Briggs "900" OHV No-Start, Tried Everything, Any Tricks With These Models? - Snowblower Forum : Snow Blower Forums
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post #1 of 55 Old 01-16-2020, 11:00 PM Thread Starter
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Briggs "900" OHV No-Start, Tried Everything, Any Tricks With These Models?

Hello!

I'm a new member with a problem that's driving me crazier than it needs to, seeing as how I've got another snow blower I can use.

Let me first say that I've been fixing motors since I was a kid (and that's over half a century) and I have never found myself unable to get an engine started, if it was possible for it to run at all.

The motor in question is a Briggs "900" series 205cc 1 cylinder, OHV snowblower motor from 2014, model number 12D105-0172-F8 with a build date of 4/15/14.

It is in a snowblower that I bought from an elderly neighbor last month. He's a fairly straight shooter about these things, not a mechanical guy, told me he bought it, used it a few times, less than 8 hours total, and felt it was "too much for him," so he left it in his barn. Looking at it, in terms of rust, oil leakage at seals, wear on auger, etc., I have no reason to disbelieve him.

I went over to his barn, unscrewed the bottom bolt on the float bowl, wiped out the crud, ran some gas out of the tank, put it back together, and it started right up. I ran it about 600' to my barn and it quit. It was getting dark, so I left it. Next day, I filled the tank with fresh gas, gave the float bowl and jet a better cleaning, and it started right up. I blew some snow for about half an hour, it ran well, then it quit.

After that, I could never get it to really even fire.
It will crank faster and almost catch when I spray ether into the carb, but it never really catches, will "sound good" for only about 2-3 seconds after a spray of ether, then return to normal. It will not pop even once if I stop cranking it.

What I've done:
  • Checked spark - maybe a little too orange - hard to tell on a magneto 1-banger, so I installed a new B&S coil (with wire). No real change. Could be bad out of the box. Got another factory coil, still no change.
  • Replaced spark plug with a cheap one, on sale for $1! Looked a bit better. Still no change.
    Replaced with a fancy gold B&S plug. Still no change.
  • Removed carb. Disassembled, blew out, reassembled. Still no change.
  • Removed flywheel, looked at key and keyway. Perfectly aligned. Retorqued (60 ft/lbs, right?).
  • Removed valve cover, set cylinder to TDC, rough feel for endplay is about 0.008" for both.
    Confirmed both valves push down and move freely.
    Removed 1 pushrod - Not bent.
    Rotated engine (on electric starter), watched valve & rocker movement, smooth and equal between the sides, no binding.
  • Bought new B&S carb, installed. No change.
  • Motor has had good compression by feel on pull-starter and at spark plug hole throughout.

So, I feel I can say that:
  • Fire is good.
  • Air is good.
  • Fuel is good.
  • Compression is good.
  • Timing is good.
  • Valves are good.

Speed control is wide open, varying choke position doesn't matter, air screen on or off, shrouds on or off, kill switch connected or disconnected (same spark all the time anyway), fuel runs out freely when valve is open and either hose is disconnected or float bowl is off.

What the heck else is there???

Is there anything that fails on these after low use but long storage that I"m missing?

Aside from actually putting a compression gauge on it, is there anything I haven't done?

I'm at the point where I know it has to be something simple and obvious, but I can't for the life of me figure out what I haven't checked.

Anybody have any ideas?

The guy said he'd give me my $200 back, but at this point it's not about money - it's a matter of pride.

Thanks,

- Eric
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post #2 of 55 Old 01-17-2020, 10:44 AM
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to SBF Eric

It's not pride, you're on a mission from God now

I'd pull the plug, let the cylinder and plug dry out for an hour or two and then put it back in and try hitting it with starting fluid to see if it will pop.
If it does we go from there.

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post #3 of 55 Old 01-17-2020, 11:07 AM
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post #4 of 55 Old 01-29-2020, 05:49 PM Thread Starter
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Hi Frog and Stogey.

Sorry for the late reply - I don't seem to be getting e-mails when there are responses. I'll have to manually subscribe.

Yes, I did remove the plug, air it out, etc. Did so several times. Left it open for several days. Used different plugs (unusual for me, I generally just clean the old plug with a wire brush and lacquer thinner).

The one thing I haven't done is to actually measure the valve lash (I put it at TDC and just felt for a normal amount of play), so some time in the next few days, I'll have to do that. The guide I saw said 0.005" intake / 0.010" exhaust, a couple of degrees past TDC, presumably with the engine cold. I doubt that's it, but I have to be able to say I confirmed it.

I'm at the "just walk away for a while" stage right now. Usually when I do this, something comes to me, but it hasn't yet.

Thanks,

- Eric
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post #5 of 55 Old 01-29-2020, 06:22 PM
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I would check compression, and if the cam skipped a tooth at this point. And as you are going to do, check the valve lash. If I recall, the piston should be 1/4in below TDC, to check lash.




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post #6 of 55 Old 01-29-2020, 06:35 PM
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There is a setting in your profile to allow e-mails for responses to your posts. Kiss4afrog let me know the setting. I will try to find it.

I went through much the same process on my son's 11hp Tecumseh OHV. It would fire on full choke but die when choke was turned slightly toward off, and backfire through exhaust. The spark was white and spark plug was wet with gas. Compression was/is good.

Cleaned the carb and adjusted the low speed jet to 1 and 1/2 turns; set valve lash to 8 thou (turned out to be close but not stock) and cleaned the magnets for the magneto which were well rusted. The magneto contacts were clean and the gap was/is 10 thou (spec is 15 thou). The spark was stronger but still white, but still no improvement in starting. So either change spark plug or magneto. The new magneto was in stock but $70 and not returnable so I put in a new NGK BR7ES spark plug (same as old one) and that solved the problem. Engine ran perfectly and started easily on first pull.

In your case I would get a spark plug from a recognised manufacturer and clean any rust from the two flywheel magnets if you didn't do that with the new magneto. Just my thoughts.

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post #7 of 55 Old 01-29-2020, 06:36 PM Thread Starter
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Quote:
Originally Posted by Motor City View Post
I would check compression, and if the cam skipped a tooth at this point.
Okay, these are two good questions.

I never checked compression with a gauge because on any small engine I've ever worked on before, if I felt good compression on pulling the starter, I knew it was good.
If I can pull the starter, and, if I don't pull it hard and fast enough, the compression will actually stop me cold, do I really need to use a gauge?

Do the cams skip on these?
I looked at the exploded view, and it looks like the drive gears are not located in any way that would allow them to skip or lose their synchronization, unless one stripped, in which case the valves wouldn't move at all.
Is this something that actually happens?

Thanks,

- Eric
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post #8 of 55 Old 01-29-2020, 06:43 PM Thread Starter
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Quote:
Originally Posted by Town View Post
In your case I would get a spark plug from a recognised manufacturer and clean any rust from the two flywheel magnets if you didn't do that with the new magneto. Just my thoughts.
As I said in the first post, I have tried three different spark plugs, the original Champion, which looked great, some brand I never heard of from "Lowwws," which was on sale for a buck, and a gold-colored fancy Briggs & Stratton super-deluxe one from the "Despot," and there was no change.

I have also tried three different Briggs & Stratton coils (with embossed logo and attached wire), the one that came on it, and two I bought on line from different dealers (in case one was bad). No change.

It's really burning my behind.

- Eric
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post #9 of 55 Old 01-29-2020, 06:50 PM
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But the original champion plug may have been faulty, so try a new one of good quality. Did you clean the flywheel magnets for the magneto?

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post #10 of 55 Old 01-29-2020, 07:05 PM Thread Starter
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Quote:
Originally Posted by Town View Post
But the original champion plug may have been faulty, so try a new one of good quality. Did you clean the flywheel magnets for the magneto?
As I said, I tried three different spark plugs, the original, and two new ones.

I cleaned the flywheel edge with a sanding block until it was nice and smooth. Got a decent amount of dust off of it, too.

I gapped the coils (all three of them) with the included card, which was in the 0.010-0.015" range.

- Eric
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