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Tecumseh Valve Seats


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#1 TerryD OFFLINE  

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Posted August 18, 2013 - 10:02 PM

Does anyone know if Tecumseh HH100's have replaceable valve seats? If so are they still available?

The reason I ask is that I had sent my troublesome carb to Mark at Carb Rescue (cudo's to Mark) and while it is off and out of the way I thought I'd check valve clearances. I found .025 on exhaust and I can barely get a .002 shim half way into the intake side. They should be .020 and .010 respectively. It runs, but not well, part of it was carb related and I'm sure the valve clearances being what they are doesn't help. Anyway, I'm wondering if I've dropped a seat on the intake side or if they are cut into the cylinder. If cut into the cylinder then the stem will need to be shortened otherwise I need a new seat. What does a dropped seat look like?

As always, thanks!
Terry

#2 MH81 ONLINE  

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Posted August 19, 2013 - 07:00 AM

Pretty sure they are in the block, don't think they are replaceable.

If you dl the service manual, it will help you out here... I believe the replacement valves had longer stems and were meant to be ground down. Also, the compression release will mess with the valve gap.

As for the manual, here is the teccy section of ours.
http://gardentractor...ry/73-tecumseh/
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#3 Bruce Dorsi ONLINE  

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Posted August 19, 2013 - 08:06 AM

If I am not mistaken, all HH100's were valve-in-block (flathead) engines.

 

Although the manual states to check valve clearances with the piston at top dead center (TDC) of the compression stroke, I find it is better to always check valve clearances with the opposite valve at full lift. ....Check the intake valve clearance when the exhaust valve is fully raised, and check the exhaust valve clearance while the intake valve is fully raised.

 

Some engines have a mechanical compression relief, while others have compression relief ground into the cam lobes.  ....By checking & setting the valve clearances as described, the compression relief does not affect the valve clearances.

 

Without knowing the history of your engine, it is possible that someone replaced the intake valve, or refaced the valve seat, without setting the clearance properly. 

 

It is possible, but unlikely, that the intake valve and/or intake valve seat could have worn enough to close the intake clearance that much if it were properly set.

 

The valve seats can be re-faced if necessary, but the valve clearances need to be re-adjusted to compensate.


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#4 TerryD OFFLINE  

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Posted August 19, 2013 - 09:33 AM

If I am not mistaken, all HH100's were valve-in-block (flathead) engines.
 
Although the manual states to check valve clearances with the piston at top dead center (TDC) of the compression stroke, I find it is better to always check valve clearances with the opposite valve at full lift. ....Check the intake valve clearance when the exhaust valve is fully raised, and check the exhaust valve clearance while the intake valve is fully raised.
 
Some engines have a mechanical compression relief, while others have compression relief ground into the cam lobes.  ....By checking & setting the valve clearances as described, the compression relief does not affect the valve clearances.
 
Without knowing the history of your engine, it is possible that someone replaced the intake valve, or refaced the valve seat, without setting the clearance properly. 
 
It is possible, but unlikely, that the intake valve and/or intake valve seat could have worn enough to close the intake clearance that much if it were properly set.
 
The valve seats can be re-faced if necessary, but the valve clearances need to be re-adjusted to compensate.


I was hoping someone would describe checking the valves just as you mentioned. The engine was "professionally" rebuilt 10 years ago and i've talked about that in earlier posts. Seems they were more interested in the money they collected than a well built motor.

I talked to a well known local repair shop about a valve job and they told me they just replace the valves. I asked about grinding the end of the stem to set the clearance and they didn't know what I was talking about. Okay, scratch them off the list.

Found another machine shop that will charge $10 to clean up the face and take .005" off for an initial check, then when I come back they will take the rest off to put me at the .010" clearance on the intake. I think I am going to do that plus lap the exhaust to see if I can get a little closer to .020" than the present .025".

Thanks for your insight Bruce!

#5 Bruce Dorsi ONLINE  

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Posted August 19, 2013 - 06:31 PM

Found another machine shop that will charge $10 to clean up the face and take .005" off for an initial check, then when I come back they will take the rest off to put me at the .010" clearance on the intake. I think I am going to do that plus lap the exhaust to see if I can get a little closer to .020" than the present .025".
 

 

You really don't need a machine shop to set the clearances.  .....You can do it with a sharp, flat file.  .....File a little, check clearance, file some more, re-check, etc.  .....Just keep the valve stem perpendicular to the file, so you don't file the stem at an angle.  .....Rotating the stem as you file, will help keep it square.  .....You can use a grinder, but you have to be very careful that you don't remove too much!!  .....I would often hold the valve in my hand and rub it back & forth on the file.

 

Clean the valves well with a wire brush.  ...If there is no ridge or groove around the seating area, they probably do not need refacing.  ....Lap the valves and check for an even width ring around the valve & valve seat.  ....If you get a nice even ring, you are good to go!


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#6 TerryD OFFLINE  

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Posted August 20, 2013 - 01:21 PM

My valve faces seem to have a curve in them. Shouldn't I have them ground to cleanup and at a 45 deg angle?

#7 Bruce Dorsi ONLINE  

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Posted August 20, 2013 - 06:35 PM

My valve faces seem to have a curve in them. Shouldn't I have them ground to cleanup and at a 45 deg angle?

 

Yes.  :D 


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#8 olcowhand ONLINE  

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Posted August 20, 2013 - 07:30 PM

If the valves have very much of  curved wear in the face, I'd recommend to get new valves.


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#9 TerryD OFFLINE  

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Posted August 20, 2013 - 08:37 PM

I am taking them to be refaced in the morning. I have all the specs and hope to have enough stock left when they are cleaned up to use one more time. Exhaust valves are $60 + and intake valves are NLA. I guess the only other choice is used. Hope I don't have to resort to those.

#10 olcowhand ONLINE  

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Posted August 20, 2013 - 08:44 PM

  Exhaust valves are $60 + and intake valves are NLA. I guess the only other choice is used. Hope I don't have to resort to those.

 

WOW....like I said, I'd just have your present valves faced!  :smilewink:


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#11 TerryD OFFLINE  

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Posted August 20, 2013 - 08:51 PM

Yea. MF10 with an HH100 engine by Tecumseh. I really expected more parts to be available. The local JD dealer has been very helpful with gaskets and such as many JD 100 or 200 series had Tecumseh motors.
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#12 TerryD OFFLINE  

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Posted August 21, 2013 - 02:43 PM

Intake valve face cleaned up at .020. Just need to lap it and wait for the new exhaust valve to come in. Old exhaust valve head was bent over .030. Everyone's recommendation was to replace it now while I still can. The cheapest I could find was $69 from the local Deere dealer.




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