G16 won't fire up

[AGrayson84]

Thanks for the help guys, I'll end up trying the compression test tomorrow.

I just tried firing it up with the help of starting fluid and can't quite get it to come to life. Here's a video below. I have the throttle pedal weighed down so I can manipulate the carb linkages. This was immediately after a 3 second blast of starting fluid past the choke blade and throttle blade (both were open).

Yamaha G16 Golf Cart Won't Fire Up - YouTube

Yamaha G16 Golf Cart Won't Fire Up - YouTube

[AGrayson84]

This video was filmed after 4 failed attempts to get it to fire up with starting fluid tonight. I played with both the choke and the throttle (throttle cable is disconnected from the pedal because it's broken) and can't seem to find that sweet spot or something, I don't know

The choke doesn't seem to have much effect. Am I maybe introducing way too much air, not having any filter or box on it right now? It's a brand new carb and I haven't fiddled with any of the adjustments so maybe something needs adjusted, but I'm not familiar with 4-stroke carbs though I'm sure they are very similar to 2-stroke carbs.

[craig tn]

Have you checked the valves?

[AGrayson84]

Good call Craig... I just got done popping the the valve cover off about 15 mins after my last post. Yeah, the intake valve is just sitting still while the exhaust valve goes to town. The pushrod on the intake rocker isn't moving.

So what kind of trouble am I looking at now?? I've entirely torn down several pushrod V8 engines, DOHC V6's and V8's, as well as dirtbike and four-wheeler engines... so I'm up to the challenge if it's worth it. I assume a broken pushrod but you guys would know better than me. What do you think??

[craig tn]

Could it be stuck ?

[AGrayson84]

Originally Posted by craig tn

Could it be stuck ?

Guess I should've looked closer to see if it the valve was stuck opened, or closed, eh??

I assume if it's stuck open then something may be jammed up somewhere, and if it's stuck closed then the pushrod or cam may be damaged. Is that about right, or not exactly? Thanks!

[craig tn]

Can't help you there. Maybe someone else will chime in about the valves.

[junior1954]

Your intake valve is stuck open-it's allowing the gas/air mixture to be blown out of the carb. on the compression stroke. The pushrod could be broken and hung up. If it is, you should be able to loosen the 10mm adjustment nut and loosen the adjuster, in which case you should feel tension on the adjuster from the valve spring and see the valve close as you loosen the adjuster. More likely the valve is hanging open because of inadequate clearance between the guide and the valve stem (if it is, the pushrod and rocker should be loose except on the intake stroke, one of the two down strokes). If the valve is stuck open you will probably have to remove the cylinder head to see if crud from combustion has fouled the valve stem or (more likely) you need your intake valve guide/valve replaced and the valve seat lapped. As long as you have the head off, do both valves, have the exhaust guide checked and replace both valve guide seals.

[AGrayson84]

Originally Posted by craig tn

Can't help you there. Maybe someone else will chime in about the valves.

No problem Craig, you've been a great help so far!

Originally Posted by junior1954

Your intake valve is stuck open-it's allowing the gas/air mixture to be blown out of the carb. on the compression stroke. The pushrod could be broken and hung up. If it is, you should be able to loosen the 10mm adjustment nut and loosen the adjuster, in which case you should feel tension on the adjuster from the valve spring and see the valve close as you loosen the adjuster. More likely the valve is hanging open because of inadequate clearance between the guide and the valve stem (if it is, the pushrod and rocker should be loose except on the intake stroke (one of the two down strokes). You will probably have to remove the cylinder head to see if crud from combustion has fouled the valve stem or (more likely) you need your intake valve guide/valve replaced and the valve seat lapped. As long as you have the head off, do both valves, have the exhaust guide checked and replace both valve guide seals.

Thanks so much Junior! That was a wealth of information there and it helps a ton. I'll loosen the adjuster tomorrow and see what I can determine, and I'll take pics. If I can't get it done tomorrow for some reason, I'll get it done Sunday and let you guys know what I find and whatnot.

When I pulled the valve cover, there did appear to be some crud in the top portion of the head, and possibly more crud on the intake components than the exhaust. It was dark outside when I pulled the head, so I'll have to get a better look when I tear the head off. Thanks again Junior!

[AGrayson84]

Hey guys, so here's the update:

I took the head off tonight and found a bent pushrod. The intake valve seems to operate just fit when I push on with my fingers, so I removed the push rod and noticed that the intake lifter wasn't doing anything when the engine rotated. I gently hammered the bent pushrod against the intake lifter and got nothing. I'm going to work on getting the drive clutch off Sunday so I can start tearing down the insides and see if it's the cam, lifter, or what. Anyone want to take a stab at what probably failed?