4 stroke engine won’t fire

[Timbone]

I am moving forward quickly on my 4 stroke build. I’m using a brand new 140cc Briggs motor that was designed for a vertical shaft lawnmower application. I made all the crankcase changes necessary for horizontal counterclockwise running. My slipper is awesome and I welded a new metal mount to lock the carburetor onto the cylinder jug.

I cannot get the motor to start. I’ve been trying normally, just making sure I had gas in the float bowl and tugging like crazy.

I have very high compression and great spark. I’ve disconnected the governor and there’s no kill switch. I sprayed starting fluid in the intake, expecting something. But nothing at all.

I figure that, even if I have an air leak, the engine will fire and then try to rev high. The float bowl is level and fuel is flowing.

I have no kind of throttle attached. One throttle setting, held by springs closes the choke and opens the butterfly mostly open. I figure that’s the starting mode.

I am 98.9% sure my timing marks in the cam are right. I’d really hate to be forced to open the crankcase to check that. I am pretty sure my valve lifters are doing what they are designed to do.

Everything tells me it’s a carby problem. But what could it be???

 

[curtisfox]

Did you have this engine apart before? Cam could be 180 degree off, just a thought

 

[Timbone]

I’m thinking it’s timing, too. There are so many details maybe I missed that! Thanks! (I gotta break the case anyway...)

 

[darwin]

Did you have the motor apart? How is the engine oil lubricating the moving parts using a vertical engine horizontally?

 

[Timbone]

I plugged a couple of holes with JB Weld and made a couple of new oil channels with my small files.

The biggest addition was an oil slapper that dips into the oil pan and flings oil everywhere. I am not too concerned about lubrication now.

I got the engine to fire today but I had to open the case and change the cam 180 degrees. Laying the motor on the side is very confusing for me. At some point I determined which lifter was intake and which is exhaust - but I got confused. I think the now outside cam kicks the exhaust but I am not sure. I just know that, now, the timing marks connect with the outside cam a full half turn away. That would make sense: engine pops and then the exhaust opens when piston goes to the bottom. The main problem I had was not considering that the cam turns twice for one crankshaft Revolution, so you got a 50 50 chance of getting it without knowing what’s going on.

I poured a teeny bit of gas into the carb and got it to run for a few seconds with a burst of starting fluid. To be honest, I don’t even know if the choke was on or off. It was too hot to try again.