Help me choose carburetors for 1979 RD400F

[rearwheelslider]

Would you recommend the TDR reeds or YZ reeds?

[pdxjim]

Would you recommend the TDR reeds or YZ reeds?

For you, I'd recommend kx100 v384a Vforce3 reeds.

[m in sc]

^ agreed

[pdxjim]

[m in sc]

im running those rm reeds on the lightweight with a fairly radically ported motor (where i figure out that they would work) &  set of PJ34 keihins thru them, they flow plenty for that so they will handle smaller carbs zero issues

[rearwheelslider]

PWK 28's on my Rd400F update:
First start was with 155 mains, JJH needles on third clip, 40 pilots, 2 turns out. Started and idled okay, but would not rev out past 4k.
I then dropped needle to first clip(full lean), got a little better.
I then went to 145 mains, same needles/clip positions, 38 pilots, 1.5 turns out. The low speed fueling is great, gonna keep that in there.
I then dropped mains to 138's. Much improved and will pull through the rev range. Good power. Still feels a tad rich up top but I will need to ride it for a bit to see how it pans out.

[m in sc]

interesting the main is so low. however, im used to 350s , the swept volume of a 400 is more and therefore -should- cause a stronger vacuum signal which probably explains a 138.

[pdxjim]

Mutts suggested to me stopping down the airscrew to .5-1 turn out max.

Said 1.5 (which is generally a good starting point) is usually too much air and they like it richer just off idle regardless of pilot size.

Worth a try before detailing the mains as (so I've been told) the overlap/influence of one circuit to the next is greater on PWKs than some other carbs (Mikuni)🤷�♂️

As always, take my comments with a grain of salt as I'm usually just repeating what the real smart guys have said.

[m in sc]

that's all dependent on the slide cutout, jim.

[rearwheelslider]

interesting the main is so low. however, im used to 350s , the swept volume of a 400 is more and therefore -should- cause a stronger vacuum signal which probably explains a 138.

Something to note.. These are the knockoff PWK's and they do have a powerjet. The powerjet orifice is TINY, not sure how much it is affecting the wide open fueling if at all. But if it is, it explains the reduced main size.

Either way, the rear tire is not holding air and they are from 1988, so not much ride/tune going to be happening. Neighbors loving the noisy chambers, too!

[m in sc]

true. the powerjets that come in those i think are about equivalent to a 17.5 or 20 mikuni pilot jet size, they are very small

[teazer]

I hope we aren't confusing Keihn jet numbers with Mikuni large hex numbering.  Keihn jet are numbered according to their diameter IIRC, so a Keihin #138 is roughly equivalent to a 230 or so large hex mikuni.

[rearwheelslider]

I have a bit of an issue maybe you guys can help me with. The throttle cable is the one from HVC. Dual cable, made to fit PWK, TM, stock carbs.

I currently have the short adjusters on my carbs and the throttle cable adjustments are all near maxed. When the cable stretches, I wont have much adjustment left at all. Also the angle of the cable is a bit much at the carb top.

Do you know if these angled adjusters will take up enough cable slack, but not make the cable too short? I cannot seem to find them, other than Ali Express. Another source and more info would be appreciated!

[pdxjim]

I used these off Amazon. They worked perfect to fit a genuine standard LC cable to my genuine PWKs.

Sudco Adjuster Asmbly 40 Degree... https://www.amazon.com/dp/B00T6J9VHY?ref=ppx_pop_mob_ap_share

[m in sc]

^ive used those as well.