Techy acting weird

[formariz 11,987]

So I have this H40 installed on a small log splitter for years. This issue just started this week. If I start engine cold, it will start on second pull and run fine the same way it has for years. Let it run for hours and no problem. 
  The problem  is however if I stop it and then start it again. It will start not as easy , however it will consistently backfire severely into carburetor. 
I let it get totally cold and again no problem. Is it possible that intake valve gets stuck once I shut off and then as metal cools it frees up?

[wallfish 17,011]

The problem is it's a Techy! Throw one of numerous K91s you have on there and be happy.

That's a new one on me but I've had some that started better cold than warm.

[formariz 11,987]

10 minutes ago, wallfish said:

The problem is it's a Techy! Throw one of numerous K91s you have on there and be happy.

That's a new one on me but I've had some that started better cold than warm.

LOL. This has been a very reliable engine for many years specially with the Carter carb in it. It always started on second pull. And yes I could easily replace it but really want to pinpoint the problem. 
 Possibility that carb is flooding engine when hot?

Edited November 17, 2021 by formariz

[Handy Don 12,235]

Sounds like classic vapor lock to me, but I've no direct experience for how to solve it on that sort of engine.

Vapor lock comes from fuel vaporizing in places where the carb needs liquid to operate properly.

I would start by making sure that it has adequate cooling airflow (pull the tins). Maybe also put a heat shield where the exhaust routes near the carb. 

 

BTW, I've never seen before a pulse fuel pump that taps into a spacer between the block and the carb. 

[John2189 454]

Could be the intake valve is tight And needs adjustment. Stretches when hot. Shrinks when cooled off.  

[formariz 11,987]

25 minutes ago, Handy Don said:

Sounds like classic vapor lock to me, but I've no direct experience for how to solve it on that sort of engine.

Vapor lock comes from fuel vaporizing in places where the carb needs liquid to operate properly.

I would start by making sure that it has adequate cooling airflow (pull the tins). Maybe also put a heat shield where the exhaust routes near the carb. 

 

BTW, I've never seen before a pulse fuel pump that taps into a spacer between the block and the carb. 

Didn’t think about vapor lock . Pulled spark plug and it’s soaked. I am thinking something going on with carb also.

3 minutes ago, John2189 said:

Could be the intake valve is tight And needs adjustment. Stretches when hot. Shrinks when cooled off.  

That was also my initial thought

 

Edited November 17, 2021 by formariz

[stevasaurus 22,764]

If you dry the plug does it start right up??  

[formariz 11,987]

6 minutes ago, stevasaurus said:

If you dry the plug does it start right up??  

Just finished doing that and drying combustion chamber. Starts right up and runs well. Run it for a few minutes , shut it down and problem all over again. It’s flooding somehow when hot. Pulling carb to check it. 

Edited November 17, 2021 by formariz

[stevasaurus 22,764]

If it has been sitting for a while??  Anyway, if you can dry the plug and it runs great...it is not the intake valve.    Take out the screws and spray carb cleaner in the holes and on the screws.  Check the bowl and float.  I've got a 3.5 Tecumseh on my Arien's snow blower, but it is not close to your H4.  

[Pullstart 62,906]

1 hour ago, wallfish said:

The problem is it's a Techy! Throw one of numerous K91s you have on there and be happy.

That's a new one on me but I've had some that started better cold than warm.

Seeing the subject “Tecky Acting Wierd” made me think I bet it’s doing what it’s supposed to for a change!  

[Maxwell-8 4,277]

She running a bit to rich?

[squonk 41,150]

Sounds like fuel bubbling in the carb filling the combustion chamber. Perhaps the intake valve has some caca on it and isn't sealing 100%

[Pullstart 62,906]

In a more serious manner… Could it be as simple as a float adjustment?  Debris in the float needle valve?  

[formariz 11,987]

Will be pulling carb tomorrow , cleaning, and adjusting everything to eliminate that possibility. As suggested possibly float is acting up. This set up has been working correctly for a long time and since it always starts easily and runs great I did not consider the possibility of it being the carburetor. It always sits for long periods although empty of any fuel ,tank included. I did remove bowl prior to starting it to inspect and there was only some minor debris in there. Unfortunately I am not able to keep any fuel filters on any machinery which is kept outside. Some animal always eats the damn filters within a week. Filters, gas lines at the joints and plastic fuel caps are the normal victims of what ever attacks them.

[Achto 27,601]

One other possibility that comes to mind. If this is a points engine, are the points burned back opening the gap and advancing the timing? Advance timing will make a cold engine start easily but make a warm engine start hard. 

 

When I ran demo derby cars I would put a bar on the distributor that ran into the inside of the car. This would allow me to retard the timing to get a hot/over heated engine to start. Note: a Chevy small block will run a long time with the engine temp at 300 to 350 degrees.

[Snoopy11 5,714]

Have you thought about plumbing in a fuel shutoff valve as well... just to keep fuel from continuing to get sucked through tank into carb...? It just seems as if to me... there is still vacuum on the fuel line when the engine is off... 

 

Just a thought...

 

Don

Edited November 18, 2021 by Snoopy11

[formariz 11,987]

7 minutes ago, Snoopy11 said:

Have you thought about plumbing in a fuel shutoff valve as well... just to keep fuel from continuing to get sucked through tank into carb...? It just seems as if to me... there is still vacuum on the fuel line when the engine is off... 

 

Just a thought...

 

Don

There is a fuel shutoff at tank. 

[echris 1,425]

38 minutes ago, Achto said:

One other possibility that comes to mind. If this is a points engine, are the points burned back opening the gap and advancing the timing? Advance timing will make a cold engine start easily but make a warm engine start hard. 

 

When I ran demo derby cars I would put a bar on the distributor that ran into the inside of the car. This would allow me to retard the timing to get a hot/over heated engine to start. Note: a Chevy small block will run a long time with the engine temp at 300 to 350 degrees.

 

I have nothing to contribute to help @formariz other than an old story @Achto's post reminded me of.

My older brother has had a '66 Chevelle convertible since around 1983-84. Back then we did a frame off, complete restore. 327 with around 400HP or so, worked Turbo 400, 4.11 posi, the works.
One day, we're on our way, all decked out in the only suits we owned, to our little sisters confirmation.
Big brother hits the 2 lane 55MPH road on the way to the church and guns it.

She's purrin' along like a demon and suddenly, "blub, blub, blub." 
She ded.

We open the hood in our Sunday best to find all the ignition wires wrapped tightly around the distributor, like a neat little ball of yellow, silicon yarn. 
Turns out big brother left the distributor clamp a teeeensy bit loose as he was always monkeying with the timing.

We fixed it there on the spot more or less. You guys know; Locating as many plug boots as we can, (most were still on the plugs) stripping the cables back and getting the center conductor kinda crimped in the mangled connectors and jamming the boots on. Hahaha.

Not sure how our Sunday Best ended up, that was a long time ago. Not that we really cared.

We made it to the church, likely looking the way we always looked. 

 

[Snoopy11 5,714]

4 minutes ago, formariz said:

There is a fuel shutoff at tank. 

Hmm... interesting. I would definitely wager along with Kevin, @Pullstart... on the float...

 

What else COULD it be for heaven's sake...? 

 

Don

[formariz 11,987]

We will see tomorrow after I redo carburetor if that fixes problem. Interesting thing about this backfire which ordinarily one does not see. If you notice on photo the fitting from the line on pulse pump that goes into adapter flange at engine is a light color plastic. During the backfires it actually lights up. I guess if air filter wasn’t on one would see it out of there.

[roadapples 6,983]

As far as critters chewing stuff, everyone on utube says peppermint oil/water mix works.....

[squonk 41,150]

9 hours ago, echris said:

 

We open the hood in our Sunday best to find all the ignition wires wrapped tightly around the distributor, like a neat little ball of yellow, silicon yarn. 
Turns out big brother left the distributor clamp a teeeensy bit loose as he was always monkeying with the timing.



 

We had a Ford Ranger 4 banger delivery truck at Napa where the distributor would not stay tight no matter what anyone did to the hold down. New bolts new clamp loctite, lockwashers ect. You'd be driving down the highway at 55 then BLEAH! Bout went thru the windshield if it wasn't for the seat belt. finally we had enough and took it to a shop. Had them set the timing to spec and tack weld it in!