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Show Parts for Model:

low compression on all cylinders

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Herbert Goff

04-28-2013 18:39:24




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I did a complete rebuild on a TO-30 ferguson z-129 engine, including sleeves, rings, pistons, new crank and cam plus gears, rebuilt the oil pump, and had new vavles, seats, and guides installed plus had the head checked for leaks. I also had to buy a new intake, exhaust manifold. After all was put together, it would not start. Timing was checked and it was right. We checked compression on all 4 cylinders and they were 45 to 50 lbs. We tore back into the engine and redid the head with different seats and reassembled. It started, but the governor was stuck so we shut it down and redid the linkage. Now it will not start again and compression is low again. The head was checked for warpage and we ran a pressure test. All 4 cylinders held 17 which is right. We also changed the head gasket both times, so that is not the problem. Everything was torqued to specs. Does anyone have a clue as to why the compression is low.

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john[mo]

05-03-2013 22:19:12




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 Re: low compression on all cylinders in reply to Herbert Goff, 04-28-2013 18:39:24  
sounds like you had the low compression /low octane cam.a little too low! bet you felt good when she fired up!



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Herbert Goff

05-03-2013 19:54:50




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 Re: low compression on all cylinders in reply to Herbert Goff, 04-28-2013 18:39:24  
The problem with my TO-30 turned out to be the wrong camshaft. The one I purchased has a different dwell than the old one, causing the intake valves to be open at the wrong time and lowering the compression enough to cause the low compression on all cylinders and cause blowback through the carb.
Thanks for all the tips.



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jon corbett

04-29-2013 17:14:09




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 Re: low compression on all cylinders in reply to Herbert Goff, 04-28-2013 18:39:24  
b 4u take apart,3 squirtsof oil all cylinders,spin over without plugs.reinstal plugs and start.rings must have a oil seal to have compression and suck fuel.



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Jerry/MT

04-29-2013 15:22:34




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 Re: low compression on all cylinders in reply to Herbert Goff, 04-28-2013 18:39:24  
With the number that low, the problem is most likely in the valves! Are they closing at the correct timing? Is the cam timeed correctly to the crankshaft and is the valve lash correct?



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2tractors

04-29-2013 06:03:09




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 Re: low compression on all cylinders in reply to Herbert Goff, 04-28-2013 18:39:24  
Check the ring gap.



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Bruce(OR)

04-28-2013 22:33:11




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 Re: low compression on all cylinders in reply to Herbert Goff, 04-28-2013 18:39:24  
I would suspect a multitude of problems. Comp guage is not accurate.
Timing is off.
Firing order is off.
Me? Starting fluid and check for spark. Just enough to make it bark and let me know I am on the right track. You could also oil the cylinders slightly to seal the rings.



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Duner Wi

04-28-2013 20:03:55




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 Re: low compression on all cylinders in reply to Herbert Goff, 04-28-2013 18:39:24  
I assume you have 3 3/8" overbore pistons which are same for Z129 Z134 . However Z145 3 3/8" pistons have a shorter piston pin to crown height by about .050 th. Any chance you have the wrong pistons? Just a wild guess.



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Retired Farmer

04-28-2013 19:58:43




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 Re: low compression on all cylinders in reply to Herbert Goff, 04-28-2013 18:39:24  
Did you put the rings on the pistons upside down or leave some out, too large a ring end gap, got the valves adjusted right and all working, got the right size pistons in it? Are the valve seats ok? Had a supposedly good shop do a valve job for me once. Looked like they used a rattail file on the seats. Had to take it to another place and get it done right.



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Tony in Mass.

04-28-2013 19:26:13




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 Re: low compression on all cylinders in reply to Herbert Goff, 04-28-2013 18:39:24  
Well, atleast it is a US made z129... The English made Standards do not have timing marks at all... it a geometry lesson with certain valves in certain positions, and a wild guess where a gear will be at 9 o'clock when another is at 6 o'clock... could be worse! Atleast all the bolts are free and - oh! I ALWAYS start a rebuild BEFORE I put the pivot basket on, just keep some antifreeze in the block for the few seconds it takes me to decide if it all went together well.
Does it do... not do other weird things? it must backfire? hard to crank? all the valves at 13-15 thou?

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Tony in Mass.

04-28-2013 18:52:56




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 Re: low compression on all cylinders in reply to Herbert Goff, 04-28-2013 18:39:24  
Cam not timed to the crank? Seems like you are so far apart again, triple check the timing marks. You have pre assembly grease or atleast oil in the rings? You should have atleast 100 more pounds after all that work.



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Herbert Goff

04-28-2013 18:57:15




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 Re: low compression on all cylinders in reply to Tony in Mass., 04-28-2013 18:52:56  
I hate to go back in, but tomorrow we are pulling the front off the tractor and check the gear timing and also the keyways. I know the compression is the issue but I have 3 mechanics helping me and we are just shooting in the dark trying to figure this one out.



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