Hello all you guys out there just thought I would let you know how the bike is performing, as the needle jet and needle were the only parts in the carb that I had not replaced with genuine parts, I took RT325s advice to replace them, and with a Mikuni stockist recommended by GR8UNCLEAL the items arrived yesterday , so thank you so very much both of you.   At the moment all carb parts are stock and at the correct sizes and settings, so today I went for a test ride and boy what a difference, I would say that there is a 75% improvement with a lot less shunting . Going up through the gears I could feel the bike just wanted to go, but as I am running in a new piston and ring set I had to control the revs, so I am not allowing it to go past 4,000 revs, even at that l ow power the bike feels crisp, sounds great and pulls like hell. So all I need to do now is experiment with some of the other suggestions from other readers to iron out that last bit of shunting when your slowing right up to a junction or roundabout etc. I hope my posts are helpful to other readers with this problem .

That is good news and gives me hope that when I can get my 400 going again I have a direction to go.  Thanks for the update!

Thanks for posting an update.

 

Hi

Where did you buy the needle jet and needle?

Thanks

Hi there Hatrick1960,   sorry for the late reply as I have been away, and only just noticed your question to me, I live in the UK and in the city of Nottingham there is a Mikuni stockist called Allens performance LTD, this is where I purchased all of the jets and parts for my 400 B carb.

Another source of genuine Mikuni carbs parts in the UK is Moto Carb www.motocarb.com/ run by a bloke called Steve.

I have found him really helpful if you give him a call.

I am told to avoid anything made by, or under the name of "Keyster" for Mikuni carbs - they are known to cause problems, certainly on Kawasaki Triples.

Just sayin'

Hi again to all of you out there, had to have a break from my DT for a while due to work and family commitments, but I can now tell you all that I have now managed to fix the shunting and surging on my 75 DT 400 B as mentioned in past posts, so here is my set up
. New needle and needle jet tube.
. 16 tooth front sprocket up from standard 15 tooth.
. Pilot jet up to 50 from standard 40.
. Mixture / air screw out half a turn from fully closed.
. Needle clip position 4 from top as opposed to standard position 3.
From my settings you would expect it to be running rich, but the plug is a lovely light tan colour and the bike now runs like a dream idles smoothly, revs crisp and cleanly pulls through the gears like hell, sounds great and most of all comes off the gas without any shunting nonsense, what a pleasure to now ride. My thanks to RT325, Garydean, Turbodan and Masavitt for their input and pointers on this subject, what a happy man I am Thank You.

That's great news and information! Can you tell us what plug you're running? I ask because when I first got my DT400 I went to Yamaha and asked for a plug, they gave me a B8ES but book says B9ES and after asking here on the forum the consensus is to run the B9ES. Thanks and congratulations!

running smooth and strong is so good to hear!

#40 pilot sounds so small to me because stock on my DT360 was #50 and going to #55 and raising the needle one slot richer from 3rd position really helped with the shunting.  And another point of reference, my 78DT400E is listed as #80 and it chug chugs less and is a beast.

I couldn't find your 75 on Partzilla, but did find 76 400 and pilot was a #40...seems so lean
anyhow, if you think you have a bit more to gain you might want to try a #55...but you have the screw in making it way richer....when I put the #55 into my 360 I had to take the air screw out to almost 2 turns out because it was much richer, but it really helped with the chug chug and really hauled ass and the plug stays a nice dark brown. My hypothesis  was that I was getting more fuel / air at a rich enough ratio into the engine...or maybe I had too much beers and just got confused.

So great that you got the bike running great, so much fun riding these up a mountain and hoping the 50 year old CDI or whatever doesn't konck out!

+1 on the beers