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I just fitted a gianelli exhaust expansion to my old Yamaha DT125 lc -87. The bike lost 20km/h with the new exhaust. It revs better and accelerates better but when I get it to 100km/h with 3rd gear at some 10000rpm and change to fourth gear the bike just bogs down. I tried a bigger mainjet without any help. The bike works like a dream with the original exhaust. It's jetted to size 250 mainjet and has a pod type airfilter and fiber flaps. I'm thinking that the original mikuni vm26 carb just is too small. Am I right??

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Go to a smaller exhaust or a longer exhaust (not practical. Engines need some back pressure. That is why headers on dragsters are all of equal length.

Posted on May 30, 2017

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1 Answer

On my dt 125 road bike but wen i start it an rev it sputters an cuts out


Hi, Anonymous and the usual suspects are:
1. Severely drained or faulty battery.
2. Faulty regulator/rectifier or high output coil.
3. Faulty power valve, solenoid or installation.
4. Clogged air filter or exhaust.
5. Cracked or incorrect float level.
6. Float needle is not seating.
7. Faulty reed valve.
For more information about your question and valuable "FREE" downloads that you will need please visit the website below. Good luck and have a nice day.
dt175 won rev above 7k Yamaha 2 Stroke
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http://www.motogelnar.cz/manual/YAMAHA/DT125X_RE-05-Service_Manual.pdf
OEM parts for Yamaha
http://www.dt125.cz/download/Owners_Manual-DT125X_RE.pdf

Btw, I’m available to help over the phone in case u need at https://www.6ya.com/expert/gregg_c0ec1df182c7330e


Jun 22, 2014 | 2000 Yamaha DT 125 R

1 Answer

Bike was running great on saturday. Went to the races bike started right up when the gate dropped bike won't rev out all the way. Didn't have this problem yesterday. When we got home i cleaned the car


Hi, Anonymous and the usual suspects are:
1. Severely drained or faulty battery.
2. Faulty regulator/rectifier or high output coil.
3. Faulty power valve, solenoid or installation.
4. Clogged air filter or exhaust.
5. Cracked or incorrect float level.
6. Float needle is not seating.
7. Faulty reed valve.
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.
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YAMAHA YZ250 LC Owner Service Manual
OEM parts for Yamaha
http://mybikemanuals.com/yamaha/yamaha-yz-owners-manuals

Btw, I’m available to help over the phone in case u need at https://www.6ya.com/expert/gregg_c0ec1df182c7330e

May 19, 2014 | 2007 Yamaha yZ 250

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Clutch not activateing with gearbox.


Hi, Anonymous sorry you can't find the first and best tool you ever bought for your Yamaha despair, not for a mere $0 you can download another one. For more information about your issue and valuable "FREE" downloads that you will need please visit the websites below. Good luck and have a nice day.
https://yamahaclub.com/forums/topic/24877-78-dt125-clutch-issues
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http://www.motogelnar.cz/manual/YAMAHA/DT125X_RE-05-Service_Manual.pdf
OEM parts for Yamaha
http://www.dt125.cz/download/Owners_Manual-DT125X_RE.pdf

Btw, I’m available to help over the phone in case u need at https://www.6ya.com/expert/gregg_c0ec1df182c7330e


Jan 18, 2014 | 2004 Yamaha DT 125 R

1 Answer

Yamaha 250 will not rev


Hi, Anonymous and the usual suspects are:
1. Severely drained or faulty battery.
2. Faulty regulator/rectifier or high output coil.
3. Faulty power valve, solenoid or installation.
4. Clogged air filter or exhaust.
5. Cracked or incorrect float level.
6. Float needle is not seating.
7. Faulty reed valve.
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.
http://www.r6-forum.com/forums/57-garage-mechanical-help/158952-bike-starts-wont-rev.html
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YAMAHA YZ250 LC Owner Service Manual
OEM parts for Yamaha
http://mybikemanuals.com/yamaha/yamaha-yz-owners-manuals

Btw, I’m available to help over the phone in case u need at https://www.6ya.com/expert/gregg_c0ec1df182c7330e

Oct 02, 2013 | Yamaha YZ 250 Motorcycles

2 Answers

Expansion chamber


Hi, Jason for this situation I would call my local dealer or reputable shop's service/parts department and inquire about any possible quick fix, answers, or parts inquiry. If necessary, transport your bike to the dealer or shop and have a professional technician take it for a test drive, if it is in running condition, and give you a written estimate of repairs and answer any specific questions you may have about your problem. Good luck and have a nice day.
Big one and dep exhaust systems dtr 125
https://www.youtube.com/watch?v=SeURiw9IXmg
http://www.motogelnar.cz/manual/YAMAHA/DT125X_RE-05-Service_Manual.pdf
OEM parts for Yamaha
http://www.dt125.cz/download/Owners_Manual-DT125X_RE.pdf

Btw, I’m available to help over the phone in case u need at https://www.6ya.com/expert/gregg_c0ec1df182c7330e


May 30, 2013 | 2000 Yamaha DT 125 R

1 Answer

Lost key 2001 dt125


Hi, Anonymous for more information about your question and valuable "FREE" downloads that you will need please click on the links below. Good luck and have a nice day.
https://yamahaclub.com/forums/topic/29607-i-have-lost-my-only-soddin-bike-key-help
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Yamaha DT125RE 2005 Service Manual
OEM parts for Yamaha
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Btw, I’m available to help over the phone in case u need at https://www.6ya.com/expert/gregg_c0ec1df182c7330e


Jan 31, 2013 | 2006 Yamaha DT 125 X

1 Answer

Yamaha dt 125 looses power at high acceleration


Hi, Anonymous for this situation I would call my local dealer or reputable shop's service/parts department and inquire about any possible quick fix, answers, or parts inquiry. If necessary, transport your bike to the dealer or shop and have a professional technician take it for a test drive, if it is in running condition, and give you a written estimate of repairs and answer any specific questions you may have about your problem. Good luck and have a nice day.
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http://www.motogelnar.cz/manual/YAMAHA/DT125X_RE-05-Service_Manual.pdf
OEM parts for Yamaha
http://www.dt125.cz/download/Owners_Manual-DT125X_RE.pdf

Btw, I’m available to help over the phone in case u need at https://www.6ya.com/expert/gregg_c0ec1df182c7330e

Dec 15, 2012 | Yamaha DT 125 R Motorcycles

2 Answers

Why does my DT125 splutter at hight revs


Sounds like either the bike is starving for gas at higher RPM's, or you're hitting the rev limiter.

Jun 15, 2012 | Yamaha DT 125 R Motorcycles

1 Answer

Intermittent misfire/loss of power at higher revs..


how are your intake and exhaust valves? are they set to specs? my racing quad use to do that. so i set the valves to spec and whala!!!!better than ever.

Mar 26, 2009 | 1989 Yamaha FZR 1000

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