD View Post
Your series engine, 280000 Series OHV single cylinder, the valve clearances are as follows..

Intake - 0.03"-0.05"
Exhaust - 0.05"-0.07"


How to Adjust Briggs & Stratton Overhead Valves

  1. Turn the flywheel to close both valves.
  2. 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. PLEASE NOTE: This procedure must be performed for each cylinder on V-Twin engines.
  3. Check the valve clearance by placing a feeler gauge between the valve head and the rocker arm. Clearances differ for the two valves and typically range from .002 - .004" to .005 - .007". Use the correct clearances for your model engine.
  4. Adjust the clearances as required by turning the rocker screw. Once adjustments are completed, tighten the rocker nut.
  5. Install the valve cover, using new gaskets, as required, and make sure the cover is secure.
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Old 04-01-2011, 10:17 AM   post #11 of 17
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Default Re: Briggs OHV valve adjustment

I noticed in the video, when he turned the engine past TDC, he just moved the flywheel and didn't check if the piston moved 1/4" down.
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Old 04-01-2011, 11:28 AM   post #12 of 17
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Default Re: Briggs OHV valve adjustment

Quote:
Originally Posted by 38racing View Post
missing some zeros I think, should be .003-.005 and .005-.007
You are correct sir.....Put the decimal in the wrong spot...never liked math anyway. My old eyes and brain don't catch things like they used to..lol
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Old 04-01-2011, 08:58 PM   post #13 of 17
Dave M
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Default Re: Briggs OHV valve adjustment

Further investigation has revealed that the boss that the upper (intake, I think) rocker stud screws into has broken away from the head. Needless to say it increased the valve clearance dramatically. I'm going to see if its weldable. Heads on ebay look to be kind of pricey. I did rig everything back together so I could see if the valves moved (or were stuck), and while the lower rocker moved the valve substantially, the upper rocker only opened the valve slightly. Is this normal? I always thought valve opening was supposed to be pretty equal. And, thanks for the corrected specs on the valve clearances. Approaching 1/16" (.06) sounded like a pretty big gap.
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Old 04-02-2011, 08:41 PM   post #14 of 17
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Default Re: Briggs OHV valve adjustment

[
There will be no seal on the exhaust valve however the guide may have worked up with the valve retainer hitting it. Guide should not extend more than 1/8" above the head casting.

Since exhaust valve push rods do not bend for no reason, as said above, finding the cause is very important.

Walt Conner[/QUOTE]

I pulled the head and found that the exhaust valve guide is about 9/16" above the surface of the raised boss on the head that the guide travels through. No apparent valve seal on the guide, as you stated. I guess that explains the bent pushrod and the limited travel of the exhaust valve. A light tap with a hammer and a block of wood did not move the valve guide. It is tight. I'm wondering if I can just press the guide back into the head to the proper spec and be good to go, or if I need a machine shop to knurl the guide and press it back in. Any suggestions? The intake valve guide is about 3/8" above the surface of the head with a valve seal on top of it. It looks like it's where it's supposed to be. Are you sure about the 1/8" dimension above the head? If so, I'll need to reset both of the guides. Thanks. BTW, lots of debris inb the cooling fins. I'm pretty sure this motor got hot.
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Old 04-03-2011, 03:02 AM   post #15 of 17
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Default Re: Briggs OHV valve adjustment

The excessive heat probably caused the guide(s) to move in the head. Yet another reason to allow the engine to idle for a couple of minutes before shutting down after a work session. And an annual check of the cooling fins is mandatory, in my book - if not more often. It's cheap insurance, especially in the spring after the rodents have nested in there all winter.
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