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Old 05-12-2015, 11:13 PM   #1
ajmick OP
n00b
 
Joined: May 2015
Location: WA
Oddometer: 2
76 DT400 Carb Issue - Need Help

I have a 76 Yamaha DT400 that I can't get running after a few months sitting.
It fired and ran for a minute or two right after taking it out of storage, then died. Since then:

Turns over
Has spark
New gas, and fuel is getting to the float bowl
Fires with gas poured into the carb, but it won't stay running for more than a second.
Won't push start

I cleaned the carb (mikuni vm32) as completely as I know how. There was plenty of green gunk in the float bowl, and I scrubbed everything and got spray through the fuel intake, main jet, and pilot jet. It still seems like I'm not getting any fuel unless I put it directly into the carb via the slide.

Any help is much appreciated! Also if there is a way to confirm that a carb is providing fuel, I'd love to know it.
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Old 05-13-2015, 11:09 AM   #2
Tim McKittrick
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Joined: Dec 2003
Location: Wasilla Alaska
Oddometer: 1,760
Since it makes noise on raw fuel and the problem began after the bike sat for a period I'm going to assume the carb still has an obstruction, most likely in the pilot jet or the passage from the pilot jet to the front of the slide.

Your plug will probably be dry after a few kicks, and that's your easiest indication that you aren't getting fuel past the carb. I would take the carb apart again and make extra sure there isn't a bit of goo blocking a passage.
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Old 05-13-2015, 04:32 PM   #3
emti
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Joined: Aug 2010
Location: northern n.y.
Oddometer: 271
When you disassemble your carb boil the carb body in water, let it boil about 15 minutes or so then blow out the passages with air, the boiling softens the remaining varnish so it can be blown out.

don't use the "good pans"
don't do this in the kitchen unless your single, or you soon will be
emti
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Old 05-13-2015, 04:54 PM   #4
ajmick OP
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Joined: May 2015
Location: WA
Oddometer: 2
Thanks for the reply. I cleaned out the carb again for good measure, but everything is all clear. I checked the plug and it had gas on it, so the carb must be doing at least some of its job right. No spark though! Somewhere in the middle of this job I must have fouled the plug. So on to the parts store for a few new ones.
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Old 05-15-2015, 10:30 AM   #5
baldman1
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Joined: Jan 2013
Oddometer: 266
All those Yamaha DT400's were pieces of shit, just give it to me so you don't have to deal with it any longer.
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Old 05-16-2015, 02:35 PM   #6
noman
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Joined: Jun 2007
Oddometer: 923
You may have cleaned the carb properly but then it got clogged from crap in the tank or rubber bit from a failing fuel line. I'd rinse out the tank, clean out the pet cock and replace the fuel line to ensure clean fuel going to your carb. Then clean the carb again and give it a try. On my dt250 the PO did a poor job of soldering the points wire on and it failed leaving no sprk. You might check that.
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