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The Secret Scrambler build

Discussion in 'The Garage' started by Phoenix, Sep 5, 2020.

  1. Phoenix

    Phoenix XS400 Member

    Told myself I wanted a 400cc bike at the start of the summer. I wanted something cheap, something to restore, something that could be a project for the p(cough)demic. I got this DOHC for $250 Canadian. As I drove away with her in the bed, I knew I was getting myself into something deep.

    After gaining lots of wisdom from this forum, I thought I'd share what I've done so far. Pretty much everything except the indicators.

    I was inspired that it was a monoshock, thinking I'd find something from a dualsport to turn this into a scrambler. That was the only inspiration. Needless to say, scope creep happened, and now I have a bike with everything changed. I only ever welded a table for my dad, and now I've built an entire trellis frame, and a full exhaust for this beast. Never made a seat before, now I have. This is why I love motorcycles.

    Notable findings for the next generation follow. If you're looking at building one of these, here are some things to note:
    - Rear wheel off a kawasaki gpz 1.85 x 18 giving more off road tire options. - Narrower than stock, by 10 mm, But now that I know how simple the swap is, I'm on the lookout for my next wider rear wheel that will fit. The spacing allows for probably a 130 mm rear, maybe even a 140. I took the bike to the local motorcycle parts warehouse, there's one in the lower mainland with a BUNCH of old bike parts, and just test fit a bunch of wheels straight onto the bike.
    Many of these old rear wheels will work. I found I had to build spacers to space out the calipers and to make sure the chain lines up, but once I had base material, I could just use my angle grinder to shave down the spacer to size.
    - Front wheel is off an xs 400. Still needs some spacers cut, for the wheel as well as the caliper.
    -Rear shock is off a honda xl 450 R, which needed some shaving to the shock mounting point, and some drilling into the swingarm clevis. Not too much, should not compromise the strength of the rear. I used some brass bushings from an alternator as well.
    - Tank is off an 1100 Virago. Just moved the rear tank mounting point, and part of why I modded the frame the way I did. Otherwise, The petcock hits the valve cover. This means you must raise the rear of the tank up, which I did by simply welding in a new set of top tubes.
    - I had to, due to the rear shocks' size, put uni filters on the bike. I got a jet kit direct from 6sigma racing on ebay, who do the math for you. The kit is $80 CAD and includes 145 and 150 mains, and 42 pilots. Strange that the pilots are smaller, I'll be testing the bike today, and will report.

    This was a kick-ass adventure,and I'm very excited. I wanted to build a sort of long-range dualsport bike. I think I'm pretty close. I'll report after testing the bike today and let y'all know how it rides. Just need to rebuild the front caliper and figure out the indicators which are LED.

    Again, thanks for all the wisdom from this forum, you guys are some good people! 101982073_10163682523410022_4826538229200627091_o.jpg DSC03608.JPG
    Scotty4 likes this.
  2. amc49

    amc49 XS400 Addict

    Man, raise the front of that tank up, you are hurting my eyes.

    Not to mention you are wasting a half gallon of gas that won't go through the petcock.
  3. Phoenix

    Phoenix XS400 Member

    Then don't look at it
    There, I fixed it!

    Quick update after the maiden ride, the jet kit seems to work well, but something's amiss. Either an air leak or the slides are stuck; her rev's are outta control, simply wants to rev. Will be cracking the carbs open right after I clean the disaster of a garage.
  4. amc49

    amc49 XS400 Addict

    Of course, yours and do with it as you will...................the hanging idle thing is likely a vacuum leak somewhere. If you are not using a petcock that has vacuum shutoff then make sure one carb does not have a vacuum fitting unplugged. Assuming the idle speed screw is backed all the way off. Carbs out of sync can do it too. Carbs coming off bike can crack old rubber manifolds to leak too.

    If you go off-road you may well need something to prevent rocks and such from impacting the back of the UNIs, that tire will be throwing stuff forward left and right.

    Didn't occur to me until now but the dead space where gas sits to be unused because of tank angle will be an issue if you have to use ethanol in your local fuel, that is a low spot and water will stack up since you don't empty that part and tank will likely rust like lightning.

    Still, I'm no longer looking at it..................LOL.
  5. Phoenix

    Phoenix XS400 Member

    Good points, all. I'll be adding the rest of that rear fender to the top of the swingarm, to account for what's uncovered. There are apparently socks for the uni's to keep dust out, I'm sure they'll double duty for rain, in any case that's on the list. Thanks for the tips.
    The xv1100 tank actually has another petcock on the other side, which allows for the draining of the fuel at the low point on that side. Since the one you're referring to is on the side of the kickstand, I'm assuming it'll get slopped around enough and eventually the old fuel will get used up over time. If anything else, I'll gladly do some patching/sealing in the winter. This'll be a project for a while, with a big bore and a bigger rear eventually.

    The hanging idle, I found to be due to the PO trying to patch up the old carb boots with some type of rtv silicone, but I'm guessing they didn't use high-heat stuff. I started there on my quest to find the leak this morning, and found the silicone used was long since deteriorating, and once heated, were likely worse off. Spent some time meticulously scraping the old stuff, and applied high heat copper silicone sealant, and it's curing till 4 tomorrow. Another issue might be a slightly bent needle, which I'll be ordering a new one of, but in the meantime will do my darndest to straighten.

    Also today lengthened the sidestand due to the rear shock raising the bike enough to give it a MAD lean. IMG-20200905-WA0012.jpg IMG-20200905-WA0013.jpg
  6. amc49

    amc49 XS400 Addict

    'I'm assuming it'll get slopped around enough and eventually the old fuel will get used up over time.'

    If the tank vent is big enough and the day is warm and humid you can agitate the fuel to phase separate to then have pulled water in less than 10 minutes, I've done it in 5 before using ethanol laced fuel as a cleaning agent. FYI. Your long term time factor only applies to cars which have evap systems to contain that now, motorcycles don't and the wide open venting leads to issues. My CB550 will stick carb needles shut in one week of sitting, hot weather to evaporate fuel in carbs (the ethanol ramps that evap rate up like 400%) 4 days.

    Also, no silicone RTV on earth will work on fuel vapor exposed parts like the manifolds, RTV comes loose with exposure to fuel (seconds) and vapor (minutes or hours depending on how shielded the RTV is, er, the size of the crack it is exposed to). RTV doesn't even work well on oil and why so many car makers steer clear of it now. Stick a wad of it on a part good and then immerse the part in fuel and watch it close to see what happens............it will fall right off. Read the back of the product card, do NOT use where exposed to fuel, I used to sell the product all day long.

    Bent needle? Induced by somebody working on it, I haven't seen a bent needle in ages of working on bikes unless the needles are not flopping loose in the slides like they are supposed to be. They are NOT supposed to be tight. When they get tight they stick to bend, the loose allows them to align to the needle jet. Straighten one? You can try but odds are no.

    You need new needle(s) and manifolds.
  7. Phoenix

    Phoenix XS400 Member

    Right now I'm trying to figure out why my rear flashers aren't working, just staying on solid, while the fronts flash (albeit rapidly). They are LED's, though they're wired up to the same circuit. So I'm looking through the loom, since they are different varieties, It could be the fact that they have different loads, though shouldnt' matter if they're on the same circuit.

    Good points on the fuel.
    I got some fuel-safe rtv. It's already on, and I'm about to start up the bike and see how my straightening worked. The needle looks straight, undoubtedly probably off by microns, which means my beast won't be a beauty, but she's probably going to be close enough till the new needle comes in.

    Lengthened the sidestand, gonna button it all up and hopefully the idle don't hang.
  8. Phoenix

    Phoenix XS400 Member

    Sorry, I meant Oil-safe
  9. amc49

    amc49 XS400 Addict

    Luck.......on the turns, measure the resistance to compare front and rear and you may need to make them closer to equal. More resistance will dim the lighting though and less the opposite.
  10. Phoenix

    Phoenix XS400 Member

    Turn signal update:

    For the LED's it was actually very simple. The flasher relay I was using was an Ep34. It's a plug and play 3 pin, you just have to ground the one which goes to the self-cancelling unit to the frame. Then, plug and play, bingo bongo it works.

    And the Rear shock, I just remembered, was actually a stock shock from an XR650L. This has a 10KG/mm stock spring in it, which made the rear end really stiff. The whole point of this shock was to raise up the rear of the bike for greater clearance so when I take it on dirt roads, logging roads, etc, I'll feel confident with an off-road linkage shock in the back. However: The rear shock has quite a linkage distributing the weight, which is why they load their bikes with such heavy springs. LUCKILY: I found a pair of eibach springs on marketplace which just happen to fit, and they're 8kg/mm, which is a great improvement. BUT the rear end is still very stiff, so for now I'll ride it, when winter hits, or we get a week of rain, i'll go into the shop for a rebuild and a revalve.

    The high revs: i am embarrassed to say they were from a poorly adjusted idle! Go figure, I was in initial tuning, trying to compensate for something by cranking my idle screw. I was confused as to why I would need to crank it all the way in, but this was in the early days of the build. I ended up finding quite a hole in the exhaust, which might've made everything harder. Of course, I'd cleaned all the passages in the carbs all the way so that carb cleaner was spraying through each hole, something was just off. Anyways, now I have my idle adjusted correctly, and the bike pulls quite strongly.

    The uni filters, jet kit and exhaust sound VERY nice, my neighbor thought I was riding a 650. I will say this: these engines like to rev. Otherwise, they don't like to climb hills. Or minor inclines.

    My current work on the bike, while we wait fires to die down, is to craft some luggage cages around the back using some old BMW saddlebag frames.
  11. amc49

    amc49 XS400 Addict

    It's not unusual to have to refine your tuning setup once an engine gets running to change slightly to how it will run long term. The pistons have to carbon coat and then the top end settles into a normal running condition. Idle settings can change through that. A throttle hang may not even show up until that has happened.

    If you have a modern idle mixture limited to lean side setup like EPA stuff with idle limiter caps I even expect things to change. I remember my big Honda DOHC idling perfect when it came new off the showroom floor, it took a couple of days to really carbon coat in whereupon it began to get worse at idle to go lopsided like something wrong with carbs. I cut the tabs off the mixture screws and readjusted back to perfect and then it pretty much stayed that way after that. You learn to look for it if the engine is new. Same with one that has sat unused for a while just not quite as bad. Part of it is no carbon to soak up fuel vapors to hold them (or carbon completely dried up of vapors) and the carb/intake walls have not been fuel wetted lately, those things lead toward an engine that lights up instantly as it has recently been used to establish those conditions. It's much worse on say older car with carb to have to re-wet the intake manifold surfaces, you'd be amazed how much fuel it may take to do that if the intake is porous cast iron.
    Last edited: Sep 16, 2020

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