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DT125E Won't Start

26 Mar 2020 04:32
C Team
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DT125E Won't Start #21
I am going to do a compression check to to see where this motor stands. I'm pretty sure I will pull the carb and do a thorough cleaning and hope that will help with the bad throttle response too.
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26 Mar 2020 18:47
RT325
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DT125E Won't Start #22
ok maybe pull the reed block while carbs off & see if piston windows are obvious. Unlikely to be wrong--but!!, easy to see while there.

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27 Mar 2020 03:26 27 Mar 2020 03:27 by C Team.
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DT125E Won't Start #23
UPDATE: So I got a little over 90lbs. on the compression check. After kicking a few times with key off and throttle wide open, I removed the compression gauge and re-installed the spark plug. I turn the key and and gave it it kick and she fired right up! it idle fine but as it warmed up is started to bog down and you had to work the throttle to keep it running. Why would it idle/run fine until it got warmed up? Would this still be something in the carb or possibly a coil acting up as it gets warm? I decide to remove the carb and give a thorough cleaning. I am going to buy a ultra sonic cleaning bath today for the carb.

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27 Mar 2020 03:47
RT325
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DT125E Won't Start #24
Sorry, out of ideas without listening to it but does still sound carb related or to do with sucking fuel at least, like crank seals or cylinder base gasket sucked in, which you'd see looking around the base--all unlikely though. That little pilot jet i can see in the pic, give it a poke with something or at least see if you can see through it--& it's a small hole. I unblocked one yesterday using an acupuncture needle that was 8thou thick as i couldn't get a 16thou wire brush strand through. Was a super small jet out of a 4 stroke scooter though. If you try that & make sure its all clean in every way & its no better then the problem is likely elsewhere.

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27 Mar 2020 04:11 27 Mar 2020 04:12 by Gr8uncleal.
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DT125E Won't Start #25
Good, progress at least! :likey

Maybe it's running out of fuel? By that, I mean that the float bowl is emptying quicker than the flow from the tank can keep it filled up.

After you've started it and then struggled to keep it going, turn it off and wait just for a minute or two - enough time for the bowl to fill up, but not long enough for the engine to cool down. See what happens then when you start it up.

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27 Mar 2020 04:53
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DT125E Won't Start #26

RT325 wrote: Sorry, out of ideas without listening to it but does still sound carb related or to do with sucking fuel at least, like crank seals or cylinder base gasket sucked in, which you'd see looking around the base--all unlikely though. That little pilot jet i can see in the pic, give it a poke with something or at least see if you can see through it--& it's a small hole. I unblocked one yesterday using an acupuncture needle that was 8thou thick as i couldn't get a 16thou wire brush strand through. Was a super small jet out of a 4 stroke scooter though. If you try that & make sure its all clean in every way & its no better then the problem is likely elsewhere.


I will make sure I can see daylight through all the jets when I get to cleaning. I will take a video of it after I get the carb back together.

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27 Mar 2020 04:55
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DT125E Won't Start #27

Gr8uncleal wrote: Good, progress at least! :likey

Maybe it's running out of fuel? By that, I mean that the float bowl is emptying quicker than the flow from the tank can keep it filled up.

After you've started it and then struggled to keep it going, turn it off and wait just for a minute or two - enough time for the bowl to fill up, but not long enough for the engine to cool down. See what happens then when you start it up.


Good idea. I do have a new inline fuel filter that is clear and you can see it is filled with fuel. I will try your idea if it still acts up after putting the carb back together this weekend.

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27 Mar 2020 07:21
MarkT
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DT125E Won't Start #28
The pilot jet is tiny on these later bikes.... they are set to run lean for emissions... a 22.5 if I remember correctly. It's so tiny that the smallest amount of crud will make a big difference. I just swap to a 25. I think the Yamaha Banshee has the same type pilot jet.

The well in the float bowl has a tiny starter jet... the later models are almost impossible to start if that jet gets clogged up... and it's pretty common.



And don't get fooled by a clear fuel filter or fuel line. You can have plenty of fuel flowing and the filter or line will look like it's full of air. If you're concerned, flow test, visual test is useless. Before installing carb, connect to fuel line with bowl plug removed. Hold carb over a container and measure how much fuel flows over a timed period. Or just make sure lots of fuel flows and doesn't slow/stop. Do this outside in a well-ventilated area. Make sure gas cap is on for the test... plugged cap vent can restrict flow.

I know it's a pain to remove the carb but I think you're on the right track... later models are very sensitive to even tiny amounts of fuel deposits....

Pull the ignition cover too and make sure no fuel/oil is in the flywheel area. Crank seal is common failure... use the IT175 part if you change it.

1963 YG1-T, 1965 MG1-T, Allstate 250, 1970 CT1b, 1971 R5, 1973 AT3MX, 1974 TS400L, 1975 RD350, 1976 DT175C, 1976 Husqvarna 250CR, 1981 DT175G, 1988 DT50, 1990 "Super" DT50, 1991 RT180, 2017 XT250

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27 Mar 2020 17:00
RT325
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DT125E Won't Start #29
Yeah starter [choke] jet that Mark is pointing to--if blocked & you use the choke all ya doing is opening an airway making a bad situation even worse [leaner & possible high idle].

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30 Mar 2020 03:34
C Team
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DT125E Won't Start #30
UPDATE: After ultrasonic cleaning all carb pieces, the bike is back together and running great. I will try to post a video. Now all I need is a taillight so I can make this bike street legal! How do I save a video to work? My video us saved with .3gp but I see this is not allowed on the site.

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