Same problem with my 89 Tenere its all down to a sticking float needle, got it out the dark recess of the garage today, drained the float bowl with the fuel tap off, then turned on the fuel with the drain open, zilch fuel flow, quick blast of carb cleaner into the float bowl , remove fuel pipe from tap and a good blow job reconnect pipe turn on tap bingo fuel! turn on ignition press button bump bump bump spent the rest of the day cleaning it

Bump on this? I have been starting on only the left tap and it seems to start much better?? Any ideas? I don't use the right tap now... should I be?

You're supposed to use both taps in the same position.
It could be your fuel pump isnt working properly and letting fuel past and flooding the carb when you have both open? I know mine does that,which is probably the reason it's a bitch to start when it's been ridden for a while.

Try and start it on just left tap, it works for me, then switch on both, my bike seems to work ok just on one tap, don't know why.....

Well, there could be a lot of reasons. This may or may not be one but give it a try, it will cost you nothing.
What I have found on my 3AJ is that after rebuilding the bike and replacing the fuel hoses the bike started having these exact symptoms.
It's why I put a kickstart on her.
Turns out the hoses were marginally longer than the originals and had a slight rise at one point that trapped a gas bubble which would form if I parked the bike for any length of time.
I struggled enormously with the bike until one day after having had the tyres changed and embarrassing myself in the tyre shop sweating like a pig unable to start the bike, this old mechanic shambles over and starts fondling the fuel lines with little squeezes and pinches. She fired right up. The old boy said; sort the fuel pipes out, and if neccessary drain the petrol tank and remove and clean the filters on the end of the petcocks too.
Which I did (make sure you have replacement petcock gasket if you do this tho!!!). Turns out the flow of fuel is not great enough to shift a bubble until you try something like draining the carb. It's not the carb that needs draining, it's a greater fuel flow to shift the airlock. I felt such an idiot that such a small thing could have been overlooked and even worse simply missed but there you go.

The result is now my bike will start first time everytime even after a winter in the garage. Fuel going off in the carb??? After several months maybe, but tbh, where as fuel does loose it's volatility this is invoked to quickly and sounds more like a move of desperation to me.

Thanks mate, will give that a try.....

I'm having issues when starting my bike from cold, especially when it's leaning on the kickstand. I found out yesterday that by leaning it to the right it actually stays running and it runs well. If I lean it back to the left when it's still cold it will start to cut out and want to die.

This is only when the bike is cold. Once warmed up it runs great without any issues even if it's leaned left or right.

Anyone have an idea why this is happening? The fuel line is fine, no air bubbles and, like I said, the bike runs great when it's warm.

Thanks

have you checked your float level is correct?

Last time I checked it (about a month and a half ago) it was ok... Towards the low end of the spec. Maybe I should adjust it so it's on the higher end of the spec?

When you check you float level it is recommended that you do it with the carb full assebled using the silicon tube connected to the tit on the carb sump bowl and bent back up with the drain screw fully open; rather than a manual check with the bowl off and the carb inverted as the specific densities of the floats can vary and hence how high they will ride above the fuel line. It sounds suspiciously here that one of the floats has some fuel ingress raising it's specific density allowing for a change in the level that it will float compared to it's twin. Hence why you may find a higher float level on one side when you lean compared to the other. With the carb off and the catb level check the float level. Then lean the carb one way and check the float level. Then lean the other way and check the float level. If all three are not the same, change the floats.

Fuel mixture is more critical when the engine is cold. This is exacerbated when the vaporised fuel starts to condence before the ignition sequence.