Full throttle bog. By chucke (Read 563 times)

[chucke]

Hello everyone I'm ChuckE Chuck. I'm new to this forum and glad to be here. Okay before I get started I am aware that there is other threads that touch on this topic but seems like no cigar for me. My bike:  2013 Jonway yy250t. It fires up well and idles good between 1500-1800 rpm. Issue is if I full throttle from a standing still point (idle), it starts to bog and engine wants to cut-off. Also this sometimes happens when I ride for 30 mins or more at higher speeds like 45+(sometimes). No bogging if I easy on the throttle. I believe it is a carburetor setting related issue. Somethings I've replaced:  New carb, new mainifold and I replaced the air filter intake pipe with a new 42mm cone air filter. New carb has a main jet that read the number 108 on it and the other has 40 on it. Older carb has a main jet that reads the number 105 on it and other has 38 on it. I swapped both old jets to new carb (same issue). Also reinstalled the air filter intake pipe. I tried both stock and aftermarket filters and setting the carb needle on different positions. No luck. Now I currently have new carb with the jets that came with it (108,40) and the carb needle is set on 2nd notch from the top, and the fuel/air mixture screw is set at 1&1/4 counterclockwise. I've turned the fuel/air mixture screw in different directions with no luck. FYI the is NO room for the worlds smallest screw driver to turn this screw while carb is on bike and running. What I know so far besides the bogging is that there is no vacuum leaks anywhere, the exhaust smoke has no color and the spark plug looks clean (no black,white or grey color). What I have done so far is:  New stator and rectifier, new spark plug (I also swapped in old with no luck), new battery, new fuses, both new exhaust gaskets (no leaks at all), fresh oil in motor and trans,fresh coolant, new thermostat, water pump and cylinder head temperature sensor, new fuel filter and what you already know by now, new manifold (No air leaks) and new carb. One last thing, new carb is clean and float is set fine. Any help would do. Thanks in advance. PS. I've learned to work on this bike and others from this site and others (YouTube) thanks again.

Parts in question: 

CARBURETOR-

www.amazon.com/gp/product/B07776NM4L/ref=ppx_yo_dt_b_asin_title_o05_s00?ie=UTF8&psc=1

MAINIFOLD-

www.amazon.com/gp/product/B00Z0KQY50/ref=ppx_yo_dt_b_asin_title_o03_s00?ie=UTF8&psc=1

AIR FILTER-

www.amazon.com/gp/product/B00U5SOC74/ref=ppx_yo_dt_b_asin_title_o04_s00?ie=UTF8&psc=1

[kz1000st]

The fuel pump on these scooters is vacuum powered. A crimped vacuum line or bad pump could lead to your problem.

[chucke]

Thanks for the reply. I will check all vac lines and replace accordingly. Will update asap. Thanks again.

[cyborg]

Any progress ? Find the problem?

[chucke]

Not yet but I did replace the fuel pump (Petcock). Checked all vacuum lines and tuned the carburetor with the same results or worst. Seems like it is firing off wrong. Spark plug is good and no leak inside of spark plug hole, We tested it with compressed air. I believe it needs a new CDI. I've ordered a new CDI and will be here in a few days. Will post the results soon. Thank you guy. Peace.