1986 Honda NS400R - Freddie Spencer GP replica

Discussion in '1st & 2nd Generation 1983-1989' started by straycat, Nov 28, 2020.

  1. straycat

    straycat Member

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    So, hopefully this is a couple of simple fixes on the NS400R. I have a fuel leak from the carbs somewhere and I have a coolant leak which im guessing is from an Oring that fits on the metal coolant pipes, much like the ones in the VF's (under the carbs).

    For those that are not familiar with the NS400R, its a 2 stroke triple with 2 cyl forward and 1 up (90 degree), 3 carbs and 3 pipes, the front 2 cylinders/pipes have power valves, the upper cylinders /pipe does not.

    Small bike, and unfortunately for me, an absolute bugger to work on when it comes to the carbs/cooling system. Getting the airbox off this bike is the single worst job on the bike, and getting the carbs off is a close second. There is very little room and the carbs have no plenum, rather 3 rubber horns that attach the carbs to the air box and god help me if theyre not the biggest basterd to get on (and off if they have been on a while).

    My remedy this time is to soak the horns in my wintergreen and alcohol softening solution, hopefully that makes re install easier, that and silicone rubber grease. its toss up if its easier to install the horns into the airbox first and then try and get them on the carbs or if its easier to install the horns on the carbs and then try and get them to simultaneously fit in the airbox. if you go with the former you need a 2ft screw driver to reach the band clamps.

    So far, I have pulled the carbs with also meant I had to pull the airbox and the electrical box and the rad cooling fan and the lower rad bolts. The cooling fan is a bit of a joke, it sucks air from about 6 sq inches of the radiator, a funny looking snorkel affair and almost useless.

    parts for the carbs are NLA, so im hoping my carb kit from Crusisn' Image gets here quickly

    IMG_1812.JPG

    Bike was absolutely filthy once I got the bodywork off, hard to believe it was a full restoration 8 yrs ago and I only put 300km on it


    IMG_1821.jpg IMG_1828.jpg IMG_1826.jpg



    The tiny Radiator fan with a whole 6 sq inches of surface area


    IMG_1836.jpg

    Carb horn's /velocity stacks will soak for 2 days each

    IMG_1839.jpg
     
    Last edited: Nov 28, 2020
    Viffer J likes this.
  2. straycat

    straycat Member

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    This may show you how small the frame is on the NS400R. Remember I have hands the size of a racoon....
    IMG_1837.jpg
     
  3. straycat

    straycat Member

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    As usual , one thing leads to another, to get the cooling T-pipe off the lower exhausts have to come off and also the ATAC power valves and their studs. What makes it worse is I find the power valves are stuck shut. So now I have them all stripped off and ill need to clean those and test the servo before it goes back together .

    The power valves (or ATAC valves - Automated Torque Amplification Chamber - In HONDA speak) are a bit of a nightmare in setup, not sure who came up with it, but Suzuki's and Yamaha's are simpler by far.

    Following the Pics Below in order, you have the 1) Electric servo, 2) the vertical Link assy and 3) the Horizontal Link assy. The servo pushes a rod (pic 1) which pushes a lever (pic 2) , which pushes another longer adjustable linkage rod (pic 2), which is attached to a pivot/spring and gear arm (pic 3) which turns a gear (pic 3) , which rotates the shaft that the butterflies are on (pic 4 exploded). Simple as that ! (Reminds me of the nursery rhyme I knew when I was a kid in England, think it was called "The House the Jack Built" ?)

    I have to say, cleaning ATAC valves is a filthy job. theyre gonna have to come right apart, take the butterflies too maybe, put them in the US Cleaner.

    IMG_1844.jpg IMG_1846.jpg IMG_1849.jpg IMG_1853.jpg
     
    Last edited: Nov 28, 2020
  4. Terry Smith

    Terry Smith Member

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    Good on you for keeping this alive mate. I had a ride on a 400 back in 85 or 86, my main memory is how little it needed to lean to take bends, I rode a VF1000F2 at the same time and the contrast was suprising. Probably a result of the really short wheelbase. Best of luck with the resto.
     
  5. straycat

    straycat Member

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    Thanks Terry, yea they handle like a dream. They were way better in the twists than the RZ500 or the RG500, but not as fast in a straight line. I had an RZ500 (sold last yr) and the NS is a much better bike to ride.
     
  6. Jim McCulloch

    Jim McCulloch New Member

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    WOW, that is awesome. I have never seen one of those in N. America. Reading the thread now!
     
  7. Jim McCulloch

    Jim McCulloch New Member

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    I raced several CR125's in the 80's and that ATAC was a pain in the rear. It was mechanical (non electric) on the dirt bikes but needed constant attention to be at it's best. I remember the "valve" would carbon up pretty easily and get stuck. Proper jetting and gas mix helped a lot but I never had time to do it right!

    Yes, Yamaha and Suzuki did it better, seemed like less maintenance needed.
     
  8. Waylander

    Waylander New Member

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    Wow if you get bored with bikes you can become a gynaecologist,

    That looks quite a fiddle to get that lot out and even harder to get back in

    Really need a video with sound once it’s back up and running, never managed to get a ride on one back in the day

    But seem to remember the RG having a really narrow power band, was the 400 the same


    VF1000F2F, in bits
     
  9. straycat

    straycat Member

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    There were only 300 of these brought to North America , and all in 1986. Only Canada got them, none in the USA. many have made their way south the States subsequently. Cool fact, mine is VIN number 86. It sounds like 3 CR125's running at the same time. Ill get a video once she is back together.
     
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  10. straycat

    straycat Member

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    My wife would love that wouldn't she. LOL

    Video will follow, ill put a link to Youtube

    yes pretty narrow power band, 7500RPM to about 10,500 rpm. You need to keep her on the pipe and ride her hard to get the best from it. I dont tend to ride it very hard really and maybe part of the reason the ATAC's clogged up with goop.
     
  11. straycat

    straycat Member

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    Im wondering if any sort of lube would be good on the butterfly shafts on these power-valves ? on one hand lube sounds a good idea but given the extreme heat these are subject to I dont know of anything that wouldn't turn to a crusty deposit quite quickly. I may be best to assemble it dry and rely on any unburned fuel (that you usually get during low rpm in a 2 stroke) to lube it.

    Thoughts ?

    copper grease good to 980 C. ?

    the Honda Shop manual says nothing a bout lube. I guess that tells me something right there but alot of time has passed since 1986.
     
    Last edited: Nov 29, 2020
  12. Waylander

    Waylander New Member

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    Put some graphite powder on them, that’s slippery without being sticky


    VF1000F2F, in bits
     
  13. raYzerman

    raYzerman Member

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    There is a dry moly in a spray too...... fyi
     
  14. straycat

    straycat Member

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    Well I got the Power-valves all cleaned and back on the bike, the new water T-pipe and Orings are on, but I decided to bench east the Power Valves and it seems like my solenoid/coil is F'd so the power-valves dont operate. I tested the solenoid and No click, and when I measure Ohms (1.9-2.5 ideal) I get very erratic readings. So I have a good used one coming from a reputable seller in the UK.

    It was little wonder the PV were stuck, someone (a PO) had assembled the linkages incorrectly and the whole lot would bind up once the covers were on. I sorted all out only to find the solenoid itself is also FUBAR.

    Now ill be painting the clutch cover, its peeling really badly down to bare metal, I can shave it off easily. then Ill detail the engine and other parts while I wait for the carb kit and the new solenoid to arrive.

    Im also going through my bodywork stash, may swap out some panels for some NOS stuff i've had hoarded away for a while.

    IMG_1817.jpg
     
  15. RllwJoe

    RllwJoe Insider

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    I copied this from your 1000R build forum:
    straycat;
    "While it handles really well Its a bit of work up and down the gear box to keep it in the power band. Under 7000 rpm its a total dog. (more than most 2 strokes, nature of the beast), then the power valves activate and its like being strapped to a missile. Its an On/Off switch, all or nothing. It will pull 160km/hr in 3rd gear with no trouble, not sure why 4th, 5th and 6th are there."

    I would think that properly working power valves would help to increase the lower rpm power. That was the reason for them in the first place, no? Were they stuck open? If so, the poor power at less than 7000 rpm makes sense.

    I used to ride and work on my 2 stroke snowmobiles years ago (haven't owned one in the last 10 yrs or so), and I remember Yamaha's new power valve system. At the time they required full synthetic 2 stroke oil in order to avoid
    "gumming" up. Also the valve would cycle after the engine was stopped in an effort to clean the valve. Is this designed to work in the same way?
     
  16. straycat

    straycat Member

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    They were stuck closed, which would have made the low RMP performance worse for sure. Theyre supposed to be open at low RPM and closed at high RPM on the Honda

    This is the second NS400R Ive had and my buddy has one as well, they all suck under 7500rpm, they're still dogs even with the Power valves working under 7500 rpm. they just suck more when they stuck closed. Over 7500 they're the most fun you can have with your clothes on. Its the "nature of the beast" so to speak.

    I only run Amsoil full Synthetic in my 2 stroke bikes, but honestly I have no idea what the PO was running. You are quite right a low ash full synthetic oil is critical for power valves in bikes and sleds, I run BRP Full Synthetic in my sled .

    The ATAC Power Valves on the Honda do not cycle when you turn the key on or off (Yamaha RZ's and Suzuki RG's do)
     
    Last edited: Nov 29, 2020
  17. Captain 80s

    Captain 80s Member

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    Reminds me of Paul Newman talking about turbo lag.

    If you're complaining about turbo lag, you're driving it wrong.
     
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  18. straycat

    straycat Member

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    So, good news and bad news.

    Good news is my Solenoid is fine.

    I took it to a local guy here to test it, and all is well. He told me (makes sense) that these things typically only work if the voltage is 12v + and since the bike is generally generating more than that (~14.5v) it will work. BUT, if your battery has been sitting a while (mine had) and is only putting out 11.5v for example, you'll net nothing. He said they're quite sensitive to that. Mine was putting out 11.4v, needed a charge I guess.

    So, good news is, thats all ok, and I learned something.

    I knew the NS400R was very sensitive to voltage in other ways. Even if your charging system is ok (Reg Rec OK) but your battery is FUBAR and wont take a charge, the bike will start and run just fine but things like the horn, turn signals and tach will not function, but the headlight will.

    Bad news is, I just paid for a spare solenoid I don't need.

    My impulsive/lack of patience nature has bitten me in the arse once more. I never learn
     
  19. Waylander

    Waylander New Member

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    Remember I’m in the U.K. , need anything from here with sensible postage, just let me know

    My brother and I sell old car panels, repair sections and all sorts, been at it for nearly 30 years, so we ship stuff all over the world all the time


    VF1000F2F, in bits
     
  20. straycat

    straycat Member

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    Much appreciated

    thank you !!
     
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