Fuel problem??

I did a relatively long journey yesterday of 30 miles and after about 15 the bike would idle but when I pulled the throttle it would cut out. It was also the case that I would pull up to traffic lights after a few miles flat out and it would stall as I put it into first to pull away. Is this a fuel issue? Do I just need to adjust the carb float or is it likely to be something else? Maybe something overheating?

Ive had this with mine check the on/off on fuel cap and see if it runs better with cap off, i drilled my cap with a very small drill and bobs your uncle lee

Thanks for the responses Lee, didn't think to check the fuel cap. Will do so tomorrow, I like the idea of drilling it a small amount to. Ben

Lee is right.
It could be either the fuel cap, or dirt in the carb / fuel lines.

Lifted the seat to see the fuel cap hole was shut. I have the problem of sometimes closing it when I put the cap back on after filling up. Opened it and didn't have any problems on my journey to work this morning Thanks for the help guys.

So today I did the first long Rubin my bike since checking the fuel cap ( I drilled a small hole as suggested to) and the problem returned. It only happens once the engine is hot after about 30 mins of riding. The bike starts to stutter and I have to reduce the throttle to stop it. If I try and give it full throttle it pops loudly before not responding. If I pull over and turn the engine off for 5 I can then go for another 10 or so mins vefor it happens again.

I have tried various positions on the carb needle but this doesn't make a difference.

I have a non standard exhaust and cheap k&n style air filter but other than that all is standard.

Spark or fuel?? sounds like spark to me!! have you changed you condenser can break down when hot,

Have you sorted the problem?? i had exactly the same issue,after changing the coil,cleaning the carb,fitting fuel filters,checking the points,PROBLEM STILL EXISTS !! :?:have you changed the condenser? i am reluctant as you have to re-set the timing ? i think? also need special tools ?

Hi arny,

I have purchased a new condenser to change sometime in the next few weeks, however I have a spare flywheel on another 6v st70 engine I have (and was running fine) so am going to pop this in as it will be easier and see if the problem still exists. I fear the problem is getting worse as the bike is starting to stutter a little even on short runs. I know the carb is clean as I clean it every few months and I have a few inline fuel filters and they do a good job and the fuel lines run good.

I can't see that you would need to reset the timing when changing the condenser, however this really isnt as conplicated as you would thing anyway. I was wondering if it could be the coil, but you have changed yours and still have the same problem, which seems to rule that out.

I will change the flywheel over within the next week or so and get back to you.

Let me know if you find a solution other than this.

Cheers
Ben

Also, by special tools do you mean a flywheel puller or is there more I will need to change the condenser???

Is the condensor soldered on??