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Discussion Starter · #1 ·
I just purchased an older model Craftsman tractor.

Model #917.255912 18hp twin

I was wondering if anyone could provide me with some information on this tractor as far as production, the best place for parts, reputation of this model, etc..


I have a few issues with mine as well that I hope someone can shed some light on.

After I bought it, I noticed that the sector had damage on the left side. About 3 teeth were almost completely gone, causing slipping of the steering wheel when turned all the way to the left. I have had no luck locating a new one of these. Does anyone know where I can get it? It's discontinued from Craftsman, and i ordered it from one place, only to have them contact me and tell me they couldn't get it either.

In the meantime, I have built metal up with a welder where those teeth were so wheel doesn't slip.

I also have a surging problem with it, and it generally will not run right unless the choke is part way out. From searching on here, it seems it could be the fuel pump. I see others posting about getting rebuild kits for their pumps. Where can you get these?

Other than that the tractor is in really nice condition, no rust at all. I just changed the engine oil, and transaxle oil yesterday, and am putting a new fuel filter and drive belt on it tomorrow. The tractor also came with 55lb wheel weights for each side and a 46" dozer/snow blade, which is the main reason i bought it, to move snow in winter.

Any info is appreciated.
 

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I thought that I might have one for you but...the numbers don't match, the one I have is for a 917.252683 so I assume that yours is newer than mine. I checked all my suppliers and none of them had that part. Funny, they seem to have one for my older tractor!?

In reference to your surging, kinda sounds like it's not getting enough fuel, possibly a plugged fuel filter. I would try this which has worked for me in the past. I would take the fuel hose off the carb and replace it with another fuel hose connected to a funnel that will fit the hose. I then have a friend hold the funnel up and pour some gas in it. I start the engine and see how it runs. If it now runs smooth without have to choke it, you've found that you have a fuel delivery problem. The last one I had had junk in the tank which was blocking the fuel screen. There are other, neater ways of doing this but this is just a fast test. You're just by-passing the tank and fuel filter.
 

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Cranky Motorsports
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your best best may be to find a parts tractor. Keep asking on here though, I know several members have those!
 

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Discussion Starter · #4 ·
Thanks for the info. I changed the fuel filter thismorning with no change.

This tractor also has a vacuum fuel pump as well, am I'm wondering if this isn't working correctly. I guess I could try your method with and without the fuel pump is the loop and see what happens.
 

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Discussion Starter · #5 ·
Update:

I replaced the fuel pump, and all associated fuel and vacuum lines, including the fuel line clear back to the tank. In the process of emptying the tank I found a screw rolling around inside of it, and I was sure that this would've been the problem, thought maybe it ended up in the hole in the bottom of the tank. No change in operation with any of this.

Right now it once it's warmed up it will sit there and idle well for the most part, but at higher throttle it still surges up and down.

I sprayed around the intake manifold and carb with starting fluid while running to see if there's a leak somewhere, couldn't find anything.

I'm starting to think there's an issue with the carb, but I don't know much about carburators or where to start as far as adjustments are concerned.
 

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The first thing i do with bns twins is clean the carb. I would bet thats the prob. There not that hard to clean, take the top half off and take the plug on the side out, spray carb cleaner in every passage, like the one behind the drain plug.
 

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Discussion Starter · #7 ·
Yeah tomorrow I will be cleaning the carb, and seeing how that goes. I dont know what else it can be. The fuel system is clean and all new lines/pump, no issues there. I guess I'll hang onto the old Walbro fuel pump since there seems to be nothing wrong with it.
 

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Ya, probably the next step is the carb...I try to do the simplest things first. They're not hard to clean at all. When you remove whatever idle/fuel screws that are on the carb, it's best to tighten them gently first till they bottom out, count how many turns they are presently set at...then remove them. That way, you can set them up the same as they were. Also, after the bowl is taken off and you remove the float assembly, there may be a jet or two to take out. Use special caution removing these because some are very hard to remove with a screw driver. They're soft brass. After using carb cleaner on everything, if you have compressed air, I blow everything out and put it back together. Good luck!!
 

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Discussion Starter · #9 ·
I also found a carb adjustment procedure in a manual online for a similar model, stating how far to turn the mixture screw back out after bottoming it out, and how to adjust the idle screw, etc...so I'm going to use that as my baseline after I put it all back together. I did check the screw positioning today and it was spot on with this manual.

One thing I noticed, was that it tells you to adjust the idle to between 900-1200rpms...dumb question, how are you going to know engine speed without a tach?
 

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I also found a carb adjustment procedure in a manual online for a similar model, stating how far to turn the mixture screw back out after bottoming it out, and how to adjust the idle screw, etc...so I'm going to use that as my baseline after I put it all back together. I did check the screw positioning today and it was spot on with this manual.

One thing I noticed, was that it tells you to adjust the idle to between 900-1200rpms...dumb question, how are you going to know engine speed without a tach?
Just estimate the idle speed...it's not that critical. By the way, how's the spark plug? I actually had one that surged and found out the spark plug gap was way off...
 

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could be a piece of crud in carb, most of these used a fixed jet carb and if you get a piece of crud in it it will cause issues with them.
Sector damage with teeth missing is common with age on these, i did replace the one on my 87 about 10 years ago for this problem.
 

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Discussion Starter · #13 ·
I cleaned the carb today, took it off of the tractor to do it, and I sprayed it out real well with carb clean, removed the drain and cleaned everything out and put it back on the tractor. After that the tractor would not run at all. I had no fuel at all going into the carb, in fact when I removed the fuel line to take it back off there was actually pressure built up in the fuel line because it wasn't pushing the fuel through the carb.

So I took the carb back off and split the upper half of it to look at the float, but that seal fell apart when I took it apart. So I ordered a new one and it will have to wait until I get it to mess with it further.

Any idea why I couldn't get any fuel after cleaning it? All I did was squirt everything out with carb cleaner.
 

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Float was stuck, if you didnt take the top half apart before, you should have couse thats were most of the passages to clean out are. Those gasgets pretty much rip on 50% of mine. Clean out all those little holes with carb cleaner
 

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Discussion Starter · #15 ·
Float was stuck, if you didnt take the top half apart before, you should have couse thats were most of the passages to clean out are. Those gasgets pretty much rip on 50% of mine. Clean out all those little holes with carb cleaner
Yeah I ended up cleaning all of those other passages once I took it apart. Hopefully everything is good once I get the new gaskets.
 

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Discussion Starter · #16 ·
I got my gaskets and put the carb back together today. The tractor started right up, but once i pushed the choke back in it wasn't running right.

I had the mixture screw at the starting point of 1 1/2 turns out. I started bringing it out more and after about another 3/4 turn, the tractor was idling fine with the choke pushed in.

Unfortunately, there's still a slight amount of surging in higher rpms. It comes and goes very quickly, but it's there. Any ideas on what I can do from here? Is it just more adjustmens I need to make, or is more going on here?
 

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How about the throttle / choke cable adjustment? If it's off, you could always have some choke applied that could cause your surging. On my 97 the will hardly run if a little choke is applied after it's warmed up.
 

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Discussion Starter · #19 · (Edited)
I think I finally figured out what the problem was.

There was very little gas in the tractor when I bought it, so I just added what I had here. When I changed the fuel lines I put the existing fuel back in a can while I changed the lines, and put it back in again.

Today I decided to get rid of that gas entirely and fill it with new, 89 octane. I started the carb adjustments over again, and this time, I had to adjust very little(maybe a 1/4 turn) from the starting point, and now the tractor is much more responsive. The surging is gone and it idles nicely, where before the throttle response was very sluggish. So I think whatever gas was still in the tractor when I bought must have been bad and was giving me trouble even after I put my own gas in.
 

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Man I don't know how I missed this post. I have a 917.255912 that I bought new in 84 or 85 I think. It has been a great tractor, I used it to plow soil, plow snow, mow, pull about anyting I wanted to including other tractors in tug a war. I have over 2,400 hours on it. Mower deck gave out several years ago so I bought a DGT6000 917.276120 to replace it. The new one does not hold a candle to the old one. I still push snow and plow with the old one and pull the neighborhood kids for hay rides.

Where did you get one without any rust, thats amazing.
 
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