How I Installed a Lectron Carb On My '99 KDX200
Posted: 09:37 pm Nov 01 2021
I registered with KDXRider.net last year and have been gathering valuable info from many of you about setting up my own 1999 KDX200.
Now I would like to share the experience I’ve had installing a Lectron. There are a couple Lectron threads already, but they discuss a wide variety of issues and I wrote this one specifically about what it took to get their carb to fit my bike, which was NOT easy!
I invite other KDXRiders with Lectrons to comment on the challenges and solutions to their installations in hopes Lectron will make improvements and everyone who is considering one will feel confident about making the investment.
When I bought my KDX the previous owner said the stock Keihin carb had been problematic. I rode the bike a few times and it ran rich so I made several attempts to lean the jetting, but it still ran rich and made a lot of smoke and spooge, and fouled the plug.
I pulled the top end and the cylinder needed re-plating and a new piston so I sent it to Millenium Technology. I also took a closer look inside the Keihin at the needle jet block o-ring. It looked to be intact so I left it alone. In hindsight, I should have just replaced it and the other seals because the carb was 22 years-old.
I put the motor back together and broke it in per Jeff Slavens recommendations. The bike ran better, but was still rich with pretty lean jets and fouled the plug after a few rides.
I did a compression check and it was within spec at 145 psi. I did a leak-down test to make sure it wasn’t sucking transmission oil past the crankshaft seal. The leak-down test showed no leaks.
I had been considering buying a Lectron rather than continuing to mess with the Keihin because I’d seen some positive reviews. I checked their website and saw there was a Lectron for the “KDX”. The webpage stated the Lectron was larger than the stock carb and was “modified for fit on the KDX.” They did warn that an over-sized reed block (i.e. Boysen Rad or V-Force), would require additional modifications to get their carb to fit the KDX. I had the stock reed block so I wasn’t concerned.
I also looked at the SmartCarb website, but they only showed carbs for the KX models. I called SmartCarb and asked about the KDX and was told they did not have a carb to fit my bike yet, but hoped to do some R&D in the future to try and make one fit.
I ordered the Lectron for my KDX in July 2021 and received a 34mm Power Jet carb, part# 1530-KDX. It was $515 and came with a new Barnett throttle cable and metering rod adjustment tool. Lectron recommends the Motion Pro Vortex MX-style throttle, but they were out of stock so I searched the internet and found one.
My Lectron looked well-crafted. I'm a retired machinist so I recognized the good workmanship. I removed the gas tank, rear fender, and air box so I wouldn’t have to struggle getting the Lectron into the rubber manifold and air box boot at the same time. I tried to insert the carb into the manifold, but it wouldn't go. I removed the manifold from the bike and tried to push the Lectron into it, but it still wouldn’t go.
There are machined sleeves on both ends of the Lectron. I measured the diameter of the front sleeve and it was 1.800” (45.7mm). The stock Keihin diameter is only 1.650” (42mm). The Lectron wouldn’t go into my rubber manifold because it was .150” (3.8mm) bigger diameter than the stock carb. The stock carb fits into the rubber manifold like a glove. I was surprised the Lectron wasn’t machined to the same dimensions. In contrast, the rear sleeve of the Lectron that goes into the air box boot was machined to the same dimensions as the stock carb and fit perfectly there.
ABOVE: I put the Lectron and Keihin face to face to show the big difference in diameter to fit in the manifold.
I emailed Lectron about the carb being too big for the rubber manifold and the Marketing Director replied, “That’s pretty normal. Throw the intake flange in some hot water for about 15 minutes and you should be able to pop the Lectron right in there.”
Before I did that, I took a Dremel grinder with a small sanding drum and ground a small chamfer on the opening edge of the manifold to help get the Lectron started into the opening. I heated the manifold and used tire installation lube and was finally able to force the Lectron part-way into the manifold, but the carb sleeve was so big it distorted the manifold quite a bit. I worried about the 22 year-old manifold splitting open.
I checked the rear sleeve that fits into the air box boot and it was the same diameter as the stock carb and fit in the boot perfectly.
I examined and measured the inside contour of the manifold and realize the Lectron wouldn’t go all the way in not only because it was too big, but also because it hit a rubber stop molded into the manifold. The Lectron needed to go another 1/8” (3mm) deeper into the manifold to be far enough forward for the top of the slide housing to clear the bike's frame, otherwise the carb was leaned over to the left about 45º.
ABOVE: I stuffed the Lectron into the manifold as far as it would go, but it needed to go at least another 1/8" to be far enough forward to clear the frame.
ABOVE: This is as far upright as the carb would go because it wasn't far enough forward in the manifold for the top of the slide cap to clear the frame.
I thought about removing the front sleeve, but then the Lectron would be too loose in the manifold. I emailed Lectron again and explained that the sleeve was too big to fit in the manifold. The Marketing Director said KDXs have numerous carb-fit issues and he didn’t have any options at the time, but hoped to in the future. I told him that 1995 through 2006 KDX200 use the same carbs and manifolds so the Lectron could be made to fit all of those models. I don’t know about previous year models.
I realized that my options were to either return the carb for a refund before I modified or damaged it, or take a chance and try to solve the problem myself. I emailed back and asked if the sleeves were attached to the carb body securely enough for me to chuck the Lectron in a lathe and do some light machining on the front sleeve to get it to fit better in the manifold. He said the carb casting was machined for a snug fit with the sleeve and epoxied to secure it. He said he believed it should be secure enough for light machining.
I carefully measured the contours inside the manifold and the outside of the Keihin and came up with dimensions to modify the Lectron front sleeve. I also noticed that the Lectron front sleeve had a shallow groove in it to allow a corresponding ring in the manifold to fit in to help seal against a vacuum leak. Unfortunately, the ring was cut into the sleeve at an incorrect location for the manifold ring to fit in it. I confirmed this by comparing the groove location on the stock carb. I noticed that if the sleeve had been installed on the Lectron the other way around, that groove would have been in the correct location for the manifold ring to fit in it, leading me to believe the front sleeve was installed backwards.
I made a list of modifications for the front Lectron sleeve as well as for the rubber manifold in order for them to fit better together. My biggest fear was of the carb coming loose from the lathe chuck and flying through the air (and hitting me in the head) while I was machining it so I made a plug to insert in the carb bore and used a live center to hold the plug. My second concern was damaging the $100 rubber manifold. Here are the modifications I made:
1. Lathe: I turned down the outside diameter of the front Lectron sleeve from 1.800” (45.7mm) to 1.740” (44.2mm). I wanted to turn it all the way down to the diameter of the Keihin, 1.650”, but that would remove the majority of the sleeve and leave a very thin wall thickness.
2. Lathe: I chamfered the leading edge of the sleeve so it would go into the manifold opening easier.
3. Lathe: The existing sealing ring groove on the sleeve disappeared when I turned to outside diameter down in step one so I had to cut a new groove into the outside diameter in the correct location of the sleeve for the manifold sealing ring.
4. I used a Dremel tool with a small sanding drum as described above to sand a small lead chamfer in the rubber manifold to help insert the Lectron.
5. I also used the Dremel sanding drum to carefully sand down the molded stop in the manifold at about the same angle as the chamfer on the carb sleeve to allow the Lectron to be inserted far enough in (forward) so the carb clears the frame enough to be able to stand it upright, or nearly upright, as it turned out. I had to beware of damaging the sealing ring surfaces of the manifold lest I suffer the dreaded vacuum leak.
ABOVE: This is the way the sleeve came from Lectron.
ABOVE: These are the dimensions for the modifications that allowed the sleeve to fit inside my manifold far enough to stand the carb almost upright. I sent this drawing to Lectron and told them these changes made the difference in fitting their carb.
Thankfully, these modifications allowed me to fit the Lectron in my bike, but there was still some minor fiddling as I put the bike back together.
* The gas tank and petcock interfered with the throttle cable and I ended up routing the cable around the outside (left side) of the petcock to ensure it didn’t get kinked or stick. Some owners have complained about the throttle cable not being the right length, but mine fits perfectly.
* The top of the Lectron rests against the frame so I cut a small piece of rubber to put between them to try to reduce vibration in the carb. I did some light filing on a corner of the top of the slide cap to reduce interference with the frame. I also replaced one of the cap screws with a counter-sunk screw for a lower profile.
* The choke knob is on the right side of the carb and the knob hit the frame when I lifted it open. I cut away part of the knob to clear the frame. It is difficult to reach from either side of the bike to open and close it. Fortunately, I only need to use the choke when the bike is cold. I open the choke, start the bike for about 30 seconds then stop the engine and close the choke. Then it’s ready to ride.
I tried to post a photo of the finished carb installed in my bike but couldn't add any more photos. I will post the photo in a posting below.
HOW DOES IT RUN???
I was happy and relieved when I started the bike and rode it around. The Lectron was a good solution to my problematic Keihin, except for the effort and risk it took to get it to fit. The bike usually starts 1st-kick and runs great!
The original metering was almost perfect. I followed the Lectron Tuning Manual for setting the idle and understanding how to adjust the metering rod and Power Jet. I have adjusted the metering rod ¼ turn leaner and turned the Power Jet adjuster a tiny amount leaner. The mixture feels and seems “right” for all throttle openings and the bike has come to life. I’m using Golden Spectro at 53:1 with non-ethanol premium. The throttle is crisp, snappy, and has nice, smooth low-end as well as good acceleration into the 2-stroke “hit” which is a blast that can lift the front wheel and/or slide the rear tire.
I have ridden various motorcycles all my long life, but this is my first real dirt bike so I am learning the basics of low-speed balance, clutch skills, and single-track maneuvering which require a lot of slow riding at the bottom of the power band. The Lectron performs well down there.
I have not had a good chance to measure my fuel mileage because I spend so much time at low speeds.
Yes, I probably could have fixed the Keihin and gotten it to run right, but it would not have ideal jetting for the varied altitudes where I ride - 2,000’ to 7,500’ in single day.
I noticed several people in the forum say they would consider a Lectron for their KDX if they were confident it would fit. I have shared the modifications I made with Lectron and encouraged them to machine the front sleeve to the dimensions I used. I recommend calling them before ordering one and asking if they made the changes to the sleeve if you don’t want to take the risks and trouble of doing them yourself. I also DON’T recommend going to the trouble I went through unless you really know your way around a lathe. Take too heavy of a cut and the carb will be ripped out of the chuck, and nothing good will come of that.
Even if Lectron does change the sleeve dimensions, KDX owners may find it necessary to do the light sanding on their intake manifolds I described to help the Lectron fit. Even still, the carb won’t fit like a glove, it will fit more like one of OJ Simpson’s gloves, but it should still work wonderfully.
Feel free to send me a personal message if you have any questions.
Good luck.
Jim
Now I would like to share the experience I’ve had installing a Lectron. There are a couple Lectron threads already, but they discuss a wide variety of issues and I wrote this one specifically about what it took to get their carb to fit my bike, which was NOT easy!
I invite other KDXRiders with Lectrons to comment on the challenges and solutions to their installations in hopes Lectron will make improvements and everyone who is considering one will feel confident about making the investment.
When I bought my KDX the previous owner said the stock Keihin carb had been problematic. I rode the bike a few times and it ran rich so I made several attempts to lean the jetting, but it still ran rich and made a lot of smoke and spooge, and fouled the plug.
I pulled the top end and the cylinder needed re-plating and a new piston so I sent it to Millenium Technology. I also took a closer look inside the Keihin at the needle jet block o-ring. It looked to be intact so I left it alone. In hindsight, I should have just replaced it and the other seals because the carb was 22 years-old.
I put the motor back together and broke it in per Jeff Slavens recommendations. The bike ran better, but was still rich with pretty lean jets and fouled the plug after a few rides.
I did a compression check and it was within spec at 145 psi. I did a leak-down test to make sure it wasn’t sucking transmission oil past the crankshaft seal. The leak-down test showed no leaks.
I had been considering buying a Lectron rather than continuing to mess with the Keihin because I’d seen some positive reviews. I checked their website and saw there was a Lectron for the “KDX”. The webpage stated the Lectron was larger than the stock carb and was “modified for fit on the KDX.” They did warn that an over-sized reed block (i.e. Boysen Rad or V-Force), would require additional modifications to get their carb to fit the KDX. I had the stock reed block so I wasn’t concerned.
I also looked at the SmartCarb website, but they only showed carbs for the KX models. I called SmartCarb and asked about the KDX and was told they did not have a carb to fit my bike yet, but hoped to do some R&D in the future to try and make one fit.
I ordered the Lectron for my KDX in July 2021 and received a 34mm Power Jet carb, part# 1530-KDX. It was $515 and came with a new Barnett throttle cable and metering rod adjustment tool. Lectron recommends the Motion Pro Vortex MX-style throttle, but they were out of stock so I searched the internet and found one.
My Lectron looked well-crafted. I'm a retired machinist so I recognized the good workmanship. I removed the gas tank, rear fender, and air box so I wouldn’t have to struggle getting the Lectron into the rubber manifold and air box boot at the same time. I tried to insert the carb into the manifold, but it wouldn't go. I removed the manifold from the bike and tried to push the Lectron into it, but it still wouldn’t go.
There are machined sleeves on both ends of the Lectron. I measured the diameter of the front sleeve and it was 1.800” (45.7mm). The stock Keihin diameter is only 1.650” (42mm). The Lectron wouldn’t go into my rubber manifold because it was .150” (3.8mm) bigger diameter than the stock carb. The stock carb fits into the rubber manifold like a glove. I was surprised the Lectron wasn’t machined to the same dimensions. In contrast, the rear sleeve of the Lectron that goes into the air box boot was machined to the same dimensions as the stock carb and fit perfectly there.
ABOVE: I put the Lectron and Keihin face to face to show the big difference in diameter to fit in the manifold.
I emailed Lectron about the carb being too big for the rubber manifold and the Marketing Director replied, “That’s pretty normal. Throw the intake flange in some hot water for about 15 minutes and you should be able to pop the Lectron right in there.”
Before I did that, I took a Dremel grinder with a small sanding drum and ground a small chamfer on the opening edge of the manifold to help get the Lectron started into the opening. I heated the manifold and used tire installation lube and was finally able to force the Lectron part-way into the manifold, but the carb sleeve was so big it distorted the manifold quite a bit. I worried about the 22 year-old manifold splitting open.
I checked the rear sleeve that fits into the air box boot and it was the same diameter as the stock carb and fit in the boot perfectly.
I examined and measured the inside contour of the manifold and realize the Lectron wouldn’t go all the way in not only because it was too big, but also because it hit a rubber stop molded into the manifold. The Lectron needed to go another 1/8” (3mm) deeper into the manifold to be far enough forward for the top of the slide housing to clear the bike's frame, otherwise the carb was leaned over to the left about 45º.
ABOVE: I stuffed the Lectron into the manifold as far as it would go, but it needed to go at least another 1/8" to be far enough forward to clear the frame.
ABOVE: This is as far upright as the carb would go because it wasn't far enough forward in the manifold for the top of the slide cap to clear the frame.
I thought about removing the front sleeve, but then the Lectron would be too loose in the manifold. I emailed Lectron again and explained that the sleeve was too big to fit in the manifold. The Marketing Director said KDXs have numerous carb-fit issues and he didn’t have any options at the time, but hoped to in the future. I told him that 1995 through 2006 KDX200 use the same carbs and manifolds so the Lectron could be made to fit all of those models. I don’t know about previous year models.
I realized that my options were to either return the carb for a refund before I modified or damaged it, or take a chance and try to solve the problem myself. I emailed back and asked if the sleeves were attached to the carb body securely enough for me to chuck the Lectron in a lathe and do some light machining on the front sleeve to get it to fit better in the manifold. He said the carb casting was machined for a snug fit with the sleeve and epoxied to secure it. He said he believed it should be secure enough for light machining.
I carefully measured the contours inside the manifold and the outside of the Keihin and came up with dimensions to modify the Lectron front sleeve. I also noticed that the Lectron front sleeve had a shallow groove in it to allow a corresponding ring in the manifold to fit in to help seal against a vacuum leak. Unfortunately, the ring was cut into the sleeve at an incorrect location for the manifold ring to fit in it. I confirmed this by comparing the groove location on the stock carb. I noticed that if the sleeve had been installed on the Lectron the other way around, that groove would have been in the correct location for the manifold ring to fit in it, leading me to believe the front sleeve was installed backwards.
I made a list of modifications for the front Lectron sleeve as well as for the rubber manifold in order for them to fit better together. My biggest fear was of the carb coming loose from the lathe chuck and flying through the air (and hitting me in the head) while I was machining it so I made a plug to insert in the carb bore and used a live center to hold the plug. My second concern was damaging the $100 rubber manifold. Here are the modifications I made:
1. Lathe: I turned down the outside diameter of the front Lectron sleeve from 1.800” (45.7mm) to 1.740” (44.2mm). I wanted to turn it all the way down to the diameter of the Keihin, 1.650”, but that would remove the majority of the sleeve and leave a very thin wall thickness.
2. Lathe: I chamfered the leading edge of the sleeve so it would go into the manifold opening easier.
3. Lathe: The existing sealing ring groove on the sleeve disappeared when I turned to outside diameter down in step one so I had to cut a new groove into the outside diameter in the correct location of the sleeve for the manifold sealing ring.
4. I used a Dremel tool with a small sanding drum as described above to sand a small lead chamfer in the rubber manifold to help insert the Lectron.
5. I also used the Dremel sanding drum to carefully sand down the molded stop in the manifold at about the same angle as the chamfer on the carb sleeve to allow the Lectron to be inserted far enough in (forward) so the carb clears the frame enough to be able to stand it upright, or nearly upright, as it turned out. I had to beware of damaging the sealing ring surfaces of the manifold lest I suffer the dreaded vacuum leak.
ABOVE: This is the way the sleeve came from Lectron.
ABOVE: These are the dimensions for the modifications that allowed the sleeve to fit inside my manifold far enough to stand the carb almost upright. I sent this drawing to Lectron and told them these changes made the difference in fitting their carb.
Thankfully, these modifications allowed me to fit the Lectron in my bike, but there was still some minor fiddling as I put the bike back together.
* The gas tank and petcock interfered with the throttle cable and I ended up routing the cable around the outside (left side) of the petcock to ensure it didn’t get kinked or stick. Some owners have complained about the throttle cable not being the right length, but mine fits perfectly.
* The top of the Lectron rests against the frame so I cut a small piece of rubber to put between them to try to reduce vibration in the carb. I did some light filing on a corner of the top of the slide cap to reduce interference with the frame. I also replaced one of the cap screws with a counter-sunk screw for a lower profile.
* The choke knob is on the right side of the carb and the knob hit the frame when I lifted it open. I cut away part of the knob to clear the frame. It is difficult to reach from either side of the bike to open and close it. Fortunately, I only need to use the choke when the bike is cold. I open the choke, start the bike for about 30 seconds then stop the engine and close the choke. Then it’s ready to ride.
I tried to post a photo of the finished carb installed in my bike but couldn't add any more photos. I will post the photo in a posting below.
HOW DOES IT RUN???
I was happy and relieved when I started the bike and rode it around. The Lectron was a good solution to my problematic Keihin, except for the effort and risk it took to get it to fit. The bike usually starts 1st-kick and runs great!
The original metering was almost perfect. I followed the Lectron Tuning Manual for setting the idle and understanding how to adjust the metering rod and Power Jet. I have adjusted the metering rod ¼ turn leaner and turned the Power Jet adjuster a tiny amount leaner. The mixture feels and seems “right” for all throttle openings and the bike has come to life. I’m using Golden Spectro at 53:1 with non-ethanol premium. The throttle is crisp, snappy, and has nice, smooth low-end as well as good acceleration into the 2-stroke “hit” which is a blast that can lift the front wheel and/or slide the rear tire.
I have ridden various motorcycles all my long life, but this is my first real dirt bike so I am learning the basics of low-speed balance, clutch skills, and single-track maneuvering which require a lot of slow riding at the bottom of the power band. The Lectron performs well down there.
I have not had a good chance to measure my fuel mileage because I spend so much time at low speeds.
Yes, I probably could have fixed the Keihin and gotten it to run right, but it would not have ideal jetting for the varied altitudes where I ride - 2,000’ to 7,500’ in single day.
I noticed several people in the forum say they would consider a Lectron for their KDX if they were confident it would fit. I have shared the modifications I made with Lectron and encouraged them to machine the front sleeve to the dimensions I used. I recommend calling them before ordering one and asking if they made the changes to the sleeve if you don’t want to take the risks and trouble of doing them yourself. I also DON’T recommend going to the trouble I went through unless you really know your way around a lathe. Take too heavy of a cut and the carb will be ripped out of the chuck, and nothing good will come of that.
Even if Lectron does change the sleeve dimensions, KDX owners may find it necessary to do the light sanding on their intake manifolds I described to help the Lectron fit. Even still, the carb won’t fit like a glove, it will fit more like one of OJ Simpson’s gloves, but it should still work wonderfully.
Feel free to send me a personal message if you have any questions.
Good luck.
Jim