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Stuck throttle 74 DT175

  • chhst30
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Stuck throttle 74 DT175 was created by chhst30

I went for a ride today and the throttle got stuck open, pulled in clutch, parked. Was able to get to garage, and after jiggling and massaging the throttle cable assembly bike kicks over to high throttle in neutral. Twisting the throttle body/grip there is little resistance to "open throttle". Grip does return to closed position, but with very little "snap" and no change to RPMs. Where should I start with my efforts to free the throttle?
23 May 2019 12:40 #1

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Replied by Midlife Motor on topic Stuck throttle 74 DT175

Your slide may be stuck in the carb. Take carb cap off and pull out slide. Throttle cable should move freely and throttle grip should twist and return. Clean sides of slide with WD40 as well as area inside carb where slide moves.
It's better to remain silent and be considered a fool than to speak and remove all doubt.
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23 May 2019 13:41 #2

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Replied by chhst30 on topic Stuck throttle 74 DT175

THANK YOU! That sounds dangerously straight forward....I haven't disassembled the carb on this bike before. Is that an operation that can be done with the carb still mounted in place, or will I need to remove it from the bike? Any "small parts may explode" warnings for pins/seals/springs/etc that may come free and get lost to the shop floor or need tended when reassembling?
23 May 2019 13:48 #3

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Replied by Midlife Motor on topic Stuck throttle 74 DT175

Loosen the clamps that hold the carb in the rubber boots and rotate the carb 45 degrees or so, leaving the ends in the rubber boots. Unscrew the cap to the carb and the slide will come out. No small parts will jump out. The slide, slide spring, and needle should all come out in one piece. If it's stuck in the there, squirt some WD40 around the edges and patiently work it out.

When you put it back in, pay particular attention to the notch on one side of the slide. You will notice it's kind of angled. This is where the screw on the left side of the carb goes to adjust the slide position. Let us know when you get the slide out. Post a pic if you can. Also make sure your threads are lined up when screwing that carb cap back on. They are fine threads and can cross thread real easy.
It's better to remain silent and be considered a fool than to speak and remove all doubt.
23 May 2019 14:00 #4

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Replied by chhst30 on topic Stuck throttle 74 DT175

Looks clean? Slid out without issue....
23 May 2019 15:33 #5

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Replied by Midlife Motor on topic Stuck throttle 74 DT175

OK can you roll on and off the throttle now without it binding? Does it return fairly easy? It should still function well with the slide assembly out of the carb. If not, you need to check out the other end of the throttle cable. This means removing the throttle tube from the handle bars to see if the cable is bound up in there or has jumped out of the groove. Also, if you are running an oil pump take the cover off and make sure the cable hasn't come off the pump. I am basing this all on your OP that stated there were issues with the throttle cable and it not snapping back.

This is excellent experience for you. If we eliminate throttle cable issues etc, it's time to start looking elsewhere.
It's better to remain silent and be considered a fool than to speak and remove all doubt.
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23 May 2019 17:51 #6

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Replied by chhst30 on topic Stuck throttle 74 DT175

I cleaned the slide and throttle body with carb cleaner and blasted them out with compressed air...there was some flaky black carbon on the top side of the slide body. As you guessed the throttle had normal return and "snap" when disassembled and no sign of rust on the cable. Reassembled and throrrle was restored to normal functionality!

Thank you for your help; it was a great learning experience. NJ pine barons riding tomorrow made possible by the support of viewers like you!
The following user(s) Liked this Post: Mothersbaugh, Midlife Motor, DouglasDT, Gr8uncleal
23 May 2019 20:01 #7

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Replied by MarkT on topic Stuck throttle 74 DT175

Great advice and good job getting it fixed! :OnFire
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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23 May 2019 21:19 #8

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Replied by Midlife Motor on topic Stuck throttle 74 DT175

Great to hear it works. Happy riding.
It's better to remain silent and be considered a fool than to speak and remove all doubt.
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24 May 2019 07:55 #9

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Replied by John 15 on topic Stuck throttle 74 DT175

Hi. My name is John. I recently got a 1978 dt100e Yamaha and I've trying to restore it. I've replaced the oil pump, throttle valve, spark plug, battery, ignition, and all the fluids. Yet every time I turn it on the throttle is stuck wide open. Any suggestions?
Last edit: 19 Sep 2020 16:00 by John 15.
19 Sep 2020 14:49 #10

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