I wonder how exactly i would increase the diameter of the carburator (my PWK 39). Everybody is talking about "boreing" but do people mean turning?
And which diameter do you exactly increase? If it is the full way through, how can you avoid not to remove the "needle housing" (red arrow on the pictures)? On the pictures you see pwk 41 so how did these guys do that?
And the last question is: how far can i go? I heard that people with a PWK 41 measure 41.5 - 42 mm out of it and it still works. i would go for 41.5...
The whole jet block assembly is removable from inside the float bowl. There are a couple torx looking screws that hold it in place. I have never pulled one apart myself, keihin says to not remove it but obviously guys do all the time... Then just bore to the size you want.. Most shops charge $60 to $80 not a big deal to have someone do it right.
Yes you need to remove that section of the carb from the bottom there is a special o-ring in there you can get from sudco!! You should off set bore it because you really don't want to lower the bottom portion of the carb as you can run into problems with it at idle???
I just did my 38mm air Stryker punched it out to a 39.5, I offset it .030 and bored it to clean
I use a mill with a boring head verses using a lathe the mill is easier to dial in the carb I also use a inside dial indicator to set it up
00'cr500 trailclimber
93'cr500 beater
92'cr500 hillclimber
08,KTM SR500r hillclimber (conv)
89'cr 500 bent frame
04'crf230(wifeys)
02' cr125(sons)
02,pro jr 50 open exh. hill climber(sons)
02'sx65(sons)
03'xr50(sons)
100hp honda wrote:been a while since i had a carb bored but im assuming they pulled the middle section out and bored right through. never payed attention to be honest.
you never paid attention to the two previous posts either.
1. If you bore the carb out on a mill (so straight through) then you couldn't open up the air inlet side with the angle - so this has to be done on lathe right?
So it seems that the carbs on the pictures above (and also sudco carbs) are done with a lathe.
2. If you would do it on a lathe you couldn't offset the bore. If Sudco does its work for the PWK 41 Pro Series on a lathe it seems that it still works fine?!
3. Do you have to modify the slide (on top) that it opens up the bigger bore completely? (either way if normal bore or offset bore - but offset will cause more problems right?)
here what a found recently:
So that looks completley like done on a lathe - what do you think?
100hp honda wrote:been a while since i had a carb bored but im assuming they pulled the middle section out and bored right through. never payed attention to be honest.
you never paid attention to the two previous posts either.
i know what they said.
but heres what i was saying. you could probly bore in half way then flip the carb and bore from the other side without removing the middle section. or you could remove the middle section and bore straight through. i didnt pay any attention to how mine was done. thats what i was refering to.
Sudco hand blends the intake side it's not all done on a machine
You can put it on a 4 jaw chuck and offset the carb, I like the mill better it's easier to watch were it's cutting when the carb is stationary and you can make more precise adjustments with the mill table then a 4 jaw!!!
00'cr500 trailclimber
93'cr500 beater
92'cr500 hillclimber
08,KTM SR500r hillclimber (conv)
89'cr 500 bent frame
04'crf230(wifeys)
02' cr125(sons)
02,pro jr 50 open exh. hill climber(sons)
02'sx65(sons)
03'xr50(sons)
oggo69 wrote:this is the reason carbs should be ovalised or elipsed .... not parralell bored , even with an offset
What reason?????
no fear of messing with the needle and MJ axis ... for the same reason u offset urs .... ovalise across the X axis (if u take the needle as being Y)
it also speads the gas across the cylinder
i called Sudco and they told me that they bore the PWK 41 Pro Series, but that they don't offset bore them.
So does anybody have problems with their Sudco carbs concerning idle?
Can anybody with a Sudco 41 or more 42.xx approve that statement from Sudco that they don't offset the bore? (i guess you could see it easily on the engine side of the carb - how thick the wall is and if its everywhere the same - then it's no offset, right?)
Oh and that guy told me that they don't modify the air intake side of the carb - which is wrong from the pictures I posted above - so I don't know if his statements are all right...
I thought of adding a gasket under the assembly to pull it out of the airstream, but that complicates jetting somewhat as it lowers the fuel flow area of the part in relation to the needle position.
Then I thought about "ramping" it to take out the step.
Then I though the increased turbulence might atomize the fuel better...
Then I bolted it on and said "F" it.
For someone like Karty, this might me something to address, but I just let it go.....
the 450 will have less power and will be harder to start, and will be heavier, but to make up for it it will require more maintenance.
4stroke=dead fish
had it opened up to 41.75mm when a hole on the air intake side appeared which connects to the fuel supply bore at the bottom. DAMMIT!
Also the thread from the idling screw appeared on top.
So this was the absolut maximum a can get out and now I screwed the carb up. I have absolutely no clue how sudco can get 42.29 out of it. But it could be that the hole to the fuel supply was also caused by a little casting defect at that position which adds up to a hole - but the idling screw still would show up on top.
Trying to fix that hole with a special 2 components glue but i really hope that this can stand the fuel all the time!
And I will remove 1.375 from the top of the slide to open it up as wide as before... if i can fix the carb
