Bringing Max IV back to life- lack of power issue

[Smurfwarrior]

I purchased a Max IV about a week ago and have been working hard to get it back running well. The previous owner let it sit a year and I've done the following- Removed and replaced fuel with ethanol free fuel, put seafoam in the fuel, replaced the fuel filter, replaced both plugs, replaced the fuel pump, cleaned the interior of the carburetor (it had yellowish film on the bottom), adjusted the idle and tightened the chains. The clutch belt looks like it working fine, climbs to the top of the top wheel and moves into a tighter radius when the upper moves to a larger radius.

Here's the issue, on flat ground the power is fine, goes about as fast as I'd like it to but as soon as I hit a slight incline (and I hit a ton of those short very steep hills where I hunt) it bogs down and will sometimes die if I don't apply a little choke, and sometimes it dies anyway. It slows to a crawl, I could walk faster that this can get up those hills. I have the B&S Vanguard 18hp engine in it. Am I expecting too much from this? Should I be able to power up hills or is this normal behavior? Any hints as to what to try next would be greatly appreciated.

[garrett1308]

Needing to apply choke points to a fuel problem. Take the jet(s) out of your carb and clean it, blow some carb cleaner through all the holes in the carb.

[Smurfwarrior]

I did all of that when I cleaned out the carb today, no change in lack of power.

[Smurfwarrior]

Here's a thought I had, the fuel line comes out of the body where the upper and lower body meet, the fuel line is long and hangs down almost to the bottom where the fuel filter is located, then the fuel line climbs up a couple feet to where the fuel pump is located. It that too much distance uphill for the standard pump to pump?

[garrett1308]

What kind of motor do you have, and what fuel pump? I doubt that your pump is having issues, or youd be having more trouble than just climbing hills. Are your clutches working?

[Smurfwarrior]

B&S Vanguard 18hp. Fuel pump is a brand new B&S one. As far as the clutches working properly, They seem to be, but hard for me to tell as I'm not sure what to look for other then the band expanding and contracting with throttle applied. Would increasing the tightness make sense? It seemed tight when I checked it, but it could be tightened. If that is the suggestion, please let me know how to tighten it as all I've seen is to shim the engine to increase the distance, and I guess that's the only way right?

[garrett1308]

If you see the primary clutch close in on the belt, and the secondary open up, then it's working. We'll assume it's got the right belt length and tension. Re clean your carb, its easy, won't hurt, and could well be your problem. Currently, can you run the machine at WOT on a reasonably flat surface? Does choking the motor at WOT help or hurt? It'll be an odd situation if it only happens at the base of a hill.

[john swenson]

if possible, have the engine cover off the machine and try going up one of the hills. if it's only going as fast as you can walk...have someone looking in on the clutches and belt while you climb, making sure they are functioning properly under load. maybe that will reveal an issue . johnboy va.

[allwheeldrive]

When working properly the engine sound should remain constant. Assuming WOT when you hit a hill the machine should slow down but the engine should not bog or reduce in RPM since the gearing changes on the clutch belt so as to maintain power. IDK without seeing a max IV hill climb how fast it should move but it should not stall or even sound slower. This machine should spin all 6 tires and dig into the ground if forward progress is not possible IE a hill too steep to climb. At least I think it should, not sure what the torque limit on a 18HP Max IV is , but my machines with less HP will lose traction before they lose power.

[Smurfwarrior]

I've been watching videos of max IV climbing hills and mine is nothing like that , engine bogs down and wants to die. It's a bad feeling to be climbing a hill and have it die and start rolling backwards. LOL. On flat ground it's faster but still not running smoothly. I'll dig into the carburetor more and see if it helps.

[Toys4Me]

Something I've found especially with the Briggs on climbs. The fuel pickup in the bowl is in the front and if you get enough angle you cant pickup anymore fuel. Your right its not a good feeling when it dies and you have no option but to roll back down. As for bogging down I've found switching to a red secondary spring greatly helps this. What size tires are you running on your Max IV as this can effect the bogging down.

[Noel Woods]

This sounds like the perpetual issue with cheap mechanical fuel pumps when you also factor in fuel lines going above the fuel tank especially when going up hill. I would try a low pressure electric fuel pump (1-3 psi) which are relatively inexpensive. Tie it into the ignition switch so that it only works when the ignition is on. It won't hurt to also keep the mechanical fuel pump connected. Between the mechanical and the electric pump you should have a good supply of fuel.

I did the above trick on an old classic vehicle and the truck runs so well now it almost seems like it is fuel injected.

What's the compression on the cylinders? The little B&S motors will sometimes wear themselves out quickly when they are abused, and that may have been caused by the prior owner's lack on maintenance.

[Smurfwarrior]

I have the small 21" tires to fit the tracks that are not installed. Haven't done a compression test yet. I'll grab a low pressure fuel pump and see if that happens. I've heard lots of talk about the red spring. I'll get that ordered.

[Noel Woods]

I have the red spring kit on all my t20 equipped machines, its the best way to keep the machine in the low power band, you will lose some on the top speed though but it's marginal.
Your machine should run well with the small tires and 18hp motor. The 18 is as small an engine that should be in a Max 4 though. If you upgrade ever, I would switch to a Kohler.

[Smurfwarrior]

Where's the best place to get a red spring?