Cold Natured KLX250

"Cold" might not be the right term. "Freezing" might be more descriptive.


Here's what happens: Bike sits for 4-5 days and you walk out, turn on petcock, pull choke knob, hit the starter and she chugs for 2-3 seconds before coughing out. This goes on, over and over, until I'm just about convinced the battery will die and then she'll actually idle long enough to warm up. Thank goodness it isn't a kick start (I'm too old for that).


What could I be doing wrong? Is there a KLX technique I'm missing? If I mess with or ride bike every day she starts with a quick application of choke and then idles fine and away we go. After a few days it is as described above... "freezing natured"!


A few points to make: as I've done for 30+ years I turn off my petcocks before I hit the driveway. When this bike runs, it runs very well. Bike is bone stock. Hot starts do require a very light "blip" of throttle. Bike sat for a year (maybe more) before I bought it, BUT I have flushed the tank and all the fluids have been replaced. 


Maybe I just need to suck it up and do a carb rebuild? I would have been all over that but the bike does well until it sits a few days. Ideas, thoughts, comments, all appreciated :-)


Have you tried looking under the carb? There is a screw that you can turn "left" maybe try a half turn, if the bike is setup stock. Then you will probably never need the choke again. I've done it with several 4 stroke bikes over the years and it works every time.  

What year is your bike? I recently picked up two of these bikes, one an 09 the other a 10. The 09 did the same thing you are describing. Cleaned out carb and now starts and runs good. Had a bit of build up in the choke and one vent hose and touched the exhaust and was completely melted closed. The 10 was better but ended up getting a pipe, header, and rejet for it. Much improved ride!! Pulling carb is pretty simple once you figure it out the first time. Just pull the seat, tank, hose between airbox and carb and few other hoses here and there and pulls right out top. Clean it and sure will run good.

Also from what I've read the bikes are set pretty lean from factory to pass emissions. Think the stock jet was a 118 so maybe put in a 120 and possibly a quarter turn on air/fuel mix screw. On my 10 I bought a kouba extended one so can adjust more easily.

After a year I drilled out the cold start jet and now it starts so easy like it should.

Well, I'm hearing a lot of what I kind of didn't want to know...quit being lazy and do a carb job! I'm guessing the DynoJet kit will do in spite of the $50 price tag. At least I will have all the goods to work with future mods. 


Maybe I will try drilling the EPA plug out of low speed jet/screw first and see if that is the cure. I don't want to do anything right now but RIDE!

There's a number of owners reporting cold start issue from '06 on KLX250.

The "best" fix IMO is drilling out the enrichment (choke) jet ever so slightly so that it gets a little more fuel with the choke lever out. I think this is an 0.018" drill bit.  Did it to mine and it works like a charm.  Read up on this mod over on kawasaki forums.

The dynojet kit won't help.  It doesn't do anything with the pilot or enrichment jets. Nor will installing a larger main jet.  The main jet has no affect on starting with this CVK carb.

Turning out the pilot fuel screw a little may help. But that screw is covered with a little plug that needs to be removed, and it's darned difficult to get there without removing the carb.  If you're removing the carb, clean it, and drill out that enrichment jet. Your DJ kit will come with a drill bit and wood screw for removing this plug. 


In my experience, DJ's stock instructions will leave your bike overly rich.  Just so you know.... :prof:


It also helps to run more fuel out of your carb bowl before shutting down.  Think 1/10th of a mile from home or so to shut off petcock.  Others shake the hell out of the bike while pressing the starter, or laying the bike down on its side with the petcock off to drain some fuel out, then after picking back up open the petcock and start.


While you have the carb off, its a good idea to check float height the proper way with a clear hose to the bowl drain. 


If your bike is setting for more than a day or two, empty that carb bowl and get the fuel out so it can't evaporate and gum up the system.

Edited by IDRIDR

Idridr: thanks for the detailed feedback! I've been riding the last few blocks home with the petcock closed since my first xr75 :-) I believe it is part of routine maintenance to park the bike with the petcock closed and if sitting overnight or longer, the float bowl empty via the method described above. Excellent advice that I've passed on to my kids and they've shared with their cousins.


I just ordered the DJ kit 10 minutes ago and might have waited had I seen the comment about the choke circuit. Oh well, carb's coming off ASAP regardless, DJ will be installed as stage 1 and I will run the leaner DJ settings as bike is otherwise stock. I think drilling plug and adjusting air/fuel screw will cure most of the problem, but can't do that in place either. Gotta get to it to drill, it has to come off (might twist sideways enough, but what a hassle and risk to intake et cetera). I will seriously consider the choke circuit drilling as well.


Note, the bike runs well once running, but i'd not commute on it like this. I'm irritable in the morning and I'm used to hopping on and riding off. Even the 1972 FLHP, kick only, started right up every time and was a decent commuter- I only let it warm enough to fasten my helmet and pull on my jacket. Not so with this KLX. But I still love the bike and I will get it running right by golly :-)

Edited by Sweetwater Farms

You're welcome.  If you are already running the bowl dry and its not starting easy, I'm guessing you will benefit from both adjusting the fuel mix screw and/or drilling out the enrichment jet.  Be careful drilling that jet.  Make sure you use the correct bit.  The 0.018" should be just a tad larger than the current jet size.  Get a good bit; not a dozen for a buck from ebay (mine ran $2 for 2 bits from Hobby Town USA).  Go slow and easy with a proper hand bit holder.  Some use a small vice grip to hold the bit while others reported just holding in their fingers.  You should feel the bit drop a little once it turns through the jet; stop there.


Not every KLX needs this.  Some are darn hard starters.  Some have no problem at all.  And in between. 

Follow up for those who might be interested:


Bought DynoJet #2152 from "Powersport Superstore" on Amazon. I was a little nervous, because I only paid 46.59 and that included shipping. The old saying, "too good to be true" and all that...


Well, the box arrived exactly on time and was exactly as advertised: a perfectly new, genuine, DynoJet 2152 kit for my 2010 KLX250S.


I installed per stage 1 instructions using 116 main and air/fuel 3 turns out, needle clip 3 from bottom, two spacers on top. Interestingly enough, the air/fuel was ZERO, yes 0.00, turns out after I removed the plug. In all fairness to Mama Kawi, I gently tapped the drill bit into the screw while removing plug, but still, it was 0 turns out when it was uncovered. No wondered the bike was lean on the low end; even if I accidentally turned it in it was 1/2 or less from the bottom at most at factory setting.


Anyway, I also de-smogged the bike and plugged the holes with suitable vacuum plugs from auto store.


Ta-DAH! The bike starts rather easily and runs great. Decel popping has vanished, hot starting is 99% perfect and I am one happy KLX rider. 


IDRIDR is right, the cold start/choke circuit could/should be drilled but I couldn't get the drill this weekend and had to try this kit first. Overall pleased, but will be back in it this winter, just because I'm a busybody.

Edited by Sweetwater Farms

Thanks for reporting back.


With the fuel mix screw out three turns, you may not need to do anything to the enrichment jet.  I think three turns out is excessive and you may be a bit rich now in the pilot circuit, but that will help with starting issues.  Watch for black soot on your exhaust.  I'm a fan of the Kouba T-handle fuel screw for simplifying pilot circuit tuning.

I also plan on watching the MPG.


Think I can get the adjustable screw in there without taking it all apart again?

I also plan on watching the MPG.


Think I can get the adjustable screw in there without taking it all apart again?

Eh, maybe not.  But other riders have had success using just a flathead driver bit and turning with their hands, or getting a small screwdriver and putting a bend on the end, to adjust the stock screw.  Maybe give that a try? 


When I had the larger #38 pilot jet in, the bike would start cold without choking even with the screw turned into 1/2 turn or less.  That to me was a sign of an overly-rich pilot system. Went back to a #35 and it's about 2 turns out (3500 ft elev).

Edited by IDRIDR
What did the Ol' Jolly Elf bring???




Burr Monster???




While surfing the another thread a few weeks ago I mentioned my cold start again and later spoke with a rider who very, very graciously offered to ship me a #77 drill bit, as he'd already completed the starter jet mod on his KLX.


As I had already done the DJ Stage One tune using the smallest recommended DJ main jet and the DJ needle setting with 3 (!) turns out on air/fuel screw, I knew the  carb removal steps. I used an Exact-O blade holder as my bit driver and aside from some minor grumbling, opened up the starter jet as so many others have done. Total job time, one hour.


Temps this morning are low 40s and bike never starts easy regardless. Today, all seems pretty normal, like all my other bikes: fuel on, choke on, key on, switch on, no throttle, push magic button.


VROOMmmmmmmmmmm...thanks Jules   :D


And big thanks to IDRIDR who got me going in the right direction to begin with. The DJ kit was an improvement as was the air/fuel adjustment, but the drilling was the answer in the end (I think!). Time will tell.


Also happy to report that as of today the mods are all the same as posted in previous replies except for drilling the starter circuit. No soot on tail pipe and backroad efficiency is in the mid to high 60mpg. A full weekend in the OHV trails yields high 50s mpg. So, the bike is efficient and will hopefully continue to start easy. Might revisit the air/fuel screw soon just because...  

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