A challenge
I loved seeing your Honda GB500TT restoration article in issue 80 of Old Bike Australasia and, as a GB enthusiast, it is great to see somebody valuing and enjoying one. I have had eight GBs since my first GB400 in the 1980s and currently have two lovely of page 64. Yours looks like it still has the rivets for the stay but the stay itself has been removed, not unlike the mudguard on the US model although that was chromed or black and shorter. Yours also has the US-model decals on the side covers rather than the correct ones for a Japan/NZ bike. When yours left NZ, it was fitted with the dual-seat footrest brackets whereas it originally would have had a single-seat one on the left and no pillion footrest on the right where the muffler mounts. I have been known to cut the left one down although it is still not exactly like the original single unit, missing a small loop foot guard on the top of it. You have commented on the exhaust system on yours and others, none of which are original. The original mufflers are prone to internal rust on the baffles that show up externally as two ring bulges in the chrome and eventually rot through. I treat them with fish oil, refit them and take them for a ride to
cook the oil into a varnish. That will hold them for years. I have also obtained several good ones, including the headers/expansion box section, from a Japanese auction site although they tend to be GB400 ones which, while identical externally, have a different part number and are quieter with, presumably, more baffling. I have seen the four rivets at the back end drilled out to ease the baffling and the sound is improved considerably. Like a quiet Norton Manx. For the Japan market, 1,726 GB500s were manufactured, quite possibly all in 1985, according to dates on wheels, and sold there until around 1987. Honda in New Zealand managed to get hold of some and, according to our Transport Agency, 312 are currently registered here, which is quite a healthy proportion of those produced – and more to the point, those that are left. Around 2,000 more were manufactured in 1989/90 for the US market but, as you observe, they were not a success and around half of those ended up in Germany. I have heard two stories regarding that: the purchaser was a private individual as you state; and that it was actually Honda Germany. Those ones have an emissions cheating device that pumps air into the exhaust ports to help them pass emissions tests. Many owners remove them and blank off the holes into the ports. Honda records show that around 12,000 GB400s were produced in three models: naked with dual seat; the MkII with a half fairing and cowl on the single seat; and the Special Edition which is configured like the naked original with a two-tone tank, badges instead of decals on the tank and side covers and chromed mudguards. Interestingly, there are fewer GB400s in NZ than GB500s, but not by much. Other comments I have included: the XR engine the GB was derived from has a single carburettor whereas the XLs had two; the original tool kit has a device to fit to the oil tank drain so that it does not dribble down the frame; the carburettor can be removed without the strip down you describe but it is a fiddle; and pretty much all of the starter motor sprag clutches failed and most were replaced on warranty in NZ with a superseded part. The value of GB500s is on the rise. In the US, a nice one can fetch US$10k. In the UK, up to GBP6,500. And the Japanese dealers have woken up to them so that they are putting in high bids at the auctions and then doubling the price on their yard without even replacing the perished tyres etc. to the degree that to land one and get it legal in NZ would cost up to NZ$12k! On the other hand, with comparably so many in NZ, the market value here is still relatively low. I have attached images (left) of one of my GB500s, my GB400 MkII and a page from a Japanese magazine from way back with after-market accessories to make your GB look British. Mike Murphy New Zealand
Thanks for your in-depth information on the GB500/400. You may be correct about the front mudguard, but to me, it certainly looks better without the Swiss cheese bracket. The decals attached to our bike were manufactured in New Zealand and fitted there. I have seen numerous versions of these for various markets.