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By Emilios garage
Just bought a new Sector 750. It's slightly better looking and equipped than the Axis 700 models they sell at Lowes or the RK and other versions but there's very little difference in the frame and drive train. Seems to be a good machine to use around the farm and riding around the neighborhood. If you own any of these Hisun made machines, you may have similar issues. After driving this around on some country roads doing some break in riding, an extraordinary amount of radiant heat was emitting out from behind the seat and under the dump bed. The engine temp was showing normal on the gauge. The source of the extreme heat was mainly the muffler, and it was even hot enough to soften the plastic underside of the dump bed. You could smell the plastic was almost at that melting temp. I've never seen anything like this on any brand of machine. This could possibly qualify for a safety recall. Back at the shop afterwards to study the situation revealed some suspected bad exhaust designs to be the main cause. The pipe going into the muffler from the engine is 1 3/4 inch in size. The pipe coming out of the muffler is 3/4 inch. A one inch difference! That's a lot of very hot gases going in through a large opening, compressing inside the chambers of that muffler, and trying to get out through a much smaller hole. Simple science will tell you that even cool air when compressed gets hot. Science has also shown that hot air flows faster than cool air. This muffler by design is causing already hot gasses emitted from the engine to be accumulating, compressing and therefore amplifying that temperature to far greater temps than what the engine itself was emitting. I'm sure all that back pressure is also causing the engine to labor some too and wasting HP. The same muffler appears to be used on the 550, 700, or 750 Hisun variants. The exhaust tip on the back of the muffler is removable and when you do there will be even more engineering issues revealed. The 3/4 inch pipe extends inside the rear chamber of the muffler about 3 inches. There is a metal case over and around the internal 3/4 inch pipe section with a steel screen around that. If the 3/4 inch outlet wasn't bad enough, that case and screen cause even more restriction and back pressure compression. Those of us who turn wrenches already know that screen is only in there because of certain mandated requirements, but now we're talking about outflow that would be around the equivalent to a 1/2 inch outlet with all this. The first attempt to reduce the extreme exhaust temps was done by just removing the screen and cage from the internal section of the exhaust tip. The 3/4 inch tip was reinstalled as just the pipe and the machine test driven again. No longer had quite the extreme scorching heat but still felt like the exhaust temp was still too high. I did notice that the radiant heat from the lower exhaust pipe section which is about 4 inches from the drive shaft was enough to melt and burn the rubber boot that covers the shaft yoke just behind the u-joint. Don't know yet if the rubber parts of the u-joint were compromised. The next attempt to mitigate this problem was to manufacture a new exhaust tip with greater outflow. One that would have the same size pipe on the outflow side to relieve this engine of back pressure and fix the heat problem. My car, my riding lawnmower and other brand UTVs have mufflers designed this way, why not this Hisun machine? I could not find any aftermarket companies that already make this part, so now I do. If you are handy with a mig welder, a drill and some hole saws, then you can make this part too for around $20 worth of materials. (Bi-metal hole saws not included) It's up to you what angle you want coming out of the tip. I went with 90 degrees and a slight downward angle, but 45 degrees will work too. The exhaust outlet is now also a 1 3/4 inch pipe. This seems to have fully solved the extreme exhaust heat problem. The engine idles smoother now, and I do not notice any louder exhaust noise than what I had before. In fact, it's actually quieter now because the high-pressure air release noise the original tip made is gone. The issue of the lower pipe heat next to the drive shaft is still being evaluated. Possible fixes for that if still needed would be a shield wrap on that section of the exhaust pipe or a clamp-on aluminum shield. People, this is an engineering issue, no warranty can fix this. Attached are some pictures I took during this project. Good luck with your Hisun machines.
Safe trails, E
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By AlphaSerenity
Hello,
Before I invest $10k+ into a brand new UTV for the farm, I want to get my feet wet with a fixer upper and learn the mechanical side of things. I acquired a 2022 Hisun Axis 500 (Lowes-specific model) from an auction for $500. It has only 200 hours and 120 miles on the engine. It looks like the previous owner used it for ranch work and didn't drive it on trails, deep water/mud, or anything too crazy.
While it runs and moves, it has some problems. It struggles to accelerate up any incline in high and low range and sometimes stalls when I let off of the throttle or change gears. When I apply throttle in neutral, it sounds like it is struggling for fuel/air and pops. When I decelerate, there is a grinding sound coming from the clutch, which I've read to be related to the one way bearing and is semi-common. The last thing I've observed is sometimes the speedometer display sometimes will show a much higher value for a few seconds after barely touching the throttle. Based on the documentation, if a problem is detected from the sensors, the instrument panel display should have an error code rendered on the screen in place of the time, but this isn't happening. Here is a video showing some of these issues (engine is exposed with console removed):
https://www.youtube.com/watch?v=FFAkO5TaGps
Here is another video of the clutches in action:
I've done some research, but information on this specific unit and sister units is limited. There does seem to be transmission and clutch issues reported. I still need to check into the head gaskets. I don't have the equipment to test compression right now, but I do plan on ordering what is needed soon. I do have an order in place for some cables to read the diagnostics from the computer. There is a shop two hours away from me that works on Hisun products, but I am hoping the problem can be identified and is something within my ability to handle. Below is what I've already investigated. I am leaning towards the primary clutch needing replacement right now.
After getting it home and unloaded, I did the following maintenance/checks to it prior to operating it further:
Changed the engine/clutch oil (and filter) and gear oils using manufacture recommended viscosity Changed the air filter and checked for cracks in the air intake flow. Verified good suction. Cleaned the throttle body Changed the spark plug and verified the gap was within spec (0.6-0.7mm) Changed the coil and coil wire Changed the fuel lines, fuel injector, and verified the fuel pump was outputting the correct initial prime pressure for ignition and continuous pressure after ignition. Also completely emptied the fuel tank and made sure octane 91+ fuel is being used per manufacturer specs. Ran seafoam through system too. Cleaned the spark arrester and verified no cracks or gaps in the exhaust flow Changed out the O2 sensor Checked all wired connections to ensure they were secured and no breaks were visible Checked the belt for tightness and for any signs of wear and tear Verified 4WD and the differential lock function as expected - still hesitates and struggles uphill Verified the fan gears in the shifter are not corroded and working as expected ECU was reset after replacing sensors and fuel-related parts
Thanks!
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By Bryan g
We see a lot of the UT400 with shift problems, not going into gear, popping out of gear, grinding etc. There is a bulletin Im sure everyone has saw about adjusting shift cable. That dont always fix it. I went round n round with coleman on couple units. We are a Coleman warranty repair center"AFS Small Engine Repair " I told them shift lever does not have enough travel . No amount of cable adjustment will increase travel . I extended lever with piece on flat iron by 3/4 of inch . This gave shifter enough travel to properly engage into gear completely . Last couple units to come in for this Coleman sent me a modified shift lever, with longer travel . Problem solved! Also , heads up if you get any new unit ,,,go over and check it out, grease all zerks, check air filter for being in backwards, check wiring harnesses for rubbing on rotating parts, brake hose routing , make sure not touching exhaust . These are just few of the more common failures I see .
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By Werhat
Hi folks,
I have a Mule 550 (FE290D engine) that sat for several years and would not start. A few years ago I replaced the fuel filter and carburetor, at which point it started right up and developed full power. More recently, I've changed the air filter, fuel pump, ignition coil (gapped to spec), and spark plug, and adjusted the valves. The engine still has a lope/surge at part throttle and at idle. Rather than idling at a stable speed, it speeds up and slows down until it quits. It snaps to life right away if I open the throttle, so I don't think it's starved of fuel. I can always get it to restart immediately if I choke it while cranking, then it will die after several seconds again. It takes some cranking to start hot when not choked. I've tried adjusting the idle mixture, but no setting seems to make it stable. It won't idle at all with the throttle fully closed; I have to turn the stop screw to hold it slightly open.
I suspect it's getting idle air, since the passages are open, but that the idle jet isn't providing adequate fuel, such that I am having to hold the throttle open and idle it off the main jet which isn't stable. This is just speculation. I've cleaned the idle jet and tried a larger size, but it made zero difference. The carburetor seems to be clean. It's been doing this since I installed the new carb. The gas tank seems to be clean, although it's hard to see inside.
I posted a video of what it's doing:
What's next? Try another carburetor?
Thanks.
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By Kingfish
I've had a battery failure and need one replacement. The local distributor told me it might take up to four weeks to get one. I'd like to order one in sooner than that if possible. Any help would be appreciated.
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