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DT 400 B shunting update.

  • p.wells
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DT 400 B shunting update. was created by p.wells

Hi again to you all out there, thank you all so much for the interest you showed on my topic and all off the helpful suggestions and advice that you posted. So I thought that I would let you all know how things are going, as it may help others with the same problem.
RT325 wrote about needles and needle jet tubes wearing after years of sliding up and down, so this got me thinking that last year I purchased a  carb rebuild kit, but I only used the main jet, pilot jet, air screw, idle screw and gasket but I left the needle as I thought mine was ok, then RT325 put up his post on needle wear, so I took my old needle out and checked it against the new one and sure enough there was quite a difference. With the new needle installed at stock position 3 I took the bike up the road and straight away noticed the difference, the bike did not splutter or shunt at all and I had a great ride for a few miles. But as the engine got up to full operating temperature I noticed that the shunting was slowly starting to creep back in. So thank you RT325 as your input  has partly solved the problem, I now have to try some of the other guys tips to find out why it does it but only once fully warmed up. 
20 Jun 2022 10:31 #1

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Replied by Gr8uncleal on topic DT 400 B shunting update.

Preference is to use original Mikuni jets and brassware wherever possible - some are still available through Yamaha and most through a Mikuni dealer.
20 Jun 2022 10:39 #2

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Replied by msavitt on topic DT 400 B shunting update.

learn to enjoy this surge, its not going away!
20 Jun 2022 11:58 #3

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Replied by AirborneSilva on topic DT 400 B shunting update.

Watching with interest!
1976 DT400C
1981 DT175H
1972 DT2 250
20 Jun 2022 13:29 #4

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Replied by RT325 on topic DT 400 B shunting update.

Thanks for the thanks P Wells but don't forget--to get it back to as good as factory you must do the needle & the needle jet [emulsion tube] which is the long column tube up the middle of the carb.
The following user(s) Liked this Post: MarkT
20 Jun 2022 15:33 #5

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Replied by p.wells on topic DT 400 B shunting update.

Hello RT325, yes I would like to replace the emulsion tube but Yambits here in the UK do not stock  many carb parts for the DT 400 B, I have tried Babbitts in the USA  and CMLS in the Netherlands but no joy. where do you guys get your DT parts from ?. one other thing that I was thinking about was have you heard if the later DT 400 E monoshock 1977-1979 bikes have this shunting issue just a thought. Pretty much the same engine unit and carb, but looking at the specs I noticed that the main jet is 190 and the pilot jet is 80, but all other settings are roughly the same as the 400 B. What are your thoughts on this.
20 Jun 2022 22:42 #6

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Replied by Gr8uncleal on topic DT 400 B shunting update.

As you're in the UK, try Motocarb or Allens for genuine Mikuni parts.

Yambits and the other suppliers are a useful (and much appreciated) source of parts, but genuine is always best.
20 Jun 2022 23:42 #7

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Replied by p.wells on topic DT 400 B shunting update.

HI  GR8UNCLEAL, many thanks for the info I will check them out.
21 Jun 2022 00:13 #8

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Replied by RT325 on topic DT 400 B shunting update.

Sorry, i'm too out of touch [old fart] but i know [or like to think i know lol] what could help--just going by experience. So far as where to get parts Greatuncleal above looks like 'the man' Cheers.
21 Jun 2022 00:14 #9

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Replied by RT325 on topic DT 400 B shunting update.

For the cost of something like this & the listing after it i'd be keen to try something like this. Available in different sizes i think--or was the one in the next link. I have a Chinese 28mm on my 175 & its great but had to devise a way of changing the main jet to a common mikuni by memory. Think i just altered the thread up the needle jet, just ran the right thread tap up there a few turns. Anyway--what could go wrong--ummmm.

www.aliexpress.com/item/32844300091.html...%2165110799532%21sea

 
Last edit: 21 Jun 2022 00:32 by RT325.
21 Jun 2022 00:25 #10

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