I seem to remember from my farm/tractor days a stem patch? You cut the old stem from the tube and applied the new stem in it's place using rubber cement. Pretty sure they had various styles (angles) and lengths too?
Might ask a Napa or TS store in agri-country?
EDIT - just did a quick search for "tube stem patch" and found this:http://www.gemplers.com/product/168047/ ... Valve-Stem
Good call, thanks for the advice. I think that is the long term solution.
In the short term, I just got back from the motorcycle shop. Here is some info for that guy who finds this post in a year and is looking at the same issue:
For motorcycle tubes with right angle valve stems (Tr78) there are three common sizes. The 8" and 10" are for scooters. The 15" is for Harleys and is not only huge in width, but the stem is too long before the bend (about as long as a standard motorcycle tube stem).
The 10" tube valve stem fits. You have to insert it with the stem pointing forward on the bike and then rotate it once you clear the hole.
So, I am going to try the 10" tube on a 14" rim and see what happens when I inflate it. For trials we run really low pressure so it might just work. The moment of truth will be when I inflate it high to set the bead.
If I pop the tube doing that then I will try using part of Ykick's advice and cut the stem from the blown 10" tube and glue it into the 14" tube. For longer term I will order up a stem patch kit. For right now I have a really tight deadline as we leave for the nationals on Wednesday and I really want my daughter to be able to use the new bike.
Sparky Bikes: Oset dealer stocking 12", 16" and 20" bikes. www.sparkybikes.com
Homebuilt e-trials motorcycle for my kid
Magic Pie II, Lyen Mark II 12 fet, 2.6kW, 60V, 40A, 15s2p lipos
14" rear 16" front motorcycle rims and tires