17/18 KTM 250sx KEIHIN JD carb

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2/19/2018 11:18 AM

Wanted to see if anyone has tried this from JD? Fitment issues, performance etc.

https://www.jdjetting.com/xcart5/jdkh38-keihin-38mm-pwk-airstryker-ag-short-body-w-jet-kit.html?category_id=62

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2/19/2018 11:44 AM
Edited Date/Time: 2/19/2018 11:45 AM

Ran a 36mm and 38mm Keihin on my 17 TC250 and now have it on my 17 250sx. Fitment is perfect but you have to run the older style throttle assembly and cable. As far as performance, both the Keihins work a ton better than the Mikuni in my opinion. The bike runs a ton cleaner off the bottom and the jetting is much less sensitive to temperature change. Much more of a set it and forget experience than I had with the Mikuni where I was swapping jets a few times a day and was never really satisfied with how the bike was running.

In the end, I stuck with the 36mm as it was quite a bit better as far as bottom end power goes and did not give up much at all on the top end.

Overall I would say that it is the best upgrade that I have made to my bikes and they can be picked up quite a bit cheaper used if you can find one. Would highly recommend doing the carb swap.

Photo

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2/19/2018 11:52 AM

samcampbell wrote:

Ran a 36mm and 38mm Keihin on my 17 TC250 and now have it on my 17 250sx. Fitment is perfect but you have to run the older style throttle assembly and cable. As far as performance, both the Keihins work a ton better than the Mikuni in my opinion. The bike runs a ton cleaner off the bottom and the jetting is much less sensitive to temperature change. Much more of a set it and forget experience than I had with the Mikuni where I was swapping jets a few times a day and was never really satisfied with how the bike was running.

In the end, I stuck with the 36mm as it was quite a bit better as far as bottom end power goes and did not give up much at all on the top end.

Overall I would say that it is the best upgrade that I have made to my bikes and they can be picked up quite a bit cheaper used if you can find one. Would highly recommend doing the carb swap.

Photo

Thanks for the quick reply, I already have the older setup so that shouldn't be an issue. Think I'll go ahead and pull the trigger and get one. Nice bikes btw. That YZ125 in your build is pretty sick.

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2/19/2018 12:02 PM

No problem. I started with the jetting I had in my 15 250sx thinking it would be close... Was wrong though. The newer bikes want quite a bit more fuel.

The 125 should be a fun bike once I get it finished up.

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2/19/2018 3:10 PM

I’m on a 2017 TC250. I found a Keihin 38mm PWK from an 02 rm250 with the throttle cable and throttle assembly for cheap so I went for it. Plugged the power jet passage and tucked away the loose wires. Fit like a glove, started way easier than with the Mikuni. Runs way better, much more consistent. Much easier carb to tune IMO. Also, check the squish as mentioned in multiple threads on these bikes. I took .020” off the head to get it to .045” and night and day better. Runs like a normal 250 2 stroke now.

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2/20/2018 7:22 PM

paddyB745 wrote:

I’m on a 2017 TC250. I found a Keihin 38mm PWK from an 02 rm250 with the throttle cable and throttle assembly for cheap so I went for it. Plugged the power jet passage and tucked away the loose wires. Fit like a glove, started way easier than with the Mikuni. Runs way better, much more consistent. Much easier carb to tune IMO. Also, check the squish as mentioned in multiple threads on these bikes. I took .020” off the head to get it to .045” and night and day better. Runs like a normal 250 2 stroke now.

That's awesome. Had the head and cylinder modified by JBone Motorworks so I should be good.

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2/21/2018 1:53 AM

samcampbell wrote:

Ran a 36mm and 38mm Keihin on my 17 TC250 and now have it on my 17 250sx. Fitment is perfect but you have to run the older style throttle assembly and cable. As far as performance, both the Keihins work a ton better than the Mikuni in my opinion. The bike runs a ton cleaner off the bottom and the jetting is much less sensitive to temperature change. Much more of a set it and forget experience than I had with the Mikuni where I was swapping jets a few times a day and was never really satisfied with how the bike was running.

In the end, I stuck with the 36mm as it was quite a bit better as far as bottom end power goes and did not give up much at all on the top end.

Overall I would say that it is the best upgrade that I have made to my bikes and they can be picked up quite a bit cheaper used if you can find one. Would highly recommend doing the carb swap.

Photo

LumpDog841 wrote:

Thanks for the quick reply, I already have the older setup so that shouldn't be an issue. Think I'll go ahead and pull the trigger and get one. Nice bikes btw. That YZ125 in your build is pretty sick.

I had the Mikuni on my 18 TC250 running sweet action, with bugger all effort. What fuel oil ratio where you running?

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2/21/2018 2:32 AM

I ran a keihin CR 250 2000 carb on my sx 250 17 much much better then the Stock.

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2/21/2018 4:08 AM

Did any of you guys consider a Lectron carb

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2/21/2018 5:04 AM

nascarnate326 wrote:

Did any of you guys consider a Lectron carb

I've considered it, but for moto there seems to be some mixed reviews. I've seen some people here and on other forums , that for moto it is a little bland and getting perfect pickup off the bottom was a struggle.

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2/21/2018 11:00 AM

MadsDausel wrote:

I ran a keihin CR 250 2000 carb on my sx 250 17 much much better then the Stock.

No problem getting it to fit?

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2/21/2018 3:37 PM

Slosh 112 wrote:

I had the Mikuni on my 18 TC250 running sweet action, with bugger all effort. What fuel oil ratio where you running?

Running 40:1. Seems like some people have some better performance with 60:1, but the fuel I run is VP T2. So maybe I should stop being lazy and mix my own gas.

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2/21/2018 5:12 PM

LumpDog841 wrote:

Running 40:1. Seems like some people have some better performance with 60:1, but the fuel I run is VP T2. So maybe I should stop being lazy and mix my own gas.

Fuel mixture really doesn't effect much as long as you are jetted for a specific fuel mixture ratio. MXA stated that all there jetting issues went away on there TC250 when they switched to 60:1... I noticed no difference in either carb when I changing fuel ratios and can't imagine that it did anything for them either. I also haven't agreed with a lot of things that MXA says as of late though.

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2/21/2018 6:57 PM

samcampbell wrote:

Fuel mixture really doesn't effect much as long as you are jetted for a specific fuel mixture ratio. MXA stated that all there jetting issues went away on there TC250 when they switched to 60:1... I noticed no difference in either carb when I changing fuel ratios and can't imagine that it did anything for them either. I also haven't agreed with a lot of things that MXA says as of late though.

Yeah, I use to be a die hard MXA guy, but honestly the stuff the last few years as lacked something I can't quite put my finger on. Seems like they have articles that are 3 pages long about what they did with the bike and then 2 sentences about how it actually performed, seems they are maybe lacking the technical depth they once had. Maybe I'm just getting old.

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