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I hadn't used the bike for a few weeks but the last but one time i used her after about five min's she started to splutter, i thought she was low on gas so switched to reserve and i was only 200 yards from home, so next time i took her out i went straight to the petrol station to fill her up and low and behold only 3/4 empty so thought it must be the vent problem (but as i had just removed cap to fill up this should not be an issue)so went home and low and behold started spluttering within 500yards of petrol station, i've been rather busy the last few weeks so only had time to remove tank to make sure vent pipe not pinched and it wasn't, so any way i took her out this evening for a local run and low and behold after about five miles she started to splutter, if i keep her over 2,500 revs she runs better, just to make sure i took cap off just in case tank needed venting and still no better, i have read some threads about this tip over valve, am i right in believing it is on the tank venting pipe somewhere? or any other sugestions would be greatly appreciated. thanks in advance of any suggestions.
wayne

check the connections to the coils in the front, also be sure your battery connections are nice and clean and tight.

The tip over valve is in the vent tube clipped to the frame behind the carbs. Probably not the issue though.

If you took the fuel cap off you bypassed the tip over valve (it's in the vent line) so it's off to look at other options. After checking Pat's electrical pointers it wouldn't hurt to drain the float bowls into a small container where you could have a look-see for water or other alien material; that way you could also rule out a clogged petcock filter. And, you might as well have a look at the bowl vent line (runs from between the carbs to under the frame) and make certain it isn't clogged or the new home to some nesting insect.

What do you mean "sputtering?" Is it a hiccup, or a complete loss of power and then a quick surge, is there a backfire associated with the restart? I would definately look at the gas in the float bowls(which is super easy), but also, I would start looking for a vacuum leak. It is easy to find a leak with a can of ether or wd40 or some kind of flammable propellant sprayed near the bike when running. If your RPM's go up when spraying the solution, you definately have a leak somewhere...then starts the hunt! It sounds just like mine did one day home from work. I had a tiny tiny crack in a carb cap that would seal itself until warm then she leaked liked the exxon valdez. Changed her out, and no probs since...in that area anyway! Good luck, let us know what you find. Ride safe!

took the plugs out, they look fine, had a good look around carbs couldnt fine find any obvious probs, checked battery connections and connections on the coil and they all seemed fine, i have just left it running for about 20 mins, it did start to splutter (around 1000 to 1500 revs) but then seemed to fade away, i'm just going to put it back together and have a run around the block, see what happens?? will let you know, cheers for the tips.

well still the same, drained right side float chamber, petrol clean as a whisker, no muck or water. starts ok but lumpy up until 2/2.5k revs not sure what to try now, quess i'll have to put her into local triumph dealer and see if they can find anything? may try some petrol additive first and see if that does any good (seafoam not available in UK).

Try changing the spark plugs.
Aside: When she starts to sputter and cough, try pulling out the choke. If she runs better, then you have a fuel issue: Clogged jets, dirty hidden fuel filter or some such thang.

I THINK I WILL GET SOME NEW PLUGS (SHE CAN HAVE AN EARLY SERVICE) AND YES SHE DOES RUN BETTER WHEN I PULL CHOKE THE SAME IF I REV HER UP OVER 2.5K I'VE FOLLOWED THE FUEL LINE FROM PETCOCK TO CARBS AND I CAN'T SEE ANY FILTER

Fuel issues. To observe fuel flow, place a tube/hose on carb bowl nipple, place other end in a jar. Open bowl drain screw and observe fuel flow. Do this for both sides.

Methodical process of running down the problem. Remove petcock. Inspect, clean, reinstall. Remove and clean then replace the hidden filter. Find anything dirty/clogged yet? Yes? Then after cleaning it up try riding her again. No help? then on to dropping the carb bowls. Using a mirror inspect for debris clogging jets. No obvious material blocking jets? Drop jets. Blow out each jet. Do not use wire to clear out the jets.

How old is your sickle? Sometimes a very little bit of filth is all it takes to starve the jets. Given that she runs better at 2.5K rpms, it would appear that your pilot circuit is dirty. (usually throttle position is what counts not rpms. odd that one.) Pilot jets under the bowls and the air mixture screws outside the bowls. Do your research on this site for the components that comprise the air mixture assemblies. Place a towel on the top of your engine case to catch the tiny little o-ring , washer and spring that are part of that air mixture screw assembles.

If this fails, you may have to blow out the internal low speed circuits of each carb. Also you may want to check the float height. That same tube/hose you placed on the carb bowl nipple , if clear, can be used to do that.

Don't forget the hidden filter shown above can not be seen until you remove the gas line where it connects the to T between the carbs. Pull the line off that comes from the tank and look in the T. The filter above is shown after pulling it out of the T fitting.