Hi Pie. You've got the honour of being our 100th forum member!
Glad to have you onboard. Pull up a zebra striped beanbag & make yourself at home.
If you can build a trike there's no reason why you can't narrow your own axle you know. Here's a reply I posted recently on the 100% Biker forum, (100-biker.co.uk), to that very same question:
I am a stoopid Monkey & know nuffink. Honest.
Step 1: Measure up your axle & decide how much you need to take out.
Step 2: If you've got any sense, forget it & bugger off to the pub. The propshaft's got 2 universal joints so will run at an angle of 30 degrees or so in any direction quite happily, though be careful if you're using suspension -all my trikes are hardtails. Makes life so much easier!
Step 3: Pull the drivehsaft out of the axle tube -easiest way is to leave the hub on & give the back of it a sharp crack with a lump of wood & a big ol' 'ammer.
Step 4: Drill out the 3 rivets holding the axle tube into the ally diff casing. The steel tubes are a sweated in fit, but it is possible to drive the tube out of the casing with a similar sized tubular drift & that hammer again. You risk cracking the casing though so much easier to take it to any competent car repair shop -is there such a thing? & give 'em a fiver to push the tube out with their hydraulic bench press, (like a glorified bottle jack in an upright framework).
Step 5: Note how far the tube goes into the casing, hacksaw off the required amount, (measure twice, offer it up, measure again, then go back & do it again just to make sure).
I think Reliant made their axles out of any old bit of scrap tube they found lying about cos very few of them are actually round. I was lucky with the Yam & it pushed straight back into the casing, but when I tried one last year I split the casing. Had to get a mate to put the cut-down tube in his lathe & spin it true for me -& find another casing. Replace the rivets with new bolts or rivets. If you use nuts & bolts make sure they're done up very tight. Use locking washers, threadlock & anything else you can think of cos you don't want a nut vibrating loose & bouncing around inside your axle!
Step 6: Cut the same amount out of the centre of the drive shaft -it's splined on the diff end & tapered on the wheel end so cut it in the middle. It's hardened steel so your B & Q hacksaw will just bounce off it. Use an angle grinder. Accuracy is nice but you've got a little bit of room for error cos the splined end which pushes into the diff gears can be moved in or out a little to compensate. Persuade someone with a lathe to machine you a mild steel sleeve, 2 if you're narrowing both sides -tubes of 4 or 5mm wall thickness that are a snug fit over the cut shaft, at least 2 or 3 inches long -the longer it is the greater your chances of the drive shaft running true afterwards.
Step 7: Slide the sleeve an equal distance over the cut ends & butt them together inside it. Get a competent welder to weld around the ends of the sleeves. When it's cooled down -hot welded steel STINGS! roll it along a surface you know is flat to check it's running true. If not, exchange words with your welder.
Some people leave it at that, but for extra peace of mind I drill both ends of the sleeve, all the way through sleeve & shaft & out the other side, drive in a steel pin, cut it off flush & weld over the ends.
Or forget it & go down the pub.
Obviously the sleeves have to be a small enough diameter to clear the inside of the axle tube & obviously you need to check the direction of rotation of your propshaft if you're only narrowing one side, but XS750 Yams definitely need you to flip the axle over before you start. Not difficult, just take your time, think about what you're doing & double check all your measurements. If you're not sure of your welding capabilities get a qualified guy to do it for you & ask a responsible adult to do the cutting.
__________________
http://www.mankymonkeymotors.co.uk --------------------------------------------------------------------------------
