Just bought this old 4 wheeler at a garage sale. Its been sitting for years so I pulled the carb and put a kit in it, cleaned the gas tank and made sure the oil injector was working.

After doin all that, it does start but it takes alot of cranking to do so, and regardless of wether its warm or cold it wont idle, and nothing I do to the mixture or idle screw makes a difference.
AND.....omg this is getting old.......it wont run unless you have the choke on a little bit. If you turn the choke off it runs ok for about 5 seconds then stalls in a manner like the gas was turned off.

If anyone has a minute to help out this ATV neophyte I'd really appreciate it.


Thanks,
Mike

 

You said you put a kit in it. I don't know what the "kit" included but it sounds to me that your pilot jet is clogged. If it is the same pilot jet that was in it sitting all that time the gas has probably turned to varnish and plugged the jet. It does not take much as the pilot jet orafice is extremely small. Remove it soak it in carb or brake cleaner for an hout and then blow the orafice out. Look to see if clear. Bet it idles.

 

xler8ion is right. you also want to make sure your idle circuit is not plugged. like he said if gas has been sitting in this for a long time then you realy need to throughly clean it. maybe spray some carb cleaner in all the small openings you can see. i take it off and disassemble it and stick it into a carb bath.

 

Well I have cleaned the carb quite thoroughly. Every jet, passage, needle, and seat is gleamingly clean.

I took it off again last night and cleaned each piece in a sonic cleaner filled with carb cleaner (boy my wife is mad at me for using her jewerly cleaning machine......) but this morning the bike still does the same thing. While it starts a bit easier now, it still wont run unless you have the choke on.

Here's a bit more backround on the machine specificly....maybe someone could get a better idea this way.

The engine in a single cylinder, 2 stroke, 244cc
carb is a mikuni slide (plunger) type, gravity fed, with a dual-float config
the parts i replaced in the carb are
1)needle and seat
2)idle jet
3)main plunger needle
4)main jet (145 size)
4)mixture screw and tensioner spring
5)idle adjust screw and tensioner spring


Thanks,
Mike

 

I agree with both of these guys. Your missing a circuit in the carb somewhere. Something is not clean in there somewhere.
You might also want to do a compression and see what you come up with.

 

I think I might be narrowing down on the problem. Heres the only thing I havent been able to check.....does anyone happen to have the float height measurements for a 30mm mikuni carb? It was used in the 1986-1991 TrailBoss as well as the BigBear (or bigboss, something like that) 1986-1991


Thanks,
Mike

 

In addition to my 800 I have an 87 tb 250 4x4. I would suggest you order the parts and service manual from bigbuckrack.com which is all on one CD from them and an absolute lifesaver. I will have to look at my shop for the spec but although I think it is smart to check it, it would have to be essentially allowing no fuel to enter the bowl for it to effect the idle circuit. Even though you have soaked and cleaned the carb the idle circuit is puny in every orafice. You need to make sure you are getting flow out of the idle port in the carb. Use compressed air and run the circuit with it feeling the idle exit port in the carb throat and make sure all portions of the circuit are clear. Also I assume you have change the spark plug. If you have not do it. I found that motor does not like old plugs starting or running. Gap s/b .028.

 

Thanks xler8ion! I intend to get the manual, I was just tryin to get it runnin for this weekend [img]i/expressions/face-icon-small-smile.gif[/img]

Thanks again, I'll keep my eye on this thread for those specs.


Mike

 

im asuuming this has the lever style enrichener(choke as you call it). this is a plunger style correct? if so what this does is to allow more gas to flow at start up by pulling up and exposing a passage in which gas flows w/ the idle circuit. if you say you need to run w/ this open (on) then it does sound like there is a passage blocked. if you do a compresion check, it should be around 100 psi

 

With the bowl off and you're looking at the main hex jet. Directly in front of that is a hole. In that hole sits the pilot jet. You need a very small flat blade screw driver to remove it. Is this something you have done?