Honda GB400TT Special Edition ( circa mid eighties )

Discussion in 'Technical' started by finnomick, Aug 1, 2011.

  1. finnomick

    finnomick Ol'Timer

    I ( rightly or wrongly ) have just bought a mid eighties Honda GB ( yes, GB not CB ) 400 TT Special Edition. Story goes Honda produced this bike to commemorate the numerous wins at the Isle of man TT races. Can anyone point me in the right direction for original spares such as indicators, exhaust system and instrument housings. A workshop manual with a wiring diagram would be extremely useful. Also, does anyone know if this bike was based on a standard Honda model of the era. The engine is a 400cc twin. Thank you one and all for any information forthcoming.
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  3. DesmoNut

    DesmoNut Active Member

    Hi Finnomick.
    The GB400TT is a sleeved-down, Japan market version of the GB500TT which was on sale worldwide, I think. Certainly was in UK. In turn, the GB500TT was a tarted-up version of the XBR500. which was a reasonably popular bike although not as popular as many thought it might be given that it's a BIG SINGLE - yes, that's right, your bike is a single, not a twin although I can see where you were mislead since it has two exhausts.

    What I've got to say relates to the 500 but will apply equally to the 400. It is a 4-valve head but unlike most (all??) current 4-valve heads, it has radially-sited valves.

    The engine is dry sump with an oil tank behind the right-hand-side cover. The oil capacity is very low - I seem to remember about 1.2 litres - and the tank was prone to running dry because the engines were quite heavy oil consumers, even though they didn't leak oil. Make sure you keep an eye on the oil level and also check that, when the engines running, you can see a flow of oil back into the oil tank when you take off the filler cap. If oil flow falls off even for a short time, the top end is likely to be badly damaged.

    Performance was OK but mine was really a day-to-day hack. Very good for long-distance moderately fast trips, though.

    It might well have been made to commemorate TT wins but those wins almost certainly weren't by a bike using this engine. A nice machine nonetheless but no road scorcher. But it'll certainly be fun.

    Most engine spares will probably be the same as the XBR500 and the XBR workshop manual would be useful too, for maintenance procedures & electrical diagrams..


    XBR500 photo attached for comparison.
  4. David Learmonth

    David Learmonth Ol'Timer

    I'm impressed by your knowledge! I thought I was fairly well genned up on motorcycles - especially Hondas - but I'd never even heard of this beast!
  5. finnomick

    finnomick Ol'Timer

    Well DesmoNut, you certainly know your bikes. I am impressed. I've had bikes now for 42 years and I can't even scratch the surface when it comes to engineering. However, I DID notice the single spark plug and wondered how Honda managed to get this to fire off 2 cylinders! I sit corrected, thankyou. What now impresses me even more is how smooth the bike is. I've just sold a Kawasaki Estrella 250 single which really did thump. I bought the bike more for runs to classic bike events in and around Buriram where I live, so it'll not be for every day usage. It'll also spend a lot of time getting polished because it has a lot of aluminium -- thank God for Peak polish which I sneaked over from the UK. Thanks very much for all the information. I've now got a very good base from where to start. ( By the way, back I don't remember how many years, I had a Ducati 900 SS, the black and gold one with a half fairing. Now that did shift )!
  6. lotuseater

    lotuseater Ol'Timer

    Congratulations on your new purchase. I am sure you are going to love the bike, if you don't already.

    Yep, it is a single though I can see why you would think it is a twin. Coming from an Estrella, or if you have ever ridding another big single like the SR 400's you will notice a huge difference in terms of power and smoothness. The 400 was actually a special Japanese market only bike. The 500 that was sold in the States for only two years was a actually a sleeved down version of Honda's XL600 dirt bike engine which had already developed a reputation as being bullet proof when it went into this bike.

    I have always had my bike serviced by Burning in Chiang Mai which specializes in Japanese singles. Ill send you a private message with my contact info and I can send you the contact info for Burning, they have always been able to get spares and original parts for this bike, though it can be a bit slow as they have to order most things from Japan.

    Hope you are loving the bike. It sure is a beauty.
  7. finnomick

    finnomick Ol'Timer

    Hello Lotuseater, yes, I just had to buy this bike cos I had already fallen in love with it. The misses will testify to that because I spend more time polishing it than I do paying attention to her ( now ). She realises she has competition ! She also wishes she hadn't relented on the embargo she placed when I wanted to buy it originally. However, I feel an emptying of the wallet is in the offing -- maybe I'll buy her that Kawasaki 400cc Zephyr I've seen. HaHa. She is a good rider and disappeared on the Estrella several times. She says she'll not ride the Clubman -- we'll wait and see. Look forward to hearing from you regarding Burning. Thanks for your help.
  8. stubzi

    stubzi Ol'Timer

    Hi DesmoNut,
    Do you think this is a similar engine to the Japanese only CB400SS? The reason I am asking is I own a CB400SS and am having trouble finding technical information on the bike. I did manage to get hold of a parts catalogue however it is in Japanese!


  9. Eddie The Eagle

    Eddie The Eagle Ol'Timer

    I regret selling my GB500TT ... but I needed the space.

    Attached files [​IMG] [​IMG] [​IMG] [​IMG]

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