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Author Topic: gtr125 carb setup  (Read 274 times)

steveadkins

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gtr125 carb setup
« on: October 07, 2018, 05:38:50 PM »

Hi I'm new to owning a 125 after 16 years of car ownership.
Ive been having a few issues with the running of the engine, its not pulling smoothly, wont idle lower than 5000rpm without prodding the throttle body on the carb, and when riding if I crank it right open it actually slows it down almost as if its flooding it.
Ive also found if I ride it through town slowly when I come to pull away at some pace it runs like a bag of nails as if its starved of fuel??

I wanted to see if there was any carb pros on here that could point me in the right direction before I have to pay somone to sort it out.
Other than this its a nice bike and I like riding it.
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Stag

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Re: gtr125 carb setup
« Reply #1 on: October 08, 2018, 01:12:35 AM »

On your carb, you will have two very thin pipes coming from the bottom of the carb, near from where they leave the carb is two screws. unscrew them and they will drain the carb. You might just have some water in there
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Joss

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Re: gtr125 carb setup
« Reply #2 on: October 08, 2018, 08:25:42 AM »

We can talk you through the carb setup if your happy to take them off and do the work. Everything you need is in the service manual also.
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steveadkins

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Re: gtr125 carb setup
« Reply #3 on: October 10, 2018, 08:05:09 PM »

Ive had a look, managed to drain the back carb but the screw on the front one is seized. I will have to get the carbs off and look at them tomorrow night.
Joss can you let me know what needs to be done.
once the engine is hot it wont idle any lower than 7k, and that causes everything to get crazy hot and start to miss fire when riding through traffic.
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Stag

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Re: gtr125 carb setup
« Reply #4 on: October 10, 2018, 10:43:50 PM »

I know it sounds silly, But have you turned down the idle screw ?
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Joss

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Re: gtr125 carb setup
« Reply #5 on: October 11, 2018, 08:25:32 AM »

Ive had a look, managed to drain the back carb but the screw on the front one is seized. I will have to get the carbs off and look at them tomorrow night.
Joss can you let me know what needs to be done.
once the engine is hot it wont idle any lower than 7k, and that causes everything to get crazy hot and start to miss fire when riding through traffic.

Yeah dismantle them and check they match the service manual, jet sizes both mains and pilots, float height should be 7mm. Check for any muck in there and clean them out thoroughly. I'd also look at diaphragms to see if they have any holes, check mixture screws for how many turns etc. Just give them a service, simple.
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steveadkins

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Re: gtr125 carb setup
« Reply #6 on: October 11, 2018, 07:28:11 PM »

I know it sounds silly, But have you turned down the idle screw ?
yes I have even taken it off

Joss have you a link to the service manual. All I can find is the owners manual that just says this is a carburettor and it puts fuel in the engine and leave it alone lol
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umop-ǝpisdn

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steveadkins

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Re: gtr125 carb setup
« Reply #8 on: October 17, 2018, 07:08:04 PM »

Thank you all for your help. I rebuilt them the other day, the carb that was on has a 87.5 jet in the front carb and 90 on the rear. I couldn't get this carb to run right so I cleaned and rebuilt the spare carb I was given when I brought the bike. That one has a 90 in the front and 92.5 in the back, it runs so much sweeter with that one on.
Any advise on this? Ive never looked into carb tuning like this before.
 
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umop-ǝpisdn

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Re: gtr125 carb setup
« Reply #9 on: October 18, 2018, 03:23:34 AM »

No advice here. Like you, I have never before explored carb tuning.

Enjoy the journey ;)
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