74 kx125

[caseyracing222]

I know its not a 500 or a Honda but I've been working on an old rotary valve kx125 and I cant get the thing to Idle right. It fires up 1st kick but will either Idle perfect and bog out when you give it gas or Idle like your holding it wide open, I'm pretty sure its a carb problem but I'm a bit challenged when it comes to tuning them.... Does annyone have a solution or advice to fix the problem? It would be greatly appreciated

[caseyracing222]

Anyone?

[redrocket190]

From my experience with vintage Hondas I'd recommend a complete rebuild of the carb and a leak down test on your main bearing seals. Without the knowledge that these things are "right" before you start, jetting can be chasing your tail. You also need to find some vintage Kawasaki heads to help you out. Start here...

http://vintagedirtbikeforums.com/

[100hp honda]

i dont know the first thing about rotary valves. wish i did though

[caseyracing222]

From my experience with vintage Hondas I'd recommend a complete rebuild of the carb and a leak down test on your main bearing seals. Without the knowledge that these things are "right" before you start, jetting can be chasing your tail. You also need to find some vintage Kawasaki heads to help you out. Start here...

http://vintagedirtbikeforums.com/

Thanks I will do that, this problem is the only thing keeping me from riding it, some how I thought you would be the guy with an answer or advice thanks

[redrocket190]

http://vintagedirtbikeforums.com/

http://www.nightmare-racing.com/

http://vintagemx.com.au/?p=567

http://www.reproductiondecals.com/

IMHO, you would be wise to rebuild the carb and do a leak down test before you start wrestling with the jetting...

[caseyracing222]

Redrocket thanks for the links, I disassembled the carb cleaned and lubed everything, every thing seemed to work the float didnt stick or anything, I will do a leak down test on it but I think that the jetting is way off, this bike used to be ridden at high elevations and Im at see level. I picked up the bike from my neighbor its been sitting on his side yard for 20 years. I also joined that vintage bike forum theres a couple people on there that are working on the same bike so they may be able to help, thanks again

[redrocket190]

I read your original post. If it bogs when you crack open the throttle that's a good indication the jetting is lean. However if it races at idle I'll bet you have a bum rotor-side oil seal that is allowing air to be sucked in...

[caseyracing222]

this might sound like a dumb question but if the seal is bad wouldnt it leak oil? Sounds like my next step is to do the leak down test like you said. it basically changes characteristics every other time you start it

[caseyracing222]

I wouldnt doubt if the oil seal is bad like you say since this bike has been sitting on my neighbors side yard for 20 years

[90cr500guy]

Not sure if you have seen a review yet
http://vintagemx.com.au/?p=315

[caseyracing222]

Not sure if you have seen a review yet
http://vintagemx.com.au/?p=315

good write up sounds like it will be a good running fun bike after I fix this idle problem

[caseyracing222]

I got it to Idle right, the pilot jet was clogged, The clutch cable was also toast so I got a yz490 cable to work the bike is rideable now and I will be sewing a new seat cover for it. I'll get pictures up tomorrow so you can see this beauty