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Yamaha TTR90 Issues

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I bought my son a hardly used 2007 TTR90. It did not run when I bought it so I cleaned the carb and got it running. It ran ok but not right. The throttle was always really touchy. Recently it got so bad you could not turn the throttle at all, it would just die. I cleaned the carb several times. I finally had to break down and take it to a shop. They said it would just be a blocked jet and most people don't get them clean. After them taking it apart 4 times, replacing the jets it runs better but they are still working on it. They said the carb was clean as a whistle (so I feel better that I did my part right). The bike is stock. Why am I having so much trouble, it is all Yamaha bikes? I have two Honda bikes that are a lot older with no issues. I think this will be the last Yamaha in the family. Anyone else having the same issues? Thanks.

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I have several Yamaha's including a TTR-90. I have no issues with any of them.

The problems you are having are not an inherent issue with the TTR-90, it is a solid design that has been around for a long time, and has evolved into the TTR-110. The issues you are having is troubleshooting the problem with this specific TTR-90.

This is an excellent forum to help solve the problems you are having.

I have some questions:

1. Did you confirm the intake track is sealed and that you do not have an air leak? This is best accomplished by spraying a can of carb cleaner around the carb and intake while idleing.

2. Are you sure the jetting is stock? I have seen this issue make people crazy. Also, these bikes are lean from the factory and do not tolerate changes to the air box and other plumbing. If the intake is changed, richer pilots/main jets are needed. Exhaust changes (removing baffle or end cap for example) can impact jetting.

3. Have you checked the valves?

4. The best way to clean the carb is to use a dip-style cleaner (Berryman). Disassemble the carb, soak all metal parts in this stuff overnight, then clean in hot water, blow dry with compressed air checking all passages for flow (I use spray carb cleaner for this). Reassemble and check the float height before putting the bowl back on. Make sure the throttle slide is in correct.

Specs are available if you ask here.

Good luck, don't give up!

TJ

Edited by tjackson
Added throttle slide bit

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TJACKSON, thank you for the detailed post and information. I got the bike back from the shop last night. It is running a lot better but they said they could not get it running as good as they would like. They also researched the issues and found all the posts on jetting and carb issues with almost all of the TTR models. He had the same feeling I did after researching the issues. He would never by his kid one, if they have this many problems from the factory. My bike is completely stock no modifications. I expected it to be a low maintenance bike for a kid learning to ride. My son has been so frustrated dealing with the bike while his younger brother flies past him on his little CRF50. We will be taking them out next week for some long rides for the holidays. Fingers crossed.

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Check your valve lash. I would expect the shop you brought it to would have done this, but valves that are very loose or very tight will behave in a manner that screams "carb out of whack".

Also, it wouldn't hurt to simply replace the jets in the carb since it's a used bike. Normally it isn't a problem, but with what you're describing it's possible somebody cleaned the jets by ramming a wire through them and this altered the orifice size. It's a $10 investment in peace of mind.

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TJACKSON, thank you for the detailed post and information. I got the bike back from the shop last night. It is running a lot better but they said they could not get it running as good as they would like. They also researched the issues and found all the posts on jetting and carb issues with almost all of the TTR models. He had the same feeling I did after researching the issues. He would never by his kid one, if they have this many problems from the factory. My bike is completely stock no modifications. I expected it to be a low maintenance bike for a kid learning to ride. My son has been so frustrated dealing with the bike while his younger brother flies past him on his little CRF50. We will be taking them out next week for some long rides for the holidays. Fingers crossed.

Glad to help. Most of my 4-stroke bikes are lean from the factory, I have had to change the jetting on not just my Yamahas (I have a TTR-90, TTR-125, TTR-225, and a TTR-250), my Suzukis (GSXR-600, LTZ-50, and DRZ-400) too. The pilot jet is always too lean.

I hope you have a successful ride, please post back how you made out. I understand the frustration, my kids are the same way (without a broken bike adding to the stress).

TJ

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