Hi, I have a tgb 125 bullet , it runs fine on flat or downhill but uphill it struggles and when I open the throttle it keeps coughing and looses power .

SOURCE: spluttering/backfires on low throttle opening/struggles to build

yes clean carbs, use Berrymans B12 fuel additive in the gas, double dose run til hot, then put it away overnight. try next day. also change fuel filter if it's been standing all winter long.

you can try spray in carb cleaner too, remove aircleaner, raise slider in carb with finger or something and spray a bunch in there, let it sit overnight to get to work and try next day

also if fuel is old then get fresh

SOURCE: I have a three year old Piaggio 50cc Zip scooter.

I have had the same problem with my stepsons zip 50 and have done all the usual checks. The solution is from a piaggio technition. Take off the air cleaner and housing, start the scooter and bring it to the point where the engine dies. At this point spray easy start or a gasoline spray direct down the carb intake. If the revs pick up, you have a lack of crank case compression and the most likely reason is worn oil seals on the crankshaft. It sounds odd but the worn seals cause all kinds of strange problems.
Thats 2 stokes for you. Hope it helps, good luck

SOURCE: suzuki gn 125 lacking power

I assume you dumped out the half pint of old gas and rinsed out the tank. Get a new spark plug and clean the air filter. Remove the carb and dis-assemble it then soak the parts in denatured alcohol for 30 minutes. Do not soak the rubber diaphragm. Finish the cleaning with a can of spray carb cleaner from the auto parts store. Be sure all internal fuel and air circuits are clear and that the diaphragm is not torn or has pin holes. The top cap must have a good seal. Go to www.babbittsonline.com/parts/viewbybrand/parts.aspx to see a diagram of the carb and the rest of the bike. It looks like they have lots of parts for your bike.

Testimonial: "GREAT HELP THANKS"

SOURCE: ttr 125 starts good but

Hello and welcome to FixYa!

Have you checked the vacuum lines? It can be a vacuum supply issue that's why it bogs down. You may want to replace soft vacuum hoses.
Hope this helps and thank you for using FixYa! Have a good one.

SOURCE: Peugeot vivacity runs and starts ok open throttle fully starts to loose power

I wrote all of this below and figured I'd come back up here and clearify...I think it sounds most like a carb issue...but I'm leaving everything else just so you have other things to check.

Sounds like it might be running over rich. Check your plugs to make sure one isn't fouled completely out. If they look good, check and make sure they are firing (you can pull one at a time and touch the threads to the outside of the engine block to ground it and crank it over...you should see it spark. If they are firing, check your filters (a blocked air filter can cause insufficient air flow and it would toss out until it could pull enough air in). Has the bike been sitting for a season or two with the same gas? If so, get rid of the gas in the tank...it's most likely turpentine now and would be better as a paint stripper then a combustion agent (yes...gas does spoil and depending on how well your tank is sealed...it can happen faster than that). Could also have some water in your tank. So if its been sitting, honestly longer than a month, I'd get rid of that the gas in the tank. From there check the carbs. You could have a float valve sticking or a bent needle. Last but not least...if you've done any major work to the engine...check your points or have someone check them for you. You could be off by just a degree or two and it will muck up everything. Hope this helps in some way and best of luck!