KX125 Doesnt stay running

[KawiBGB]

i just bought a 88 kx125, i thought it had less hours on it than i was led to believe. My main issue is the bike wont stay running once the choke is off. It will kick over on the first kick with the choke open, but after that it will run and then start to die down, when you crack the throttle to keep it running it has this loud suck from the intake but the motor takes a second to catch the revs. Anyone have any idea whats this could be? the carb was taken apart and cleaned with some carb cleaner after this happened, but its still having the same issue. PLEASE HELP!!! i wanna ride this thing this weekend.

Thanks guys!

 

[chilli1]

hope u can get it working

well u shuld take it in2 ure local moto shop but try leaving te choke in for 5 mins get it reallty warmd up rev it n then take iy of keep it reving n then wen u go go str8 in2 powerband but clutch it in shuld work i got the newkx85 08 model lot of power for 85s

 

[SBC383STROKER]

Bike wont run w/o choke

I believe your engine is running too lean because you said it will not run w/o the choke. The reason why i'm saying that is because when you engage the choke, it delivers a super rich mixture therefore helping the lean running condition. I think the problem you might have is that there is an air leak before or after the intake port making the motor go lean on you. Air leaks can happen at the cylinder base, reed valve, or magneto side seal. Check the connections from your airbox-to-carb and carb-to-rad valve. Worst case scenario is that you have a blown magneto side seal, again, causing your engine to run lean and bog out like that. That will eventually cause a piston seisure. The magneto side seal is prone to blowing out because it runs dry meaning that it is not drenched in oil all the time like other seals are. This might also be the problem too because you said the bike is an 1988, so if you do the math right, the bike is old, and its time to see problems like come and go.
Check everything i said and you might just go out riding this weekend. lol :)

 

[ZOMBIE666]

like sbc said, you probably have a lean condition. either the carb wasnt cleaned well enough or you have an air leak somewhere. when you did the carb, did you clean the jets out or just spray them with cleaner?

 

[KawiBGB]

i did have it running decent today, i let it run with the choke on for 5 minutes, turned it off, then it started to die, then i opened the choke then closed it right away and it came back to life, i did that 2 times and it was running fine. I took it around the block(dumb thing to do) but it ran good, but when i shifted it would go into gear and not gain anymore speed as the motor revved higher. I took it back home, and it was leaking anti freeze outta the runoff line. I parked it let it sit for a few minutes, then it started right back up without the choke. I came home today after about 5 hours and tried to start it, it took a few kicks, then it idled really slow like it almost died. I turned the choke off and it died instantly. I havent fooled with it since that happened so...any idea whats going on here? I feel like for 500 bucks i got gipped :(

 

[2strokerfun]

For $500, you're lucky it runs at all. Take your carb apart completely and clean it again. Including the jets.

 

[ZOMBIE666]

youll get it working bro, these bikes are so simple. Try cleaning out the carb again: its free. One of the bikes im building right now, an FZR ive cleaned the carbs 4 times now, each time it looks good. run it for a minute and bam dirty jets again. Old bikes that have sat love to gather crap in the carb passages. Hit up your local home depot/ lowes and get yourself a mig welder nozzle cleaner (same exact thang as what shops sell as jet cleaners) if you dont have one already. makes cleaning out the jets very easy and fool proof.

 

[KawiBGB]

so you dont think its anything big thats gonna cost me alot to rebuild the motor or anything? you really think that was a good deal for 500?

 

[Kx85Krazy]

make sure you have the right carb screws. My kx85 was a little wacked out when i cgot it. I took it to the shop, ended up buying a whole new carb. Gas mixture is a big part of it tooo. you may think its the choke and that thats the only problem, but get some advice from a local rider or dealer and see what you should be mixing.

 

[DannyB728]

Anything that runs ( or sort of runs) for 500 bucks is a pretty good deal. I agree with what was said above too, you have an air leak....

 

[MROLP84]

hey i have an '87 kx125 that i got for 400 bucks and it did the same thing when i bought it. i would do what the rest are saying and clean the carb really well and check for leaks. the bogging down could be some gunk in the jets. my bike was sitting in a shed and had not been started for 6months but after a good carb cleaning shes been running strong. if you have any other questions let me know cause i have a clymer manual for that bike..... :cool:

 

[snb73]

When you say,"The bike won't keep running", do you mean it won't idle? If thats the case, adjusting the idle screw will help.

Considering the age of the bike, there may be some mechanical issues as well.

Start with a cleaned carb, cleaned air filter and a fresh plug and gas, then see how the bike runs. That will give you a good indication if the problems are internal.

The bog you're hearing may be a jetting issue.

 

[mox69]

Did you put brand new mixed gas in the bike, as well as draining any other gas that was in there? If you haven't you should.


Did you inspect / clean the air filter?


You can check for air leaks pretty easily. Get the bike running and hop off. Grab a can of WD-40. Now spray some WD where you think the air leak might be. If the engine changes RPM when you spray, you have an air leak (ie the bike just sucked some WD-40 into it). This will also work with starting fluid.


I would advise on not riding it much until you can figure it out. If it is running lean, you could be causing some engine damage. Especially since it may have overheated a bit (coolant coming out).