560 mystery

[Al in Il.]

Bought a non-running 1961 560 gas, got it unstuck, checked the valves to see if they were free, none seemed to be stuck (some were probably
partially stuck though after thinking about it) - cranked it a few times with the starter just to see if it would fire. Got 3-4 backfires then
it locked up on the last backfire. Tried to pry on the flywheel with reasonable force like I did to unstick - it's stuck again - but why? I took
the valve cover off (again) both #3 push rods to that cylinder are tight (won't spin/turn) with #5 and #6 cylinder push rods on the right side
or towards steering wheel tight - guessing they're the exhaust valve's as they are more likely to stick. Iv'e owned roughly 75 plus tractors
over the decades, most were in the 1930's or 40's,each with there own issues but no previous experience with a 560, even though they're roughly
the same basic engine design.

My question is: Why will it not turn over after backfiring? It locked up IMMEDIATELY after the backfire. SOMETHING happened because of this.
Cylinders are not dry - far from it. This is unique to me. Wanting to address/investigate the most likely issue first of course. Thanks guys.

 

[matthies]

Loosen starter mounting bolts, maybe starter drive and flywheel are bond up.

 

[Al in Il.]

I'll give that a try tomorrow. Easy possibility. Thanks.

 

[Janicholson]

Mice and insects build nests in intake systems and down exhaust pipes. The nest/fluff gets sucked into a cylinder and first causes incomplete combustion and flame back into the carb and out the exhaust. Then the material gets stuck between the piston and cylinder head in the squish areas and locks the engine. Pull the plugs and use a fiber scope to see what is inside each cylinder. Surprise. Jim

 

[rustred]

a backfire is valve related. either a stuck or burnt valve did you run a compression test ? and did u oil the cyl's and top end when valve cover was off? did you check the lash on each valve and watch them when turning engine over? not very concrete information, none seamed to be stuck( some were probably partially stuck though thinking about it).if cyl's have rust in them then that why its stuck.

 

[Al in Il.]

Iv'e did everything everyone has mentioned dozens of times over the decades except loosen the starter as Matthies suggested. I'll find out soon. Thanks Jim.

 

[dwragon]

if the backfire broke a ring and or ring land, it could have cause it to seize up that way, if you can, pull the pan and try removing one rod cap at a time to see if the pistons move, that would at lease eliminate them, and you could check to see if a bearing spun on the mains, which will also do what you are describing (Common with Hysters.).

 

[rustred]

how bad have you tryed to move the engine.?? trying backwards is the thing to do.

 

[rustred]

that is very possible. one time my friend had his super wd9 at the pulls. he comes running over to me and says my engine just seized up. i walked over to it and loosened the starter and the drive retracted back in. i said try her now and then away he went big relief on his face. BUT you said you had the starter out so that eliminates that.

 

[rustred]

ok, first of all the push rods are on the left side of the engine not the right side. and #1 cyl is at the front of the tractor. AND... if it stopped with #4 cyl on compression,... then yes #3 cyl valves will be tight. all the pushrods cannot be loose at once. you need to check valve lash with each cyl at top dead centre on the compression stroke .027 hot setting. you did not verify the valves were set so till you check that its a stand still for now. this is your valves from #1 cyl. E I I E E I I E E I I E.

 

[used red MN]

One more complication that has not been mentioned. If this tractor has a TA and the one way clutch holds as it should it can hold the engine from turning backwards. If the machine clutch releases properly that should allow it to turn backwards. And if the TA dry clutch releases properly it should allow the engine to turn backwards if the TA is placed in the Lo side position, lever back. So if the engine did lock up in the forward direction due to one of the suggested scenarios the TA may be holding the engine from being turned in the backwards direction. Which is fan turning clockwise viewed from the back.

 

[rustred]

yes that is true , forgot about it. to turn engine backwards you need to pull the TA lever back.

 

[rustred]

when u shut down tractor the engine will never rock backwards. pull the TA lever back before shutdown and you will see the fan rock back and forth. just another tid bit.

 

[cuby]

I have found a walnut on top of piston when working on a AC D17 when engine would not turn over.