Troy Bilt Horse III - Carb Issues

[TWG1572]

So, I picked up a Cragslist find yesterday. 1984 TroyBilt Horse III, with the 8 HP Briggs I/C engine. Engine # 1954432-0291-01

On the phone, the guy says he had a friend who "is awesome with engines" go over the tiller last year. (we all know how this ends). Get there and there is gas all over the carb. Engine isn't running at full power. Hmmm... But I bought it.

I get it home and look closer and it is really tough to see where it's coming from. The whole carb body is wet. We are talking wet above the float, on the upper body all the way up to where it joins to the intake elbow. The gasket between the the upper carb body and the intake elbow looks wet too.

I did some internet research last night and learned that these old updraft carbs love to leak. But the diagrams I saw indicated that they would leak from the bottom - there two likely failure points - one at the high speed needle on the bottom and the other at the float. But the diagrams also showed channels that would take the leakage away from the spot internally and dump it on the bottom of the air intake. I also read that these things love to leak when they are choked.

Anyway. I'm thinking a tear down is in order. I'm looking for input on what to look for, since this is the first time I've seen one of these things. Right now, I'm thinking an issue with the float/needle but that doesn't explain to me how the entire carb above the float is getting wet.

I should have left the gas turned on last night to see if it dripped when sitting, but I forgot. I'll try that today.

Appreciate any thoughts/wisdom/etc...

 

[TWG1572]

I got about 20 minutes before I picked the kids up. Fired it up and thought I'd make sure the carb was set right. Runs best with the high speed needle at 1/4 turn. Low speed does nothing. I'm feeling more and more like a rebuild is in my future.

 

[Bobaloo22]

I had the same issues with mine, (Pony). The carb was shot could not run under a load it felt like it would run out of gas. A new carb or rebuild should take care of it, also I use Startron in my fuel to keep the carb from going bad. Wish the previous owner did.

 

[jeepman3071]

Sounds like a carb rebuild is a good idea. Partstree.com has good prices on carb kits.

I always cringe when someone brings me an engine that won't run even though "their guy who is awesome with engines" got it running last year.

Those Troy Bilts are good machines, nice buy!

 

[Pop_Rivit]

Those carburetors are pretty simple. Pick up a decent kit, search YouTube for some instructions, and just rebuild it.

 

[Doog]

Originally Posted By: Pop_Rivit
Those carburetors are pretty simple. Pick up a decent kit, search YouTube for some instructions, and just rebuild it.


1+ That is a good machine...well worth the time and energy of a rebuild. Nice find.

 

[AandPDan]

Nice tiller and the engine is very rugged.

On the 2 piece flo-jet, a common source of leaks is the upper carb body warping.

Before you try to take it apart, be sure to remove the fuel nozzle. You'll bend it if you just try to separate the carb halves. Remove the high speed mixture screw (bottom) and use the correct size screwdriver. The nozzle does not come in new B&S kits.

 

[TWG1572]

I was able to find a shop locally that had a kit and got the rebuild done this afternoon. I wish I could say success, but still have some leaking issues. I know I got the gasket surfaces clean, so I guess it's on to the next possible cause. The carb definitly needed cleaning anyway - gobs of yellow stuff came out with the high speed needle.

When I had it running, it looked like it was actually getting some spray between the upper carb body and the intake elbow. The gasket on that was brand new-ish, while the gasket in the carb could have been origional from how brittle and stuck on it was. So, that newer gasket leads me to believe that's maybe where someone else tried to fix the trouble spot in the past.

Is this a sign of upper carb body warpage? If so, I'm guessing the easiest fix is a new upper carb body?

The thing is puffing through the intake more than I'd expect, compared to my briggs twin. I'm hoping that's not a sign of more fun to come.

BTW - thanks for the heads up on taking the high speed nozzle out first. Never would have guessed that.

 

[TWG1572]

Just a clarification - when I said puffing out the intake I'm not talking about backfiring. Just that I can feel air coming out the intake end of the carb. I did have the filter off, if that makes a difference.

 

[AandPDan]

By "intake elbow" do you mean the lower carb body?

It sounds like the upper is warped. Again, it's common. Take the carb off and see if you can insert a .002" feeler gauge between the upper/lower body at the air vent boss, that's the spot just under the low speed (upper) needle.

You can try to tap it flat or even file it.

A new carb is probably best but they're pricey, $140 or so. I've seen aftermarket carbs in the past for about $60.

Edit: air shouldn't be coming back. If it does I'd think you might have a sticking intake valve.

 

[TWG1572]

What I'm calling the intake elbow is the section of pipe that goes from the top of the carb, curves 90 degrees and enters the block. There's a gasket between that and the upper carb body - that's where I saw the fuel spray.

 

[AandPDan]

OK, I thought you meant the lower body since that's where the air comes in.

That's not a normal sign of a warped upper body. You'd see fuel leaking/oozing between the two carb halves.

Check the flanges for straightness.

 

[TWG1572]

Yeah, sorry if I used the wrong term. I'm pretty much self taught, so there are a lot of thing-a-ma-jigs and whatcha-ma-call-its in my world. Thankfully there are forums like this that have always helped me figure stuff out!

Last night I pulled the intake off the block and carb and re-cleaned both surfaces and checked the flanges with a known straight edge. Not seeing any gaps using a flashlight behind the straight edge. Not sure if there is a better way or not - I'm guessing this would be a pretty small gap. Figured I'd put it back together, make sure everyting is good and tight and give it a test run tonight. Ahh, the joys of having my little kids rooms above the garage - no late night engine running.

While I was at it I took a peek at the intake valve. It's definitly moving up/down smoothly as I pull the recoil. Since I had the plug out I just threw the compression tester on it - 95 psi. I know that doesn't tell me much, but I do feel a bit better about the overall condition of the engine.

I'll try firing it up when I get home and see if I eliminated the fuel dripping by re-cleaning/tightening the flanges. Odds are low, but I'm hoping.

The highest wet spot is right at that gasket on top of the upper carb body, so I'm hoping that's the only trouble spot on the carb. Gotta get that dried up first.

 

[jeepman3071]

Did you clean out the carb real well? I've dealt with a few carbs that leaked badly and dripped gas out the carb. Every single one had a sticking needle valve or the float had a small hole in it, which filled it with fuel and prevented it from floating. If you take off the float and shake it next to your ear you can hear if there is fuel inside of it.

 

[TWG1572]

I feel good about the cleaning, but that's always a loaded question. I used carb cleaner, soft thin wire through holes, then compressed air. Plastic razor blades to scrape and clean off gasket material. Needle valve and seat were replaced. I did the float shake thing - nothing splashing around.

One could argue I should have let the whole thing soak in a vat of cleaner overnight, but I didn't have that on hand. Overall I feel OK about the cleaning, but I know enough about these cleanings to know that sooner of later your are gonna miss something and have to go back in...

The fuel coming from above the carb body is a bit odd. If it was the float - woudn't it be dumping from the bottom of the carb?

Hoping to have time tonight to play around with it a bit.

 

[AandPDan]

Any chance you can post a picture of where the fuel is coming from?

 

[TWG1572]

I've posted a pic I found on google of the same engine. The area where I saw a bit of fuel spray is circled - it was on the engine side of the carb. Anything under that gasket is fair game for being wet with gasoline. It pools a bit on the flat top of the carb. The only other thing that high which could leak would be the throttle shaft I guess.

I'm definitly looking forward to playing with this a bit more tonight. I would have thought there would be enough vaccum in that section of the carb to keep the fuel/air mix in, but evidently not in this case.

http://i46.tinypic.com/2i8y73p.jpg[/IMG]]Picture

 

[AandPDan]

That is unusual.

It's well above the float level.

Is it wet from the carb body leaking?

Kind of a chicken and the egg thing I guess, where does the leak start first.

 

[TWG1572]

So, it appears that me re-cleaning and tightening the intake manifold screws into the carb did something because it stayed dry for 15 or so minutes while I was running it. That's the good news.

On to the bad news...

It ran OK at full throttle with a bit of popping. I could never get the high speed needle just right to make it run super smooth. But when I engage the transmission for the wheels, it just pulls down and runs out of power. It will move on its own power, but it's not running strong. Definitly not in tilling shape yet.

The blowing of air out the intake of the carb (where the choke is) has continued. It's not as strong as the exhaust but you definitly know it's happening when you put your face down there. The blowing air is also carrying some oil with it. The breather valve appears to be working, because you can feel the air pulsing from that too. Nothing like what's coming from the intake though.

The bolt hole going into the bottom of the carb that attaches to the metal plate where the throttle/governor/kill wire all attach appears to be stripped. I'm hoping I can figure out some sort of solution rather than buying a new $60 lower carb body.

So, after kicking myself for ever buying this - I got a wild hair and decided I might as well take the head off and look at the valves. Lord knows I can't screw it up more. While I was doing that I noticed the prior owner had electrical taped the spark plug wire where the insulation had been cut. I didn't pull the tape, but by the way it flexes its pretty much down to wire. Guessing I should add a new ignition coil to the parts list.

The valves were really dirty so I cleaned them up. Lots of black sticky stuff on the intake valve and in the area under them where the intake manifold attaches. I've got the block cleaned up down to the metal/valve seats and the valves as good as I can get. Both valves are moving up and down ok, and I can spin them in their guides without feeling them binding. The exhaust is a little tighter, if that matters.

I'm feeling like I've left the beginner level course and jumped right into the advanced one. I suspect I should lap the valves/check clearances since I'm this deep. Never done that before, going to have to check out some youtube videos I guess.

Definitly wasn't planning on this much work. It's a good learning experience, but I'd preferred it would have ended with the carb rebuild!

Appreciate the help everyone!

 

[TWG1572]

Just to provide a quick update, I measured valve tolerances last night. The intake valve had no clearance - couldn't even get the .002 gauge through it. Exhaust was .008, which is a hair low.

Loads of nasty carbon on the head (see pic) so I got it and the valves all cleaned up. I ground the intake valve within the correct tolerance. Figured I'd also lap them since I had everything apart. Now I'm just waiting on the head gasket to come in so I can put it back together.

Since the guy said this sat forever, and the pic looks like it's burning oil I figure I'll give it a MMO piston soak tonight. Not gonna hurt anything, and if there is a stuck ring it may free it.

http://i46.tinypic.com/oay72a.jpg[/IMG]]