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Hello! First time poster here hoping for some wisdom. I had a small fire (not my first) in my late 90s 18hp 345 this weekend. I think the fire originated in the muffler guard which had quite a bit of collected debris. In any event I put it out quick and there was minimal damage to the grey plastic intake and new vs old damage to the fuel line just before it goes into the fuel pump. The throttle cable is also not working and I have one on order.

Now I replaced the fuel line and fired her up but the tractor isn't running right. It is surging at idle and it seems not to run at high enough RPM and it isn't running as loud as it usually does. It is running fast enough to get the blades going but the blades spin slow. When driving the tractor it maybe moves at half speed with full force on the pedal. Also when I disconnect the left or right spark plug wire the engine stops surging.

So far in addition to the fuel line I have replaced the carb, both spark plugs, fuel filter, and air filter with no change in the problem. I don't know if the carb requires adjustment I have never worked on a carb before but I would think not because it is running just as it did with the old carb. I also have a fuel pump which I was thinking about throwing at the problem... help!
 

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Is there a plastic spacer between the carb and intake manifold that got melted? Or one of the gaskets in the intake system has been burnt?
 

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Discussion Starter #3
Not from what I can tell, the grey plastic elbow between the air intake and carb looks good and the o ring between it and upstream has seen better days but it's not too bad, gaskets in either side of the carb were replaced.
 

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Hello! First time poster here hoping for some wisdom. I had a small fire (not my first) in my late 90s 18hp 345 this weekend. I think the fire originated in the muffler guard which had quite a bit of collected debris. In any event I put it out quick and there was minimal damage to the grey plastic intake and new vs old damage to the fuel line just before it goes into the fuel pump. The throttle cable is also not working and I have one on order.

Now I replaced the fuel line and fired her up but the tractor isn't running right. It is surging at idle and it seems not to run at high enough RPM and it isn't running as loud as it usually does. It is running fast enough to get the blades going but the blades spin slow. When driving the tractor it maybe moves at half speed with full force on the pedal. Also when I disconnect the left or right spark plug wire the engine stops surging.

So far in addition to the fuel line I have replaced the carb, both spark plugs, fuel filter, and air filter with no change in the problem. I don't know if the carb requires adjustment I have never worked on a carb before but I would think not because it is running just as it did with the old carb. I also have a fuel pump which I was thinking about throwing at the problem... help!
If the throttle cable is not working, then there is your problem. The plate that the cable is mounted to is what controls the fast idle speed. You will need to loosen the screws that hold the plate and adjust to get higher RPM's. I believe it should be at 3500 rpm at full speed.
 

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Discussion Starter #5
I've just been pushing the arm that the throttle cable connects toward the right (facing the machine) to start it and then letting it sit far right when running which as far as I can tell should be full throttle. Will this not work?
 

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Discussion Starter #6
Progress??? So I shifted the aforementioned plate to the left so that when the arm goes to the right there is further travel on the linkage and this definitely did help however the engine is still surging and I'm pretty sure it isn't quite running at full speed....
 

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Your coolant bypass hose looks like it is almost sitting on the exhaust in that picture - seems like a problem waiting to happen.

Not sure if you are just testing out the fit, but the throttle cable doesn't normally run through the hood hinge hood bracket.
 

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Discussion Starter #8
Yes the throttle cable was there temporarily. The coolant hose does live a little close to the radiator and isn't in the best shape. I'm going to have to figure out some way to tether it up and will probably replace it also. After running the machine for about an hour today I believe it is at least 90% better after moving the metal plate... I still feel like it is running a little slow. How else can I adjust the engine speed? I just ordered a tachometer on amazon so I'll figure out tomorrow if it really is running slow or if I'm imagining things.
 

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Make sure the governor spring is attached correctly from the arm to the carburetor.
Also, there is a procedure for adjusting the governor arm/linkage. Should be some good info online that you can find with a little searching.
 

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Discussion Starter #10
Thanks a ton, I bet that helps a lot. Just looked up the procedure and I'm hoping that will get me the rest of the way there. Thanks everyone for your help!
 

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I off this in the sense that misery loves company. My Craftsman LT 18.5 HP Kohler twin, has the same muffler fire problem, but luckily never burnt anything up on the engine. Happened in mid summer when grass was dry, and especially in the fall with lots of leaves.

When I was still using that tractor, I'd have a metal "stick" aboard, just to pull smoldering leaves out of the space between the muffler and the heat shield. Sometimes open flame would erupt but not real big ones.

Would remind me of the old days, the smell of burning leaves in the fall and all of that...
 

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Discussion Starter #12
So I got the new throttle cable in and adjusted the throttle plate and governor with no success. According to my vibration tachometer It's running at 2700RPM. I did a little research and tried the idle speed screw on the side toward the top of the carburetor. I turned it in (clockwise) a few times and the RPM kicked up nicely to 3400RPM. Perfect... except after running it for about 30 min I'm getting smoke out of the right side of the exhaust along with sweet smelling white smoke. There is quite a bit of smoke on startup and the machine continues to smoke to some extent while running. What is going on here? Is this related to messing with the carburetor or do I have another problem ?head gasket? also seems to be something dripping out of the exhaust on the right. The tractor has always smoked a little on startup but always cleared and never had an odor.
 

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Have you checked your coolant level? The sweet-smelling white smoke is an indication of coolant leaking into the combustion chamber. The two most likely causes are a bad head or intake gasket.
 

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Sweet smelling smoke?.....coolant getting into a cylinder?...also sniff that liquid coming from the exhaust, and check the oil...is the oil getting discolored or foamy?...Usually surging is an indication of a restricted passage in the carb......you changed the filter, possibly fuel line needs replacing also?...it could have dislodged something in the line when you were extinguishing your fire and gotten into the carb....also...One of my brothers live up on Cape Cod and does some volunteer work for a land trust....someone had donated a Gravely walk behind with duallys on it..my brother was the only one who knew how to work on it and use it and he was always telling me what a great machine it is. In October he was clearing some land when the muffler just blew off, sending out a flame that caused some fire....the gas tank caught on, the gas dripped on the tires and you can imagine the outcome....total loss right after he told me about that I saw an ad for Ace Hardware...it was national fire prevention week and extinguishers were on sale...I already have one in almost every room in my house, out in the garage and shed, and one for automobile fires in my truck ...now I got a couple extras and mounted one on each tractor that I use regularly....may be something to consider if this is likely to happen again
 

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First. Let me inform you that the muffler/fire situation was a recall by Deere back in about 2002. Deere would send you a modified plate to replace the factory one to prevent a fire that grass clipping would create a fire there. From looking at the photo you supplied in a post above, I cannot see if this tractor has the modified plate.

Also, back to the present oil burning from the muffler. You must check to see if the fire has melted the plastic valve covers and the 'o-ring gasket causing oil to drip down on the muffler making it smoke. I also notice the carburetor/governor plate assembly appears to be different that what was installed on a late model 345. I have a '99 345 and it has a complete different carburetor/governor assembly that was you show.
 

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The 345 is notorious for smoking at the exhaust on either or both sides and it is nothing but the valve covers leaking oil that runs down to the exhaust connections. The valve covers are black plastic and they warp with age and HEAT. I bought a GX 345 this Summer because the PO thought there was a big problem with the engine because of the smoke from the exhaust. I have found that it helps to buy both types of valve cover gaskets and use both at the same time. I use Permatex form-a-gasket in the "O" ring slot for the "O" ring gasket and then I put some of the Permatex on the flat gasket on the head side only. Tighten them down slowly and do not over tighten them. That will fix the smoking problem that appears to come from the exhaust but isn't. The surging is a carb problem and even if new, means you have a partial blockage in one of the jets. There is no short cut except taking the carb off and giving it a thorough cleaning. Do as mentioned above and replace the filter and fuel lines before putting the carb back on. Stay away from the governor control. So far, I have had about ten GX 345's and 345's and none of them have had any governor control issues and they all surged. That procedure to fix the governor is difficult to get right and it is a mechanical link. If the set screw isn't loose there is no way for it to have moved. Good luck. You have had enough problems already.
 

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Discussion Starter #17
The surging went away once I got the new throttle cable installed. Runs smooth now and at the correct RPM now that I adjusted the top screw on the carburetor. Since I adjusted that screw there is a TON more smoke than usual that I am 99.9% sure is coming from the tailpipe... I think it smells a little sweet like burnt coolant but I don't have any experience with this. From what I can tell I am not loosing coolant. I typically have a little smoke on startup and a little smoke on both sides just below the valve covers... I went ahead and ordered new gaskets but I'm doubting that this will fix the new smoking problem... I changed the oil today and added oil stabilizer. I already did the fuel filter and line from the filter downstream. I am in the process of cleaning out the fuel tank and replacing the line from the fuel filter upstream. I doubt this will do it but I'm trying to get the easy stuff before taking it in... as far as the throttle plate looking different I'm not really sure that is my problem at this point since the RPM and surging issues are no longer...
 

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I seem to recall that there is/was such a thing as chemical test strips that you could dip into your coolant and they would change color in the presence of dissolved combustion gases, which of course would indicate a leak between at least one combustion chamber and coolant passage. Might be worth looking into.
 

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Discussion Starter #19
Valve cover gaskets installed today with no change in the problem. Still smoking a ton, smells sweet. No noticable change in oil or coolant level. Fluids appear uncontaminated.

New things tried
1. I removed about 10 ounces of oil to bring it down to 1/4 above the low mark. This seemed to decrease the smoke a little while operating the mower however at idle it smoked just as much.
2. I also tried messing with the idle speed screw on the carb since speeding things up with this screw is when the problem started however this didn't help at all. The smoke did clear momentarily just before getting it to 3400RMP and when decreasing the RPM from 3400 but only for a few seconds.

New Problems/Observations
Overheated several times today, coolant light flashing.

I'm going to try the old carb and see if I get anything different. Seems like I'm getting nowhere.
 

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Discussion Starter #20
Swapped the old (cleaned) carb in with no improvement.

To Recap:

Small fire damaged the fuel line and throttle cable which lead to:
1. Throttle cable replacement
2. Fuel line replacement

After which the engine surged and RPMs were low which lead to:
1. New Air Filter
2. New Fuel Filter
3. New Carb
4. Throttle Plate Adjustment (this is what seemed to eliminate the surging)

After which the engine still was running low RPMs (2700) which lead to:

1. Adjustment of screw on the top of the carburetor brought RPMs up to 3400

After which the engine started smoking (white and sweet) a TON at startup and while running which lead to:

1. Oil Change with Lucas Oil Stabilizer
1. Replacement of remaining fuel line
2. Replacement of valve cover gaskets
3. Trial run with old carburetor
4. Adjustment of screw on the top of the carburetor which started the problem

Unfortunately it is still smoking! Anything easy left? I don't think I could tackle tearing into the engine so I guess I'm going to have to take it in :( I'm concerned that whatever engine repair it needs is going to be too expensive to be worth doing....
 
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