hiccup under hard acceleration

[mike_schoettler]

just rebuilt my 1999 kx 125 and just took if for a little drive and as before the rebuild when you give it a good amount of gas at low rpm in the lower gears it will give one big hiccup for about 2 seconds then run perfect all throughout the rev range. no matter what i do with the carb it does not change and it some times does it when letting the clutch out in first gear it will bog so you must pull in the clutch and give it more revs and proceed till it is moving fast enough to stop the bog..

because at idle it revs free and never bogs it is just once you start to move and put a load on it..the bogging is comparable to the sound my 81 yamaha mx 100 makes when it is cold and you turn the choke off and try to rev it

any help would be nice

 

[Blink-182]

try adjusting your jet needle put it in the stock clip myn used to hiccup and then catch on until i adjusted that now it just trys to throw me off the back

 

[2strokerfun]

Sounds like you are a tad rich on the jet needle. You indicated you tried adjusting the carb. What did you do?

 

[mike_schoettler]

i just adjusted the air screw and the idle speed screw nothing serious would ..how would i adjust the main jet? im pretty new to the thing

 

[hot125mod]

It isn't adjusted you change the size of the jet.

 

[2strokerfun]

i just adjusted the air screw and the idle speed screw nothing serious would ..how would i adjust the main jet? im pretty new to the thing

Adjust jet needle to start with. Take off top of carb where throttle cable runs in. Take apart and remove needle. Raise the clip at top of needle one notch, which will lean your carb a bit between 1/8 and 1/2 throttle.
Look at manual or find someone that can show you.

 

[BSWIFT]

Read thru this thread, http://www.dirtrider.net/forums3/showthread.php?t=42618.
After performing this proceedure you will know your bike better and understand the jetting process. Follow it closely and you'll get it right.

 

[mike_schoettler]

does anyone else have any more ideas that can help? just put a new pipe on it today cause if you slowly roll on the throttle it is fine ,but if you crack it to half real quick and keep it there it will die. as well as when you start moving in first gear it some times bogs if you dont give it propper throttle?

 

[SVandal]

Did you move the jet needle? If not, try this first as this will essentially lean out the main jet.

Also, what mods have you done to the bike? New pipe, what kind? New airfilter? Take off air filter box top? What is the current jetting? It might also be your float height. More info needed in order to help.

By the way your bike should rip when you open the throttle, not bog. You may also have some crud in your float bowl that gets sucked up into the main when you open the throttle fast. If you haven't cleaned the carb this year, now would be a good time and you can check your jet sizes while your in there.

 

[mike_schoettler]

well its got a fmf sst pipe and silencer as well as boyseen reeds and i took the carb off and its clean as it gets.. but there is a hose that goes upwards off the carb ..is it an overflow? are all the the holes in the carb over flows? cause it almost seems like it should go over the carb and wrap around to the other side and into the carb again?

 

[Clint3240]

dont connect the hoses they are vents, turn your pilot air screw 1 turn out, start the bike, adj the idle screw so its at a speed where it just stays running. then turn the pilot screw in and out untill you get the highest idle speed. count that many of turns out..if its close to all the way in go one up on the pilot, if its more than 2.5 turns out go pilot size down. then when you find the right pilot jet adj the pilot screw to give you the best throttle responce making .5 turns.....correct?

im pretty sure that would stop you bogging when you go wide open

 

[mike_schoettler]

i will have to try that method this weekend..i jsut connected them cause it looked like they should be because they both point staright upwards and there is already a vent off the one right by were it connects..i drove it today and you can roll on the throttle pretty fast underload with no hessitation ..but when you crack it open to 3/4 throttle from a slow speed in 1st its all bog till it catches up with itself. it only seems to do it under load in the bottom two gears