125-200cc Mikuni to Keihin PWK Swap

Swapped the stock Mikuni for a PWK 38 Airstryker on my 2012 WR144.

First kick over and the thing is revving to the moon. Thought it was going to detonate before I could get to the kill switch.

Idle speed screw has little to no effect. The slide is closing properly on a closed throttle and there are no kinks in the throttle cable.

Any suggestions would be really appreciated.

Thanks in advance guys.

You have an air leak some where

Yup.

Thanks for the replies guys. That would make sense, seeing how the Mikuni and Keihin are different dimensions, maybe now one of the carb boots isn't sealing properly any more.

I will investigate and try to find the source of the leak.

Front boot

If all looks ok and the slide is DEFINATLY closeing (pop the carb and look) was it when on choke??? I have a carb here that does the same thing when started on choke, revs are real real high and for the life of me I no idea why
If started on this carb I would as soon as it started put the choke off then put it on again and it settled down to normal.
This was a 36mm pwk and as stated I really have no idea why it does it as its been on two different bikes and does the same on both but runs fine other than the first cold start
All therory / ideas will be welcomed as its always baffled me

Keep playing the cable adjustment I think mine did that too and it just went away .
try adjusting near the throttle
One of the best things about the Keihin is that when you start it it doesnt do that - like the Mikuni does when its cold or take as long to warm up

Update: thought I'd try the easy fix first, so I played with the throttle adjustment and it seems much better. Did a couple of test start ups, it's idling normally and the idle speed screw now actually controls idle speed! Going for a ride today to play with the jetting and will keep an eye on the idle situation. Hopefully it's cured but I just read air leaks can be intermittent so I guess I can't rule that out just yet. Thanks again for the suggestions.

How'd it go ?

Did plenty of riding over the weekend and no more problems....so the cable adjustment seems to have cured it

Am very pleased with the PWK - got the little 2 smoker running nicely at last!!

Good to hear
What needle? And setting
The leaner setting seems to work best on needle
Depending on temps etc
As I said in other thread ...other needle options ie kx125 99 model N7Nw
part No 16187-1084

Are worth trying

Just looking at this needle it has a very thin end and quite sudden taper and a thicker main shaft . Than the R1469 which from memory looks similar to the JD needles.
So it will give a rich top end and lean bottom to mid - which will suit what i need

Temp 80 - 90 degrees, humidity 80%, 0 - 300 feet.

Started off with the standard pre-set needle setting from JD i.e. JD blue needle, clip in position #4.

That was way too rich, blubbering everywhere and reluctant to rev out. So I gradually leaned it out and ended up at: JD red needle, clip in position # 1 (leanest). Big improvement. Motor feels much crisper and stronger in the midrange now. But I would like experiment with leaner still.

Is the N7Nw generally leaner than the JD red? Or just leaner in low to mid?

Also, maybe you could let me have the link to the other thread you mention?

Thanks

Sounds like what is happening to mine and why I am changing
The recent thread is below "who's riding a 125"
The needle info came from Ausky who did a lot testing with noz range of needles
This needle should be able to be run lower
And I believe it will give more hit
I can't test it yet but looks good!

It's richer up top lean mid
I did have rich low mid but wide open test was still too lean

I think that jd needles suit 250

OK found it cheers. Looks like it's worth a try

By the way I just got off the phone to JD Jetting. They are going to send me 2 needles to try off a CR500. Both are leaner than the JD red. Don't know the part numbers, but will report back.

Should hopefully give us guys that ride in hot/humid places some adjustability on the needle