125 Pit Bike Carb Problems
Posted January 18, 2008 - 08:37 AM
Things got a little better, but then the bike became hard to start, some smoke came from the air filter when I tried starting the bike, I am able to get it started but it cuts out if I don’t open the throttle at least ¼ turn.
I am able to higher the rpm by turning the screw on the carb so the bike doesn’t cut out, but its way to high and isn’t exactly purring, I’m sure its not doing the engine any good.
As you can probably tell I don’t know much about bikes, I don’t really want to try making things better incase things get worse.
An easy solution will be taking it to a garage but getting charged a fortune.
If anyone has any advice PLEASE LET ME KNOW!
Posted January 18, 2008 - 09:26 AM
Is the carburetor a mikuni? If so, there is a screw where the carb attaches to the manifold. It is very hard to reach on the bottom of the carb. Try turning that screw in until it bottoms (lightly, don't force it) and see how many turns in it went. Should be around 2.5 but may vary. If you turn that in, it will lean the idle mixture a bit. If you have to go any leaner than a total of 1.5 turns out from bottomed, then your pilot jet needs to be richened.
If it runs best at more than 3 turns out then you should probably use a leaner pilot jet.
Make sure you have fresh fuel and try the new plug to start with. The cable should not make any difference as long as you are getting smooth full movement of the slide. (you can remove the air filter and look in as you actuate the throttle and see if it moves from the bottom to all the way open.
Posted January 18, 2008 - 06:25 PM
Can you find out what carb you have or take a picture of it?
Anyway, commonly there is an idle adjust screw that is pointing towards the slide. In fact if you take the air filter off and screw that screw in you can see the slide moving up. The other screw is usually a fuel or air screw. Usually (but not always) on a four stroke it is a fuel screw and turning it in leans the mixture. Turning it out richens. If, however it is an air screw, the opposite applies.
I'm no carb expert, but if you post a picture, maybe someone can tell you more.
Posted January 18, 2008 - 07:52 PM
Posted January 18, 2008 - 08:06 PM
If the screw is located in the front of the carb, usually underneath by the fuel bowl, it is a [COLOR="DarkGreen"]fuel[/COLOR] screw and [COLOR="DarkGreen"]turning it out richens [/COLOR]the mixture. If the screw is located to the rear (airbox) end it is an [COLOR="Navy"]air[/COLOR] screw and [COLOR="Navy"]turning it out leans [/COLOR]the mixture.
That's how I've always heard it also. I do think there are exceptions to this rule though.
Posted January 19, 2008 - 04:28 AM
i found out it is a mikuni carb.
can you give me a standard setting to work from with both air and fuel screw?
i will be getting a new spark plug soon and will see if its any better.
Posted January 19, 2008 - 05:20 AM