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Honda GB500 thread

Discussion in 'Old's Cool' started by Spurlock, Aug 27, 2016.

  1. XRLated

    XRLated Long timer Supporter

    Joined:
    May 6, 2017
    Oddometer:
    1,001
    This may be a particularly solitary obsession of mine, but I believe I've determined the model GB with the sweet aluminum fuse cover:

    20200513_151830-1.jpg

    Here is the link:

    http://suprememotos.com/honda/48996-1988-honda-gb400-tt-039special-edition039.html

    Here is the bike:

    1988-honda-gb400-tt-039special-edition039-7.JPG

    1988-honda-gb400-tt-039special-edition039-5.JPG

    1988 Honda GB400 TT 'Special Edition'

    This makes sense, as Honda also splurged a bit on the fancy metal badges on the tank and side covers...

    Screenshot_20200909-193557_1.png

    ...and chrome front fender:

    1988-honda-gb400-tt-039special-edition039-6.JPG

    AnNoGBer and anyone else, please weigh in, correcting and filling in any blanks, but, since this model appears to have only been sold in Japan (right?) I can't find an OEM parts fiche on any USA websites or CMSNL. Not sure if it is possible to track down a parts fiche for this version in order to know the OEM part #.

    These aluminum fuse covers have proved to be pretty rare in my experience--nearly every cover I've happened upon these past many months is the standard plastic supplied with all the other model GBs and XBRs--but the aluminium versions do sometimes turn up: I myself have acquired two of these aluminum versions, now on the shelf ready to go onto GB1 and GB2 when the time comes.

    What got me back on this track is I stumbled on a pretty corroded speedo on Yahoo auctions at a ~$75 price that also included the fuse panel and a scruffy silverish ignition cover--either a bad paint job on plastic or an aluminium cover with a sad life story:

    i-img1200x900-1599357616mnbadm3214388.jpg

    I asked which, and the sellers says it's the latter.

    If anyone is willing to pay to buy the entire speedo assembly including fees and international ship charges, and then expend the elbow grease in order to bring the finish on this one back to its shiny glory, PM me and I'll give you the link. Caveat emptor of course--I'm only going by the pictures and the seller's assertions that it is indeed the aluminium version.

    Likewise, If anyone wants me to keep my eye out for one of these aluminum covers in better condition or cheaper (as well as look for any other parts you are needing) as I scour the web for GB parts for my GB1 & GB2, PM me and I'll keep an eye out.
  2. AnNoGBer

    AnNoGBer 89 GB500, 85 VF750S, 84 V65 Sabre, 85 V65 Sabre

    Joined:
    Oct 23, 2016
    Oddometer:
    154
    #XRLated Hey, I just take a nerdish interest in logistics in general and acknowledge the value of factory documentation of all sorts, thx for the trust anyway. Re the alu fuse box cover, I would ask owners of the more common silverblue GB400TT Spec. Ed. to verify their cover's execution. The '87 parts list at CMS NL suggest the part being common to both paint schemes:

    https://www.cmsnl.com/products/coverfuse-box_38210kn8730/#.X1xyFHp5Pag

    or look up the 32810KN8730 if link does not work, CMS NL tend to change the suffix, it seems.

    Looks like painted, however, I would not trust their picture alone given they show a black fuse cover of the other GBs and XBRs (and CB350/450S et al), the 32810MK4 variant...

    Will check the paper GB TT fiche later on, but afaIr it covers both paint schemes of the "'87 GB400TT Spec. Ed./H3" If a specific '88/J model existed, I never saw a parts list covering it, maybe a brochure issued in '88 acc its numbering, will check my copy later.

    The vintage of the linked GB would be documented by the frame and engine nos in this style of Honda numbering, the 2nd digit after the dash being one higher than that of the '87 model listed in the parts list table. (1st digit typically being 1 for JP home market (maybe all of Asia) like 2 for EU/UK/AUS/ZA/USA/CAN etc. the last 5 digits constituting the serial).
    XRLated likes this.
  3. Chankly Bore

    Chankly Bore Been here awhile

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    Victoria, Australia
    I think the part no. may be 38210-KN8-730. It is listed for the Special Edition only.
    XRLated likes this.
  4. AnNoGBer

    AnNoGBer 89 GB500, 85 VF750S, 84 V65 Sabre, 85 V65 Sabre

    Joined:
    Oct 23, 2016
    Oddometer:
    154
    Indeed, the JP paper parts list version 4 confirms the Spec. Ed. fuse box had that part no.

    As to the vintage, I have found:

    * the above part list mentions two colour schemes for the Spec. Ed., NH-132-H Max silver and NH-167-E Iron nail silver of which the latter has got to be the brass-silverish colour in the linked bike, like here at Tachi's GB TT site:

    http://tachik.web.fc2.com/images/bike/catalog/GB400SECATALOG06.jpg

    where as the former colour appears more like the silver of the ancient Hondas. Dunno.

    * Honda introduced the '87 GB400Tt Spec. Ed. in a press release in June '87 showing only the blue-silver version and issued a brochure for that in July afaIcs
    * Honda apparently issued no press release for the brass-silver version alas a brochure of, apparently June '88. Tachi mention brochure as an '88:

    http://tachik.web.fc2.com/bike/catalog.html

    As to the frame and engine numbering, Honda did not follow its usual scheme as mentioned above but kept the 2nd digit 0 as the '85 GB TTs and instead changed the 3rd digit following the dash, the digit normally representing 10s of thousands, to 1. They also only mentioned an expected sales of 2,000 unit in the release press release. And acc the parts list only made some 1,200 bikes of that model.

    This side of a newer version of the JP parts list, I tend to hold both Spec. Ed. colour scheme-versiosn for -87/H partswise.

    Again, it would be interesting if owners of the blue-silver Spec. Ed. (fully sure of its original condition) would confirm the fuse cover being of aluminum ;-)
    XRLated and Chankly Bore like this.
  5. Aah5

    Aah5 russ

    Joined:
    Feb 28, 2009
    Oddometer:
    80
    Location:
    Brisbane,Australia
    Fuse cover on my blue/silver is black plastic
    AnNoGBer and XRLated like this.
  6. Wumpletoad

    Wumpletoad Adventurer

    Joined:
    Nov 22, 2019
    Oddometer:
    75
    Location:
    Devonshire
    Oil is a perennial subject. Comments about lack of specific bearing materials have prompted me to write.

    Engines like the GB/XB have quite specific demands of the lubricant and as the camshaft middle bearing, being the only one of its type in the engine, appears to demonstrate, is not tolerant of deficiencies in this regard. As Charlie (and Phil Irving) have observed, too thick a viscosity is more damaging than having the oil too thin. Plain bearings operate with a continuous film of oil separating the static/dynamic components; the flow of lubricant "washes" the surfaces, carrying away small solids and, more particularly, heat. This type of bearing frequently exceeds 200,000 miles in properly maintained car engines. Our Honda units have quite good filtration systems, so solid material should get filtered out of the loop, particularly with detergent oils. Provided a good flow can be maintained, the camshaft centre bearing (which is of decent proportions) should not give any problems and I share Bill's doubt that it carries any substantial radial loading.

    Running this type of journal bearing without white metal or similar substances is not new; I well remember the post-War Watson/Bentley-designed engine for Lagonda having camshafts running directly in the parent material of the iron head. It never gave any trouble, other than in the circumstances mentioned by Bill. Nevertheless, regular oil changes remain vitally important, not just because of cleanliness considerations but also for other reasons.

    Modern multi-grade oils primarily are formulated to meet the requirements, inter alia, of plain bearings. In this regard they function very well but their long-chain plasticisers and modifiers used to vary the viscosity as a function of temperature, are damaged by the shearing forces generated by the very high line and point contact loads imposed by the rolling element bearings common in motorcycles. This causes the viscosity characteristics to change during the service cycle of the oil which will gradually revert to its base monograde. Thus it needs changing at regular intervals.

    Combustion of 3,8 litres (1 US gallon) of petrol will produce roughly 4 grams of water. Given the hygroscopic properties of mineral oils, it is evident that water contamination of the engine oil can happen fairly quickly. The GB/XB engine runs quite hot by design and this is helpful as it promotes oil temperatures in the region of 230C which will allow water and sulphur derivatives to be boiled off into atmosphere. It is for this reason that unless I can cover 20 miles per trip to guarantee an acceptable engine temperature for a reasonable period of time, I'll use a bike other than the Honda.
    I change the oil and filter at 2,000 mile intervals and replace with good quality 20W/50, medium detergent semi-synthetic. This seems to work with my 32,000 mile engine.

    A bit long-winded but I hope of some interest.
    Chankly Bore and XRLated like this.
  7. AnNoGBer

    AnNoGBer 89 GB500, 85 VF750S, 84 V65 Sabre, 85 V65 Sabre

    Joined:
    Oct 23, 2016
    Oddometer:
    154
  8. schnicks

    schnicks Adventurer

    Joined:
    Nov 29, 2019
    Oddometer:
    28
    Location:
    EU

    Here are some pics from a worn out head:

    DSC00480.JPG
    DSC00483.JPG
    DSC00486.JPG
    DSC00489.JPG

    A pre owner installed the filter incorrectly, the filtercase cracked and the lubrication to the cylinderhead was cut off.

    Regards
    Kurt
  9. Spurlock

    Spurlock Long timer

    Joined:
    May 5, 2015
    Oddometer:
    1,996
    Location:
    Vacaville, N. California
    Member Chankly Bore (Charlie) sent me the following contribution to post here. It fits with the nostalgic era that the GB500 attempts to evoke. I hope everyone enjoys it as much as I have, it's pure gold!

    -Bill

    ************
    MICK

    I am reminded as I start this of the dictum “let fiction please be near the truth”. Mick never existed as one person, but he is the motley that clothed my youth, cheerfully enmeshed with drugs of a harmless nature, beer, Drambuie, the occasional cigar and the limitless exploration of complex hydrocarbons married to decrepit British motorcycles.

    I first met Mick at Merton, a small stop for food and petrol on the way to the motorcycle races at Winton. It was a cold windy day late in May and I stopped for a couple of very deeply tanned dim-sims, petrol and a leak. As I rounded the corner into the toilet a strange vision greeted me. A fairly beefy gentleman was standing on an upturned milk crate with his Belstaff trousers bridging his knees. He had the electric hand dryer angled down to waft over his ghoolies, and a fairly manly fog clouded his upper body. He was singing “The Last Rose of Summer” in a piercing bog-Irish tenor. Being a singer myself, this interested me strongly. I stopped, as I thought silently, to memorise and reflect inwardly on the scene. Mick, however, must have heard my approach, for without turning he observed, “Isn't it odd that no matter what yer ridin', where the wind is from and where yer goin' the feckin' rain always seeks to congregate in yer soddin' privates?” I muttered a gentle assent to this observation and left him to steam whilst I filled the Comet with overpriced fuel. As it turned out Mick was riding an S2 Kawasaki triple which he'd parked around the far side of the building so we travelled together on the beautiful narrow road to Euroa then on to Winton.

    This road we rode on deserves a thorough description. As far as I know I have not a trace of Aboriginal Australian blood, though my mother's line is decidedly native Briton- rural Welsh for at least three hundred years on her father's side. That being said, this, and one other stretch of road in East Gippsland entwines about me a feeling of native country like no other landscape. The road is narrow, but with a good bitumen surface and it winds through beautiful fragrant bush for about five miles before opening out to patchy small farms and a creek on the right hand near where the Gooram Falls reserve is sited. Huge grey granitic boulders then appear on the left, stained with orange and brown lichen. They don't frown exactly, but rather appear indifferent and perplexed by far older problems than are set by our insignificant passing. The only problems that engage the two of us are the Toyota Land Cruiser types that are as wide as the road, and don't expect to share it. I always travelled this road when visiting my uncle Dai in Euroa or on any other occasion when I want to avoid the nastiness of a 70 m.p.h. truck up my clacker on the major vaguely northern road from Melbourne, the Hume Freeway. I remember one other such journey of a sadder nature. My eldest brother Les. was in Albury Base Hospital after a bowel resection due to stomach cancer. He was a timber getter most of his life and had the high cigarette and booze consumption common to that hard, risky and solitary trade. I arrived there on perhaps the best bike I ever owned, a Vincent Touring Rapide. I came into his room and he was propped up in bed.

    “How are the stitches holding, sport?” I enquired.

    “All right,” came the reply.

    “What's the worst thing about a colostomy bag?” I asked.

    “I dunno mate,” he replied.

    “Finding the shoes to match!” I then bade him a fond farewell and rode back to Melbourne. If this interchange seems callous and inconsiderate you just needed to know Les as I did. I had no father around as a child, and Les's infrequent descents on our suburban poverty, usually scrounging truck parts for repairs or visiting to Cameron's, the Kenworth agent in Doncaster were the stuff of excitement and wonder. Although he cultivated the image of the tough and taciturn “bushie” I can remember him in helpless tears of laughter listening to Spike Jones and his City Slickers on our Astor radiogram.

    I can't remember much about that particular Winton meeting. In those days the facilities were primitive, the only colour for leathers was black and you still saw a few wonderful old gaspers like Manx Nortons, 7R A.J.'s and even the occasional cammy Velocette. I always made an effort to get to Winton meetings because being so far from Melbourne only the dedicated and diehard types considered the journey worthwhile. I have a recollection of later meetings, seeing Mike Hailwood pilot Charlie Edmonds' Manx around. The lasting impression was his strength and accuracy. Coming up to the START/ FINISH line there is a tight left/ right bend in the course. All the other riders could be seen wrenching their machines from one approximate angle to the other through there; but it would have taken a camera with a very fast shutter speed to detect Hailwood at anything between the two angles of maximum lean needed to negotiate the line. All done without apparent effort, and no movement in the seat from him either. On another occasion I was a flag marshal on the long sweeping left- hander during a sidecar race. One of the machines overcooked the corner and went shooting off into the track centre were there was very tall weed growth and pooled water. The effect of a hot engine meeting this combination was an immense cloud of very theatrical steam. Pilot and passenger emerged very grubby, but unscathed.

    Mick and I would sometimes meet by chance on a Saturday morning in Elizabeth Street. This was where the motorcycle trades were, and still are, largely concentrated. On the eastern side was Mota-Bitz and Modak, Stanco and possibly a shop where you could get sprockets re-toothed, my memory is unclear on this. On the western side was the B.M.W. dealership whose denizens regarded the other side of the tracks with contempt. I still recall seeing one young B.M.W. rider in white one-piece leathers, in those times evidence of ambivalent, if not degenerate sexuality. If he had crossed the street he would have been roughly handled at least. Around the corner in Little Lonsdale was a holy site, Vic. Bogner's painting shop. One entered to the sound of an asthmatic one lung compressor thudding away in a dark corner and usually Vic, equally asthmatic, would emerge from the same
    gloom. He was the human equivalent of Moley from “The Wind In the Willows”. His spectacles were flecked with a prismatic array of colours, as were those vertical surfaces you could see. Work, including beautifully pin-striped bicycle frames and British motorcycle tanks lay awaiting collection, all faultless. A couple of memories survive , and here I beg the indulgence of the modern reader. I once spotted the major parts of a Vincent “Rapide” done in an eye-gouging metalflake blue. I made some casual remark on the venturesome finish and Vic's reply, verbatim was “last bloody metalflake job I'll do, Razor (his nickname for me), the jigger will look like a Poofter Gypsy's caravan!” On another occasion I had a tank- slapper on my Comet, which I'll describe in a later episode. I brought a badly deformed headlight shell to Vic and nervously asked if there was any possibility of it being repaired. “Jesus, Razor”, he replied, “I could beat that out with me old feller.”
  10. ItalJap

    ItalJap Adventurer

    Joined:
    Feb 1, 2020
    Oddometer:
    31
    Location:
    The Netherlands (Europe)
    Regarding the camshaft centre bearing, I feel it takes a fair share of the cam loads, especially from the right inlet & the left exhaust lift forces:
    CAM4.png
    The diagram is proportional to Kurt's (head cover) picture.
    I will not try to estimate the bearing reactions, as these are (apart from the distances) no doubt depending on camshaft flex and bearing play.
    But it's noteworthy to see the lower half being damaged and the upper half intact.
    I then became inspired by the reports of a Dutch bloke who (becoming fed-up with cam bearing failure & having the skills) modified a XR500L head (which has a very short camshaft, 2 cams only) to all-bronze bearings, apparently successful; he stopped reporting after a few thousand km's without trouble.

    More or less in his way, it would be possible to machine a welded head with a cutter bar in (precision roller) bearings, carrying a sprocket and mounted like the camshaft.
    That is, if one has the skills and the resources...
    AnNoGBer, Wumpletoad and XRLated like this.
  11. Wumpletoad

    Wumpletoad Adventurer

    Joined:
    Nov 22, 2019
    Oddometer:
    75
    Location:
    Devonshire
    More or less in his way, it would be possible to machine a welded head with a cutter bar in (precision roller) bearings, carrying a sprocket and mounted like the camshaft.
    That is, if one has the skills and the resources...

    Ah! That is the problem.

    I don't understand why Honda designed the head this way as it seems unnecessarily complicated to manufacture. If the camshaft housing ends had been "capped" in the conventional fashion, it would be possible to line bore the workpiece quite simply and without the need to make special fittings and tools in order to reinstate the bearing surfaces.

    I'm wondering if all the "pressure relief" holes on the cam lobes have reduced (and possibly starved) the oil supply to the centre bearing.
    XRLated likes this.
  12. ItalJap

    ItalJap Adventurer

    Joined:
    Feb 1, 2020
    Oddometer:
    31
    Location:
    The Netherlands (Europe)
    I've owned a 1985 VF700 Sabre for 11 years and liked it a lot.
    The model was new to me so I searched the web and found out (as the poet said: like so many have before) that the first editions suffered of severe cam trouble. After the first year or so, Honda declined warranty and advised owners to change oil as prescribed, warm the engine at low revs as prescribed, etc. Several causes were opined, with cures to match, a popular one being tapping in the filter pressure line and directing extra oil to the cams.
    (A by-effect was that these bikes gained a reputation and became hard to sell, many were relocated to unknowing Europe and I had to let mine go for a knock-down price).

    The heads were NOT line bored. The fact that not all engines were affected (cams in f.i. mine were OK) smelled like the possibility of fatefully combined manufacturing tolerances. This was even said to be confirmed by ex-Honda USA men.
    By now you see where this is going to...:
    Line boring pairs head and cover in an early phase of production, which is undesirable for mass-production from a logistic/efficiency point of view. So production-wise, there's a lot to be gained not to. Try to produce identical parts and the reward will be huge.

    So they did, even before GB/XBR times. And kept doing it. And eventually mastered it.
    Some may call it stubborn (or worse), the Japanese themselves call it Kaizen (改善).

    Like another poet said: "I don't say that it's true, I'll just leave that up to you".

    johan
    Wumpletoad and XRLated like this.
  13. Spurlock

    Spurlock Long timer

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    Vacaville, N. California
    The good news is that, absent an oil system failure or a bonehead mechanic installing parts wrong, the plain center bearings will run just about forever. They just do not fail under normal usage. Note that in the photos posted by schnicks here, the cam lobes are scored and worn, indicating lack of oil to the top end.
    -Bill
  14. XRLated

    XRLated Long timer Supporter

    Joined:
    May 6, 2017
    Oddometer:
    1,001
    Are the spokes between GB models different lengths due to 36- vs. 40- spoke wheels? Or are the spokes the same lengths, just in sets of nine each instead of ten each?
  15. Chankly Bore

    Chankly Bore Been here awhile

    Joined:
    Sep 17, 2017
    Oddometer:
    243
    Location:
    Victoria, Australia
    Check the cms nl. website!
  16. XRLated

    XRLated Long timer Supporter

    Joined:
    May 6, 2017
    Oddometer:
    1,001
    Hi CB, I tried looking at the parts fiches: different part numbers (kn8 vs. mk4), but--to me at least--that didn't sufficiently answer whether the spokes are the same lengths, etc. or not, or whether there are other differences, so hoping the wisdom of the collective knows of any differences between the corresponding part numbers.

    Maybe geometry dictates that 36 vs. 40 spokes spaced out along the same diameter rims creates a sufficiently great difference so that the spokes need to be different lengths to fit, or some other difference is required? Beyond my own cognitive powers or experience, so without outside help I'm forced to make my own shaky logical hunches, unless by chance someone here (maybe someone with both types wheels on their GBs) has an answer from actual observation or experience.

    Trying to make a buying decision...
  17. RowBust

    RowBust Long timer

    Joined:
    Sep 6, 2013
    Oddometer:
    1,022
    Google spoke length calculator
    XRLated likes this.
  18. Chankly Bore

    Chankly Bore Been here awhile

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    Oddometer:
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    Location:
    Victoria, Australia
    Further information just to muddy the waters a little more: The r.h. spokes, 446A0-KN8-003 and 446B0-KN8-003 are both listed as B8x199mm, and I assume only differ in the radius at the butt end. The l.h. spokes, 446C0-KN8-003 and 446D0-KN8-003 are both listed as B8x197.5mm and presumably differ in radius because of the same inner or outer mounting requirements at the butt end. I regret that this information will only help Japanese market 36 spoke machines. The best option you may have is someone like Buchanans in the U.S.A. who must have done these wheels, or someone who can roll their own threads to sample supplied like my bloke here in OZ. Let us know what you find. I don't do geometry very well because I read too much poetry, but one would think the 40 spokes must be a freep shorter because there is one every 9° instead of 10°. Get out your sly drool I fancy. Good Luck.
  19. RowBust

    RowBust Long timer

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    Oddometer:
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    The difference between the inner and outer is the bend where it goes through the hub
    XRLated likes this.
  20. XRLated

    XRLated Long timer Supporter

    Joined:
    May 6, 2017
    Oddometer:
    1,001
    Full set of Honda NOS spokes in OEM packaging for cheap on Yahoo Japan auctions that fit a 36-spoke GB front tire:

    https://www.jauce.com/auction/m442616139

    [​IMG]

    Seems like a bargain for anyone who can put them to use.