By Dave B. on Unrecorded Date: Edit

I was recently on an outing with a few friends, they on new 4x4s me in a new Max 11 18hp , Although I was slower I felt I could do things that they could only wish to do,until, well ,I began to descend a very steep and long hill, I began to feel that this was to steep so I applied the brakes shifted to reverse and tried to back up the short distance to where I started, NO luck, Max just grunted unable to turn a wheel(or 6 in this case)My friend put a tow rope on and pulled Max and himself back up the hill to a safe area. Why is Max so underpowered ?? The elevation was aprox. 9700 which is high I know but the factory had re jetted the machine when I ordered it, I have 70 hrs on the machine now--Please help with any fixes or mods that may inhance the power to at least be able to spin a wheel at higher elevation Thanks Dave B.

By syff_uf on Unrecorded Date: Edit

too high up ? not enough oxygen ? what's the fix ? supercharger ! (centrifugal / roots)

~phil~

By MaxRules (Brandon_price) on Unrecorded Date: Edit

I know exactly what you are talking about but the Max is not under powered. You are simply not pulling the sticks back far enough. The springs that push them forward make it difficult to pull them all the way backward. You could unhook the springs to make it easier. Next time just give it some gas and pull back hard on the sticks. They aren't going to break.
Above all, don't be such a chicken. If you had any more feathers you could have flew down that hill!

MaxRules

By Fred Sowerwine, Montana's Max Dealer (Fred4dot) on Unrecorded Date: Edit

Dave, Two possibilities: (1) you didn't have the sticks pulled back far enough to engage the bands or (2) you have glazed your drive belt. If you think the belt is slipping, use belt dressing (I use the liquid stuff and put it on both edges with my finger - if you use the spray stuff, take the belt off first).

I have never tried to back up a steep hill, but I, on a regular basis, stop going up hill and have never had trouble restarting (might have to roll backwards just a little to get traction if really soft, but the times you will be able to "spin a wheel" will be few and far between). Actually the mechanics of stopping and shifting into reverse and getting the drive belt engaged and backing up the hill are more than I would care to tackle on a real steep hill - I would just do a 360 and drive up going forward (if you haven't tipped over going frontward, you will not tip over going sideways because the max II has a 50" wheelbase with 56" spread).

Is this your first time in the steep stuff? It does take practice to learn what works and how to get out of your machine what it is capable of doing. Your Max II with 18 HP has more than enough power to handle a 600 pound load up about anything. My guess is your bands were not engaged, but if they were and belt dressing doesn't solve the problem, you could try a new belt.

Actually, you want to try to never spin a wheel with your max - spinning breaks traction and if you ever do spin, stop and restart easily - digging holes is just about the only way you can get a max stuck!

By Attex Bob on Unrecorded Date: Edit

Dave:
The reason your Max is underpowered is because your not high..........your half way to the moon!!! Two more thousand feet and you will need oxygen if you were in an airplane!! An engine is an air pump and if there is little air to grab, your power output will be WAY down. I have 4 fixes for you: 1. A turbo charger (High in cost and hard to find a kit for your engine) 2. A super charger ( High in cost and your going to have to rebuild your engine) 3. Nitrous oxide ( you will be able to use this for only a short time before your bottle goes dry) 4. MOVE!!! You can get brain damage if you live up there to long!! Just kidding about #4, I just remember when I was a little kid and went to Pikes Peak. I got sicker than a dog. But seriously, your going to have to get some O2 to that engine for it to make any power. I bet that 18 horse is making maybe 8 to 10HP that high up. Your buddies on the 4x4's have alot more power to begin with so they have alot more power to spare. Any one of your options are not going to be cheap. Good luck Dave!!! P.S. If it was me I would choose #4!!!

By Fred Sowerwine, Montana's Max Dealer (Fred4dot) on Unrecorded Date: Edit

Dave, I really don't think elevation has anything to do with it. My brother lives on top of Cedar Mountain, Cody Wyoming and it is about 9200 feet (now 500 feet might be that proverbial straw); I had my first 14 hp max II up there in about 5 inches of snow and it hauled the two of us (his 250 lbs and my 190 lbs) everywhere we tried to go. I have had a 600T Max IV (18hp) also up there and it ran just fine. I have regular jetting in all of my machines and I did notice a loss of power, but nothing drastic enough to worry about (my guess is about two horses).

I will assume you did not have a fouled spark plug: The vanguard is so well balanced that it will run just fine with one good plug, just no power! If you ever do have a bad plug and keep running, check your oil level - a lot of gas will get pumped into your oil real quickly (and your oil should be changed).

By Dave B. on Unrecorded Date: Edit

This is not the first MaxII I have owned, my first was the Big Max with a 440 2cycle in it(lots of speed and power)but this situation was just plain power related im afraid, the engine just plain could not pull me up that hill, I did as brandon indicated reved it up and pulled back hard but to no avail the traction was good Max doesnt spin out often just no power to pull the load at that time. Has anyone had any luck with aftermarket air filters like K&N for example ?

By MaxRules (Brandon_price) on Unrecorded Date: Edit

If you think it is not getting enough air, just remove the air filter when you get to the hill. K&N filters should not be used in overly dusty conditions because more air flow = more dirt in your carb.
You can tell if you are slipping the bands (not fully engauged) by going forward up that hill. Get on the steepest point and stop. Put some force on your sticks forward and give it some gas. I bet it goes up easily. My 14hp will go even with 3 people in it.
Another thing to try to back up: My 14hp has never failed to spin the wheels going up a hill. Backing up is more difficult and sometimes you just have to work it a little. Get on the hill again backing up, leave one stick forward (brake), nail the throttle and slam the other stick into reverse. The engauged side will start to spin and try to turn the Max. As soon as this happens slam the other side into gear and I bet it goes right up. This is like "popping the clutch" in a truck to get maximum torque to the wheels quickly.

MaxRules

By syff_uf on Unrecorded Date: Edit

dave:

a k&n air filter is good for a few percent horsepower boost. i have one of their largest filters in my truck... a dodge ramcharger. it compliments the cam, manifold, and carb changes. unless the 'stock' air filter is garbage you won't notice much change.

oxygen is the limiting factor in horsepower production. in off roading low end torque is often more important than maximum horsepower... any diesel can attest to this, as can the big blocks. a stock dodge 413cid put out only 220 horsepower but with over 400 ft lbs torque at 2000 rpms nobody was complaining.

the complicated solution is this: replace the engine with a 350cid (see i'm not leaving out the chevy people here), put on a roots type blower, and mount a nitrous oxide switch on the dash... and the next time you get in a similar situation instead of backing up... aim your machine proudly down that hill, rev it up, and press that button.

~phil~

ps you have a helmet don't you ? :p

By Fred Sowerwine, Montana's Max Dealer (Fred4dot) on Unrecorded Date: Edit

Dave, How is your air filter? They need cleaned about every 35 hours or so (some people get too much oil on the foam pre-filter, making the main filter cartridge fail very fast). If it's not tranny related or drive belt related and your spark plugs are good and your air filter is clean, then I would look in the compression area (bad rings, too much oil, plugged vent, etc.) I think you should take it to a Briggs & Stratton dealer who will call RI for guidance (My customers have run across a couple of service centers who must have forgotten to go to the new schools as they seem to have no knowledge of the Vanguard whatsoever). Make sure they don't try to drop your Maximum RPM to 3600 (keep it at 4000 unloaded).

I just can't help but believe your problem is yours alone, even a properly operating 14 HP Max II should have more than enough power to climb anything that it won't tip over on. Is there any chance you are pinching your fuel line between the seat and lower body?

By Snowco on Unrecorded Date: Edit

Here's something to think about,Al at Performance Carting in Charlotte,tel 704-291-7825 "builds" Vanguard 16hp to 30hp,sounds like "fun" to me.

By Dave B. on Unrecorded Date: Edit

Hi Fred, I just returned from another ride this time at a much lower elev. aprox. 2000 ( by the way I was at closer to 12000 elev. when I had power concern)I had been at the top of Cedar Mtn.right across from Brian Head Peak which is at 13000 ft. (see southern Utah)My lower elevation ride was in the Hurricane sand dune area, what a fun time, power while not up to my friends 4x4s was great and I climbed, slid, spun tires even pulled my buddy up and over a couple of times when he burried in. Fred I checked the filter for to much oil and it looked fine, I have changed the filter every 25hrs. and I believe they should be OK. The lower elevation must have allowed Max to breath better and boy did he perform even with my wife and I aboard. If anyone ever hears of simple up grades to a vangards power plant please post. Thanks to everyone who responded, will check in later Dave B.

By Alan Harper on Unrecorded Date: Edit

Has been a while since I dealt with horsepower calcs but without digging out the books I think I remember a few guidelines. Assuming your jetting is close to perfect you lose about 4% for every 1000 feet above sea level, about 7% for a high humidity day and something like 1% per couple degrees above 58 degrees. I suppose you can neglect the effects of high temp and humidity at your altitude so that leaves the 40% loss due to altitude or 11hp at WOT from the 18hp sea level engine. I assume the machine was jetted for something lower than 10,000 feet so as you go up into the thinner air the engine will run richer resulting in a huge power loss. Don't know of a rule of thumb for incorrect jetting for a given altitude but from experience you could easily lose over half of that 11 hp.

By Attex Bob on Unrecorded Date: Edit

Thanks Alan: I was just about ready to look up an alt. adjustment chart but you beat me to it. Your figures are very close to mine. I said that he was putting out about 10 hp about 8 posts ago and I will say it again.......no air (o2)= no power!!!!! It's that simple!!! K&N makes a very good filter but if there is no air....... Dave, there is no cheap fix for your problem, it can be fixed, like I said above, but it ain't going to be cheap!!! If you want I can build you a turbo 16 hp that will put out a honest 16 hp or more, way more!!! at 1300'. I still think #4 is your best bet!!! P.S. Alan, do you race pro stocks in Denver by any chance???

By Fred Sowerwine, Montana's Max Dealer (Fred4dot) on Unrecorded Date: Edit

Dave, Thanks for the comeback. I will stand corrected on the elevation thing (Thanks Alan for the HP & elevation info). I knew an engine runs richer at high elevation, but didn't know it was so pronounced. Guess adequate performance ends around 9500 feet above sea level for the Vanguard.

By John on Unrecorded Date: Edit

Site with calculator to figure Relative Horsepower


Relative Horsepower Calculator

By Alan Harper on Unrecorded Date: Edit

Bob,
No, never done the racing thing. I do have a supercharged 454 in my 1 ton truck though. I also felt pretty awful on my one trip up Pikes Peak. Took me a couple months to get used to working in Wyoming, am in Wisconsin now. Dealt with the horsepower thing quite a bit while studying for my pilots license and setting up my truck engine.

Fred,
I appreciate the info on the Vanguard, I didn't know about the 4000 rpm and that a fouled plug wouldn't be obvious, I have a 18 hp Vanguard in my Coot.

Dave,
Sounds like you have jetting problems mostly. There is no easy way to set up a carb so it will work well from 2000 to 13000 feet. They have to be set rich enough to keep from leaning out on the coldest day at your lowest elevation. Nasty things happen to the engine internals if it gets too lean. The snowmobilers change jets constantly but I think that would be a pain. Too bad they don't make a fuel injected Vanguard.

By BILLY on Unrecorded Date: Edit

Alan;

Here is exactly what you guys need to put in your AATVs that are being used in higher altitudes. The Kohler Command PRO Series CH26. It is made in either vertical or horizontal shaft and is electronically fuel injected. It offers more horse power, 12% more torque, and up to 15% better fuel efficiency. No choke necessary and will adjusts the air intake automaticly.

Brand new from Kohler. Check the chart for CH26 ratings only. http://www.kohlerengines.com/compro18.html

I hope this helps any... BILLY

By Jon Danilovitz, PA Max Dealer (Jon) on Unrecorded Date: Edit

I am a Briggs dealer and I seem to remember reading/hearing about an elevation kit. I have never checked into it due to the lack of severe elevation here in PA. I can however check if you still need info. Let me know.

Jon