hello can you help,just bought a yamaha at3e,original bike came from america in 2013,just turned 930 original miles,only had it 5 weeks or so,when first got it ,it ran well since then had problems starting,strpped carb down twice,starts after strip down then stops again,put in;in fuel filer on,dosent seem to make any difference,getting good spark and fuel to carb but still reluctant to start ?

You’ve come to the right place. Couple things to start you off. You’ve got good spark. Good. Is it at the right time? Is timing verified?
Is the spark plug getting wet when you try to start it? This could mean its getting flooded. Dry it out. In the warm weather,I’ve found mine starts most of the time right away with no choke, no throttle. Sometimes need a blip or two as soon as it starts. Go brought the basics again and I think you’ll find you’re problem. Better minds with more literate fingers will be along to help you more. Good luck!

Is the tiny jet in the float bowl clear?

Is the float valve sticking?

Is the petrol tank venting ok?

Oh, and   from the Dorset/Wiltshire border!

Welcome. I guess it's electric start not kick only like my earlier model.
So are you getting the choke wrong & running with it on choke.
Try electric starting it on a wide open throttle & 'no choke' just to experiment. Should get a result after 5-10 seconds.
If not then try choke operating & throttle fully closed & if it starts then let it settle & ritchen up before setting choke to off--normal running.
Not easy to offer useful advice without being there.
Carb will have a small Oring sealing the bowl onto the needle jet so the side mounted bowl main jet does its thing correctly.
That Oring is important--but would still start & just run very rich depending how bad its leaking.
Possibly not 'that' at your mileage but then again, it's 50 years old.

Greetings from Tennessee  
 beautiful bike I like that Blue color 

I will always have a soft spot for the 73 DT125.
It was the first bike I ever owned and learned to ride on with my Dad. I was 12 and I could only reach the floor on tiptoes.
It had a horrible stars n stripes paintjob on the tank very easyrider- esq.

Underneath that paint, the blue was like yours, maybe a bit more turquoise. Lucky the top layers came of easily as they had been painted over the wax polish on the tank.

thanks for your suggestions,much appreciated,my bike seems to run beautifull for say two rides out around the country roads of norfolk,then for some reason tends to die the death as if fuel starvation,switch ro reserve,still very difficult to start,if my problem was a timing fault,would i have the starting problem all the time ?

thanks for your time,dont think its the float or the small jet as ive stripped the carb down twice now,all clean in there,you might have struck a cord with the venting though,ive noticed i seem to the problem when the fuel is on the low side,never when tank is full,thanks ill look at that

Is your fuel tank clean inside? Make sure the float level is correct. When you went through the carb, did you replace any of the brass parts? Aftermarket carb kits do not have the correct jets, needles etc. Also make sure your battery is in good condition.

thanks for sugetions,choke on my carb dosent stay on unless you hold it out manually,use to start first time with choke on then straight of when engine running,its baffling me as i strpped the carb down last week as it wouldnt start,after that ran lovely for two rides out,got bike out two days later after being stood in shed got all me gear on,then wouldnt start again baffling.