Can anyone tell me where the hose that comes from the bottom of the expansion tank on a mk 1 should go to. Have had overheating problem and just found this hose hanging down the front of bike and expansion tank empty. Cheers in anticipation

not having that hose connected will not cause your bike to overheat. Many people just take the expansion tank off. As long as you keep an eye on your coolant level via the rad cap then your fine.

sorry, did not explain myself, overheating is being caused by a fueling problem/ running lean i think, just found the hose while checking everything else and wondered where it should go to. bike has recently been re-bored and now overheats after a couple of minutes when riding then cuts out and will not restart for a couple of minutes. starts again after about 5 mins. Sits happily at idle all afternoon.

Air lock?, drain the system down, refill SLOWLY, squeezing the rad pipes as you fill the rads, start the bike with the cap off, refill as the level drops slightly.
Use a 50/50 mix of [ safe for aluminium] coolant.
Check the ally, matrix's are clear of debris.
The pipe is merely an overflow pipe, zip tie it to the main down tube of chassis.
It's worth checking for air leaks, as this will weaken your mixture.
Have oiled the air filter?
Put some clean sponge of any description in the air box, this will also richen the mixture, [ but this is only to verify that weak mixture is the issue], do not carry on using the bike with the sponge in the air box.
Mike

dont think pipe is an overflow as it comes from the bottem of the expansion tank and so anything i put in comes straight back out. Overflow pipe from top of tank is cliped to frame behind exhaust manifold.

The pipe from the bottom of the overflow tank should be connected to the top of the RHS rad by the cap.