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Honda GB500 thread

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

  1. jethrocephus

    jethrocephus His Honorable Right Minister of Flying Monkeys Supporter

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    Looks cool, is that the horn on the frame? Enjoy the bike‼️
    #61
  2. bran.c

    bran.c Adventurer

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    yeah thats the horn, havent tried it yet
    #62
  3. bran.c

    bran.c Adventurer

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    Thanks Bill, is there any special way to drain or refill the oil when changing it?
    First dry sump motor so want to start off right.
    Thanks
    #63
  4. Spurlock

    Spurlock Long timer

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    Nothing special, the only difference is you need to drain both the engine and the tank. Both have the same 12mm hex bolt drain plug. The original tool for these bikes came with a little sheet metal oil guide that slips over the tank drain spigot to keep the oil away from the bike. For anyone missing this part, below is a tracing I did of an original. Just cut it out of sheet metal and bend to shape.
    [​IMG]

    Here it is on the oil tank -
    [​IMG]

    I made a similar thing for the engine drain bolt, shown below. Keeps the oil off the frame tube -
    [​IMG]

    Here is the pair -
    [​IMG]

    -Bill
    #64
    solidol and bran.c like this.
  5. MuddyK9

    MuddyK9 Adventurer

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    Hello Bill!
    I wondered what happened to everyone after the demise of the old GB forum. One day, like my youth, it was just gone. There was some good information on there.
    I was kicking myself for not making a copy of all your great engine rebuild info and now here it is!
    Maybe some more of the old crew will stumble in here.

    Muddy
    #65
  6. Spurlock

    Spurlock Long timer

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    Hey Muddy, so glad you stumbled in here! And yes, hopefully others from the old forum will catch the scent and come around, there were lots of great contributors there.

    How is your bike doing these days?

    -Bill
    #66
  7. MuddyK9

    MuddyK9 Adventurer

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    Bill-
    The bike is doing well. Very happy with my Dart fly screen and suspension mods, including those Ikon rear shocks.
    I bought a second GB early this year, so like you I now have twins. I've left the second one stock so far. It only has 400 miles, so I hate to ride it.

    I did run into an odd situation on bike number one that may be of interest to someone out there. The worm gear in the speedometer gear drive broke. Naturally GB gear drives are no longer available, but after a lot of research I found that a drive from an '86 Honda CMX 450 Rebel would fit up perfectly. There may be other Honda drives that work also, I just stopped when I fond that one fit.

    Speedometer error seems to be about the same as with the original GB unit; indicated 65 in 5th is an actual 60mph.
    Just something to keep in mind.

    Muddy
    #67
  8. bran.c

    bran.c Adventurer

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    Brilliant thanks for all this info, when refilling the oil is there any trick to it? Can I get airlocked?ill be making up some drain guides in the meantime.
    #68
  9. Spurlock

    Spurlock Long timer

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    Oh yeah, forgot to mention that you can't add all the oil at once or the tank will overflow. First add about 1-1/2 quarts, then run the bike a bit, idle, check the level, and add a bit more. Leave it a bit low on the dipstick until you have a chance to run it more and check a couple of times over a few days and adjust if needed. As I mentioned before though, oil level is somewhat of a moving target on these, so I just put in a total of just under 2 qts. and call it good. Manual says 1.7 qts needed after draining, 2.3 qts after engine disassembly.

    -Bill
    #69
  10. Spurlock

    Spurlock Long timer

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    Hey thanks for the tip on the speedo gear. I'll make a note in case of future need. My speedo seems 3-5 mph fast too.

    What model Dart screen did you get?

    Wow, a GB with only 400 miles? Must look fantastic. It's surprising how many very low mileage bikes have shown up on ebay in the past couple of years. There's one on there now with 1,270 miles that looks mint.

    -Bill
    #70
  11. bran.c

    bran.c Adventurer

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    Thanks, thought there might be a knack to it, new oil and filter tomorrow, can't wait to get back out for a spin before winter, need to get a back tyre too what works well on these in mixed weather?
    #71
  12. MuddyK9

    MuddyK9 Adventurer

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    Bill-
    Yep, there seem to be a quite a few low mile GBs. There were two a couple years back still in the Honda crates, I believe they sold in the $14,000 range. I've been watching that 1,270mi one just to see what it goes for.

    I think some guys put them away thinking they would become the next AJS7Rs, maybe they will in time. Given that roughly 2,500 were brought in to the USA and 1000 of those were later shipped to Germany, then add in 26 years of accidents and attrition and I wonder how many are left?

    I got the Classic Dart screen intended for the Moto Guzzi. It adapts pretty easily to fit the GB; just expand two holes and make up two small spacer/braces and you're set. Some of the screens intended for other bikes may adapt too, I just know the Guzzi one works. I like the Dart Classic a lot.

    I also have Dart's Manta model. It's larger and should give more protection, but I'm not sure it really does. Fairings and air flow are funny things. One day I taped strings all over mine and rode around doing "wind tunnel" type testing. I learned a lot, but that's a post for another day.

    Muddy
    #72
  13. Spurlock

    Spurlock Long timer

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    Hey bran.c, are you in the UK? Just wondering since you wrote "tyre" for what we nutty yankees call "tire." Also, you speak of mixed weather, but here in California it is sunny, dry and warm and will continue to be dry for at least another 4-6 weeks, not that we would not welcome some rain after 4 years of drought! So if you are starting to get some wet weather I am jealous! Anyway, it would be fun to know where you are from.

    As for tires on the GB, I am happy running the stock Bridgestone BT45's year round. But I also seldom ride any bike in wet conditions, and especially the GB after getting it thoroughly polished up and not wanting to desecrate it with wet road muck. I have ridden the Bridgestones in winter conditions with frost and damp patches on the roads and have been satisfied with their traction. But on any bike, as soon as I see any wet patches I slow way down, so don't take my word as a final endorsement. Hopefully others will chime in with their tire (or tyre) experiences.

    Thanks for your posts!

    -Bill
    #73
  14. Spurlock

    Spurlock Long timer

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    Thanks, I have almost no experience with these tiny windscreens. Can you describe the effects and benefits? A big issue for me is helmet wind noise, and often when a windscreen directs turbulence around the base of the helmet that makes the problem worse. With no windscreen on my GB, due to the lean-forward riding position, I find wind noise a problem. I noticed that scrunching up my shoulders to close the gap between jacket and bottom of helmet killed the noise. So my remedy is home made shoulder pads installed into my jackets. They take up the gap and make a world of difference. But I'm really interested in knowing if you feel your windscreen helps this issue.

    And I'd love to hear your conclusions on your "wind tunnel" testing! Taping strings to your windscreen, man after my own heart.

    -Bill
    #74
  15. MuddyK9

    MuddyK9 Adventurer

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    Bill-
    I remember your old post about helmet noise and shoulder pads. I have noticed the same thing. There are airflow issues off the shoulders but I don't know what they are. Alas I suspect the Dart may not help you with this.
    Indeed some say the Dart doesn't do anything. But on a GB you sit low behind the gas tank, leaning forward and presenting a small frontal area.
    I find the Dart creates a bubble of calmer air above the tank extending back to the torso reaching as high as one's neck. Your head is outside in smooth, fast air. Remarkably, I find no turbulence zone or buffeting. You can see this with strings, but it is easy to feel with your left hand while ridding. This bubble expands a bit with speed but remains stable from 30 to 70mph. Beyond that it is too fast to experiment.
    On the down side, the Dart won't protect you much from the weather. If it rains, you are going to get wet. It just isn't a true fairing and can't do a fairing's work in that regard.

    As for my string testing conclusions; well most are intuitively obvious. You can use a small size screen and get nice smooth laminar airflow, but modest coverage. Start displacing more air and buffeting and turbulence suddenly start to appear. Kind of like the water faucet example in chaos theory I guess. You get more coverage but at a price.
    One interesting thing I found on larger screens was the formation of a rolling wave above the gas tank. I see the same thing in my pickup bed going down the road. Dried leaves don't always blow out, they swirl up, over and back down again. Same thing happens above the tank between the screen and rider. I have not found this effect with the Dart Classic.

    Muddy
    #75
  16. Spurlock

    Spurlock Long timer

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    Silver paint for fuse box cover
    If anyone needs to spruce up their scratched fuse cover, I found this Dupli-Color to be a very good match.
    [​IMG]

    While at it I added the white lettering back on the switch cap. After blowing the remaining bits of white paint off with compressed air and brushing with rubbing alcohol, I applied white enamel with my finger tip, then wiped lightly with a cloth to remove the excess. Did and second coat and now the "dash" looks prefect!
    [​IMG]

    -Bill
    #76
  17. bran.c

    bran.c Adventurer

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    Hi Bill
    Im not in the UK but in sunny Ireland where even on a good day it will probably rain at some point, the bike has bt45s on it so I might just go with the same to keep them matching, havnt had any problems with grip but the rear is squared off and 13 years old so deffo needs changing.
    Thanks
    #77
  18. bran.c

    bran.c Adventurer

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    Well just to update, fitted new rear tyre and changed the engine oil and filter, want to check valve clearances next, whats are the specs on this?
    also would like to get some fresh oil in the forks, again looking for info on oil quantity etc.
    Thanks
    #78
  19. Spurlock

    Spurlock Long timer

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    Here you go:
    Valve clearance IN - .10mm, .004"; EXH .12mm, .005"

    Fork oil - Honda used ATF in the front forks.
    Fork oil capacity is 335cc (11.3 US oz.), but the most accurate measure is to pull the fork springs, add new oil, then slide the fork lowers up and down several times to get the air out. Then collapse the forks completely and measure the oil level. It should be 116mm (4.6") down from the top. Remember that is with the fork collapsed and no springs inside.

    Hope this helps,

    -Bill
    #79
    DisturbedDonut likes this.
  20. bran.c

    bran.c Adventurer

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    Thanks Bill
    Thats great info
    #80