Tricky Question: Why wont my engine start?

[FreeRunner15]

Compression is good at about 82 psi.

Spark is good enough to shock me during a spark test. i even tried a cold plug a3910x.

Fuel pump works perfect. Tested with carburetor open. It pours fuel if i make it/want it to with slide completely open.

Everything is sealed ( no hissing sounds) so i'm sure it gets air.

Timing is correct. Crankshaft dot lined up with the camshaft dot.
\
I guess it could have to do with the valves? i did tinker with them trying to put 18# springs on .

Let me go tinker with the valve lash a bit. If it works i'll let everyone know so people in the future will have an even further view of what could keep the engine from starting.
Performance-wise everything is still stock besides the governor.

 

[Jrgunn5150]

I don't think valves are your problem, assuming they are opening and you can pull it over easily? If your timing is correct, the valves would have to be hung open or closed to cause a no start.

 

[FreeRunner15]

i just checked my valve lash and there was 0 clearance.
Opened them a tad bit and went from a no-start to a temporary start.

It is twice as hard to pull-start now but it turns over.
Just need to adjust the exhaust lash now. It acts like too much back-pressure/spent gasses killing it. (stock exhaust is on)

Took me two months to figure this out.

 

[Poboy kartman]

Compression is good at about 82 psi.

Spark is good enough to shock me during a spark test. i even tried a cold plug a3910x.

Fuel pump works perfect. Tested with carburetor open. It pours fuel if i make it/want it to with slide completely open.

Everything is sealed ( no hissing sounds) so i'm sure it gets air.

Timing is correct. Crankshaft dot lined up with the camshaft dot.
\
I guess it could have to do with the valves? i did tinker with them trying to put 18# springs on .

Let me go tinker with the valve lash a bit. If it works i'll let everyone know so people in the future will have an even further view of what could keep the engine from starting.
Performance-wise everything is still stock besides the governor.

So....you don't fathom a thing we say....be happy it's not starting before you put a rod through the block.

Short answer: because you worked on it. (Or did you NOT put the valve springs on?

 

[mckutzy]

What about the timing key? Is it sheared? Have you removed the flywheel(replaced with billet)?
Is the flywheel nut at spec torque? And hasn't loosened off.

Edit: I'm liking the Poboy's reply........ Kinda beat me to it.

 

[KartFab]

So do you know how to check valve lash? You will need feeler gauges, and you select the one that has a slight drag to it and that is your lash. If you put in a cam, you set the lash to what the cam card says when piston is at top dead center with the head on, and side cover on. I'm not saying this to make you feel dumb, just saying it to be thorough.

 

[cavfire]

Need to set the valve lash on the compression stroke also. You should use a feeler gauge as kartfab pointed out. Once they're set get a feel for the amount of play in the rocker arm, and you'll be able to set them without gauges in a pinch.

 

[landuse]

This is supposedly a new engine, so there cannot be much wrong with it. I would set the lash correctly for both intake and exhaust and then take it from there

BTW....82 psi isn't really the greatest pressure for a engine. It is adequate, but for a new engine like yours i would have thought it would be more

 

[FreeRunner15]

Okay. Everything is stock right now. Everything but the removed governor, removed oil sensor, and added billet rod and fuel pump. Stock springs also due to needing a compressor as well as the stock never-been-tampered-with flywheel.

As far as checking valve lash goes: i don't have a feeler gauge for that small of a size. i assumed that the smallest bit of wiggle room would be fine with barely more wiggle room on the exhaust side?

I do have the intake side adjusted and the engine starts 1 out of 2 times maximum but for only a few seconds maximum. I will adjust the exhaust side and report back on that tomorrow.

 

[landuse]

As far as checking valve lash goes: i don't have a feeler gauge for that small of a size. i assumed that the smallest bit of wiggle room would be fine with barely more wiggle room on the exhaust side?

Seriously?? Are you kidding us?? There is no way you can just fiddle and wiggle and hope that the distance is correct!!

Wiggle room... LOL

 

[ML-TOYS]

Seriously?? Are you kidding us?? There is no way you can just fiddle and wiggle and hope that the distance is correct!!

Wiggle room... LOL

Wait, this is not the correct way to work on stuff ?
I guess that strapping a weight to my foot and pushing down on a wrench is not what they mean by foot pounds either ?

 

[mckutzy]

Most auto shops or machine supply houses will sell you a bit of shim stock... Usually brass in what ever thickness you'll need. A few layers will make your proper lash measurement.

 

[KartFab]

Okay. Everything is stock right now. Everything but the removed governor, removed oil sensor, and added billet rod and fuel pump. Stock springs also due to needing a compressor as well as the stock never-been-tampered-with flywheel.

As far as checking valve lash goes: i don't have a feeler gauge for that small of a size. i assumed that the smallest bit of wiggle room would be fine with barely more wiggle room on the exhaust side?

I do have the intake side adjusted and the engine starts 1 out of 2 times maximum but for only a few seconds maximum. I will adjust the exhaust side and report back on that tomorrow.

.... or you could just buy a $5 set of feeler gauges at any auto parts store and do it right the first time.... because, there will be more problems later if you don't. Why spend $60-$100 on a connecting rod, if you arent going to set valve lash properly with a $5 tool? Why ask for advice if you are going to do the opposite of what you should do? Its pretty striaght forward, and CANNOT be done correctly without feeler gauges.

I feel like looking up the valve lash specs for your engine, but i doubt you care enough to even set it to that, so if you really want to do it right, please just look it up yourself.

 

[Poboy kartman]

You beat me to it.I was going to do some shopping today and hop into O'Reilly and price a set....but that's exactly what I was thinking.

 

[FreeRunner15]

So i got it running but the throttle needs to be feathered to stay running at an idle like a bad Idle Air Control on a vehicle.
Opening the air valve at all will just kill the engine.
Adjusting the idle control will just let the engine rev high and stay alive for longer but will still die unless the throttle is constantly opened and closed. There is no in-between.

Thinking... i do have a .031 jet i still have yet to try.

 

[ezcome-ezgo]

What is this "air valve" you refer to?

 

[ML-TOYS]

What is this "air valve" you refer to?

Choke perhaps

 

[bob58o]

I was scared to look at this. Not as cruel as I thought it would be

 

[FreeRunner15]

I was scared to look at this. Not as cruel as I thought it would be

ha, i know what you mean.

But in my thread i posted an attempted burnout all while the kart moves the lawn mower in the process if you havent looked there yet.

That was after i installed a drilled jet..a .03125 to be precise. still needs to be drilled bigger.
That bigger jet let me be able to use the choke but still dies. So i believe fuel flow is the problem. and thats with the stock muffler on.

 

[bob58o]

In prep for my 390 carb install tomorrow, I read up on tuning 4 stroke carbs but still have no experience.

Like they said. Set lash at TDC when compression stroke turns over into power stroke. Buy the feeler gauge. I didn't need more than a box wrench, a socket, and 4hrs (LOL) to install the 26lb springs. The 4 hrs was from the stupid SS valves which require stupid retainers and stupid lash caps. Stock valves shouldn't be that hard.

You've got a Predator right? Bring it back to HF. LOL That's what i did for real. But mine was in 90 days.