9hp VanGuard is VERY Hard to Start

treefrog99January 13, 2008


I picked up for free a BCS tractor (like a Gravely, takes attachments) with a snow thrower attachment. Its pretty new but had some issues with the engine which I thought I fixed. The engine is a 9HP B&S Vanguard horizontal shaft, single cylinder with a Mikuni carb. The issues were:

- woodruff key sheared off on crank, caused bad timing.

I put a new key in and got the flywheel back to where it should be for proper timing.

- sparkplug wire had corroded end and was not giving spark.

I replaced the wire and now there is lots of spark.

- cleaned out the carb with a long soak in cleaner.

Now, I can sometimes get it to start, sometimes it only chugs and coughs once or so. It acks like it wants to start but won't quite get going. When it starts, it just starts right up and runs very smooth with plenty of power...i run it on full choke for 15 sec then shift to no choke and its runs smooth.

To try and get it to start, if I squirt a few drops of gas in the cylinder that doesn't work. It has 90psi compression. I can't figure out what it wants.

>spark yes

>compression, yes

>fuel, yes

I am missing something. Any ideas?



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Forgot to mention:
- put in new sparkplug
- put in fresh gas
- it actually runs sometimes but only when IT wants to!!

    Bookmark   January 13, 2008 at 8:35PM
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Sounds a bit strange???
I would check the valve lash to eliminate that as a possibility. Make sure the rocker arms etc. are operating properly.

    Bookmark   January 13, 2008 at 10:19PM
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On/Off aspect points to ignition problems which should probably be fixed with a new coil? I did find recently some kind of solid state device wired in parallel with the coil grounding circuit on a mag fired Kawasaki that was the problem. Replaced that and the tractor started right up again, and I'm not familar with a Vangard or if it has one of those or not.

Why did the flywheel key shear?

    Bookmark   January 14, 2008 at 5:05AM
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What Bill said. You may have a sticky valve stem as well. The carb was varnished? The first 2 numbers on the code will tell you how old it actually is. The flywheel key shearing is an odd thing as pointed out above. On a horizontal, it is usually either improper torque on the flywheel nut or something went bad inside and stopped the engine. That is unless you have some real positive power link to the crank that can stop it suddenly.

    Bookmark   January 14, 2008 at 12:15PM
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I would use carb cleaner to prime it instead of gas, safer and a side benifit. Compression sounds low to me? Also sounds like a vacuum leak if you have to leave the choke all the way on. I would double check the carb and where it seals against the head. I would also check the valve lash. Some times soaking is not enough you make have to blow with compressed air or run wire through the little passages to get them clear. I use a can of carb. cleaner with the red nozzle installed. cleans and blows all in one action!?!

    Bookmark   January 14, 2008 at 8:32PM
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Hi and thanks for the feedback.
Key sheared on crank - I believe this happened because the nut on the end of the crank became loose and the flywheel had some play. But this is just a guess. The key slot on the crank side was pretty banged up when I got it. I filed it smooth then put valve grinding compound on the shaft and spun the flywheel to mate the surfaces.

Valve Lash - I checked that early on and it was within spec, I seem to recall about 0.10. I watched the valves open and close so I conclude that they are NOT sticking. I am not familiar with sticking valves, I have juet heard of it happening.

Ignition Grounding - well I thought about this and getting a new coil (solid state) and sparkplug wire. But I sort of hate to guess only to find that I spent $80 and didnt fix the problem. I may do this but for the moment, when I pull the cord gently I can see a good spark.

Vacume Leak - the engine side, paper thin gasket tore when I removed it from the carb manifold (rubber block). I thought that repairing it with some of that blue pipe dope would make a good seal. Maybe not. When it starts it just uses choke for 15 sec until it warms up then it runs fine without the choke.

Carb Cleaner - Well dont laugh but I soaked it once in laquer thinnner and then a few weeks later when I got really frustrated and wanted to clean the carb again, I soaked it in Pine Sol for 24 hours. Yes Pine Sol. People swear it works as a carb cleaner, try google-ing it. And I used compressed air to blow it out ... I went somewhat carefully with the blow guy , not wanting to damage or blast out any parts or orfices.

So.... per your suggestions, I will
get a new gasket
clean it with aerosol carb cleaner Gunk
use carb cleaner to try and start it
get new high octane gas (actually now the gas is 1mo old)


    Bookmark   January 14, 2008 at 11:35PM
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I think your valve lash is supposed to be about .003" for that engine.

    Bookmark   January 15, 2008 at 5:29AM
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Happy Ending to this story.

Deciding to start with the cheapest fix first,
I drained all the gas out of the fuel tank and
carb bowl. I poured all this and what was left in
the gas can into my car and got a gallon of fresh premium
gas. Just for insurance, I added fuel stabilizer. When I
put the new fresh gas in the Vanguard, it started right up.
I read on that gas has a shelf life of 30 days and after that it wont atomize. In this case it was true.

Read this: http://www.jackssmallengines.com/fuelissues.cfm
1. The gas you purchase at the pump has a shelf life of thirty (30) days. The law dictates that it has to be oxygenated and these additives evaporate and leave gum and varnish coating the internal parts of the carburetors, which also blocks critical passages and orfices.
Once all the aromatic parts are evaporated the liquid that is left will not atomise . The most common complaint from this issue is, âÂÂIt wonâÂÂt start.â Often we need to replace the carburetor to repair this problem, because of the gum and varnish build up within the carburetor.

What can I do to prevent this? When a piece of machinery is out of service for thirty days or longer.

  1. Drain the tank and carburetor, this will solve the problem bu.........
    Bookmark   January 16, 2008 at 10:29PM
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It isn't over yet.

That darn thing didn't start today and its snowing!

Well, I guess its time for some new parts.

I ain't the small engine genius I thought I was.


    Bookmark   January 17, 2008 at 10:50PM
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I can consistantly get it to start with the following process:

  1. Drain the carb bowl either manually or run it dry w/ petcock off.
  2. Put it choke give it a pull when it fires up turn on the gas.
  3. turn on the gas petcock.

If I leave the gas petcock on, it seems to flood and not start. This has a Mikuni carb. This is the exact behavior I have to use with my other 11hp Briggs leaf blower...keep the gas OFF until it fires up otherwise it floods and no start.

    Bookmark   January 20, 2008 at 6:07PM
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How did you change the spark plug wire?


    Bookmark   January 22, 2008 at 7:00AM
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I was de-bugging the engine and trying not to spend a lot of money. So to get it working, I cut the corroded end off the sparkplug wire and spliced in a good wire end I had laying around (from a volvo). To splice, I used a stainless steel 1" pin cut from a bike spoke, one end is threaded and screws into one side the other end i sharpened and pushed into the other side. Taped it all up and it works. Probably will not work forever and needs to be replaced with a new coil&wire unit $60.

    Bookmark   January 27, 2008 at 9:30PM
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Kind of reminds me of my youth when money was tight! I've "spliced" plug wires too.
A copper "core" would be better, like the conductor from a piece of house wire.
Stainless will have some amount of resistance, depending on the amount of nickel and chromium. NI-Chrome wire IS used in heating elements, although it contains much higher percentages. Your spoke is probably 18-8 vs approx 16-60 (Cr-Ni) used for that purpose.

    Bookmark   January 28, 2008 at 3:39PM
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Treefrog, you sound like a small engine expert to me. I'm not sure about the gas 30 day story. I never drain any of my machines, and don't bother to use the fuel cutoff if one is provided. I try to us Shell as it has some fuel cleaners in it, that may include stabilizer.

At high voltage I'd guess the little additional resistance of stainless steel shouldn't be a problem, but there may be some reaction between SS and Cooper, I know one should not splice copper and aluminum wire together, for example.

Sorry to read about problems with the Vanguard, that's the premium engine for B&S. My lower grade B&S and other engines run after sitting all winter with gas in the tank.

    Bookmark   January 28, 2008 at 6:17PM
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Hey guys, I got some bad news to report on this 9hpVanguard engine. After I got it running right and put the console and switch panel back on, I tried starting it and stopping it repeatedly. I never ran it for more than a few minutes and not under any load to speak of (just spinning the snow thrower blades).
All of a sudden I hear this metalic screeching and I shut her down...and following that, she is real hard to turn over, almost cant budge it with the rope pull start. Well it seems like I siezed her up - the 'autopsy' report is that on one occasion, I disassembled/reassembled the carb for a soak in cleaner. Well, on re-assembly, I put the float in upside down and this allowed gas to flood into the carb and overflow into the cylinder, down past the rings and into the sump with the oil. This gas in the oil, caused the oil to lose its lubricating properties and she frooze up.
I started up a new thread on the diagnosis and rebuilding of the seized engine over on the tractor forum.
I sure appreciate all your help and I am very disappointed that it came to this but I hpoe to turn it into a learning experience.


    Bookmark   February 3, 2008 at 1:17AM
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How in the world did you manage to get the float in up-side down? SHEESH!
I suppose a BFH would make it fit, tho!

    Bookmark   February 3, 2008 at 11:40AM
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Its that Mitsui carb with the pink plastic float and I either got it upside down or forgot to get the spring clip around the tab on the float ...anyway the valve was not closing and the gas flooded in.

    Bookmark   February 3, 2008 at 12:50PM
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SO, what ever became of the BCS tractor after the engine died? Did you mount a new engine, sell the thing, or is it sitting outside in a shed wating to be sold to me?

    Bookmark   March 5, 2010 at 10:15PM
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