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Tecumseh HS50 valve fix

makoman1860

Registered
Hey guys,
Had a co-worker being in a Tecumseh HS50 ( 5 horse small frame ) engine from his snow-blower (1983). As typical the exhaust guide and seat were shot along with the valve. You can fit a dura-bond valve seat P/N 71037 counter bored into the original cast-in "seat". The Tecumseh valve has a oddball guide size so a new guide was made from Ampco 45 bronze and reamed/honed to .2500". Along with that the stem is an oddball size (.244") so a Briggs valve p/n 211119S is fitted by shortening it and re-cutting the keeper groove. The briggs valve is higher grade material. I have tested this material combination for about 7 years now and found it to eliminate all the valve troubles with the small frame horiz. Tecumseh engines 2-5 hp. Just passing the word :)
-Aaron
 

makoman1860

Registered
I've been doing that for years. I love those Briggs guides and the nice kit they make to install them. :wave:
Im not using the briggs guide. Part of the problem is poor heat transfer from the valve stem to the aluminum block in the tecumseh engine since they used an iron guide. I pull out the entire tecumseh guide and machine a new one from bronze. Now I have a direct heat path from the guide to the aluminum. Pressing a bronze ( BTW the service briggs guide is pretty soft ) sleeve into the iron guide doesnt buy you much if anything over the original design other then tightening things up. In some cases it may be worse since now there are 3 boundarys for heat to cross and not 2. Yeah the briggs service reamers work OK, I used to use them quite a bit, now I use reamers the same size as the valve stem, and hone to final fit. Overkill on an engine like this I know :)
-Aaron
 

anthonyg

Registered
new to this forum. have tecumseh hs50 both valve guides are worn. I'm in spring hill fla. were are you located and how much would the guides and valves cost with labor. email antgen700e@aol.com thanks anthony.
 
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Motormowers

Subscriber
Age
55
Last Subscription Date
07/13/2019
That sounds like how Tecrapsa should have made them from the start. Very common issue with those engines esp once they went to an EPA fixed jet carb. Its actually less common to see those engines NOT having a burnt exhaust valve LOL.
 

JF671

Subscriber
Last Subscription Date
12/11/2019
It's not "Tecrapsa", it's "Tecumsuck", or at least that's what we called them back in the early '80s when I used to run a wrench. Not all of it was bad, but some of it sure stunk.
 

anthonyg

Registered
I'm new on this forum and having areal hard time navigating. i posted a question yesterday did not see any response today i see six. i have a tecumseh hs 50. both valve guides are worn. id like the briggs sleeves installed and reamed to except stock valves. who can do it and what would it cost. email me please.antgen700e@aol.com thanks anthony
 

JF671

Subscriber
Last Subscription Date
12/11/2019
Anthony,

The post you responded to is about ten years old. Tecumseh bit the dust, and as such the stock of left over parts is drying up too. I don't think there's an easy answer to your question. Most likely you're gonna have to engineer the fix yourself, live with the problem, or replace the engine.
 

anthonyg

Registered
well thats not good news. i already located nos 20 over piston had the block boared and on professional equipment. the motor runs strong. just a light puff of smoke when i first rev it. thanks for the reply.
 

K-Tron

Registered
Anthony, You can buy oversized valves for your engine. Tecumseh was good about supplying 1/32" oversize stem valves for their intake and exhaust valves. How sloppy are your valve guides? or is the wear in the actual valve? Tecumseh 31470 for 1/32" oversize exhaust valve with pinned keeper (31470A for slide on keeper), and Tecumseh 31468 for 1/32" oversize intake valve with pinned keeper (27879A for slide on keeper). Tecumseh 32784 is the latest part designation for oversize stem slide on keeper style valves for your block. This valve can be used for both the intake and exhaust. You will need to have the guide reamed to size. A simple job that can be done on a Bridgeport, jig borer or worse case a drill press. I believe that the valves sit just off 90* on the H50. Might be a few degrees off. Use drill rod in the guide and a good dial indicator to fixture the block for concentric guide reaming. You do not want to change the angle of the valve guide. You'll never get it to seat properly.

Chris
 

anthonyg

Registered
thanks for the reply. my hs 50 tag reads hs50-67046. i looked up the 1/32 valves from the factory manual to make sure i got the right part numbers. they are as follows. 1/32 over intake 32645a. 1/32 over exhaust. 29315c. it took six hours to find them because tecumseh went out of business. i got lucky. people on two forums told me i would never find them. now i need to find a qualified shop to ream them. from what you said i am afraid to try it myself. if i did what size ream would i need. i am retired now. i was a sheetmetal fab and tig welder. the shop had two old bridgeports. wish i had access to them. anthony.
 

K-Tron

Registered
Anthony, as per the Tecumseh master service book:

"The guides should be reamed oversize with a straight shanked hand reamer or low speed drill press. Refer to the "Table of Specifications" (Chapter 10) to determine the correct oversize dimension. Reamers are available through your local Tecumseh parts supplier. Consult the tool section in Chapter 11 for the correct part numbers."

Chapter 10 - HS50 valve guide oversize dimension = 0.2807" - 0.2817"

Chapter 11 - Tecumseh Reamer 670283

I believe this reamer has a piloted tip so that the original guide will locate the reamer for being reamed oversize at the correct angle. Reamers like to be run very slow with a lot of lubrication. You should definitely check the stem size on your new valve with a micrometer before reaming the block. You can buy a reamer in any size you like if you do not want to buy the Tecumseh specific reamer. Tecumseh liked to supersede part numbers whenever another engine came out, so the same valve might have five or more different part numbers. Take a good measurement of the reamer as well. The reamer should only be a few thousandths larger than the oversized valve stem. You probably only want 0.0035-0.005" valve to guide clearance on that engine. An inside micrometer can tell you what size your guides are already at, to compare with the original valves. A lot of people replace valve guides or valves without realizing that they have a somewhat "sloppy" fit from factory. It is somewhat normal for these engines to blow a little blue smoke when the engine is cold, but it should not continue when the engine is warmed up. I havent done a guide in a Tecumseh in many years, but have done several Briggs and Wisconsin guides lately on the engines I mechanically restore and run.

Chris
 

anthonyg

Registered
k-tron. it took a long time to locate tecumseh 670283 reamer. i found it on eBay under power equipment deals. witch turns out to be mchenry power equipment. they sent me the wrong reamer. box and invoice had correct number but the reamer was marked 11/32 0.3438. i called the they said they did not have the 9/32 in stock and to file a return with eBay. i have a brand new neway valve seat cutter and pilot set. four new oversized valves and hs40 and hs50 waiting to be reassembled. there are no tecumseh 670283 reamers for sale anywhere for any price. i spent two full days looking for a manufacturer and finely found regis manufacturing. they have pilot reamers of every size. i just orderd a 9/32 0.2812 for $42.00 and a flex hone $15.00 that will give me an extra half thousandth or so if need be. i am righting all of this to save the next guy some trouble. regis manufacturing. telephone # 1 800-527-7604.
 
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