Tecumseh Snow King...Valve Clearance???

[AdmiralYoda]

Been chasing my 2004 Murray with an 8HP Tecumseh HMSK80 Snow King around in circles for a couple years. Originally bought by by grandfather, barely used and I got it when he passed 7 years ago. It has low hours and is in pretty good shape but it has always performed poorly under a heavy load.

It just loses RPM's and can't keep up with the heavy stuff, like snowbanks and sidewalks. I've been through the whole machine and performed all the maintenance possible. Adjusted the governor and put a new adjustable carb on there to really dial it in. Runs great until you put it under heavy load...it just loses power and RPM's.

I measured the valve clearance and the exhaust valve was at .005". Factory spec is .008-.012". I figured it wasn't that bad but a member on a snowblower forum definitely thinks that tight clearance is going to cause some loss of compression when the engine is hot. That would result in lower torque/RPM's and explain the symptoms I'm experiencing.

Anyone have experience with these old L-head Tecumseh Snow Kings? Think .005" clearance is definitely going to cause a problem? Thanks!

 

[ironman_gq]

Clearances tighten with use and that's quite a bit out of spec by 40-60%. Being out of adjustment does a couple things other than holding the valve up, it also changes the valve timing, it'll open sooner and close later than it's supposed to.

 

[dvblanch]

Its still only 8 hp with the heavy snow sort of like bringing a knife to a gunfight.

 

[AdmiralYoda]

@dvblanch You got that right! In this case it is a butterknife I'm bringing to a gunfight.

I'm going to fix this because I may need it but I think an upgrade is in order.

 

[Trav]

I would set them both at 0.10 inch.
Edit: I have the FSM for this one if you need it.

 

[AdmiralYoda]

@Trav Thank you for that!

 

[martinq]

I would set them both at 0.10 inch.
Edit: I have the FSM for this one if you need it.

Bingo. 10 thou ( definitely not 0.10 inch) is easy to remember. I'd MUCH rather have the valves a little loose than burn one or drop a seat.

 

[marc1]

Ex OHSK120 owner here, everyone has covered everything. I'll just add the valve clearance is checked cold on these engines and, as mentioned, loose is better than tight, get it in the .010" to .012" range. I am wondering how it got to be .005"? Maybe it was like that from new? Incidentally, I used 0w30 in mine for easy starting.

 

[Trav]

Ex OHSK120 owner here, everyone has covered everything. I'll just add the valve clearance is checked cold on these engines and, as mentioned, loose is better than tight, get it in the .010" to .012" range. I am wondering how it got to be .005"? Maybe it was like that from new? Incidentally, I used 0w30 in mine for easy starting.

Unless someone deliberately adjusted them like that by mistake it is probably from valve seat recession.

 

[AdmiralYoda]

Unless someone deliberately adjusted them like that by mistake it is probably from valve seat recession.

I'm wondering if it was like this since new. This machine has had an easy life. My grandfather bought it around 2005 and barely used it. As he got older he had someone plow his driveway. He had it for 12 years and I'd be surprised if it had 15 hours on it. I can guarantee he never sent it in for service and he wouldn't have taken it apart or adjusted the valves.

Once I got it about 7 years ago I've hardly put it to the test as winters have been pretty mild the past 5-7 years. It has also been down on power under load since I got it. It has also always had slight miss/skip at high speed idle regardless of how well the carb is adjusted.

It was either not adjusted well from the factory or the valve seat wore in pretty quickly in the relatively low hours on this machine.

Last question:
Is there a special tool for releasing the spring from the valve? It looks like the retainer is slotted so I should be able to compress the spring slightly and slide the spring off of the valve. A pair of small screwdrivers might work....but an amazon special tool would be handy if they are cheap enough.

 

[dvblanch]

Yes there are small engine valve spring removal tools. Almost look like a pair of tongs for kitchen use but have a thumb screw at end of handle to close them up. Put one jaw over the retainer and jam the other into lower part of the spring tighten the screw to compress the spring and just wiggle the retainer out to the part of the hole that passes over the stem. Surely available on Amazon or place like Jacks Small engine.

 

[Trav]

I'm wondering if it was like this since new. This machine has had an easy life. My grandfather bought it around 2005 and barely used it. As he got older he had someone plow his driveway. He had it for 12 years and I'd be surprised if it had 15 hours on it. I can guarantee he never sent it in for service and he wouldn't have taken it apart or adjusted the valves.

Once I got it about 7 years ago I've hardly put it to the test as winters have been pretty mild the past 5-7 years. It has also been down on power under load since I got it. It has also always had slight miss/skip at high speed idle regardless of how well the carb is adjusted.

It was either not adjusted well from the factory or the valve seat wore in pretty quickly in the relatively low hours on this machine.

Last question:
Is there a special tool for releasing the spring from the valve? It looks like the retainer is slotted so I should be able to compress the spring slightly and slide the spring off of the valve. A pair of small screwdrivers might work....but an amazon special tool would be handy if they are cheap enough.

Lots of them on Amazon, this is one made from SS.

Valve spring compressor

 

[FordFETruck]

I would not be surprised if it was like that from the factory. I've owned and worked on a lot of flathead small engines and only ever found a few that were actually in spec. Some were super tight and some had 2-3 times the clearance they call for. Perfect example is the lawnmower I use every week my dad bought new in 1977 and last year I checked the valve clearance for the heck of it, the intake was at like .010" and the exhaust was at like .013" when it calls for .005"-.007" IN .007"-.009" EX, this engine has never had the valves out. Worked on another last summer on a edger the exhaust was like .022" and it was obviously never messed with, that's what its still at and it runs fantastic. If you haven't done anything yet I'd just take the valve out and take a file to the end of the stem to open the clearance up a bit and call it good, maybe lap the valve while you're there.

A trick with the valve spring if you don't have the flathead spring compressor tool. Getting it out isn't bad as you can trip the retainer with a screwdriver to release it, use 2 or 3 small zip ties and compress the spring with them, install and cut the zip ties and pull them out with needle nose pliers, I've done a lot of them that way.