Jump to content

2000 Suzuki 500 Quadmaster stumbles and backfires?


Recommended Posts

My Quadmaster was getting very hard to start so I put a carb kit in it except the diaphram and float. Now it is running worse, it is stumbling and backfiring. I read some of the threads with similar problems and have adjusted the valves and the float and have checked the carb several times and it still runs awful. I have ordered a new fuel valve and vacuum hose to try that, I took it apart and the diaphram in it looks kind of bad. I have 4 questions:

1. Can the diaphram or float in the carb cause this problem?

2. The needle valve goes through the diaphram assembly and has an E clip with 5 settings,I have it on the middle setting, I didn't pay attention when I replaced it, which setting is the right one?

3. There looks like good fire at the spark plug, could this be an electrical issue? (CDI or Ignition coil, generator)

4. I also left the fuel valve in the PRI position over night and most of the gas went on the ground and evaporated, it did not go into crankcase. The book says this could cause engine damage, what kind of problems can this cause? It runs the same as before.

thanks for any help


Link to comment
Share on other sites

Gas running out of the overflow tube could be a stuck float, and that could cause your problem. Did you find any fuel in your airbox? The fuel valve could be your problem too, someone just posted a similar problem and it turned out to be the diaphragm in the fuel valve. I think that you are on the right track by focusing on the fuel problem. I would forget ignition issues unless you still have problems after you get the fuel issue fixed. As far as the needle clip position goes, I would consult a dealer service tech on that one, elevation, air temp and engine mods can all affect the jetting neeeds. You may also want to get a manual for it, they are a must for anyone working on thier own machines. When you had the carb apart, did you clean it? Did you notice any debris or gummed fuel deposits?

Link to comment
Share on other sites

As far as the needle clip goes, I would call a dealer tech and ask them what they recommend, but there should be something in your repair manual. Do you have an actual repair manual, or are you talking about the owners manual? If you can't get any helpful info anywhere else, I would start in the middle and see how it runs, if it seems good then ok. If it doesn't, try moving it up or down and see if the problem gets worse or better. If it gets worse, then you need to go the other way. At anyrate, I wouldn't mess with that untill you get the new fuel valve, once that is fixed, then I would start messing with the jetting.

Link to comment
Share on other sites

  • 3 months later...
  • 2 months later...

you siad two key points to your problem that did the exact same thing my atv did. when you rebuilt your carb did you remove the needle screw out of the bottom on the front of the carb closest to the engine. that screw is known as the start/idle screw. it is running to lean whenyou try to start it. you should richen it up by turning it out.

Link to comment
Share on other sites

  • 1 year later...

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

  • Similar Forum Topics

    • By Gwbarm
      I finally got around to working on the TRX, this has been an ongoing problem with this machine. This is a machine that we keep on my Fathers property, i dont see it that often, my brother haad it professionally repaired last year and year before same problem, the new starter gears and bypass gears last about a year and the machine is not used that often, he said he was done with it , so i thought i should go take a look. Sure enough the gears were all malled again. 


      IMG_4910.mov   There is some slack in there but most is taken up by the gear cover,if anyone with history with these machines has had the same problem, let me know your findings. Where i am now im looking for finding replacement honda gears on Ebay and try those. I suspect the original was replaced with aftermarket gears years ago and they just worse quality as the years go by. 
    • By huntindog
      I am in the process of puting it back together after replacing the DPS gearbox.
      The manual I have states that it will need to be flashed by a dealer. Is this still true?
      Also , I have a mystery bolt That I cannot remember where it goes. M6x 70 or so.  Hex head with a flat washer.I will try to attach a pic.
      Pic is no go for now....Cox issue I will try again later
    • By Skindian82
      Won't cold start if I do get started with starter fluid won't start again later when cools down
    • By Werewolf
      Oil is getting in the air box from crankcase vent tube, I put the two hoses that go to the air box together then something started to smoke on the front of the engine. There is a filter? In the line I blew that out.
    • By Brantley11
      Hey everybody,
      My proficiency is with Hondas and Yamahas make me see RED!
      This bike is my brother in law's, it has 1199 miles on it and went from running great to dead with no start. Every once and a while it will start and sputter for 2 seconds. It is extremely sporadic when it fires but never runs for longer than 3 seconds. 
      Here is where we sit:
      Brand New Fully Charged battery
      Carb was cleaned with air hose and carb cleaner then into the ultrasonic cleaner with Aircraft aluminum cleaner
      New Shindy Carb kit (made in Japan version)
      Cleaned out petcock and gas tank
      New 93 Non Ethanol Gas
      New Spark Plug
      It gets a spark through the spark test light every time
      Bluish white spark
      When holding the spark plug 1/4" - 3/8" away from head it will jump and spark to the head
      Good Compression
      Here are the readings:
      Pickup Coil 519 Ohms (range 459-561)
      Charging Coil 266 Ohms (range 270-330)
      Lighting Coil 0.700 (range 0.702-0.858)
      Spark plug Cap 10.58 Ohms (10kohms
      Ignition Coil Primary Coil 0.5 ohms (range 0.18-0.28 ohms)
      Ignition Coil Secondary Coil 8.20 kOhms (range 6.32-9.48 kOhms)
      Would y'all think stator and pick up coil, rectifier or CDI are the culprit?
  • Create New...