Old Issue, New Info. CVK Carb No Start. Choke / Enricher Jet Drilling
#1
Old Issue, New Info. CVK Carb No Start. Choke / Enricher Jet Drilling
Thank you to those who posted previously on how to fix the cold start issue on early model KLX 250S. I successfully completed upgrading the pilot jet from OEM 35, to a 38. And drilling the enricher (choke) jet to a #76, (.020). I know many have had success with a #77 (.018), yet I wanted to really give the carb an easy time getting fuel to the engine.
Unfortunately, I did not find the enricher fix until after installing the larger pilot jet, and had to remove the carb (fuel lines, linkage, etc.) a second time. Ugg!! I have a few choice words for whomever designed how to remove/replace the carb.
NEW INFO: What I found missing from other posts was the details of drilling out the enricher jet.
1) The jet is about a quarter inch down from the enricher opening.
2) The drill bit is about half the width of a human hair. There are Pin Vise Hand Drills designed to hold these bits. I used a small pair of hemostats to hold the drill bit.
3) This is a blind and delicate, yet doable, procedure and you have to "feel" your way through it.
4) Make sure you are comfortable and have the time to focus. I did mine by cradling the carb between my legs while sitting in my recliner. I then rested my left hand on the carb and held the tip of the hemostats between my thumb and index finger for support.
5) I then very gently and slowly twisted, checking by pulling up, to see if the bit caught the metal. Once it caught, I'd back off a little, advance, back off, advance, repeat until soon I could simply raise and lower the bit smoothly in the enlarged hole.
6). I blew out the jet with carb cleaner.
So nice to feel I can trust my bike to start!
Hope that helps someone.
Unfortunately, I did not find the enricher fix until after installing the larger pilot jet, and had to remove the carb (fuel lines, linkage, etc.) a second time. Ugg!! I have a few choice words for whomever designed how to remove/replace the carb.
NEW INFO: What I found missing from other posts was the details of drilling out the enricher jet.
1) The jet is about a quarter inch down from the enricher opening.
2) The drill bit is about half the width of a human hair. There are Pin Vise Hand Drills designed to hold these bits. I used a small pair of hemostats to hold the drill bit.
3) This is a blind and delicate, yet doable, procedure and you have to "feel" your way through it.
4) Make sure you are comfortable and have the time to focus. I did mine by cradling the carb between my legs while sitting in my recliner. I then rested my left hand on the carb and held the tip of the hemostats between my thumb and index finger for support.
5) I then very gently and slowly twisted, checking by pulling up, to see if the bit caught the metal. Once it caught, I'd back off a little, advance, back off, advance, repeat until soon I could simply raise and lower the bit smoothly in the enlarged hole.
6). I blew out the jet with carb cleaner.
So nice to feel I can trust my bike to start!
Hope that helps someone.
#2
Alternatively, install a #38 or #40 pilot jet, set fuel screw to 2 turns out on the #40 or 2.5 out on a #38 (if near sea level), start engine and allow to warm up to full operating temp - set idle speed to specs (target 1250 rpms)..
Always drain a little fuel out of the bowl, before starting, if it has been 24 hrs or more since last startup..
Always drain a little fuel out of the bowl, before starting, if it has been 24 hrs or more since last startup..
#3
And yet some of us, particularly those at higher elevations, find snappier off-idle throttle respond with the stock #35 pilot jet with the fuel screw about 2 to 2.5 turns out, and better starting with the enlarged enricher jet. The larger pilot jet just bogs off-throttle response.
#4
Agreed, for a bike that is always at higher elevations (4k-5k ASL and up), a larger pilot jet is not called for and drilling the enrichener jet would make cold starts easier... For the rest, the #40 and #38 along with a correct idle speed will usually suffice.
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