Honda GB500 thread

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

  1. Chankly Bore

    Chankly Bore Adventurer

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    Thanks,Allen. I'll gratefully keep your offer as a backup in case I get flim-flammed. If it goes well, (or Badly), I'll inform this forum of my experience. Did about 70 miles yesterday in 95 degree heat. Cheers, Charlie.
  2. AllenS

    AllenS Adventurer

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    Why don't we wait till you get yours (or not) and see if you really need my spare. Happy to leave it in the box where it now is resting peacefully than ship it off to Oz on the off chance that the one you ordered does not arrive.

    I will save it for you if you really need it. If not I will probably pop it on ebay and see if someone else needs one. Sound OK to you?
  3. Chankly Bore

    Chankly Bore Adventurer

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    Yes, Allen, that's what I intended to convey.If I'm lucky I should have my part ex Japan within three weeks, I'll let folks know of my experience. I'm not after hoarding parts, and I will happily help other people who intend to use their bikes. Sorry if my intended meaning was unclear- blame advancing decrepitude!
  4. AllenS

    AllenS Adventurer

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    NO worries. I will just hold onto the part just in case!
    Allen
  5. Spurlock

    Spurlock Long timer

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    There are quite a few GBs listed in the Mecum auction in Las Vegas later this month. I didn't count but there must be 6-8. Suddenly they don't seem quite so rare.

    -Bill
  6. Scratch33

    Scratch33 you're going to feel a little pressure

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    Seven. Will be interested to see what they sell for.
  7. Spurlock

    Spurlock Long timer

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    I've heard that when there are many of the same model, the last to go often sell for much lower prices than the first. That Dream 50R still in its original unopened crate is an interesting one.

    -Bill
  8. Nickosaurus

    Nickosaurus n00b

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    Hi Allen, If you end up hanging on to that part, I'm interested (if Chankly doesn't need it). Mine has a rather ugly welded repair that I'd love to replace with an intact part. Cheers, nic
  9. AllenS

    AllenS Adventurer

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    Has anyone swapped the stock carburetor out for a Mikuni or Keihin flat sided unit? I have the XR650L engine and two carbs. One is a rather nasty looking stock GB500 and the other is marked as a NX650. The NX carb is completely disassembled with all the parts in a large plastic bag. At least I think all the parts are there.....

    With the price of kits and other bits I was thinking that it might be just as easy to buy a new carb. Both Mikuni and Keihin have pumper flat side carbs. Not great for fuel economy but performance should be better.

    Just curious if anyone has made the change and what their experience has been.
    Allen
  10. JCool

    JCool Long timer

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    I've got a Mikuni TM40 pumper on a 650L. They're much easier to set up than the Keihin. Much better throttle response and it increased the midrange noticeably. Niche Cycle has the best prices.
  11. AllenS

    AllenS Adventurer

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    Thanks for your reply. Any issues with choke or with throttle cable? I read somewhere that the choke might be hard to reach and operate but the pumper should allow you to give it a couple squirts of fuel for cool weather starting.

    Any tips you can give me on the install or jetting will be appreciated!
    Allen
  12. JCool

    JCool Long timer

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    I had to shorten my pull cable , Niche has cables for the L , though. My Keihin choke plunger and the fitting screwed right in , same threads , so I'm hooked up to the stock cable to the handlebar lever. You can get the carb with the knob or a short cable with a remote knob. I'm running a 160 main jet , came with a 165 and the 17.5 pilot that came in it , needle in the middle. This is a 54 HP motor at sea level, though. The accelerator pump on these (TM40-6) is externally adjustable for tip in and duration. I got my adapters from Mikuni Oz on Amazon.
  13. Claytonroy

    Claytonroy Been here awhile

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    Hello-
    I haven't checked this thread for weeks but I'm gearing up for a Winter GB project of my own & glad to catch up on the recent posts.

    Allen, I restored an NX250 front rim via a soda blasting technique. It worked great, I just polished it up before relacing. 4 years later it looks shiny & OEM, no need to re-anodize. I'd also considered a softer media blast like, walnut or hazelnut shells etc.

    Replacing the spokes is anotber task entirely. I rebuilt a GB front wheel, it took me 4 attempts to successfully lace it (first 2 efforts failed because new spoke length was off by 3mm..). As a former bicycle wrench, it was humbling.

    I'd say soda blast the entire front wheel minus the bearings! The GB front hub has an odd drilling pattern, so if you replace/relace spokes, take very detailed notes on disassembly. Also, de-tension the wheel entirely before cutting out the old spokes. Good luck!
  14. solidol

    solidol Adventurer

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    I'll be ordering flasher relay from wemoto and wonder if anyone local (bay area) needs anything they have. Shipping charges aren't too bad but combined works better I'm sure. Please message me if interested.[​IMG]
  15. Chankly Bore

    Chankly Bore Adventurer

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    Hello folks, I've been putting miles (or kilometers) in on my 1985 GB500. I thought I'd pass on a few observations. The bike ran sweetly when I got it, but after about 70 miles started idling lumpily and popping on the overrun. First thoughts were loose exhaust and tappet maladjustment. Tightened exhaust flange nuts and set EX. tappets to tight .006" (they were a little slack), and inlet checked at .004" (one was a little tight). I then checked the carburettor float bowl-thanks for Spurlock's tips here. As expected, a fair amount of old crud in the bottom, but nothing that affected the jets. However, during this operation I noticed two things. The bottom bolt on the carby mounting flange was loose, and the sealing flange "O" ring was a little perished. I removed the "O" ring, and as a stop-gap measure turned it upside-down and put a little Silastic on the slightly perished 1/4" length. What I concluded after considering the symptoms was that the vacuum created by larger throttle openings sealed the flange, but when the pressure was off a little whistle of atmosphere admitted itself. I then did a dumb thing, and set the pilot screw to 2 5/8 turns out, as per the 1989 manual and wondered why the idle got more precarious as the trinket warmed up. I then discovered that the '85 model needs 1 3/4 turns out! I'm off down the shed now to brew up a little device to effect this adjustment without taking the whole shebang to pieces again. Cheers, Charlie.
  16. JCool

    JCool Long timer

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    Vacuum is higher at smaller throttle openings and an air leak would have more effect at smaller throttle openings , also.
    Chankly Bore likes this.
  17. Spurlock

    Spurlock Long timer

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    Good work Charlie, thanks for sharing your experience. I suspect you've found the problem, but if it continues some of that float bowl crud might have invaded the slow jet. On the idle mixture screw, the correct setting is whatever gives the smoothest, fastest idle. You will probably find that when turning the screw out, it has no further effect after 2-3 turns. That's common and always suggests to me that the slow jet is the limiting factor, not the screw. On my GB I upped the slow jet from #48 to #50, which caused the mixture screw to be more effective. The slow jet change also affects mixture up to 1/8 throttle or so, which can stand to be a bit richer as well.

    -Bill
    Chankly Bore likes this.
  18. AllenS

    AllenS Adventurer

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    Just noticed that one of the 7 GB500's at the Las Vegas auction sold today for $13,000. Very nice looking bike with about 9,400 miles on the odometer.

    Just thought I would share with the group.
  19. Spurlock

    Spurlock Long timer

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    Man that must have been some kind of bidding frenzy. $13K is a crazy high price for a bike listed as "all original" but which has several obvious non-original mods: aftermarket turn signals, an odd looking extra long bazooka muffler and non-stock headers pipes, oversized tires, and blued header pipes that suggest abnormally high engine heat at one time and who know what else. Probably a great bike if mileage is correct, but clearly misrepresented and way above typical market value even for actual all original bikes.

    -Bill
  20. AllenS

    AllenS Adventurer

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    I had the same thoughts about the non-original parts and thought it would go for well under that price. I was thinking around $7000 - $8000. There are 6 more GB500's in the auction listing so we will see if the trend continues.