Ventrac Bogs/Stalls with Forward/Reverse

[stoneFarmVentrac]

Hi all - just acquired a new to me Ventrac 4100 (old I know but in great shape for a ~20 yo machine). It hasn't wanted to start now that it's cold out (it has a carb'd/air cooled 25hp Kawasaki FH721d) but now is the fact that it bogs down to 1200-1500 rpm, puffs black smoke, and stalls out with any sort of movement, regardless of there being an implement on or not. Not immediately but within 5-10 feet of forward or reverse. If I back off, it will rev right back up to 3000 rpm just fine.

I had replaced the spark plugs, fuel pump, and fuel filter in the last 10 hours (all i've had it for). I'm nervous it's a hydraulic issue - it wouldn't start when I got it and the seller pushed it out of his shed without it in neutral. Only went about 10 feet at ~2 mph but wondering if that messed up the hydraulic system.

I am trying to figure out how I can test if it's the engine vs. the hydraulics. Was thinking compression test on the engine, and if that checks out then a pressure test on the hydraulics but I don't even know where to begin.

Curious what everyone thinks it might be and where to start.

 

[MountainBuck]

I am concerned about your seller too. If he didn't know how to put the machine in Neutral - what else didn't he know?

You could do a compression test, I believe it should be 56psi at 500rpm, but I rather doubt that is the problem.

Right off I would at least change the hydraulic filters.

Does the engine bog down if the front forks are actuated up and down and nothing else happening?

Also, make sure the transaxle shift lever is in low range, all the way forward. High range can bog the engine down on slopes and such.

If you are looking for a "wild card," you might check the emergency brake. Mine wasn't adjusted properly and would bog the engine down. But that is a real stretch.

Welcome to the forum!

 

[Roadworthy]

If you've not done so, clean or replace the air filter.

 

[LittleBittyBigJohn]

I had coils go bad on one of my mowers. It acted the same way. It was running on just one cylinder when it would bog. Pull your plugs if one is wet and a different color than the other that is probably the culprit. You may have to let it bog for a while to get the plugs to show different (several seconds bogging and don't let it rev back up then kill it and pull the plugs to look.)

 

[stoneFarmVentrac]

Thanks for the welcome, and for the ideas. I just replaced the air filter so I know that's not it. It'll be a few days before I can look at this stuff but I appreciate the insight so far, I'll come back with updates.

 

[stoneFarmVentrac]

I am concerned about your seller too. If he didn't know how to put the machine in Neutral - what else didn't he know?

You could do a compression test, I believe it should be 56psi at 500rpm, but I rather doubt that is the problem.

Right off I would at least change the hydraulic filters.

Does the engine bog down if the front forks are actuated up and down and nothing else happening?

Also, make sure the transaxle shift lever is in low range, all the way forward. High range can bog the engine down on slopes and such.

If you are looking for a "wild card," you might check the emergency brake. Mine wasn't adjusted properly and would bog the engine down. But that is a real stretch.

Welcome to the forum!

I do know that I was able to lift the forks, and even tilt the empty bucket I had on, without a noticeable bog

 

[stoneFarmVentrac]

Ok, replaced the hydraulic filters (both) and no change. Fuel filter is brand new but a little dirty so getting another one. It seems that front arms/aux hydraulics don’t bog it down.

The big find was that I think one of the cylinders isn’t firing. With the engine running (idle or WOT), I could pull off the left cylinder spark plug wire and the engine sounded the same. If I pulled off the right, the engine died.

Here is what is weird, I swapped the coils left to right, and no change. Right cylinder would kill the engine, left made no difference while running. Does this eliminate the coil being the issue?

Swapped plugs, left to right, same thing. Pics attached of right cyl plug and then left cyl plug before I swapped them into opposite cylinders.

Now I’m confused, where do I go from here? Can I eliminate coils? Is the carb not getting gas to the cyl? What else could be causing the miss?

 

[MountainBuck]

I didn't think a compression test would tell you anything but now it seems that should be your next step.

Its beginning to sound like you may have a stuck valve, valve out of adjustment or possibly a blown head gasket.

If it were me, I would pull the suspect spark plug and ground it to the engine and hit the starter just to visually see if there is actually spark.

 

[stoneFarmVentrac]

I did ground the plug to the block, spark at both sides.

Pulled the valve cover off and all seemed well, did a lash adjustment anyways. That’s when I realized the intake valve was stuck open. Took the head off. Bend pushrod and stuck valve.

In doing all this I realized how much the PO let this thing go. Dirt and grass caked in all the fins so overheating was certainly the culprit.

Now that I have it off, can I get away with just a new pushrod, head gasket, and cleaning the head and valvetrain? What else do I need to replace?

 

[MountainBuck]

Good job on the troubleshooting!

I suppose I'd clean or change the one bad spark plug. Maybe some oil additive? Clean the valve cover? Seafoam in the gas would help.

Sounding like you got it under control. Either way, let us know how you like it when its back to full power!