Dirtbike problems, Can U Fiqure It Out.

Ok bought a bike off a mate today because he needed the cash urgantly for his daughters wedding. ok well this arvo it was all fine toook it down to the track and did a few laps in it.. now im faced with a problem here are the details, see if you can fiqure out whats going wrong.

Dont want this to sound mean.. but if you dont know what ur talkin about or never been on a bike before please dont offer a "wannabe professional" opinion

Bike: (import) Yamoto 300cc
ODO: 480km (brand new)

all afternoon it was runnin fine till 1 lap on the track i think i may of thrown something internally when in gear and under load (riding) it will choke at 4000rpm (cough & splutter) ive tried illiminating things

1: In nuetral it will rev to whatever RPM like its suppose to
2: In gear with the clutch in & reved over 4Krpm, its ok too
3: When riding, each gear 1/2/3/4/5 it will choke at 4Krpm
4: Chocked on blocks it will run fine in each gear without choking/coughing/spluttering

ive drained the fuel & flushed the fuel lines.. carby is clean.

ok.. so lets see what you can come up with.. i dont really want to pull it apart as im going to be reselling it to get my cash back but i cant sell it in this condition. (liek i said my mate needed the cash):bang:

I have a '05 KTM 600 & previously '03 YZ250. Ive never seen this problem before. Fawkin jap-kr@p Yamoto

 

Dutchy yeah, seems fine up till 4000, soon as i hit somewhere like 3900rpm and change up its ok, then once in 5th and hit somewhere about 4000rpm again it will choke. had it up to 120km/h, so it should boot. now with this problem im only hitting 60 in 5th when changing at 4krpm

 

Spanners:
Air Cooled, 4 stroke SOHC
http://backend.ewock.com/ewocksql3/...&IDCat=2523&ID=868&Action=SubPage&IDPage=7723

dutchy will have a look tomorrow with more light & once its cold. unlike the KTM and Yamaha this looks like it cant be rebuilt easily in half hour.

 

yeah, ran fine on the track/trail till it just died as if it ran out of fuel.. checked my fuel tank and it was 3/4 full, restarted it no problems and rode it home slowly, called it a #%#@ing #%@^ and jumped on my other bike n went back to the track. used the same fuel which i use in my other bikes & car filtered unleaded.

 

Fixed! pulled half the plastics off and cleaned every intake and filter, pulled the spark plug out, looked clean, but of crup on points though, gave it a light scrub wit sandpaper & compressed air. took it for a strap n its kickin even better now. thanks again guys