Rebuilding Old Tecumseh

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5,460
Location
Ohio
I am rebuilding an old cast iron Tecumseh 12HP flat head engine( built in 1973) out of a Bolens 1253. The exhaust valve guide is so worn that the valve wobbles in it.How is this guide replaced?
 
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26,146
Location
MA, Mittelfranken.de
The manual i have covers all L head engines up to 11 HP but i don't know if it includes engines that go back that far or the 12 HP. It seems about right though. I can email you a copy if you want (i also have one for the OHV engines), just PM with an email address.
Quote:
The valve guides are permanently installed in the cylinder block. If they get worn excessively, they can be reamed oversize to accommodate a 1/32" (.793 mm) oversize valve stem. 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. The upper and lower valve spring caps must be redrilled to accommodate the oversize valve stems. After oversizing the valve guides, the valve seats must be recut to align the valve seat to the valve guide.
 
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5,016
Location
Southeast
neat old engine. I had a 16hp 1-lung tec from the 70's (I think, I bought it in the mid-80s needing repair) and it was extremely well-built, solid iron, OHV, counterbalanced, roller-bearing'ed, and it was fun to tinker with.
 
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1,227
Location
Columbus Nebraska
Yes, I do believe that they spec'd an oversize valve stem for those engines, but check if they are available before doing anything. Knurling is also a good fix if they aren't TO bad. Are the valve stems also worn? Usually about 1/2 of the wear is on the valve itself. Possibly knurl, with a new stock valve if oversize is not available.
 
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Lubener

Thread starter
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5,460
Location
Ohio
The valve was changed several years ago, along with a rebuild. I wouldn't be working on it but one of the screws from the throttle blade came loose and did a number on the piston, rings,exhaust valve and guide.Last rebuild, the guide was reamed and an insert was installed by a small shop. They not around anymore.
 
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Lubener

Thread starter
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5,460
Location
Ohio
Originally Posted By: old1
Was it a brass insert?
I believe so. The intake was done at the same time and it is brass. The exhaust is carboned up,I will have to knick it to see for sure.
 
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2,107
Location
Appleton, WI
Those oversized valves for old Tecumsehs are as rare as hen's teeth now. Better off trying to knurl or sleeve the current one and get a new stock sized valve.
 
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Messages
9,559
Location
Boston, MA
I restore once high end communications gear (Collins, Drake, ect) as a hobby and there are no "new" replacements which are as well built. Work better, but just not the same materials quality. Rebuilding can be fun, but in your case I'm sure you can find an up to date replacement engine from Northern Engineering or like vendor and avoid a lot of agro. I still have a Tec lawnmower engine I bought in 1975 which ran (on 20W - 50) until I bought a new Honda mower in 2000 and stopped using it , so I have some respect for the brand.
 
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