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post #1 of 15 Old 06-10-2015, 12:45 PM Thread Starter
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Briggs 20hp Twin Slow to Crank Over

Been doing a lot of reading and finally decided to ask for help. I have a 20hp briggs and stratton twin cylinder non ohv engine with flat heads. The model number is 46077-2277-E1. Here is some background info. The tractor has been sitting for a year or so because it stopped running. It would only crank about 1/2 turn and stop. I pulled the carb and it was badly corroded so i pulled one off a donor motor, cleaned it and reinstalled. I pulled the heads and they were carboned up pretty bad so i cleaned them. Drained the oil and replaced the filter. I got it to fire up and idle just fine. Shut it down and worked on a few odds and ends. Started it probably 4 - 5 times but it was a little slow to spin. Always ran tho. Now last time, it only spins half a turn. Battery is good as i have two and a charger. Im wondering if the starter is going bad, if the valve clearance is shot, or if there is internal motor damage. There was definitely water in the motor and i still have milky stuff on the dipstick. I also pulled the starter apart and greased it. I hate to waste money on a new starter if its good. It will spin fine with plugs out. Aseems like to much compression. Also, im bypassing ann electric components and jumping the starter directly. Just seems to have to much compression. Any ideas? Thanks.
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post #2 of 15 Old 06-10-2015, 01:43 PM
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Re: Briggs 20hp Twin Slow to Crank Over

This sounds like internal engine issue, I say this because water in the engine is not good, I would remove the engine and open the crankcase and inspect the decompression spring on camshaft or the decompression unit on the camshaft, before remove the engine check the intake and exhaust valve lash also make sure the valve seats are ok.


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post #3 of 15 Old 06-10-2015, 09:46 PM
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Re: Briggs 20hp Twin Slow to Crank Over

" I would remove the engine and open the crankcase and inspect the decompression spring on camshaft or the decompression unit on the camshaft,"

Well it will not have the component you mention as this engine utilizes the "easy spin" camshaft grind.

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post #4 of 15 Old 06-10-2015, 11:09 PM
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Re: Briggs 20hp Twin Slow to Crank Over

Those horizontally opposed twins do seem to sometimes be hard to crank.

If you can turn it by hand on top or bottom over two revolutions, then at least it doesn't have snapped rod.

Those valves should not get out of adjustment in the same way ohvs will.

The in block valves will recede into the block as margin wears etc and the clearance will be less- not more like on ohv.
So valves should not cause hard cranking live on ohv.

I would get some 5w-30 or 10w-30 full synthetic in there and turn it round and round...backwards too....but I have no sense.

I assume you are jumping to frame and to post on starter??

Cables are not ideal and most booster packs are weak.
I use a full size car battery with 20 inch or so heavy duty jumper cable ends on it.
I can start a large car engine with no battery in the car.
It makes sure I have all the power I need to test a starter system on mower.
Ground it to engine directly or round nub on end of starter.

Maybe spray some lube on starter gear where it meets flywheel teeth. If mesh is tight it can cause increased drag.
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post #5 of 15 Old 06-11-2015, 05:03 AM
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Re: Briggs 20hp Twin Slow to Crank Over

What is the compression reading?

Have you checked the valve clearance?

Last but not least the decompression lobe on the camshaft (Easy Spin Lobe)
could be worn down to far,

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post #6 of 15 Old 06-11-2015, 05:33 AM
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Re: Briggs 20hp Twin Slow to Crank Over

I have had several of the B & S TwinII engines.. I still have a 20 hp one on my log splitter..these things do not have the centrifugal compression release on the cams.. instead it is done by the cam grinding when it was made.. I have yet to find a cam with worn lobes on it.. what I have found when a starter spins slow.. is the top bushin get's worn eggshaped a tiny bit.. this allows the armature to make contact with the magnets.. the other issue with them is the brushes will wear down too short..

also to get the starter bolts out there is one slightly hidden under the flywheel.. if u trun the flywheel u will find a spot that allows u to remove the bolt WITHOUT removin the flywheel.. but I have removed the flywheel on some.. take the 'hard to get out bolt' out first.. (the other bolt will hold the starter in place while u remove the hard one..)


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post #7 of 15 Old 06-11-2015, 09:56 AM Thread Starter
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Re: Briggs 20hp Twin Slow to Crank Over

The engine does run and spins free by hand. I am able to occasionally get it started by jumping it and assisting the flywheel spinning by hand. I jump to the starter lug and the exhaust pipe. Ive also jumped with my jeep and it spins the same. That leads me to believe my voltage sources are fine.

Ive had the starter out and apart. It looks good and i greased the top and bottom.

Ive run and drained the oil several times.

I havent checked compression or valve clearance. Need to find a compression tester.
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post #8 of 15 Old 06-11-2015, 10:26 AM
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Re: Briggs 20hp Twin Slow to Crank Over

Let me know the compression reading.

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post #9 of 15 Old 06-11-2015, 11:07 AM
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Re: Briggs 20hp Twin Slow to Crank Over

I have a thread on here somewhere where I also experienced the symptoms with starting you had. The starter had no power, struggled to turn the engine over, slow to spin, sometimes didn't work.

After checking all the electrical systems, gounds, voltages, etc. I just ended up replacing the starter. Problem solved.
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post #10 of 15 Old 06-11-2015, 01:45 PM
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Re: Briggs 20hp Twin Slow to Crank Over

Quote:
Originally Posted by maniac2k View Post
The engine does run and spins free by hand. I am able to occasionally get it started by jumping it and assisting the flywheel spinning by hand. I jump to the starter lug and the exhaust pipe. Ive also jumped with my jeep and it spins the same. That leads me to believe my voltage sources are fine.

Ive had the starter out and apart. It looks good and i greased the top and bottom.

Ive run and drained the oil several times.

I havent checked compression or valve clearance. Need to find a compression tester.
Chances are the starter is getting lazy then. Look over the battery terminals, clean them well, and check the frame ground.

If you have a multimeter, you can do a voltage drop test across the positive battery post and starter lug, and the negative battery post to the starter mount. If you get anything excessive, you'll have to address that problem before going any further.

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post #11 of 15 Old 06-11-2015, 02:19 PM
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Re: Briggs 20hp Twin Slow to Crank Over

Sometimes starters just get dirty. Tearing em down and doing a good clean and lube job will work wonders. Of course if the starter has worn bushing this will not help as much.


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post #12 of 15 Old 06-17-2015, 06:39 PM Thread Starter
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Re: Briggs 20hp Twin Slow to Crank Over

I already tore down the starter and lubed it.

I still havent got a compression tester but i do have an update i pulled the starter and carb off the 20hp motor and put them on another tractor with a 18hp twin and it started right up so it definitely isnt the starter. Im going to let the 20 hp motor sit and get this other tractor running. Ill post an update when i tear the bad motor down. Thanks everyone.
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post #13 of 15 Old 09-19-2019, 12:36 PM
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Re: Briggs 20hp Twin Slow to Crank Over

These engines had a issue with carbon buildup on the head and pistons causing increased compression ratio. Yes the starters are under-powered Oregon makes a "Magnum" version of the starter that is a decent upgrade. Battery cable diameter is not the cause, but a underrated battery can be. I prefer the Interstate batteries SP-40 due to high CCA and overall life of use. Solenoid can be partially to blame, but I rarely see that. Valve clearance issues on these engines have never been an issue with what I have experienced, but sealing and guide leakage is.
Clean the head and pistons. lap the valves. make sure that the battery is not the cheapest that you can get. if the starter isn't burnt up, you are good to go.
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post #14 of 15 Old 09-19-2019, 09:01 PM
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Re: Briggs 20hp Twin Slow to Crank Over

That last post is over 4 years old.

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post #15 of 15 Old 09-19-2019, 10:58 PM
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True, but the information lasts. Someone may need it.
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