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Compression release


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#1 poncho62 ONLINE  

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Posted October 29, 2011 - 05:36 PM

I am working on this Tecumseh cast iron 16 hp overhead valve engine.....The starter is weak, so I took off good starter off my MF10 to try on it....It still will barely turn it over, although it spins the MF10 just fine......I am figuring the compression release isnt working properly...I have the valves set as the book says, (.005 intake, .010 exhaust)...Any ideas?....If I wanted to try something, would I go less or more on the valve lash?

#2 johnboggs21 OFFLINE  

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Posted October 29, 2011 - 10:51 PM

what kind of shape is your starting system in? Battery/cables/connectors?
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#3 poncho62 ONLINE  

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Posted October 30, 2011 - 06:00 AM

what kind of shape is your starting system in? Battery/cables/connectors?


Seem alright, but will look at that too...I was advised on another forum to set the exhaust at .007 and try that.

#4 DH1 ONLINE  

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Posted October 30, 2011 - 07:14 AM

The decompressor opens the exhaust valve the tinyest amount about 1/2 way up on the compression stroke, you can see it if you look close, this is the way the flat heads are and I think the OH series the same.
If you tighten up the valve lash then you might not have enough clearance when the motor is warm and burn the seat.
Dose the engine crank over OK with the spark plug wire off?
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#5 poncho62 ONLINE  

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Posted October 30, 2011 - 07:17 AM

No, still turns over slow........I am going to set the exhaust a couple of thou tighter to see if it helps, wont likely leave it that way.....I am selling this tractor and just want to show the gut=y that it runs good, dont want to invest in a new starter

#6 DH1 ONLINE  

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Posted October 30, 2011 - 07:23 AM

Battery, cables???
It should spin over good.

#7 poncho62 ONLINE  

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Posted October 30, 2011 - 07:26 AM

With the plug out it spins over OK.....the compression with the plug in seems to be holding it back....Going to check and clean all connections today too.

#8 Alc ONLINE  

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Posted October 30, 2011 - 08:55 AM

Does the starter have the solenoid built into it ? If not maybe the one on the tractor is not letting the full battery voltage go to the starter . Either way I would put a volt meter right at the starter stud ( if the solenoid is mounted on the starter check both sides of it one will only be hot when cranking ) and the starter case and then try it to see if you have good voltage there . Al

#9 poncho62 ONLINE  

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Posted October 30, 2011 - 09:36 AM

Dont think that is the problem Al....I have put a booster cable right to the starter terminal.......same thing....Maybe, both starters are weak, just that the MF10 may have less compression to deal with.....If I end up keeping this tractor, I will get a new starter for it....

#10 1978murray OFFLINE  

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Posted October 30, 2011 - 09:38 AM

It would spin over fine without the decomp working. My 11hp briggs doesnt have a decomp and it is fine. Also check to see if the cranking amps of ur battery are good for the engine. 300 is the min

#11 MH81 ONLINE  

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Posted October 30, 2011 - 09:57 AM

If you turn it over by hand with the plug out and the valve cover off, you should see the release occur. If not, the piece on the cam may be stuck or missing, the spring may be disconnected, etc.
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