2002 Max II 18hp vanguard swap to 25hp kohler help

[Surfer Dude]

Time for an update on how this is all going. Winch is all done and winch plate turned out great. I would highly recommend the Harbor Freight badlands 3500lb winch. Have used over 20 times already with zero problems. Only thing I didnt like is it didnt come with long enough power cables so Had to buy some and also bought a new 3 position switch and switch panel from Mudd Ox





First time I had the machine out for any severe amount of time over an hour or so with some snow on ground the engine actually started running extremely rough at idle and extremely hot. I did have motor running full bore for quite a while though due to snow slowing machine down. Not sure if any adjustments can be made to the air/fuel mixture on a 25hp kohler to keep it running cooler but I have to pull the plugs to see how the engine is running but have had out few more times after with zero issues so not sure on that.



Alright so I have finally gotten out for some severe trail riding with a club I am in in the WNY area known as ribits riders.

First off wow. I had driven these trails every year with my 18hp max ii and now it is like riding totally different machine. I only use 1/4 throttle for everything for the most part. The motor/clutch pulls extremely well up hills and out of mud with zero problems whole day. Never ran out of power and never couldnt climb up or over anything. very impressive. At one point during the ride a max IV we ride with had got stuck in a mud "ditch" and I drove through the ditch around him got in front of him, hooked the winch up and backed up and pulled him straight out with zero problems. Something I could of never did before with the 18hp and stock clutching. So all in all I recomend the Team clutch and kohler engines to anyone.





Alright now for the complaints. My machine is still not the fastest or hardest accelerating machine there. few other max II's with smaller engines and 1190 clutches and 1 with powerbloc clutches are faster then me. All same outside diameters on the clutches and same gear ratios so should all be close to the same speed depending on rpms of engine but mine was slower than 3 machines. all kohler engines. So I need to start messing with clutching to get my team clutch to pull as hard and utilize whole clutch. Also the machine seems to backshift way to easy and never lets the motor do any of the super hard work. Which isnt a bad thing at all but just to easy to backshift. Called roy at quality drive systems and got myself the correct belt. Made myself solid motor mounts to hold engine still to allow clutches to shift properly. So now it's time to mess with weights in the clutch. I Just ordered 25"X12"X9" GBC gator tires for my machine so I will wait to mess with the clutching till I have them mounted up just so I don't have to mess with clutching twice.

Well thats it for my follow up update on what i've done. I'm highly impressed with the machine right now but obviously I will continue to improve it. Check out my photos for more pictures of that particular club ride

[Mike]

Nice job. I enjoyed your photos of the trail ride. It was cool to see Max II's everywhere. For your heating issues, do you have any kind of ducting in place? A fresh air duct will help greatly. Here's mine in my Max II:

Also, heat shielding above and below the exhaust will help direct heat out the tub. You can see the lower heat shielding in that photo as well.

For the gearing, the 25" tires will raise your effective gear ratio by 13% over the 22" tires so that will buy you some more top end speed. With that motor, you should still have plenty of torque too.

[Noel Woods]

The shrouding was the first thing I thought of with the heat issues. Years ago Recreatives experimented with the 25HP Kohler for the Max2 and they ran into the same issues, and eventually opted for the smaller 20-22HP units instead which performed better but still got hot.

The 25HP was more prone to overheating for some reason which they never figured out. The compromise which worked was to draw in cool outside air via a shroud which drew cool air directly from outside the body to the engine fan. Without the shroud the hot air that percolated in the engine compartment was drawn into the engine fan which continued to heat the engine up. Cool air is more dense than hot, and the denser and cooler air allowed the engines to run acceptably cooler. All the new machines in production currently use the same shroud concept to draw in cool air.

The heat shield should be below the exhaust as Mike indicated and its ironic that not all machines have these.

Mike is also correct regarding the gearing, I predict that top speed should go up accordingly and the machines character and abilities will improve dramatically with the large tires.

[Surfer Dude]

Mike and noel.

I have also read on other forums as well as this one that for some reason the 25hp kohler ran hotter then most other engines. And also there no one had an explanation as to why. So like I said I'm going to pull the plugs and make sure it's not running to lean causing the enigine to run hot or running to rich causing the exhaust to get hot. I do have all the exhaust shields used in current production machines and although I do not have a picture of it (surprised at myself) I do have the cool air intake on the passenger side of the engine as well. also you cannot see in the pictures but I have removed the plastic cover on the top in the back of the machine and replaced with small holed screening







Like I said. next course of action is to check air/fuel ratio and after that I may even install a couple waterproof 6" fans on the drivers side upper body vents to push air out of the engine compartment.

As to the speed problem obviously I will have no problems with motor power to turn the bigger tires and I did figure I should gain about 4mph just with the tires. And should be way better in the mud with the taller lugs and ground clearance. Just was trying to get ideas as to why other machines were faster with same sized tires

[Noel Woods]

The governor may be set too low as well. I had another machine with a 18hp B&S and the governor was set at only 3000rpm, after adjustment to normal operating revs it worked out perfectly.

[Surfer Dude]

The governor may be set too low as well. I had another machine with a 18hp B&S and the governor was set at only 3000rpm, after adjustment to normal operating revs it worked out perfectly.

Which may very well be true. I havent hooked up the tachometer yet to see what the motor is turning. Kind of been procrastinating that one for some reason haha... I even have it already sitting in the box. I do need to check that yes.

[ARGOJIM]

Which may very well be true. I havent hooked up the tachometer yet to see what the motor is turning. Kind of been procrastinating that one for some reason haha... I even have it already sitting in the box. I do need to check that yes.

Many of the max II's you're running with may already be turned up, a couple hundred rpm make a big change.

[Surfer Dude]

it is kevin griffins machine that i ran against and shannas and kennys.. all kohlers and i'm sure they have them all turned up. But I want to do it safely.... not sure they did it safe haha

[Surfer Dude]

Well got my tires on and they work awesome. they dont stop pulling in the mud. And the clean out really well..... Havent been in anything serious yet. And they also do swim. Slow.... but they swim......... I also added a SPAL 6" fan from jegs.com to the exahust side to expell some heat and that seems to do the trick. Only time will tell if 1 fan is enough. Should know more when I ride in ashtabula in a few weeks....... With these tires and 1" spacers i bought the machine needed mud flaps drastically..... I do Have a picture but the file is to big and i'm not savy enough to reduce the file size to upload. But anyways. Cant wait to ride more

[Surfer Dude]

figured it out