Craftsman (MTD) Snowblower Carburetor Problems

FourtyCaliber

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At least I think it's a carburetor problem. First things first. Hello all. I'm new here. I don't know why I'm new here. I should have joined long ago as much as I find myself working on all of my equipment. I have perused this website before while searching for answers to my problems, but only joined now. I'm glad I did. I hope to learn some more in my time here and help out others as I can.

I have a Craftsman 2-stage snowblower with 5.5 HP Tecumseh engine. The engine model is LH195SP, Spec 67517D. This thing has never run right since I got it. Last year, at the beginning of the winter, during the first big snow, it died on me. I couldn't get it running and it got really cold outside, and we were getting a LOT of snow, and with all of the other things I had to do, I couldn't find enough time to try and fix it. So, I shoveled, and shoveled, and shoveled. All winter long. This year I swore I was going to try and get it running before the snow started falling. We've been lucky here, so far, as far as the snow is concerned, but I still haven't got it running right.

Before it died, I always had to run it with the choke partially on. This year I cleaned the tank out and cleaned and rebuilt the carburetor (non-adjustable, EPA compliant). The carb "looked" pretty clean before I cleaned it. Anyways, after messing with it for a couple weeks, taking the carb off and re-cleaning multiple times, I finally gave up on it. A couple times it gave a few "putters" where it attempted to start, but it never did. I used new gas and a new spark plug, even though the old plug was still fine. I checked for spark and it is good. It would just not start.

After all this I bought a new carburetor. I bought the "older" version of the EPA carb that came with the snowblower. The one I bought has the adjustable main jet and the adjustable idle mixture screw. I installed the new carb and after a few pulls, she started right up. To me, that makes it obvious that there was something wrong with the old carb, whether it was plugged-up passageways or whatnot.

After some adjusting, I got it to run "OK" at full throttle. It's not perfect. There's a little "popping" going on. The thing is I cannot get it to idle. When I move the throttle lever down, the RPMs drop and eventually it dies, even if I try and partially apply the choke. I preset the carb main at 1 1/2 turns out from lightly seated and the idle mixture screw at about 1 turn out from lightly seated.

I have good function from the main jet and the engine responds well to either leaning or enriching. HOWEVER, the idle mixture screw seems to do nothing. As a matter of fact, the engine will keep running even if I screw the mixture screw all the way in. I understand that the idle circuit doesn't even come into play until the RPMs reach a certain level.

The OEM EPA non-adjustable carb was a 640084B. The new carb is a 632107A, which is supposed to be the equivalent of the 640084B carb, but with adjustable main and idle mixture screws. As I said, it fired up fairly easily with the new carb and wouldn't even start with the old one.

I'm using new fresh gas, although it is E10. There is no E0 available in my area.

Th bad thing I did late this summer when I started working on this snowblower was mess with the governor. I don't know why I did, but I did. The thing about this governor is that the shaft barely turns. I checked it unhooked from the carb and the shaft will maybe rotate 5 degrees. I was watching a video on YouTube where a guy was showing about adjusting governors and he was showing the governor shaft movement on his Tecumseh motor (5 HP) and it was able to rotate WAY more than mine, more like 20 or 25 degrees I estimate. I don't know if this has anything to do with my non-idle condition or not. This snowblower has had very little use. I haven't ruled out any valve issues. When I did get it running with the new carb, I was able to rule out a bad gas cap, since it ran at high (not excessive) RPMs for at least 20 minutes until I shut it down.

Sorry for this long post but I'm out of ideas and would greatly appreciate any input. If any other info is needed please ask. Thanks
 

FourtyCaliber

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Hey Mark. Thanks for the links. The first link for the Tecumseh manual I already have. It's pretty much the same as the manual I got with the snowblower.

The "google" link you provided doesn't show "SERVICE DEALERS & TECHNICIANS TRAINING, K& T PARTS" when I click on it. I get a page of results but don't see anything like that anywhere on the page.

As far as the oil and stabilizer, yes the oil has been changed recently and I'm using SAE 5W30. When I bought the fresh gas, I put some stabilizer in it.

If the google link you provided is for the service manual, I already have that. I've been through it but am still unable to solve my idle issue.
 

FourtyCaliber

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Here's some new information. I went out today and messed with it some more. I couldn't get it to start. I found on the Internet some instructions for setting the governor. The instructions said to loosen the bolt holding the governor arm to the governor "clip" (not sure of proper terminology) and rotate the governor shaft all the way clockwise, hold the throttle arm wide open, and then tighten the bolt back down. This is supposed to statically set the governor. I did that and I could not get it to start. I repeated this procedure multiple times, each time moving the governor shaft a small amount counter-clockwise while still holding the throttle wide open and then securing the bolt. When I got nearly all of the way counter-clockwise on the shaft, I got it to fire up, although it ran only for about 15 seconds and died. I tried to restart it and could not. I again loosened up the governor arm and moved it more counter-clockwise, while holding the throttle open all the way and tightened the bolt. Again, it started, but only ran for a short bit.

Then, just for giggles, I removed the flywheel and checked the key for shearing. It looks fine to me. However, before I removed the flywheel, I checked the air gap between the magnets and the CDI. A .002 gap gauge was TIGHT. I checked my service manual and it says the gap should be .0125. Does that sound correct? If .0125 is correct, the air gap is WAY off. Also, on the flywheel, next to the groove, I can see evidence of a prior flywheel shearing. The edge is "chipped" slightly, about the thickness of a key, like what would happen if the flywheel spun slightly after the key sheared.

Does/can any of this have the effect of keeping this engine from running properly?

What would make this engine have to have the governor set all the way counter-clockwise (as opposed to static set clockwise) in order to get it to even fire a little?
 

mechanic mark

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Hey Mark. Thanks for the links. The first link for the Tecumseh manual I already have. It's pretty much the same as the manual I got with the snowblower.

The "google" link you provided doesn't show "SERVICE DEALERS & TECHNICIANS TRAINING, K& T PARTS" when I click on it. I get a page of results but don't see anything like that anywhere on the page.

As far as the oil and stabilizer, yes the oil has been changed recently and I'm using SAE 5W30. When I bought the fresh gas, I put some stabilizer in it.

If the google link you provided is for the service manual, I already have that. I've been through it but am still unable to solve my idle issue.

Click & download at bottom left of screen.
 

FourtyCaliber

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I have another question that I hope someone won't mind indulging.

I was looking at the flywheel key. It has a "notch" at one end. For the life of me I can't figure out what this notch is for. I remember when I worked on older motors that there was points cover and a notched key would slide under the points cover. But, my motor has a CDI ignition and therefore no points. There is a nylon bushing on the shaft, but it has it's own integral key that sits on the crankshaft groove and keeps it from spinning. There is no need for this notch in this key, as far as I can tell.

I, also, read on another forum where Sears/Craftsman would use an "offset" key. The information I gathered is that the width of the groove in the crankshaft is different slightly from that in the flywheel. From what I understand this "offset" key somehow alters the timing for some reason.

I guess what I'm getting at is if I have the right key for my engine? It was apparent to me that someone has worked on this before because of the indentations on the edge of the flywheel from a previous key shearing. I just wonder if the right replacement key was installed?
 

FourtyCaliber

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Mark, I was able to download the manual you suggested. I just did a search for "SERVICE DEALERS & TECHNICIANS TRAINING, K&T PARTS". It's pretty much the same as the manual I have, but thanks for the additional information.
 

FourtyCaliber

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I'm back.Sorry about the delay. I have some family issues going on.

Anyway, I tried some more and I still couldn't get it to start. I removed the head and the breather assembly. The exhaust valve is not fully seating. I don't think its from something stuck in the guide. There is no clearance between the valve stem and the pushrod. I think I read where there is supposed to be .004 - .008 lash? How are the springs and "keepers" removed? Once removed, I can remove the valve and grind a small amount off the end? How do I l know how much to grind off since there is NO clearance (lash) now? How do you control the grinding so as not to remove too much material from the stem? I just measure the lash between the valve stem and pushrod? Where should the piston be located when I measure lash? I checked 4 times around and the exhaust valve does not seat fully during any of the revolutions. It is definitely not seating. And how does the compression release figure into it? The manual doesn't cover this at all. I thought I read somewhere that the piston should be 1/4" down after the compression stroke and that is where the lash should be measured to account for the compression release. Is that right?

What's the best tool to compress the spring?

If I'm not right in my thinking please correct me. And please share any thing else that I may be missing or need to know.

Thanks
 

ILENGINE

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There is a lot to read through on the post above, but I will try to answer a couple of quick things. The gap being .125 is correct, and the .002 can cause it to be hard to start, no start, or not running correctly. Has minor effect on timing, as well as voltage flux.

The valve stems are pretty hard, and if you are working slow, you can just remove a small amount and keep rechecking the valve gap until you get it correctly. Valve stems are pretty tough, especially the exhaust stem, so hard to mess up.
 
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