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Rough running DT175MX


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Hello, I’m posting this as I really have run out of ideas. I’ve restored my dt175mx from a non runner. The engine is fully rebuilt, exhaust decoked, stator rewound, rotor is intact, carb has been cleaned and I’ve fitted new jets to suit the standards in the Yamaha manual I have. I’ve put a new coil and plug on. Timing is set as the marks state. Reeds look good and all rubbers are tidy. New air filter and everything nice and tightly done up. Oil pump is rebuilt and the exhaust has a nice blue tint.

she fires up first kick, ticks over nicely, but once you ride it it it has nothing from 4 to 5 k., splutters and won’t rev.  I just can’t think what I’ve missed and don’t know where to turn. I’ve spoken to a guy who sells CDIs who is adamant that is not the problem. So really not much more I can check with my limited knowledge.

i know someone else on here has experienced a similar issue, and would really appreciate any guidance to resolve it.

thanks, Martin.

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Hi  martin ,:wavey:,   did you over oil the filtre ?... ,   what colour is the Plug,?,   next time she  splutters,   shove the choke on ,[   just to see if its fuel starvation ],    if its worse with choke ON,   ,then shes neEding AIR,

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This has an air of familiarity for sure!....I certainly had a similar issue, I could rev mine over 5K + when its not under load, ie  on tick over then whacking up the throttle and it run fine, however.....go for a ride with it under load and it didnt like going above 5K.

Mine (although I wouldn't consider it at the time) was my exhaust pipe. ie the end can. I was given and fitted an original tail pipe, I was told it had been 'decoked' and I too cleaned it out with so called exhaust cleaner, and for a short time it did seem to be ok, but then the 5K problem started, it wouldn't run well at speed and top speed was only about 40~45 before it would play up, something was wrong but I carried on , but it didn't get better. After doing many things including new plug, carb, aircleaner, I eventually put back my rather noisey aftermarket can, and suddenly everything was back to normal, top speed and running all back to as it should be.

Might be of some help?


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Thanks Neo. I’ve tried it with and without the silencer. Exactly the same. I’m looking at the electrical side now I th8nk, pulse coil, coil, CDI, timing... all that, although some of it is new or refurbished. I think if 8 hand it over to a pro I will ask them to go that route first.

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