1978 TT500e will not idle. Runs good on high end. carburetor has been cleaned, new gas air needle . will idle if the choke is on but dies when...

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Answer

Customer

1978 TT500e will not idle. Runs good on high end. carburetor has been cleaned, new gas air needle . will idle if the choke is on but dies when the choke is reduced.

Last updated
Ramy De Jesus
Yamaha Tech

Hello and welcome to ExpertHelp.com! My name is Ramy De Jesus and I'm going to do everything in my power to answer your question to your full satisfaction!

Before we get started, I want to remind you ExpertHelp.com is an independent professional support company. We are not associated with Yamaha nor are we paid to provide support on their behalf. However, we have helped hundreds of customers with similar questions and believe we can help you too. OK, let’s get started! :)

I’m available to chat now. Please let me know that you are ready by posting a response. I’ll leave my chat session open for the next 15 minutes or so and wait for your reply. If I don’t catch you this time, please respond with a few times (including your timezone) that work best for you and we can connect then.

Last updated
Ramy De Jesus
Yamaha Tech

Hi Tim! Thank you for choosing ExpertHelp.com. Try checking the following listed below.

  • Stator & amp
  • Charge Coil Assy &#34 which is located under the flywheel.
  • Also check the ignition switch

Please update me what will be the result after checking this. 

Posted
Customer

Hey Ramy,  All electrical componets on the bike check out. This is a dirt bike and has no ignition switch.  Bike runs good as long as the rpm are above 1500.  I think it is burning rich but the air/fuel needle valve cannot be finely tuned because it won't idle.  It is set at factory spec of 1 and 3/4 turns. 

Posted
Ramy De Jesus
Yamaha Tech

Thank you for your response. Have you check if there is any leak? Cab you check throttle cable area, where it goes into the lid of the carb, if there is a leak in this area.

Posted
Customer

I will have to pull the carb to check this out. will take a little bit.  do you have any other things I can check while I have the carb off?

Posted
Ramy De Jesus
Yamaha Tech

No other than that. Please keep me posted what will be the outcome.

Posted
Customer

Thanks, Ramy, I will get back with you.

Posted
Ramy De Jesus
Yamaha Tech

No worries I will leave this page open and will wait for your response.

Posted
Ramy De Jesus
Yamaha Tech

Hi Tim,

I  just want to follow up with regards to your issue. Please advise me if your problem is already resolve or you still need further assistance. I will be standing by for your response.

 

Regards,

Ramy De Jesus

Posted
Customer

Good morning, Ramy,  I pulled the carb and went back thru the whole thing. It all looks good and is set according to factory specs.  This seems like a vacuum leak of some sort.  The carb is sealed properly so I am thinking it may be the rubber throat that the carb attaches to and that is part of the intake manifold which attaches to the engine.  I have visualy inspected it and it appears ok, Maybe the intake manifold gasket is bad.  I will pull the manifold and probably replace the rubber mount, the band and the manifold gasket.  Does this sound like it could be the problem?

Posted
Ramy De Jesus
Yamaha Tech

Thank you for your response Tim. That is a big possibility also. If the manifold gasket is bad this could also affect the idle. Replace both gasket and the rubber mount and check if the same issue will still presist.

Posted
Customer

Thanks, this will take some time, can I still talk with you later?

Posted
Ramy De Jesus
Yamaha Tech

Absolutely! I will leave this page open and will wait for your next update. :)

Posted
Customer

Thanks, Ramy

Posted
Ramy De Jesus
Yamaha Tech

Alway welcome. I will wait for your next update then.

Posted
Ramy De Jesus
Yamaha Tech

Hi,

Just want to follow up with regards your issue. Please advise me if your issue is already resolve or you still need further assistance witht the problem. I will leave this page open and will wait for your response.

 

Regards,

Ramy De Jesus

Posted
Ramy De Jesus
Yamaha Tech

Hi TIm,

Trying to call you but there is no one answering. I just want to follow up if your issue is already resolve or you still need further assistance. I will be standing by for your response.

 

Regards,

Ramy De Jesus

Posted
Customer

Ramy, Thanks for hanging with me.  I have gone through the entire system. All seems fine.  I do have a question: there are two outlet tubes coming off the carb, one is the bowl overflow and the I do not know what the other  is.  It is located near the middlw of the carb, above the fuel inlet, is that a vacuum line or another overflow? if it is a vacuum, where does it connect to?   Still the same issue of not idling.

Posted
Ramy De Jesus
Yamaha Tech

Thank you for your response. I just like to know if yours have a knurled knob underneath the throttle cam the part the cables attach to. Please check the picture below for reference.

380a3aeb-cc03-49cb-9586-0e6b37adc8ca_zps

If yes, can you try to adjust this and see if this will hold up the idle of your motorcycle. Please advise me of what will be the result. I will be standing by.

Posted
Customer

are we still connected?

Posted
Ramy De Jesus
Yamaha Tech

Yes Tim. Have you check the knurled knob underneath the throttle cam the part the cables attach to. Do you have this on your motor. Here is the picture again for your reference.

380a3aeb-cc03-49cb-9586-0e6b37adc8ca_zps

Please keep me updated what will be the result.

Posted
Customer

Yes, throttle adjustment screw.  The idle is set at about 1600 or better because if the rpm drop below that the engine dies.  The engine is burning rich, stock jets, did not change them.

Posted
Ramy De Jesus
Yamaha Tech

I see. So when you adjust them still the same it will not idle and the engine burning rich?

Posted
Customer

The only "jet" adjustment is the fuel air  needle , it is set at 1 and 1/2 to 1 and 3/4, factory specs.  I cannot adjust this because I cannot get the motor to idle.  I have tried  different settings on this when the engine is at higher rpm and it has some effect but seems to run better in the 1and1/2 to 1 and3/4 area.  what is that second outlet from the carb,  toward the back of the carb, in the middle section, above and behind the fuel intake?

Posted
Ramy De Jesus
Yamaha Tech

Can you tell me if this helps. Check the carburator  diagram below. 

Image result for yamaha TT500 carburetor diagram

Posted
Customer

Ramy, what is an email address and I will send you a pic.  This diagram is not the same carb as mine, but the closest thing would be #9, where does it connect?

Posted
Ramy De Jesus
Yamaha Tech

You can post the picture here Tim so I can check it.

Posted
Ramy De Jesus
Yamaha Tech

Do you have the picture? If you can't post the picture here try sending it to my email r**s@gmail.com. I will check the picture there.

Posted
Customer

Ramy, did you get the pic?  Black tube is the fuel inlet, clear tube is the one I have a question about.

Posted
Ramy De Jesus
Yamaha Tech

Yes Tim I am looking at it right now.

Posted
Ramy De Jesus
Yamaha Tech

Dear Tim, It was a pleasure helping you with your Yamaha issue today. Here is a summary of the resolution.

Issue identified : Idle issue
Solution Implemented : Live chat. Advise to clean the carburetor and the replace both gasket and the rubber mount. Still the same. Provide picture for adjustment of idle but customer don't have the knurled knob underneath the throttle cam. Customer appreciate our assistance and knows that this motor is an old motor and customer accept the answer. Chat ended. Customer provided a tip.
If issue resurfaces : Advised to contact us at s**t@experthelp.com or call us on our support number ***-***-**** )

Posted
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