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DT400 won't start

02 Feb 2020 03:53
Justin Unett
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DT400 won't start #1
Hey all been away from forum for some time
I have a 7 DT400 that is very hard to start , in the last 2 weeks its started twice, in probably 1000 kicks Ha
History
bought as non runner
completely standard
new crank seals , tested for leaks , held 5psi for over an hour ( guage didn't move )
120 psi compression
has standard decomp fitted , no leak( oring was leaking but replaced ). Also tried starting bike with decomp blanked off . no change
uni airfilter , new oiled slightly
pipes clean
new ignitoin coil and plug cap , have also tried original. when it did start was with the new one
Carbs standard , as clean as I can get it. float height set . needle jet removed and clean , fuel inrichener in float bowl clean, standard jetting(new genuine mukini . understand could be a bit lean with filter change
cdi ignition , have aslo tried point setup off a 250 . Both produce good spark . Always has spark
About 6 new plugs . I change em after say 10 kicks
timing set with dial guage to 2.9mm . tried setting to 2.00mm just to see if would start
When the bike did start it ran pretty good, good power, responsive.
For the life of me I cannot get it start again ?
The plug is always wet . Ive had top end off a couple of times to blow out fuel as was worried was full of fuel . It did have a small amount in crank case but not too much .
The bikes airing in garage now with carb and pipe removed.
Any ideas ? . Ive had a lot of DTs RDs etc all 2 or 3 kickers

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02 Feb 2020 05:42
Noviastar
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DT400 won't start #2
Humm. If the plugs are wet with gas, sparks good. My guess would be air flow issue. Maybe if it has a choke slide, cutting your air off? Would the intake valve not closing let to much in, or some other valve issue? Not enough air getting out of exhaust, odd blockage? Or some odd thing letting to much gas in. Like throttle cable not in the right place? Does it have a fuel filter? Plugged with something.

Just brain storming. I'm curious to know what it ends up being.

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02 Feb 2020 07:31
Biknflyfisher
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DT400 won't start #3
Well, one thing is for certain, it’s not a valve issue.......
Just had to throw that out there.
Biknflyfisher

1983 IT490K; 2007 Yamaha FJR 1300,
2003 KTM 450exc
Too many fly rods,,,

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02 Feb 2020 08:25
Gr8uncleal
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DT400 won't start #4
Did you buy your spark plugs from a "reputable" source?

I ask because there are a lot of copies out there and often will spark outside of the cylinder, but not under compression.

Unlikely I know, but it has to be something!

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02 Feb 2020 13:36
Eazy-X
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DT400 won't start #5
I had a run on my DT175 where it was hard to start... turns out I'd put the kicker on at the wrong and wasn't getting the full range of travel! Those last few degrees make the world of difference apparently :D

Anyhoo, have you tried push starting it?

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02 Feb 2020 14:37
Blackhat250
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DT400 won't start #6
i"d burn out your exhaust,,,

If you aint mixin gas " you aint haulin Ass

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02 Feb 2020 14:38
Justin Unett
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DT400 won't start #7
thanks for all the replys.
yes have tried push starting it. not the easiest thing. no luck this way. i have had it started on a race roll starter. it's got a lot of compression and locks back wheel
spark plugs are genuine ngks. i will buy couple more new ones
will have a look at the kick starter . it does seam to have full travel

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04 Feb 2020 15:32
Justin Unett
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DT400 won't start #8
Still total fire ban in my neck of the woods, fear getting locked up if I try burn the pipe out.
Am going to try chemical method tonight . It may be clogged ? It did run pretty good though

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16 Feb 2020 18:06
Justin Unett
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DT400 won't start #9
well she's running perfect.
swapped stator from a dt250 ( points ) small wiring change and she started first kick. strange as had good spark with the cdi setup , also it had started on the cdi setup although very difficult.
thanks for all the input ( i also cleaned out pipe , was pretty clean already )
The following user(s) Liked this Post Gr8uncleal

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17 Feb 2020 00:08
Gr8uncleal
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DT400 won't start #10
Great news! :likey

Might well have been the pulser for the cdi (well known for failing).

A previous owner had already converted my DT360A to points and I bought one of DEET's little wiring conversion "joints" to keep it all tidy.

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