Sorting out my R90/6 (sprouty115)

Discussion in 'Airheads' started by sprouty115, Sep 13, 2017.

  1. sprouty115

    sprouty115 Long timer Supporter

    Joined:
    May 29, 2012
    Oddometer:
    6,552
    Location:
    Providence, RI
    At the risk of sounding over confident, I don't think I cut any of the o-rings during installation. I actually work as an engineer and we make automotive actuators, switches and sensors, so o-ring installation is part of my daily life. So when I was rebuilding the carbs all the shafts and screws got wrapped in tape and then greased. Everything went on very easily.

    As for float bowl fuel height. I'll give the jar a shot. I assume 1/2 from the top, plus the groove depth where the gasket sits is what I shoot for?

    I will admit there has been a bit of variability in the readings as I tried to see this in the past, which has always had me wondering if the float needle seat is damaged somehow (ethanol?)...
  2. Plaka

    Plaka Brevis illi vita est

    Joined:
    Jun 19, 2010
    Oddometer:
    6,477
    Location:
    Longmont, CO
    Float needle seat is brass. Not easy to damage. But one of mine looks good, Has been lapped out, and I still got a leak.

    With the carb rotated so the bottom of the body is parallel to the ground (not quite the normal running position, the carb should tip in), when the gas shuts off the float should be parallel to the bottom of the carb body. ANd the gas should shut off.

    If I read correctly the symptom you describe is having to turn the idle air screw in too far to get a best-running condition. You also said you did not change the throttle shaft o-rings, which is wise, Don't touch those until they prove they need it, which is pretty seldom.

    The idle air screw feeds a bubbly fuel air mix to the venturi. Maybe the bubbles are missing? I don't know where the bubble air for that circuit comes from but it will be a very tiny hole and I bet it will be drilled in brass.

    I would add some Seafoam ( or Techron, or your favorite) to the gas to be cleaning things as you go. Also stabilizes the more volatile winter gas, it's a long time, and probably not a tank of gas burned until spring.

    Then balance the carbs. Just take it from the top. Chokes fully closed with the levers hard against the stops on the carbs. Throttle cables fully slack and turn the bars to full lock both ways and make sure the cables stay slack ( if they don't, re-route the cables). Set throttle stop and idle air screws to nominal settings per the book. Put your shorting wires on and two long and well insulated somethings in your back pocket. Withe motor warm enough to run with the chokes off turn the idle air screws so the motor runs best. OUt till it slows, in till it slows, then set midway between those two points. It ain't critical. If it seems you have to turn one in too far and you checked the tip of the needle leave it, get it so it runs best and move on.

    Next grab one of your insulated sometings from your back pcket and short out the plug on one side. The other side should hit 3-4 times then die. Adjust the throttle stop screws to get this. Do both sides. This should give you a good idle. Take a screwdriver on you test ride and adjust the idle stops the exact same amount if you want to bring the idle up or down.

    Next remove the slack from the throttle cables----just. The cable above the lever on the carb should still feel 'soft' when you push sideways with your finger. At this point it gets tricky. You need to be able to wind up the throttle with one hand and lock it---or have a helper. I have a one handed throttle lock. ANyway you start it, short one side and wind it up to preffered cruising RPM running just on the otheer side, Then you grab your other well insulated instrument fro m your back pocket and quickly switch sides. Go back and forth a time or two and identify the strong and weak side, then short both sides to shut it down. You want to work quickly so it doesn't over heat so practice your moves with the motor off.

    Now strengthen the weak side by taking up some cable housing at the adjuster on the carb top. Repeat shorting test. When you switch side to side the RPMS should not change in the slightest. Tighten the locknuts on the cable adjusters and go for a ride.
    sprouty115 likes this.
  3. sprouty115

    sprouty115 Long timer Supporter

    Joined:
    May 29, 2012
    Oddometer:
    6,552
    Location:
    Providence, RI
    Excellent Plaka,

    Just to be clear:

    - the bike is generally running well, but it doesn't seem as completely smooth as I think it could be.

    - along with that there is a slight, but noticeable stumble just off idle when excellerating.

    - the left carb idle mix screw is very nearly seated at the point the engine idles the highest, so it is backed out maybe an 1/8th of a turn.

    - the throttle axle o-rings were replaced. I noticed the small screws holding the butterfly in place were not staked on backside, so they needed to come out to get Loctighted (couldn't risk them coming loose and getting sucked into the engine). At that point I figured why not replace the o-ring.

    - both float needles are new.

    I unfortunately ran into a list of house chores that "needed my attention", and it didn't seem like it was up for debate, so this will get pushed out to next weekend.
  4. Bigger Al

    Bigger Al Still a stupid tire guy Supporter

    Joined:
    Oct 12, 2004
    Oddometer:
    9,328
    Location:
    Auburn, CA
    Not to hijack the thread, but I want to send out thanks to Plaka for this post. My R90/6 had developed a stumble off of idle and nothing I tried would cure it. I spent a hour cleaning the transfer ports and that did the trick!
    Seems I can still learn something about this bike after 25 years of ownership.
    sprouty115 and WRC51 like this.
  5. sprouty115

    sprouty115 Long timer Supporter

    Joined:
    May 29, 2012
    Oddometer:
    6,552
    Location:
    Providence, RI
    Glad to hear that. I'm traveling for the next two weeks but I'll be on it when I get back.
    Bigger Al likes this.
  6. sprouty115

    sprouty115 Long timer Supporter

    Joined:
    May 29, 2012
    Oddometer:
    6,552
    Location:
    Providence, RI
    So it's been quite awhile since my last update but I've got a few more things sorted out.
    First off I think the syncing of carbs is good. Plaka's post above was very helpful and I took it to a local Airhead tech day and they made one further small adjustment and it seems good (finally!)

    I also think the more I ride it, the better it seems to run, for some reason.

    Anyway, here is what else has been going on:

    - Gauges fully serviced from @Wirespokes.
    20181129_153140.jpg

    - And a Kat Dash to replace this...
    20181129_153049.jpg

    - And since I was refreshing the gauges, I put in new cables for both the speedo and tach. So now it looks like a proper bike again.
    20181201_144831.jpg

    - Then...because I was spending time looking at bikes like these...
    20190513_153931-COLLAGE.jpg

    -...I put an order in at Flatracer.com for their R90S fairing...
    4635687279.jpg

    So that leaves me with a bit of work to paint and install, but I'm looking forward to it!

    After that, when my bank account recovers, I'll be replacing the seat, as the original foam has softened to the point that it's really not comfortable.

    (BTW, Flatracer is out of the UK, so don't confuse Euro with GBP when doing a conversion to US dollars or you'll get a big surprise when it posts to your PayPal account, DAMHIK!)

    Oh, and I also ordered two more bars from Tucker Rocky as I still think the ones currently installed (Flanders BMW Flat Sidecar Bar) are too low and too far forward. They were only $25 each so if I don't like them it's not too big of a deal.
  7. Plaka

    Plaka Brevis illi vita est

    Joined:
    Jun 19, 2010
    Oddometer:
    6,477
    Location:
    Longmont, CO
    The stumble off idle is likely clogged transfer ports in the carbs. They may unclog themselves and the problem resolves.

    I left something out of my carb syncing dissertation: never lift your shorting tool (big screwdrivers_ away from the shorting wires. Rather stay in contact with the wires and slide the tool forward and backward to contact the head or not. This avoids the possibility of knocking off a spark plug cap.
    sprouty115 likes this.
  8. WRC51

    WRC51 Long timer

    Joined:
    Sep 8, 2008
    Oddometer:
    1,373
    Location:
    Santa Rosa, Calif.
    I like the looks of the fairing, I will be interested if it makes a difference with wind management. Those S-type fairing just look perfect on an Airhead, does Flatracer offer a mounting kit or do you have to piece together a mounting kit?
  9. sprouty115

    sprouty115 Long timer Supporter

    Joined:
    May 29, 2012
    Oddometer:
    6,552
    Location:
    Providence, RI
    The faring kit comes with the fairing, windshield and dash, along with this hardware:
    1 - mounting hardware.jpg
    1 - bolts.jpg

    These are also available, but purchased separately:
    1 - trun signal stalks.jpg
    1 directionals.jpg
    1 headlight trim.jpg

    I will also add that I was surprised by the quality, especially the fairing, which is very solid!
    Jim K in PA, eight90eight and WRC51 like this.
  10. Disston

    Disston ShadeTreeExpert

    Joined:
    Aug 31, 2009
    Oddometer:
    15,350
    Location:
    Silver Spring, Md
    If you want just a little fairing the S is a nice way to go. You also get to say "My bike wears a bikini". Makes her sound sexy, no?

    Nice kit.
    WRC51 and sprouty115 like this.
  11. sprouty115

    sprouty115 Long timer Supporter

    Joined:
    May 29, 2012
    Oddometer:
    6,552
    Location:
    Providence, RI
    Anyone like to offer their thoughts on a few more things I'm wondering about?

    1 - The tank is in pretty great shape for a 44+yo bike, but there is one small dent. It's about 3/4" in diameter and about 1/16" deep. Any possibility of getting it fixed without repainting the tank?
    20190516_182228.jpg

    20190516_181803.jpg

    2 - It seems to me the rear turn signal bracket is narrower than what I've seen on other bikes. Possibly cut down by the P.O.? Is that a common mod?
    20190516_182334.jpg

    3 - I'm a bit unsure about the routing of the clutch and brake cables.
    Brake - The best path for the brake seems to be down the center hole of the gauge bracket. But when I routed it there initially it took about 5 rides to wear through the plastic sheath of the cable. So I split a piece of hard nylon tubing and zip-tied it in place. It works, but...
    Clutch - The clutch has a similar problem, but not as bad. It seems to rub on the upper fork brace. So is routed correctly, or am I missing something?
    20190516_182249.jpg

    4 - Rust. I've been pretty good about cleaning the ferrous parts, and most of them look pretty good, but in New England it's a constant battle. any suggestions? Otherwise I'm considering a whipping up a home zinc plating kit (seriously).

    20190516_182348.jpg
  12. bleaknessengine

    bleaknessengine Been here awhile Supporter

    Joined:
    Mar 29, 2009
    Oddometer:
    139
    Location:
    Portland, OR
    on my old 90/6, i think my brake cable did not go through the hole but went down towards the left more, making the widest loop i could get it.
    i cut my rear signal stalk short like that to avoid problems with some panniers i had.
    you could maybe make an identical dent on the left side of the tank to balance it out?
    globalt38, Jim K in PA and sprouty115 like this.
  13. Jim K in PA

    Jim K in PA Long timer

    Joined:
    Mar 15, 2011
    Oddometer:
    4,297
    Location:
    Pocono Mountains, PA
    Dent = earned scar. Entirely your call, but I wouldn't fix it.
    T/S stalks = cut down. I cut mine about the same. I don't care for the wide set signals, especially without panniers.
    Rust will sneak up on you. Changes to SS or plate the steel, but even the zinc will eventually corrode. Entropy sucks.
    sprouty115 likes this.
  14. WRC51

    WRC51 Long timer

    Joined:
    Sep 8, 2008
    Oddometer:
    1,373
    Location:
    Santa Rosa, Calif.
    I am in the process of changing bars and installing new cables on my 76 R90. My clutch cable actually went thru the hole in the instrument bracket I think these were the OG cables. Waiting on throttle and clutch cables from Bobs they are supposed to be here early next week, I got the MC cable from a different vendor it is supposed to be for shorter bars but is the same length as the one that I removed. The bike had US bars and I wanted a lower bar so I am not sure this is going to work as the cable going to the MC doesn't have a lot of flex because of the short run to the MC...if that makes sense. I cant tell from the photos if you are using the US bars or did you go with a different bar. EDIT I am in the process of reading your thread on about page 3 I think, thanks for taking the time to post all of this info up.
    sprouty115 likes this.
  15. Plaka

    Plaka Brevis illi vita est

    Joined:
    Jun 19, 2010
    Oddometer:
    6,477
    Location:
    Longmont, CO
    Consider the dent patina. It will be costly to fix, the new paint will nee3d to be matched as will the pinstripe. You can improve the appearance of the tank by keeping it shiny and fitting the cloisonné badges from a /5

    I played with rust treatments. Matt Parkhouse once made up a bucker of bolts that needed cad plating and had a local shop do it. I think they charged him by the pound. They looked great. I used red lead primer on a lot of bolt heads on my /5. Applied from a can with an artists brush. Didn't look the best but stopped the rust. More recently I looked up DIY galvanizing on the web seeing as how there is a web now. Lot of car restoration guys doing it. Results a little rough but that's galvanizing. I tried baked linseed oil. Old time rock and roll. Very tough and stopped the rust, but extremely slippery and hard to wrench on.

    Rout cables so the bends are as big and gentle as possible. Different routing is needed for different bars. Check routing with bars at full lock both ways. If you need a cable tie to hold the routing you are probably pulling a loop too tight.

    Cutting down turn signal stalks was a precursor to the cafe craze, which started the following week. Often they are just whacked off and the original anti-rotation notch is not reproduced.
    sprouty115 and WRC51 like this.
  16. aptbldr

    aptbldr easy rider

    Joined:
    Apr 20, 2009
    Oddometer:
    1,128
    Location:
    Upstate South Carolina, USA
    What about the paint-less dent fixers?
    Does /6 tank have a filler extension tube, like those of '84 era?
    That tube inhibits the use of the levers employed by the paint-less guys ... don't they?
    sprouty115 likes this.
  17. Disston

    Disston ShadeTreeExpert

    Joined:
    Aug 31, 2009
    Oddometer:
    15,350
    Location:
    Silver Spring, Md
    Talk to a paintless dent repair guy. The subject has come up but not often. I think it only works on modern cars with very thin skin but that's probably just an opinion.

    I'd leave it anyway. Original paint. Dent not big enough to force loosing that.
    sprouty115 likes this.
  18. Big Bamboo

    Big Bamboo Aircooled & Sunbaked Supporter

    Joined:
    Sep 29, 2010
    Oddometer:
    15,025
    Location:
    Big Island of Hawaii
    View attachment 1686374
    Here's a pic from the owners manual. Note: there's a clip inside the left headlight bracket for the grommet on the brake cable: cable routing.jpg I'd keep the dent and go stainless.
    sprouty115, Jim K in PA and aptbldr like this.
  19. sprouty115

    sprouty115 Long timer Supporter

    Joined:
    May 29, 2012
    Oddometer:
    6,552
    Location:
    Providence, RI
    Ok, yesterday was beautiful out and so I bailed on the fixing-things plan and went for a 100-mile ride. We've had so much rain for the last two months that I just had to get out.

    20190518_125625.jpg

    While I was riding around enjoying it all I had to time to think a bit, so I decided to take the advice above and leave the dent as-is.

    I also think, after reading all the comments, that I should do a dry-run fitting the fairing, then decide on bars, then sort out cables (in that order).

    And yes, Jim entropy does suck. So I think I'll try the home galvanizing and see how that goes. Though I have to say I'm pretty curious about the baked linseed oil technique...
    globalt38 and bleaknessengine like this.
  20. Plaka

    Plaka Brevis illi vita est

    Joined:
    Jun 19, 2010
    Oddometer:
    6,477
    Location:
    Longmont, CO