OMG Keihin FCR33 racing carb

Thanks..good info.I started doing my first carby mods 40 years ago and have a little knowledge of them.
I searched far and wide in Phuket and Bangkok for the PWK hex jets when i changed my KDX carb to no avail,so surprised the CM parts shop had those jets.
The KDX was very mild and sedate when i got it..well you`ve seen the results. There was no info about doing what i did with the carby (28ml round slide to 30ml D slide) on the net so just my own testing and tuning to get it right.

The US terms are a bit different to what i`m used to. A slow air jet is also mentioned as a slow air screw on that chart,i`d call it the air mixture screw. They don`t come in different sizes for a specific model as they`re adjustable.

The standard cutaway on the PWK i put on the KDX was #3. I got a #3.5 from the states and it worked better.
At the start of the year i decided i`d find a machine shop in CM and get them to mill 1mm off the cutaway of the #3 that i wasn`t using and make it #4.
120 baht for a good job and it`s made more improvement to the bottom end of the rev range again :)

Must say i`m more familiar with the 2 stroke side of it than 4T and have never worked an FCR like yours.
 
This place might be able to help with carbs and jets: AKUNAR CARBURRETORS (Check bottom of page re. hex jets.) OK English, I think...

I got a PWK28 copy from them. (Think Alex got brake lines from them? You tried this place already?)
 
Yes I got brakeline from Akunar, easy place to deal with
Loop, I read that slow air jet (if that is the mixture screw) is only on 2strokes, because on a 2stroke it lets more air in as you unscrew, whereas on a 4stroke, it lets more fuel in.
Anyway, I think slow jet means pilot jet.
Correct me if I'm wrong
 
I read it to mean pilot jet Alex and from the 4T carbs i`ve fiddled with they have pilot and main jets and air and mixture screws for idle same as 2T.

crs said:
This place might be able to help with carbs and jets: AKUNAR CARBURRETORS (Check bottom of page re. hex jets.) OK English, I think...

I got a PWK28 copy from them. (Think Alex got brake lines from them? You tried this place already?)
Click to expand...

I wonder if they have slides and needles for PWK`s,maybe not as there wouldn`t be a great demand for them here in LOS i`d imagine.

Was your copy an OKO Chris? that`s what i got on mine and so far so good and similar price to Akunar....didn`t know about them.

There`s a Keihin factory here in LOS but they wouldn`t sell me any parts and i had to get them from PJ Motorsport in the US who were very helpful.
 
Can't remember, Lou - I gave it away as couldn't get it right so went back to the PE copy. Says on that page they have PWK type needles. Give them a call or email.
 
I've got spare 42 pilot, 185 main and OCEMN needle for a FCR MX39 carb if any good to anyone.
 
Great info crs, thanks for posting, at the moment trying out the new setup which is 40PJ 140MJ, needle on 3rd groove, I think I am still too rich, will check the spark plug after a couple of kilometers, to get a better reading of this.
 
The carb still uses far too much gas, same like before, The bike is boging at low rpm, I start believing there's a problem behind this of unknown species. Too many Thai mechanics probably trying out their knowledge, before I bought this carb, aniway the Keihin PWK 35 is ont it's way, now I have a direct comparison, hopefuly it will fit. I don't know sometimes why I am doing this.
 
Carby`s are certainly a labor of love.

I think the PWK may be a bit better for you to work with. Mine was easy you don`t have to take it off to change the jets or needle and slide.

It sounds like the pump on your FCR might be what is making it thirsty.
 
Loop said:
Carby`s are certainly a labor of love.

I think the PWK may be a bit better for you to work with. Mine was easy you don`t have to take it off to change the jets or needle and slide.

It sounds like the pump on your FCR might be what is making it thirsty.
Click to expand...

No, the pump is not the matter, I unhooked it and didn't get any better mileage out of it, the crux might be something else, anyway the PWK 35 is brand new and nobody has "fucked" around with yet, so this is a better way to start, then searching for faults all over again, by the way I wrote Sigma, the company that sells jet kits and even they're a little expensive, they now there work, I asked them for a kit for the PWK 35 and for the FCR 33, they can make a kit for both carbs, I might want to try this out if I don't get the PWK to work
 
I went to chang moi shoptoday for hex main jets, but was told they had no 160 or larger.
so if anyone has a 160/2/5 I can test I'd appreciate it
 
^ i don`t have any that big.

You`ll more than likely find a Thai mechanic around town that will have a set of jet drills and will be able to drill one out to near what you need,not the best way to go about it though.
 
Just an update: The Keihin FCR 33 is not easy to work on, every time the whole carb has to come off, which makes it really difficult, the FCR 33 will be under inspection for a couple of days with my mechanic, my PWK 35 has just arrived but I think for now, I want to ride a little first, so back to the stock carb for now...The PWK is jetted 160 MJ and 68 PJ, this how it is delivered from the company, I will have to try it out first, but if the setting is completely off I might have to swap out the jets, so very possible in the not so far future, Alex might be able to try my 160 MJ (in case it doesn't work), the PWK seems to be the better fit for the XR it is smaller and easier to work on from the outside, don't need to uninstall each time. In the meanwhile my valves are still having problems and I ordered a set of Kibblewhite Titanium valves, they are said to be great for the XR series, so the head needs to come off one more time, after this I hopefully will have some time riding again
 
Over a year has passed and just a couple of days ago, I took out the Keihin FCR33 again. I mailed japanwebbike about the original jetting of that carb for the XR250R/L and they gave me the following specs: 117 MJ and 42 PJ. It pulls real strong without any bog, I think this setting is spot on. Hopefully someone can use this information for their XR's one day, it took a long time and a lot of research to make this work. :MJ
 
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