Arrived home from short ride out and she revved up for no appararent reason i immediately thought throttle stuck open but no, then quickly fiddled with cable at the carb but no, tried kill switch but no(even at idle would take a second or two to knock off need new switch perhaps) put into gear but just spun back wheel up ‘cos was on gravel so let front brake off and aimed for tree 2 yards in front phew that did it, now struggles to start sometimes gives a pop or a fart but no start and sometimes will run for a few seconds then if you give any throttle dies. I took carb off checked an cleaned it all ok taped up split hoses to airbox and inlet swapped plugs but still doing same, have i done any major damage? it probably all lasted for about 8 seconds

Btw it’s a ‘77 sherpa t 191 350

Sounds like an air leak somewhere. Check both of your carby rubbers. Carb to barrel and carb to airbox. Also make sure the intake hose clamps are both tight.

3 hours ago, Shonkers said:

 taped up split hoses to airbox and inlet

So the hose from the carb to barrel is split and you've taped it up? Yeah, that's your problem right there

Iv’e ordered new hoses from inmotion it’s funny ‘cos was running ok till the rev up maybe i shouldn’t hav taped it up

1 hour ago, Shonkers said:

Iv’e ordered new hoses from inmotion it’s funny ‘cos was running ok till the rev up maybe i shouldn’t hav taped it up

It could also be a crankshaft seal, if a new hose doesn't solve the problem.

 If it's the original carb thats been sucking dirty air through a torn hose it may need replacement, or at least a new slide.                                   b                               

Iv’e read somewhere else on here that  the rev up can happen with worn crank seals, i’m going to double check the carb ‘cos i did notice  the slide had a few scuffs on it but thought it was working ok, thanks for replies chaps

1 hour ago, Shonkers said:

Iv’e read somewhere else on here that  the rev up can happen with worn crank seals, i’m going to double check the carb ‘cos i did notice  the slide had a few scuffs on it but thought it was working ok, thanks for replies chaps

Your carb may well be less than 100%, but generally it's a slow lingering death.  I'd eliminate an air leak first.

Hi b4ort, it’s a dell’orto so not original i think everything on this bike has been suffering from a slow lingering death🥴 it was running ok with the air leaks ‘cos the mixture screw was 3 turns out  to compensate possibly, i would love to do a nut an bolt resto(maybe in my old age with one of the grandkids) but i just wanted something that worked to have a bit of fun on, anyway i go back to blighty ina few weeks and the parts are from inmotion so will bring them over with me next year, watch this space it’llbe a 1 year later thread ressurection😂 cheerz mdeerz

3 turns out is a lot (assuming the carb was set up for this bike) I'm a fan of Dellorto carbs, and generally they give few problems with basic maintenance. Just check it is a petrol screw (cylinder side of carb) or air screw( filter side of carb)