Compression issue after rebuild

[Hammermechanicman]

I guess we are assuming the valves are seating and sealing properly. ????
Try rotating the engine till a valve is completely open and then check the lash on the other valve then rotate engine till the other valve is completely open and check the lash on the first valve.
It still sounds like a valve issue.

 

[Emsguy]

This must be getting pretty frustrating.

If everything ' mechanical ' is OK, as has been discussed, timing, valve clearance etc, then time to look elsewhere.

You have a spark, so the only thing left is fuel.

How clean in the fuel you are using ?

Pour a little petrol into the inlet (not to much), then start the engine, it should run OK until that fuel has gone.

If it's still back-firing and spluttering, try another new spark plug.

If the problems still exist, you are doing/have done something wrong.

Just a final reminder, the valve your adjusting must be fully CLOSED.

Fuel is almost brand new, Just got it a few weeks ago. I am beginning to wonder if something else got damaged when I ran this thing without oil (should've checked before starting.) When the dry engine stopped running, it completely snapped the arm rod in pieces, took a huge part out of the sump pan, and cracked the engine casing. Parts replaced were the sump pan (used), crank case (used), crank shaft (used) cam shaft, piston with the control rod, cam shaft timing gear, governor, and tappets. Also, during the midst of all of this the spark plug hole managed to strip out which I re-threaded with the "Sav-A-Thread 14m x 1.25 kit The push rods look straight to me. Do you think there could've been some kind of damage done to the valves during the dry run of the engine? The flywheel key was indeed partially after the engine abruptly stopped which has been replaced. At this point I am trying to rule out all options. I have not taken the carb apart yet because the thing was just replaced with an OEM Briggs last season and did not see much use. The engine ran just fine before all of this happened.

 

[thesilentone]

Fuel is almost brand new, Just got it a few weeks ago. I am beginning to wonder if something else got damaged when I ran this thing without oil (should've checked before starting.) When the dry engine stopped running, it completely snapped the arm rod in pieces, took a huge part out of the sump pan, and cracked the engine casing. Parts replaced were the sump pan (used), crank case (used), crank shaft (used) cam shaft, piston with the control rod, cam shaft timing gear, governor, and tappets. Also, during the midst of all of this the spark plug hole managed to strip out which I re-threaded with the "Sav-A-Thread 14m x 1.25 kit The push rods look straight to me. Do you think there could've been some kind of damage done to the valves during the dry run of the engine? The flywheel key was indeed partially after the engine abruptly stopped which has been replaced. At this point I am trying to rule out all options. I have not taken the carb apart yet because the thing was just replaced with an OEM Briggs last season and did not see much use. The engine ran just fine before all of this happened.

Years ago, I stuck a s/h piston and rod in a similar engine, cranked was marked, I just rubbed it with some emery tape. Welded to hole up in the engine, and ran it on the basis it would run until it died forever.

It ran for years defying all good practice advice.

You are to far in to abandon this project, however something key (and maybe simple) is missing here.

If in doubt, go back to the start and check it all again.

 

[bertsmobile1]

Thanks for the tip. Does this sound like valve issue to you? With the back firing and white smoke?

IT really sounds like a timing issue to me
My original thoughts was the flywheel is not locked to the crankshaft so is slipping & sliding back & forth .
Some times you need to lap the flywheel in with fine grinding paste to get it to lock onto the taper.
Backfiring out the exhaust :-
Spark too late
Inconsistant sparking so unburned fuel fills muffler
Too rich a fuel mixture
Exhaust valve not fully closing ,

Backfiring through carb
Overheating ( not likely here )
Mixture too lean
Spark too early
inlet valve not fully closing .

So my initial thoughts were
1) loose flywheel
2) timed on the wrong stroke
3) valve lash set wrong ( bottom of the stroke not top of the stroke )
Note, top is nearest the spark plug , a bit confusing on vertical shaft engines .

BEcause you are new t all of this the easiest way to check the valves are closed when they should be is the see if you can turn the pushrods between your fingers
As you used the IOEC method of setting valve lash I would bet you have the lash set wrong so the valves are out of time which is why I suggested the tape
What I forgot to mention was to use 3 different coloured pens so you can clearly identify what is happening
When you tape the tape off you colour in the sections between each valve opening & closing .
Because it is a 4 stroke, you need to either divide the tape into upper & lower sections or do it twice with 2 pieces of tape .
I am fairly sure you have set the valve lash wrong & will find the valves open when they should be closed

 

[Emsguy]

IT really sounds like a timing issue to me
My original thoughts was the flywheel is not locked to the crankshaft so is slipping & sliding back & forth .
Some times you need to lap the flywheel in with fine grinding paste to get it to lock onto the taper.
Backfiring out the exhaust :-
Spark too late
Inconsistant sparking so unburned fuel fills muffler
Too rich a fuel mixture
Exhaust valve not fully closing ,

Backfiring through carb
Overheating ( not likely here )
Mixture too lean
Spark too early
inlet valve not fully closing .

So my initial thoughts were
1) loose flywheel
2) timed on the wrong stroke
3) valve lash set wrong ( bottom of the stroke not top of the stroke )
Note, top is nearest the spark plug , a bit confusing on vertical shaft engines .

BEcause you are new t all of this the easiest way to check the valves are closed when they should be is the see if you can turn the pushrods between your fingers
As you used the IOEC method of setting valve lash I would bet you have the lash set wrong so the valves are out of time which is why I suggested the tape
What I forgot to mention was to use 3 different coloured pens so you can clearly identify what is happening
When you tape the tape off you colour in the sections between each valve opening & closing .
Because it is a 4 stroke, you need to either divide the tape into upper & lower sections or do it twice with 2 pieces of tape .
I am fairly sure you have set the valve lash wrong & will find the valves open when they should be closed

Know of any youtube videos showing this process?

 

[bertsmobile1]

Well as I know how to do it I don't go searching Boob Tube to find videos of other people doing it wrong .
You can pretty much trust Taryl Fixes All & Donny Boy 87 .
But you are missing the important point.
1) FIND OUT WHAT IS WRONG FIRST
then work out how to fix it .Fixing a problem that you don't have will not make your mower work

 

[Emsguy]

So to clarify, am I finding TDC on both the exhaust valve and intake valve and as I find the tdc, I adjust each correct?

 

[Emsguy]

Or just TDC on the compression stroke right before the intake valve opens

 

[bertsmobile1]

Ok lets get this right
Standing in front of the tractor looking down on the engine and turning the engine clockwise
TDC firing stroke , both valves closed
BDC power stroke inlet remains closed, exhaust just starts to open
TDC exhaust stroke exhaust starts to close inlet starts to open
BDC inlet stroke Exhaust fully closed inlet starts to close
TDC compression stroke inlet will have closed then opened a tiny amount to decompress then closed again
!/4" piston drop ( going back towards BDC is where you set & check the valve lash.
This is the fool proof method and the factory method .
The overly complicated method you picked up of face book is to allow for quietening ramps that your cam does not have and is very easy to get wrong
The IOEC method that I have to use on some of my vintage motorcycles is highly prone to error when you do not fully understand what you are doing because the inlet overlaps with the exhaust.
Apart from that the Briggs method only requires to move the piston once and you do both valves at the same time .

 

[thesilentone]

As it's the season of goodwill to all men, maybe try this

Start Ya Bastard Instant Engine Starter (SYB)

www.nulon.com.au