Daniel P

I have a RK 550 that is very similar to the 750. The engine has to be idling below 2000 RPM (around 1500) and the brake should be on with the vehicle stopped to shift gears. Also, if the shifter has been forced, it might need adjusting. Download the service manual to see proper adjustment. The 550 and 750 manuals are the same for both models. 550cc & 750cc Utility Service Manual.pdf

Yes! On the inside of the head housing, behind the chain sprocket cover, there is a little projection at the very top that the timing marks on the cam sprocket and the compression release shaft should be aligned with when the piston is at top dead center. The magneto flywheel has timing marks on it that lines up with the "peep window (behind the blower) when the piston is at top dead center. I got the engine all back together and it runs great now!

Okay guys, I found the problem on my Hisun 550. One of the compression release cam plates on the cam chain drive gear came off and fell down into the gearbox and crankcase! Luck was with me because none of it got caught into the crank or drive gears. The little torsion spring must have gotten pinched in one of the gears because it was mangled and cut in two pieces. I was able to order a cam shaft assembly from Alpha-Sports and have installed it. But I had to tear the magneto cover off to fish out all of the broken parts from the crankcase, and that took quite a bit of time. The service manual is a little vague on setting the cam timing. I found the timing marks on the chain sprocket and camshaft end, but the manual doesn't specify where those are located relative to the head. After looking at other manuals, I believe that those marks should align with the top center of the head with the piston at top dead center. If anyone knows different, please let me know. THANKS

Thanks Kenfain! It is not showing any error codes on the display, only the time and the hours. I'm thinking maybe the cam timing chain is loose but I don't want to immediately dive into that until I get some feedback from this forum. I wish I could find a service manual. I have rebuilt several motorcycle engines and the like, but it would be good to have a manual and parts diagrams to help troubleshoot. I don't think the engine has a coolant thermostat, at least I haven't been able to locate it. With a fuel injected engine, things can get funky when the temperature the engine computer senses is incorrect.

Hi Kenfain! It was bought originally a couple of years ago by someone, and when problems started happening, they returned it to Rural King. It had been setting around for a year or so after that and the store manager wanted to get rid of it, so it sold it to me with a $3000 discount and it doesn't have a warranty.

I have a rural King Hisun 550 with 16 hours on it and it seems that the timing is set too high. It kicks back when started cold and it idles too fast. Also, it seems that the thermostat is stuck open because it takes it forever to warm up and it never gets to the midrange operating temperature. I looked at the parts list and didn't see that it has a thermostat. There doesn't seem to be any way to adjust the idle and it idles too fast to change the gear range or reverse. I've replaced the fuel injector and installed a fuel filter, that didn't do much.

Okay, I contacted the factory technical person about the rear differential "problem", and he said that the model I have doesn't really have a regular differential. It is a "positrac" type that has both rear axles locked together all of the time. So, I really don't have a problem other than I don't like that feature because it makes it hard to turn a sharp radius and tears up the ground pretty bad.

I bought a slightly used (15 hrs) HiSun 550 UTV from Rural King that had been returned by a customer. It was running rough and couldn't get the gear shifter to operate correctly. I bought it at a discounted price and have fixed the rough running and gear shift problems; new fuel injector and in-line filter, and idle air control valve. Part of the gear shifting problem was because of rough and fast idle, and when I recalibrated the engine for the injector, the idle speed was smooth at about 1100 RPM. But now I notice that the rear differential stays in the locked mode all the time, 4 wheel drive or 2 wheel drive. I don't think this is normal because it is hard to turn and the wheels dig out dirt and scoot when making a sharp turn. Does anyone have a clue about how the rear differential is supposed to engage the locking mode?