KTM 125/250 carb ?

[nephron]

Anyone have any SPECIFIC input as to why the 125SX uses a PWK39 and the 250SX uses a 38S? Not exactly counterintuitive, but the flip flop is interesting. I doubt the 38 would 'smooth out' the 250's power, as that would have mostly to do with port timing, flywheel/rotating assembly, etc.

 

[k-ryder]

the 125sx is supposed to have a huge intake port (for a 125) and i think they where chasing top end power.

i have a 2003 125 sx and use a 38mm keihin a/stryker carb which in my opinion is better than the 39mm. more bottom & mid.

 

[bclapham]

i think you might find the 250 ktms run the same powerjet carb as the other 250 smokers, but i will stand to be corrected if someone knows otherwise.

it amazes me the 125 can run that 39.5 at all, but it does, especially with the long rod since that "in theory" leans the mixture also- the 04 rm125 likes the 39mm also, but as myself and MG found out, it rides better with the smaller carb.

 

[elf]

I have been thinking about trying the 38 on my 144, but I have it running so good now I dont want to mess with it.

 

[bclapham]

i am sure it would be worth trying since it should be easier to jet etc. and i cant see it losing top and there is gains to be had with throttle response and bottom, but like you say, is it worth the extra messing....suppose there is only one way to find out!!!!

 

[marcusgunby]

The only downside is we actually wore out the hose clamps for the carb LOL.

 

[elf]

The only downside is we actually wore out the hose clamps for the carb LOL.

I wore mine out trying to jet my bike lol, If I had one I could try I would do it, I just dont want to spend $150 to try it.As of right now I have 12 different needles for my bike I have never had this much trouble jetting a bike.Now that I have it good I wont know what to do with myself. Geuss I will have to find something else to tinker with.

 

[k-ryder]

if your jetting is good now, use the stock 5.5 slide ( from the 39mm ) and just transfer all your current jetting over. i'm using the exact jetting from the 39mm carb on the 38.

 

[bclapham]

what was your final jetting elfie????

 

[elf]

what was your final jetting elfie????

48 pilot, JD red needle on the 3rd clip and a 200 main.
for cooler wheather I use 1469g 2nd clip with a 195 main. it may sound weird to use a smaller main in cooler wheather but the JD needles need a bigger main. I cant get the JD needdles to work when its cooler, either too rich or to lean. You probably dont have to deal with temps in the 40s or 50s out in cal.
My ktm is very fussy when it comes to the needle!

How bout your zook? Got the jetting figured out? blow up any more engines? :laugh:

 

[bclapham]

48P, NOZI (leanest) 172 main- its a tad rich, but all the 14xy needles would ping bad at 1/4 throttle.

i am going to the longer rod soon so we will see if that changes anything- theory dictates the bike will run leaner since the piston velocity is slower!

BTW- it only blew up because i ran the 14 needle with the clip on the wrong end, LOL

 

[bclapham]

i forgot to mention, i couldnt tell the difference between mains with the 14xy and NOZI- it piings or runs good on the same main despite the needle- it still doenst make sence why they should run different

 

[elf]

i forgot to mention, i couldnt tell the difference between mains with the 14xy and NOZI- it piings or runs good on the same main despite the needle- it still doenst make sence why they should run different

Thats weird, dont the noz needles need a bigger main?
You know if ya had a ktm ya wouldnt need a longer rod. You would just have to spend all your money on suspension ;)

 

[bclapham]

You know if ya had a ktm ya wouldnt need a longer rod. You would just have to spend all your money on suspension ;)

LOL- i only spent that money since i am trying to stretch the life of this bike out as long as possible.....putting off the inevitable decision :| :bang:

 

[k-ryder]

I have been thinking about trying the 38 on my 144, but I have it running so good now I dont want to mess with it.

elf.....just use the stock 5.5 slide in the 38mm and your jetting will change very little, if at all. found out last year that they where using it on jeff gibson's 125sx....it works great on the 125sx and i've been workin with a guy on his 200sx and he likes it also. another 200sx rider has one on order.

i think you'd like it but you may end up dropping a tooth or 2 on the rear sprocket.

i guess it depends on what you are lookin for but it does add bottom and mid power compared to the 39.

 

[elf]

That would be cool if I didn't have to change the jetting, You can never get enough bottom on a small bore bike right? so I guess it would be a good investment.