Author Topic: Kx125 cuts out when I put into 1st gear  (Read 3236 times)

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Offline Timw

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Kx125 cuts out when I put into 1st gear
« on: July 31, 2017, 11:02:22 PM »
Hi everyone I'm new to the forum so hope this post is ok. Brought a supposedly 2004 kx125 yesterday. It was sat in a shed for months not being run. Picked it up for a good deal knowing it would need bits and bobs doing all cosmetically really. Right need some advice. When I got it it wouldn't tick over at all so adjusted the idle screw and got tick over just right but every now and then it will rev higher and higher on it's own? Not everytime but some times. Secondly when I've got it ticking over hold the clutch in and put it in 1st it cuts straight out. I have to rev it high to stop it cutting out? Once I've pulled of it rides fine and all the gears select fine. Can't hear any rattles. Any advice to what this might be would be greatly appreciated. Cheers everyone 👍

Offline umberto

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Re: Kx125 cuts out when I put into 1st gear
« Reply #1 on: August 01, 2017, 07:21:05 AM »
Welcome to the site Timw.  Did you clean the carburetor when you pulled it out of the shed?  It may have some crud in the jets that is restricting fuel flow causing it to run very lean at idle.  I would recommend starting there before you try anything else.  A new spark plug is probably in order as well.  Try that and let us know what you come up with.
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Offline reklessj

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Re: Kx125 cuts out when I put into 1st gear
« Reply #2 on: August 01, 2017, 08:58:18 AM »
Also adjust clutch, or inspect plates for wear
My rides: 1994 KX500, 1988 T4, 1998, ZXI 1100 JETSKI, 2003 MOUNTAIN CAT 900
WIFES (Baby Fiver) rides: 2004 KTM 105SX,1992 LT250R, 1995 ZXI 900 JETSKI,  2011 RMK 600
SONS ride: 1995 YZ125,2002 RM 250
other rides: 2007 RMZ450 RC Ediition, 2003 RMK700

Offline Timw

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Re: Kx125 cuts out when I put into 1st gear
« Reply #3 on: August 01, 2017, 05:24:44 PM »
Thanks for your reply guys. No to be fair I didn't clean carb I never thought. Will try later and report back. Il also strip clutch down and look for any wear n tear. Cheers for input appreciated 🍻

Offline KXDINO

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Re: Kx125 cuts out when I put into 1st gear
« Reply #4 on: August 01, 2017, 09:37:24 PM »
after u get it running good , keep a close eye on the compression , the one ring will wear on the exhaust bridge as with most of the jap 125  motor , if you dont replace it often it will take the bore out in that spot , so what we use to do was change ring very often every 9 hrs at least and i would drill the 2 holes on the exhaust side 1mm larger for better lubrication , did this for years with no dramas , another area to keep a close eye on is the power valve they last very well but i had one break but it stayed in  position , the rider complained it was down on power as  only one valve was working the bike kept going , so if the power valves have a lot of wear and slop replace them to be on the safe side. all ways replace base gasket and the head o rings every rebuild , i have come across the kawi o rings being slightly to large for there grooves so pay special attention to this all use another brand.

Offline Timw

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Re: Kx125 cuts out when I put into 1st gear
« Reply #5 on: August 01, 2017, 10:48:28 PM »
Thanks kxdino great advice really appreciate that. The compression is weak now to be honest. I can push kick start down with one finger. Kicks up everytime tho. Not had it out yet and had a proper ride taking it out Saturday so will no more then. No doubt il be coming to you guys for alot more advice in future lol. Much appreciated 👍