Question about Yamaha DT 125 R Motorcycles

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My 1977 Yamaha dt175 won't start.

While it was idling, the engine bogged down, blew a cloud of white smoke out the tailpipe, and then died. It will not kick start or roll to a start. It will only run while it is moving down a hill in 2nd gear and has no power. I have cleaned the carburetor several times and fuel line so it is not that.

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  • Zach Carter
    Zach Carter Jan 21, 2013

    I meant to mention this is a 2-stroke and i just put a new spark plug in it.



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  • Yamaha Master
  • 47,792 Answers

Hi, Anonymous and the usual suspects are:
1. Fuel tank empty.
2. Fuel supply valve/petcock turned off.
3. Fouled spark plugs.
4. Engine flooded as a result of overuse of the enricher.
5. Vacuum hose to the fuel supply valve/petcock disconnected, broken, cracked, or pinched.
6. Fuel valve/petcock or filter clogged.
7. Fuel line to the carburetor or throttle body pinched or kinked.
8. Carburetor float stuck.
9. Fuel injectors clogged.
10. Severely discharged or damaged battery you need 12.5 volts or better and be able to pass a load test if necessary.
11. Check battery terminals for damage or corrosion, check the battery cables at "BOTH" ends for loose, corroded, or broken connectors, "INSIDE" and outside the cable harness, perform connector wiggle test and check cables with an ohmmeter if necessary.
12. Loose or corroded wire connection at the coil, battery or plug between ignition sensor and CDI box.
Spark plug cables in bad condition and shorting check for leakage in the dark, cable connections loose, or connected to the wrong cylinders.
13. Ignition timing incorrect due to a faulty MAP, CKP, O2, TPS, sensors.
14. Faulty neutral, clutch lever, or kickstand safety switch.
15. Faulty fuel pump or fuse or relay.
16. Faulty CDI box.
17. A stuck bent or burnt valve.
18. Tip over sensor needs a reset.
19. Check for engine trouble codes.
For more information about your issue and valuable "FREE" downloads that you will need please click on the links below. Good luck and have a nice day.
Yamaha DT100A 1974 Service Manual
OEM parts for Yamaha

Posted on Feb 01, 2017


6 Suggested Answers

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Posted on Jan 02, 2017

  • 2559 Answers

SOURCE: yamaha DT175 1975 -- won`t idle back

Sounds like the reeds are bad.

Please rate this fixya

Posted on Jan 28, 2009

  • 20 Answers

SOURCE: yamaha DT175 1975 -- won`t idle back

I had the same problem recently where the idle speed was too high (3000 RPM) when the steering was pointing hard left. Here are some possible solutions to your problem. I have listed them in order of probability:

1. Choke. Maybe sounds too obvious, but if everything else is in good working order, this is usually the cause of a high engine speed at idle. Locate the choke and 'play' with it to see if this has an effect on RPM.

2. The throttle cable is tight or catching. Try loosening the lock-nut and teasing the cable away from the grip end. Don't force it too much to avoid snapping it. If it releases, check the throttle free-play is correct, and adjust if necessary. Lubricate cable at both ends to reduce any restricted movement.

3. The throttle cable is rusty. Try using a bit of WD40 at each end of the cable (handle and engine alike) and use a lubricant. 1975 is an old bike for sure, so clean & check the entire length of the cable for cracks or splits. Remember to wipe away any excess WD40 or lubricant after any maintenance. If you discover that you need a new throttle cable, these are cheap and easy to fit, and are normally available through eBay.

4. The engine idle speed setting is incorrect. There should be a screw situated somewhere around the engine case (you may have to consult the manual to find it). Turning this screw clockwise/anti-clockwise will adjust the idle speed up or down. Suggest you only perform this as a last resort.

5. Check oil. The engine idle speed can be dictated slightly by oil levels, so make sure the oil levels are between min/max on the dip-stick. Also, ensure that you are using the correct engine oil for your machine (consult the user manual), e.g. 2-stroke or 4-stroke, mineral or semi-synthetic, etc.

As I cannot guess what you mean by 'too high' when referring to the actual idle speed, I would suggest that if engine speed is more than 500 RPM above normal, it will most likely be an issue with the choke or throttle cable.

I would suggest you try finding a bike-specific servicing manual, but these are often hard to come by and can be pricey if you do eventually locate one. However, I do suggest you think about investing in the Haynes Motorcycle Maintenance Techbook: this is a generic book of bike maintenance and has loads of hints and tips that could save you loads on servicing bills. As most parts of any motorcycle are based on the same idea, much of the book answers even specific questions that apply to your problem.

Anyway, good luck !!

Posted on Jan 29, 2009

  • 1 Answer

SOURCE: yamaha DT175 1975 -- won`t idle back

Hello your problem is very likely a leaking seal on the fly wheel side. Clutch side would smoke excessively. Make certian your throttle cable is good and not pinched or routed in correctly. John H.

Posted on Apr 26, 2009

  • 39 Answers

SOURCE: YZF 250 has a hard time starting but when it's

needs a valve adjustment those bikes shim under bucket and are hard to do get a book or bring it to a dealer

Posted on May 15, 2009

  • 2559 Answers

SOURCE: XR 100 didnt move for a year.My bad so i cleaned

First Make sure you have all new fresh gas,and new fuel filter,Then check the intake tube between the head and carb for cracks or leaks,And You'll need to go back through the carb again as this is a carb issue,But without doing the above first,a clean carb won't be clean for long.

Posted on May 17, 2009

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Yamaha DT175 1975 -- won`t idle back

Sounds like the reeds are bad.

Please rate this fixya

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