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JD 630 LP has no compresion after head rebuild

A

Anonymous-0

Well-known Member
Just installed my professionally rebuilt head on my 630 LP. Got it all bolted up and torqued to 150lbs on the head nuts. All New Gaskets everywhere. Every LP component was rebuilt before I got it, Its getting fuel to the strainer, and I can hear the "click" when I turn the key on. Air Cleaner oil bath is full of new oil to the correct level.
Problem, I turn the tractor over on its own power, but it has no compression at all. It turns over like a bat out of down south, but absolutely no compression. The head was redone by the best cylinder head place in the usa so I cant imagine the head would be the issue. I took the valve cover off and turned it over and none of the valves are stuck.

Why am I not getting compression? Its getting spark to the plugs.

This is my first LP and I thought I knew a fair amount about them, but what am I missing or doing wrong?

Thank you all
 
By "lashing" the valves, do you mean adjusting them on the rocker arm tappets or? I havent adjusted or changed anything with the rockers as I figured they were ok from the last setting. Thanks for your help!
 
no such thing as ok from last setting. they are not closing. dont know what was all done to the head but as soon as you grind the seat and valve you are decreasing valve to tappet clearance. this is preventing the valves from closing. need to get the valve spec's and adjust them. then you will have compression.
 
Yes, I have heard of "the potato trick in an exhaust pipe". Please explain how it will cause an engine to have no compression.
 
Whenever you take some off the head you are "putting some on" the valves. if you get a fairly good amount taken off the head it is possible for the valves to never close. often in this case there will be spacers put under the rocker arm posts to make up for the amount taken off. Usually you can just back off on the lash adjustments and you are good, but sometimes it is too much to adjust out and the angle of the rocker arms is too great with the push rods so you have to put some spacers under the rocker arm supports.
 
Ya bettr go to the John Deere board for this. If the valves are opening and closing they are out of time i assume you tappet clearence is ok.
 
i want to know also! its just another guess or just throwing out ideas that dont make sense. the guy said he did not touch valve adjustment from dissasembly so that tells the story.in other words he needs the valves set professionally and his problem is fixed.
i hope he lets us know who wins the cigar.
 
huh, ya right! when intake valve is open, piston is drawing air into cyl.the exhaust valve is closed.
 
he said he did not adjust the valves, just bolted the rockers on,so he just told us the problem.gotta adjust valves!
 
Yes valves need to be adjusted, hopefully he didn't bend the push rods.
The vavle adjusters always need to be backed off before installing the rocker arms.
 
After reading everyone's post maybe I can put it in a way that may be more understandable. When you grind the valves and the seats this makes the vavles fit further into the head and the stem stick out farther on top thus decreasing your valve/rocker arm clearance causing the vavles not to fully close thus end result is no compression. Hope this clears the air for you!
 
so you are saying sticking a potatoe in exhaust pipe causes no compression? anytime i have dealt with plugged exhausts they still will start but stop.so explain your theory why there is no compression.
 
(quoted from post at 10:21:06 05/25/11)
1-800-522-7448
Click to expand...

buickanddeere
Are you indicating that if stormchaser12 calls 1-800-522-7448 that whom ever answers will help him by telling him what his tractors problem is??????????? I think not so.
 
Did you really just bolt the rocker arm assembly on the re-worked head, WITHOUT backing off all valve lash adjuctments and re-setting them all?
Hard to believe. If you did you are lucky things are not ruined. Do you have the OEM Repair Manual? Better get one now. Tom
 
You need to readjust the valve clearance anytime the head has been removed and reinstalled. Even removing/reinstalling the rocker arm assembly will require readjusting the valves.
It is not hard to do BUT I am not going to try tell you how in a forum. Email me at my address and I will send you my phone number. I will gladly explain how to do it over the phone.
 
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