You are currently viewing our boards as a guest which gives you limited access to view most discussions and access our other features. By joining our free community you will have access to post topics, communicate privately with other members (PM), respond to polls, upload content and access many other special features. Registration is fast, simple and absolutely free so please, join our community today!
If you have any problems with the registration process or your account login, please contact us. Looking forward to seeing you in the forums and talking about AATVs!
In another thread there was a good discussion going on about whether to use a Briggs 23HP engine in a Max II, due to overheating reports from some forum members. I had bought a used '94 Max II with a dirt-caked and punished Briggs 23 that improved when I rebuilt it, cleaned it up and replaced most of the seals and gaskets, and the fuel pump. Unfortunately it blew up its camshaft and a connecting rod when running for a half hour later.
Despite advice to do the long and expensive search for a cooler running engine, I decided to re-power with a brand new Briggs and Stratton Vanguard 23HP (386447-0090-G1, mfg August 2021). I have plenty of compatible spare parts from the old engine, and working knowledge. The devil you know, I suppose. This thread will serve as a place where I track how the latest incarnation of non-EFI Briggs 23HP performs in a Max II. For the record, I live outside of Seattle where it doesn't usually get too hot in the summer, and where the engine will see various altitudes from sea level to 4000 feet or perhaps higher. This new engine does not have the pullcord start, which might improve fan breathability a little at the expense of me needing to carry a little jumpstart pack.
When installing the new engine, I noticed a couple small assembly improvements and one change from the 386447-1138-G1 made in 2012. The bolts holding the air cleaner pan no longer have different lengths and bolt head sizes, in favor of using five identical bolts with two sleeve spacers for the pair of screws closest to the crankshaft. Also, the four hex bolts holding on the exhaust pipes now have Torx (T40 I think) recesses in them.
The crankshaft spec was supposed to be identical, 2-29/32" long, having a 1/4" keyway and 3/8-24 internal tapped hole. All these were correct, however the rounded shoulder of the crankshaft right where it comes out the bearing seal is very slightly different, which let my Comet 300421 drive clutch slide further in against the crank case cover and get hung up on some of the cover bolt standoffs (it won't spin). I solved this with a .11" thick stainless washer with an inner diameter just slightly more than 1", which keeps the drive clutch seated maybe a quarter inch from hitting any faces on the cover. I also noticed the key can slide away from the engine quite a lot in the keyway (not a new issue) and become barely engaged by maybe a half inch overlap crankshaft-to-clutch. To solve this, I made a spacer from a piece of copper pipe that fills the vacant couple inch portion within the clutch.
The dealer I bought it from said he hadn't heard of melty or failed pulse pumps before, but he had lots of experience with overheated Briggs 23 engines working as boxed-in insulation blowers. He said they solved it for one customer with a ten-inch HVAC duct elbow, up against the fan intake, drawing from a hole they cut in the floor of the truck where it was installed. I am thinking of doing something similar, with sheet metal guides drawing air in from the starboard side of the Max II engine cut-outs (mine were all cut out by a previous owner), and a couple 6" 650CFM radiator fans that I haven't yet determined what to do. He said if I want to switch to a fuel pump, I should only use a 1-2 psi pump as anything much stronger will pop the needle out inside the carb and cause a dangerous situation. For now, I am staying with the pulse pump, and installed an Attwood primer bulb near the fuel tank to help me along if I start seeing pump or vapor lock issues.
Installation was simple. Pull old engine, trace the engine's footprint onto the two mount brackets with an awl, transfer brackets exactly as aligned onto the new engine, remove the turnkey harness, drill and install the throttle cable fastener, and install everything like before. 10W30 non-synthetic for my region is fine. I pulled the Champion plugs and replaced with NGK 5464 BKR5EIX-11 Iridium. The belt lined up as expected. I ran idle for ten minutes, drained and replaced the oil, ran at varying speeds in idle for another 20 minutes, then took it for a few short drives at varying speeds. I'll change the oil at 20 hours and then the usual use/maintenance after that.
In the near future I plan to put some thermistors in a few places and track the temps, then start doing heat abatements. I could not get a straight answer from Vanguard when I called their phone numbers about what the expected temps are for an air-cooled engine. One Vanguard guy initially referenced usual engine temperatures and gave a range that seemed very much like coolant ranges (208 to 220 Fahrenheit), and I said this is an air-cooled engine. Then he said don't take the block above 250, and when I asked about other parts of the engine, he said to expect about 230 degrees above ambient temperature or so, and don't go over 300 degrees total. Even the cylinder heads. Seems to me by that math it won't run at full power above 70 degrees ambient. I got all these different answers from the same Vanguard guy in one call. I have no idea what to believe, and when I asked for hard data on a document, he didn't have one.
I will update this thread when I have observations to share, or improvements made.
Took the re-powered Max II out for a spin with my better half over the weekend for about 90 minutes, up/down some steep terrain and ugly 4x4 trails (Timber Tamer and EZ Connector, Walker Valley ORV Area, WA). We're compact people, so the engine had no trouble at all hauling us around. Had a blast, took care when needed, and didn't break anything. Headed into a deep mud puddle, hoping to float, then remembered no plugs installed! - zipped right out and didn't take on any water. Getting the hang of the subtleties and mirrored steering when switching between transmission braking and "engine" braking on steep downhills. Drum brakes on steep hills helps but won't keep us stationary on their own.
Engine-wise, I could feel the warmth in the bench seat for sure in this first go-around. Definitely need to get some heat abatement in place, even if its operating temps are fine. Some chain slapping, need to set tensions. I noticed a slight oscillating bucking/surging when cruising, and realized that it happens only when I'm pushing the sticks forward with half-hearted force. Some sort of feedback loop that disappears when just a little more force is applied consistently. Skid-steer sounds a little loud when cruising fast, not sure if that's normal or not. There were many serviced parts/chains/gears/etc that came in a bucket when I bought it, but no transmission parts; how can I tell if it's doing fine or needs TLC?
Next up is to take it back in the lake and see if all that zerked grease is staying put enough to keep the water out. Also going to start with a simple pair of 6" radiator fans on the, uh, passenger side blowing down toward the fan intake. The digital temp controller I bought tops out at 257 degrees F, so I'll have to choose wisely where I put it, and use a K-type thermocouple to check the real maximums while driving. My buddy has an infrared gun reader and a FLIR camera so we can snoop around that way too.
i have been curious how the heater in the max 2 works . in this last cold spell , 20 deg. to 30 deg. , with the top and rear curtain on , it was very comfortable in the cab . with side curtains on almost too warm with a heavy jacket on . felt nice. is it just the motor fan blowing the warm air over to that metal box , then down the side of the tub and out into the cab . the other thought , i was wondering if that heater box blocks more warm air from coming out of the engine compartment ? jboy
Reply With Quote