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23 HP B&S Vanguard loses power

Posted by jimb206 (My Page) on
Thu, May 2, 13 at 11:58

I have a Simplicty Conquest with a 23 HP Vanguard Model 386777. About 6 years old 205 hours on the clock. At the end of last season it ran fine. This year before using it I changed the spark plugs, oil and all filters. The first time using it this year it ran fine for about an hour. Then it began to lose power when under load. At full throttle with the mower deck engaged and moving forward it loses rpm and runs rough. If I come to a stop with the deck still engaged it would recover. But soon after I'd begin mowing again it loses power again. I thought maybe the fuel pump was bad as there was very little gas in the filter. Put a new pump on and same problem.

Any ideas?

Thanks,

Jim


Follow-Up Postings:

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RE: 23 HP B&S Vanguard loses power

  • Posted by larso1 So. CO Zone 5 (My Page) on
    Thu, May 2, 13 at 12:34

There used to be a common problem reported with certain model Craftsman tractors that involved the rear brakes binding up and not releasing. Just one thing you might check. Also might be a drive belt problem or sheave? I'm sure others will chime in with good/better ideas....


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RE: 23 HP B&S Vanguard loses power

I'd suspect a blown head gasket.
Disconnect one spark plug wire and ground it.
Take it for a test mow.
If it behaves the same, try the opposite side.
Compare results.


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RE: 23 HP B&S Vanguard loses power

It seems to be engine related rather than something with the brakes. But thanks for the suggestion.

There's no smoke so I didn't think it was a headgasket. But I don't know for sure. Spoke with the shop I purchased it from (who is very busy right now) he said try changing the spake plugs again before he comes to pick it up. I did change them before using the machine this year and maybe one new one was bad.


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RE: 23 HP B&S Vanguard loses power

You can still isolate it to one cylinder or not.


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RE: 23 HP B&S Vanguard loses power

You would be wise to take Bill's advice.

Walt Conner


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RE: 23 HP B&S Vanguard loses power

Thanks Bill and Walt.

Walt it's been a few years since you sent me directions on how to change the head gasket on a Husqvarna/B&S tractor I had. Job was easier than I expected and engine ran great for the 2 addition years I owned it. So Thanks again.

I'm a little confused about the current problem. Theres no smoke so does that indicate the head gasket is OK? Are Vanguard engines prone to head gasket problems with such low hours? I have 205 hours on the engine.

I'm going to wait till tomorrow and change both spark plugs. Hopefully that will solve the problem. Hopefully.

But Bill I'm confused. If I disconnect the spark plug wire (one at a time) and ground it and mow what could it tell me? I'm guessing if it runs the same that is badly on one side and dies on the other it means thats the side with the problem. Does that prove it's an ignition problem? Or could it also be a fuel problem on that side? Like I said I'm confused. I actually like working on small engines unfortunately I don't do it much and I learn as I go.

Thanks again guys.

Jim


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RE: 23 HP B&S Vanguard loses power

Head gasket problems on vanguards is not common- but the head gasket ideas may apply.

here is another idea.

check the sparkplugs to see if they are black with carbon or soot. This would indicate an excessively rich fuel mixture.

During high speed with a load, the fuel may be passing through the high speed circuit on the carburetor. If the high speed air bleed is blocked, an excessive amount of fuel will be drawn into the engine. If you stop the tractor, the load is reduced, and fuel may be drawn through the idle circuit - and the engine recovers.


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RE: 23 HP B&S Vanguard loses power

Many twins will actually mow (not well) on one cylinder.

It's a 23 HP engine. 23/2= 11.5 HP,


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RE: 23 HP B&S Vanguard loses power

Problem solved. It was a clog(s) in the carburetor. I didn't clean the carb I had the local shop take care of it.

I will adjust valves, change head gaskets change transaxel fluids etc but don't do carburetors. Would like to but just don't know how to clean or adjust them properly. I did look on-line vids of how to clean a carburetor but didn't find anything that really helped.

Thanks to everyone who took the time to respond.
Jim


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