Craftsman (MTD) Snowblower Carburetor Problems

[FourtyCaliber]

Alright, I'm back. Still have some family issues going on, so not a lot of time to work on the engine. Anyway, I did the valves. I had to grind about .015 off the exhaust valve stem. That produced a lash of about .010. After that, I bought some lapping compound and lapped the lash back down to about .007. The intake was completely the opposite. The lash was about .011. I lapped the valve down until I got the lash down to a tight .004. That was a LOT of work. I made a tool for my drill to "spin" the valve for the lapping. I bought some industrial strength VELCRO and put mating sections on the top of the valve and on the tool I made and then applied the lapping compound on the valve angle. It worked pretty well. I had to use the screwdriver and zip-tie method to remove the valve springs since I couldn't find a spring compressor in 5 stores I went to. Napa would have ordered me one, but it was $50 and I couldn't see that for possibly a one time use. If I ever do this again, I'll buy one. I put a coat of oil on the stems and between the pushrods and ends so it won't run dry when I first start it up. That's where I am now.

I went and got my gaskets today and will put the rest back together tomorrow. I also bought a new fuel line since every time I run gas through the old one, I get little black specs out of it. I cleaned the breather element too. It wasn't bad. I checked the head for warpage on a flat piece of glass. It was OK, so I cleaned the mating surface by running it on some fine sandpaper on the piece of glass. I cleaned the head mating surface of the cylinder with a fine wire wheel.

I'm not sure which torque sequence to use in the service manual for the head, since there isn't one listed for the LH195SP specifically. Is the 200 in-lb spec for the head bolts correct? What is the right torque sequence? Anything else I should know?

Thanks

 

[FIX THIS]

Couple of things.
For the head, the manual reads something like " all models except..." right? "K&T Parts House Lawn Mower Parts and Chain Saw & Trimmer Parts"

The motor ain't got no pushrods, it has tappets.

The motor also has an ACR that lifts one of the valves ( usually exh.) on the compression stroke so as to make starting easier. You may have been checking the exh. valve while it was on the ACR bump.

 

[FourtyCaliber]

I just wanted to take a second and thank everyone who provided input and suggestions on my snowblower problem and provide and update on where things are right now.

I used the snowblower a few times since the last time I was here, including after the big dump several weeks ago. It starts up easy, not even needing a full pull of the recoil. I had to mess with the governor a lot to get it to that point. It's still not running perfect, though. I don't know how perfect a Tecumseh can run. I still have some "popping" while it is running at slow or full throttle. Also, I still don't have a lot of differential between the idle RPMs and full throttle RPMs, but after messing with the governor, I do have some now. If I lean out the main jet to achieve higher full throttle RPMs, the idle throttle RPMs comes up correspondingly. I think it's still in the governor adjustment, but its just too cold to mess with it right now. When it warms up I'll try adjusting the governor some more.

BTW, setting the "static" governor using the method that was mentioned in a previous post, did not work for me. Actually, I had to set it exactly the opposite of that. I don't know why. I had to hold the throttle plate closed while I rotated and held the governor shaft clockwise and then tightened the screw securing the arm. That's what got it running half-way decent.

 

[SkiFletch]

You seem to know more about this stuff than I though I have a few things to check regarding the not reducing revs when you drop the throttle. Does the governor arm that's attached to the throttle retract the way it should? I've read that the springs sometimes go bad, and/or their oil/grease just stick and don't allow the arm to retract smoothly. The other common problem apparently for this is if the throttle on the carb is either sticking or has a bad spring itself. OR if the same part is loose between the throttle shaft and the linkage plate.

As for the not running right, I'm having similar problems with my 10HP HMSK100 though have a cheap chinese junk carb that I need to replace first to start with.

 

[FourtyCaliber]

Hey Ski. I don't know that I know all that much, really. I've always messed with engines some, but this is the first time I had to go in and mess with the valves. Well, maybe not the first time I "needed" to, but the first time I did.

Anyways. I think the governor arm is moving and retracting OK. As I said, I'm going to wait until it warms up some (-12 temp here tonight and windchills at -25) and then I'll check it out better. It might be something as simple as adjusting the spring. I made the mistake of messing with the governor when I was first trying to get it to run. I have also read where the governor innards do sometimes go bad or stick. It does seem to be doing something, though, so maybe it's just adjustment. I know the throttle on the carb is OK as the carb is brand new and I did check all the mechanisms before I installed it.

I'm pretty sure that the new adjustable carb I bought is also a cheap Chinese carb. How else could they sell it for $21.00? The engine wouldn't even run with the original EPA carb, though, so even running with some popping is an improvement. I installed the new carb and it started right away, although it ran like crap. That's when the advice I received on this forum led me to a valve issue. I also had to adjust the magneto gap.

From what I have read on many, MANY forums around the Internet, "most" Tecumseh engines never run 100% perfect, even when new. They're finicky and have their own personality, so to speak.

Does your engine have the straight valves like mine? I heard that they need periodic adjustment every 2 years or so. Not sure about the OHV engines. That exhaust valve not seating makes them run like crap until they won't run at all. You lose a lot of the compression on the compression stroke out the slightly "unsealed" exhaust valve. And if it isn't so bad and the motor does run, you get uncombusted fuel and air mixture forced into the exhaust port and into the hot muffler and it shoots out flames.


edit: I wanted to add that I can get the idle to go down to what would be considered an "idle level" if I open up (enrichen) the main jet, but then I lose full throttle RPMs at the same time. If I do that, then the slow speed circuit air screw does become active and I can further adjust the idle speed that way, too. Where I have the main jet set now, the idle RPMs are too fast for the slow circuit to be active. That's what leads me to believe that it may still be governor adjustment that's needed. I don't know if my conclusions are correct. I haven't heard anything back from any of the resident experts to comment on my latest reports.

 

[riseandrun]

fourtycaliber, great post. I have an HMSK80 that is behaving the same as yours first did. I should have left it alone, but I wanted it to run as smooth as the 5.5 MTD snowblower I had that started very easily and ran great. I now have a 27 inch snowking. I'm at the point it only runs with the gas from the prime. I'm also on the third carb! Since carb two and three run the same I'm getting ready to do the same checks as you did. Would you attribute your initial problem to the valves being the problem? I did a compression check on mine and only got 60 lbs., but read on-line you can't do a compression check because of the exhaust valve "release" that allows you to pull the cord easier. Luckily we have only had one big snow where I'm at. It will be ready to go next year....:confused2:

 

[SkiFletch]

My kingdom for one big snow...

 

[FourtyCaliber]

Would you attribute your initial problem to the valves being the problem? I did a compression check on mine and only got 60 lbs., but read on-line you can't do a compression check because of the exhaust valve "release" that allows you to pull the cord easier. ...:confused2:

Yes. For the most part. Before doing the valves, I installed the new carburetor and I got it to run somewhat, although not very well. I definitely had something plugged up in my original carb. Still, it was the exhaust valve not seating completely that was causing 99% of the problems. I believe you're right on not being able to do a compression test because of the compression release. I'd go ahead and check the valve(s). I was able to do it without buying any special tools. I used zip ties to compress the valve springs. It worked just fine. And I lapped the valves in with lapping compound and repeatedly checked the gap between the valve stem and the lifters until I got the gap right.

From all of the reading I've done online about Tecumseh engines, it seems that 9 times out of 10 it IS the valves that are the problem.