Doctor Dee,
The tube has got to come out i am afraid..... And for what it is worth, i would bin it and get a new one. Most tyre depots that do motorcycle tyres should have an inner tube to fit a 17" rim. 150x170x17 is not an unusual size ??
I doubt you will be able to do this successfully unless you have got a bead breaker to release the tyre from the rim. I have tried it with meaty tyre levers and got nowhere

It took two adult males jumping on a pice of 4x2 to break it.
Get the back wheel out and let them do it. For the tenner they will charge you it is a bargain !!!
PS. Even if it is only a small hole in the inner tube, be very wary about trying t patch it instead. For safety's sake go with a new one.
hope this helps ?