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Amir Shemirani Posted on Sep 27, 2012
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Yamaha TW 125 Sputters and hesitates when Hot

Hi, I've got a 2004 TW 125 and it's been running OK when it's cold. as soon as I've been riding for about half an hour, it starts to sputter an hesitate on acceleration. when i accelerate really gently it's OKish. I've used fuel treatment to clean the carb and it's been recently serviced too. when i use high octane fuel (97) it runs so bad that is unusable. on 95 octane fuel it runs better but still sputters heavily when warm. I'd appreciate any advice.

  • Amir Shemirani Oct 16, 2012

    so had the carb stripped and there was no rust and everything was pretty clean. the correct spark plug is installed according to yamaha and I had the valve clearance adjusted too as yamaha told me this is sometimes the cause. rode fine the first day but it started to sputter again the next day after about 1 hour riding, although it's not as severe as it was before. Choke is not sticking neither. i'm at a loss now so might just buy another engine off ebay to solve it once and for all.

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1 Answer

Luke Farenden

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  • Expert 56 Answers
  • Posted on Sep 28, 2012
 Luke Farenden
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Well first thing i'd check is the choke isnt sticking on. if so the bikes running rich, hence the temperature.


if its got the paddle switch on the side of the carb, make sure its not turning on once you ride it, if its a cable check its retracting fully by lubing the cable.

and also Fuel treatment e.g. redex isnt a problem fixer, it helps do what it says but it cant beat a thorough strip down.

check your carb jets are clean theres no rust etc inside the float bowl, and make sure your running the right spark plug heat range, as if its too high a range that wont help either.

Testimonial: "ok will get the carb cleaned by a pro. as far as i can see the choke isn't sticking and the throttle retracts OK. will report back. many thanks"

5 Related Answers

Anonymous

  • 1 Answer
  • Posted on Dec 14, 2008

SOURCE: hesitation problems 2003 yamaha wr 450 f

sounds like a jetting issue. change the main jets starting from the largest one you own and work your way down.

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Anonymous

  • 2 Answers
  • Posted on May 23, 2009

SOURCE: Runs great when cold, hesitates when hot.

Hi mmagliozzi
I bought a cbr 600 fy new back in 2000. After about 3 years I've always had the same problem in summer when sitting in traffic, ie. anything that put the temperature up to about half way causing the fan to cut in. I thought it was a carb problem. also thought it could be the spark plug caps(coils built in breaking down only when warm).
Anyway, mine had become so bad recently that it had become almost unrideable as it kept cutting out and spluttering, only at tickover and low revs. Anything over 3000rpm it was fine. I thought it might be an electrical problem so put a meter across the battery. It was only showing 11.5v when running at tickover. Rev it up to 2000rpm it was showing about 12.5v. It should at this rpm show more. If you have the same problem you can rule out the alternator by taking the plug of the rectifier/regulator( under the seat cowling, you can access it by removing the seat) and putting the the leads of the meter across the yellow wires. test all 3 wires. ie if you were to number them 1, 2, 3 then test form 1 to 2, 2 to 3 then 1 to 3. You should get somewhere in the region of 20v at tickover and 50v at 5000rpm. If this figure varies by a large amount between each wire ( alternator winding) then the alternator is the likely problem. But i reckon it will be your regulator/rectifier. They are not cheap at £141 from honda. You can get them from ebay but the guy at honda (mechanic)reckons they are inferior and he has had to repair bikes with boiled batteries and burnt wiring looms. This maybe nonsense but I took the safe route. Whatever one you do decide to get(if it is the rectifier/regulator at fault) then make sure it is the cast ally heat sink type not the original one which has the gubbins incased in rubber.I reckon its a design fault with the originals hence the updated replacement which disippates the heat better.
Going back to diagnosing the problem. I found mine by running the bike stationary until the fan cut in, make sure your lights are on then operate the front or rear brake light. by doing this you are loading the electrical curcuit. When I did this my bike cut out straight away or very nearly did so. Yours might not if your battery is very good. If you notice it running worse then I would bet that you have the same problem.
Hope this helps.
Dan

Anonymous

  • 1 Answer
  • Posted on May 30, 2009

SOURCE: Strange thigs about YAMAHA TW 125

Hi
I have been working on my carb today,the pipe from the bottom of the carb should just run down by the bottom of the swinging arm,there should be another pipe from the pipe on the left side of the carb just above the fuel intake which also runs down to the swinging arm and connect to nothing.
Cheers

Anonymous

  • 6 Answers
  • Posted on Jan 07, 2010

SOURCE: Yamaha TW 200 cuts out at high rpm

I have a tw200 and when I have this problem its from the cam chain slipping back a notch when I unload it from my truck. I leave it in gear so when I let off the cluch it acts as a brake. I ride by my self so thats why I load it that way. I am guessing you load and unload your tw the same way. So remove the timing cover and make sure you are tdc on both the upper and lower timing marks. The bike will run if the timming is off a bit. It's really easy to set the timing on these bikes. It's easier to look for how to on the xt 200 if you need more help.

Anonymous

  • 425 Answers
  • Posted on Jan 19, 2010

SOURCE: Hesitates and backfires through the exaust when accelerating

Sounds as if your timing is not quite right. You need a manual, but The best I can offer is a 98: http://www.carlsalter.com/motorcycle-manuals.asp , it may help, but if you only have 1100 miles on it, I would be taking it to a qualified mechanic to be fixed. Up to you.

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Strange thigs about YAMAHA TW 125

Hi
I have been working on my carb today,the pipe from the bottom of the carb should just run down by the bottom of the swinging arm,there should be another pipe from the pipe on the left side of the carb just above the fuel intake which also runs down to the swinging arm and connect to nothing.
Cheers
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I have solved the problem myself by buying a workshop manual for the bike. A waste of money as the bike will be sold as soon as the problems are sorted. I only needed the valve clearances for it. Thanks for not helping at all.
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