Friday, April 3, 2015

DYT4000 Engine

After dealing with the loose valve rocker stud the engine acted up again.  Removed the valve cover and that still looked good.

I figured it was time to check the flywheel key and found this.

Now this is problematic!  Makes me wonder what shape the flywheel is in.  So the flywheel gets lapped to the crankshaft and a new key.  May choose to replace the flywheel.

The flywheel is a bit stubborn so I started it with PB Blaster.

Used a 3 leg puller with an air impact the next day and it came right off.

Lapped the flywheel to the crank.  The photo shows that there are some areas that did not contact but it seemed stable so I reassembled it using a used key from another engine.


If you are thinking this does not look too much different than the key it replaced you are right.  The original key could have been reused but it was somewhat deformed and this one was not.

The key serves two purposes.  It aligns the flywheel during assembly. It also serves as a shear pin should the motor stop too suddenly.  But in normal operation the tapered fit between the flywheel and the crank is what holds the flywheel, not the key.

I mowed for a while.  The engine restarted when hot which was good.  The intake may still be a bit loose but it is useable.  But then it backfires now and then when I crank it so I don't know.

Wednesday, April 8, 2015

Took a good look at the head.  The guide plate for the push rods is missing the plastic inserts.   If I had taken a closer look I might have seen this earlier.  Started to make a post asking about the engine and decided to compare the heads first and bang it was obvious !  It shows up real good in this picture.  The buttons on top the valve stems are also missing.  I should have looked a lot harder when I found the bent pushrod.


Maybe I could have just changed the guide plate but I swapped out the entire head.  So lurch now has the head from the 1st 31P777.  I put the valve cover back on which is correct for the engine.  There must be some difference between the blocks as the replacement head came with longer head bolt screws that did not fit.  The heads are also different castings.

I started and ran it for maybe 30 seconds.  Cranks over real nice and did not backfire, throttle response is good.  Did not smoke much but I wiped the oil out of the cylinder that had collected while it was sitting.  Maybe a bad oil control ring.   Going to give it a workout tomorrow.  Maybe drive it up to coffee.

Thursday, April 9, 2015

Ran the tractor up to coffee and back to see if it would fall apart. The people said it was quite loud.  The engine was a bit hard to start on the way home.  Has started well since then.  Installed the bagger and mowed a bit when I got back.  Dumped 3 baskets.   The tube plugged once.  The new bagger hook gasket works well.

Added a set of std piston rings to the "not now list".