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F2 Tank and Monster Seat Mods

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    F2 Tank and Monster Seat Mods

    Since I've had more than a few questions about this, here's a quick 'n' dirty thumbnail sketch of what's involved in the F2 tank and Monster seat mods I've done. I'm putting them together mainly because I did them both at the same time, and it so happens that they work together swimmingly. This advice can be extrapolted to each mod individually, but since I haven't done each one individually, I can't offer direct advice, though. For that, go bug Ross Dale, Robb Zimdars, Chis Mulhall or Mike Pescetto.

    What you need for the tank mod:
    -An F2 or F3 tank. They're identical. Don't worry about paint, since you'll need it repainted when you're done with the mods.
    -A modern Harley replacement petcock. A used Harley part will work, or a new off-brand. They're around $25 new and as low as $5 used. Harley owners feel the need to cast off their stock pieces for $75 Pingle units, for some reason unknown to me.
    -Your Hawk gas cap will work without modification.
    -About ten minutes of a welder's time.
    -Large ball-peen hammer.


    This is the only modification needed to the F2 tank when used with a Monster seat: an extension of the front mounting tab of roughly an inch, center to center. A little trimming of the side of the tab to make it fit in the slot, and it's good to go.

    The bottom:

    I should've freshened that paint while I had it off. One more little item: my metalworker friend who did the welding on this project was concerned about the front underside of the tank contacting the frame. I don't honestly see it as a problem, since the tank's steel and the frame is aluminum, but since we're dealing with the potential of leaking gasoline, I decided to go with his word. I pounded in the tank in the two spots where it would rub until I could see light through the gap when the tank was on the bike, and to be double sure, I epoxied some heavy duty inner tube patches at the points of possible contact. No problem to date, about two years in.

    Speaking of leaking gas, here's something worth mentioning. Be sure to mock up the tank location on the bike with the petcock installed on the tank. The tank needs to sit back far enough so the petcock completely clears the rear cylider head by at least 1/4". If not, the petcock will vibrate against the head, fatiguing the metal on gas tank, and eventually wearing a hole in it. I didn't have the petcock when I fitted parts, and my tank wound up about 1/8" too far forward. This is the only part of the job that I had to clean up later, as the pinhole didn't wear until about two years on. And in my case, all I had to do was open the mounting holes a little to gain the clearance necessary. No big deal, but it's even easier to do it right the first time. Learn from my mistake.

    You'll also need to discard the bracket that holds fuel lines and such that sits under the stock tank, but rerouting that stuff is cake.

    The reason this tank/seat combination makes so much sense is this:

    That bracket doubles as a rear tank mount and front seat mount. The tank, clearly, sits on top, and the two tabs on the front of the seat slide under it. It functions exactly like the bracket on the OEM Hawk subframe, it's just a couple inches higher and further forward. The mounting tab of the rear of the tank is untouched.

    Here it is on the other side:

    It's pure seredipity that this bracket work so perfectly. Or maybe I'm a born fabricator...
    I'll think I'll go for a life of sin followed by a last minute, presto-change-o deathbed repentance. -B. Simpson

    Alex

    #2
    Here's another shot of that front tank mount, to give an idea of the angle involved. This is a matter of test fitting and hand bending, nothing fancy.
    I'll think I'll go for a life of sin followed by a last minute, presto-change-o deathbed repentance. -B. Simpson

    Alex

    Comment


      #3
      Necessary for the Monster seat mod:
      -Monster seat. Another good stock part that owners throw out, so you can find one for about $25. And the Ducati seat is quite comfy. There is minor filing required on the underside of the seat, but that will be plainly obvious once you fit it on the subframe for the first time.
      -A tail cowl if you like the look. I think it's the whole point, so I got it in carbon, or, as my metalworker called it 'fancy plastic.'
      -Tail light, just the housing, not the wiring. If you can find one from a Monster in your price range, I think they look better. But the SV/TL lights are $5, so I couldn't justify the cost difference. At least, not after buying the carbon cowl... You'll need to file it a bit so that the Hawk taillights fit, but that's a 20 min. job.
      -A stock subframe. Use the one on your bike if you're brave, but I bought a spare one before I started, just in case I sneezed while grinding something important.
      -Lots of cardboard to make mockups. Try posterboard, it'll bend easier.
      -An angle grinder with metal cutting and grinding discs. It'll make your Dremel seem like a kid's toy.


      This gives you an idea of what's left of the stock subframe. Not much. Actually, only the two rails on each side. All the electrical stuff, save for the rear signal wires and Will's headlight harness fits in front of the battery, and still allows for battery removal. The box inside the rails needs to be as shallow as possible for rear wheel clearance at suspension compresion, but it's ultimate shallowness is limited by the depth of the battery. I know Robb Z laid his battery down, but I couldn't finagle the stock battery cables to work with that. It fits standing, anyway. And standing it up leaves room for a little bit of storage.


      Some detail of the rear and tail light mount. Effectively, this is just an extention of the bottom of the box. I put two bends on this for the sake of structure, but again, I think this was redundancy. Those 90 tabs are the rear mounts for the seat, and the seat is secured by small thumbscrews.


      Another blurry picture of the taillight mount. Turnsignal stalks go right through the subframe rails.

      Now, about this box. It's the part of this build that requires the most fabricating, and therefore it's the most daunting. But think about it: you're building a four-sided box inside of set dimensions. It's as wide as the subframe rails, it's only as deep as the battery, and it's as long as the subframe rails, which, in turn are as long as the seat. Nothing to it.

      Pay attention to the box in this picture, and you can see it almost follows the angle of the lower subframe rail. Not necessary, just coincidence.



      And here you can see the bottom, to some extent. Just a flat panel of steel.


      These are all the pictures I have, and I'm obviously leaving out a lot of detail. But, this is basically a simple job, if you take your time and make your mistakes in cardboard, not steel.

      If you get into this project, I'll be happy to try to work you through and problems you encounter. Hell, buy me a welder and send me a stock subframe, and I'll send it back chopped, built and ready to mount.

      Nah, it's easy. Go for it.
      I'll think I'll go for a life of sin followed by a last minute, presto-change-o deathbed repentance. -B. Simpson

      Alex

      Comment


        #4
        By the way, if you have questions about this, email me or PM me, since I won't be checking this thread all the damn time.

        akcarlson at gmail dot com
        I'll think I'll go for a life of sin followed by a last minute, presto-change-o deathbed repentance. -B. Simpson

        Alex

        Comment


          #5
          the stock subframe.....is that the stock angle too? It doesn't seem like my hawk has that much clearance between the wheel and lower subframe rail. Did you cut the top rail from the bottom and have them rewelded to give you a steeper seat angle?
          -NEVER LET YOUR FEARS STAND IN THE WAY OF YOUR DREAMS-
          Most of the pics I have of my Hawk/Mods: http://gallery.me.com/stevenhowell

          "Arseing about with my bikes will end in tears." -Keno04

          "Dress for the slide, not the ride" - ParcNHawk

          Comment


            #6
            Originally Posted by Stevenjhow
            the stock subframe.....is that the stock angle too? It doesn't seem like my hawk has that much clearance between the wheel and lower subframe rail. Did you cut the top rail from the bottom and have them rewelded to give you a steeper seat angle?
            I can't answer for Alex, but I'd say it's from a taller ride height from the rear shock, along with the lack of the stock seat cowl, which hangs quite a ways below the subframe. I had the exhaust reworked on my bike, since the M4 high mount looked too low without the stock setup.

            before:
            after


            RD
            A Honda amongst a sea of Harleys

            Comment


              #7
              Spot-on, Ross. The only thing that I have to raise the rear is the 900RR shock that I'm (still) using. the subframe angle is 100% stock.

              Here's a shot from the first mockup after I chopped up the subframe.
              I'll think I'll go for a life of sin followed by a last minute, presto-change-o deathbed repentance. -B. Simpson

              Alex

              Comment


                #8
                I noticed in one of the pictures the rear brake reservoir. How do you
                top the fluid up?
                "Life may begin at 40, but it doesn't get real interesting until about 150."

                • '88 in Candy Flair Blue + '90 in Italian Red
                • Ohlins Rear Shock
                • F2 front wheel
                • VFR750 rear wheel
                • Hiperform seat&headers
                • MSMotorsport Seat Cowl
                • Steve Lenac Tokico six pot caliper

                Comment


                  #9
                  Unbolt the resevoir. It's not something I do too often.
                  I'll think I'll go for a life of sin followed by a last minute, presto-change-o deathbed repentance. -B. Simpson

                  Alex

                  Comment


                    #10
                    What year Duc cowl did you use?
                    Rob
                    88 Street Hawk
                    F2 tank, Aztec8 dual 4", Duc seat and CF cowl, Stage 3 jet, Uni Pods, M4 stubby, SV650 clips, controls & fuel pump, GSXR front mc and CFB1000 front caliper, F3 forks upper and internals, Penske 8983, Gino RCR, rear jump plates & R6 pegs and Vapor gauge...
                    04 CRF50 pit bike and stunt runner...
                    91 Suzuki GSF400 Bandit (she's a runner now...)

                    Comment


                      #11
                      If anyone sees this, old topic. How is the seat height compared to stock? I was going to repad (ie. raise) and recover my stock seat this summer. But if the monster seat gives some extra height it sounds like that's the ticket. I'm not scared of a little fab. BTW, where's the fuel pump stuck? I'm guess there's a SV vacuum pump hidden somewhere.
                      Tim
                      '89 HawkGT - Dirty
                      '07 S3 - WHEEEEE!

                      Comment


                        #12
                        I hadn't really thought about it, so I sat on my bike, then my wife's Hawk (stock seat). There was no real difference in height between the two. As for the pump, the SV pump is what I have on mine now, and it works great, along with taking up considerably less room than the Hawk pump.
                        By the way, if anyone needs the fitting for a vacuum outlet, I've got two spares. $5 each, shipped.
                        A Honda amongst a sea of Harleys

                        Comment


                          #13
                          Originally Posted by Ross
                          I hadn't really thought about it, so I sat on my bike, then my wife's Hawk (stock seat). There was no real difference in height between the two. As for the pump, the SV pump is what I have on mine now, and it works great, along with taking up considerably less room than the Hawk pump.
                          By the way, if anyone needs the fitting for a vacuum outlet, I've got two spares. $5 each, shipped.
                          Shoot, I really need more seat height. My legs start to cramp up after 40 minutes, even with straight away "calastetics". I'm 6'1+ with long legs, the rearset plates helped a lot, but not enough. I might follow Ebay anyway, if a seat is cheap enough pick it up to play with.
                          Thanks for the info,

                          p.s. I'd like to get one of those fittings from you, as my fitting isn't great, but it's worked for about a year. I'll get ahold of ya on payday and see if you still have one.
                          Tim
                          '89 HawkGT - Dirty
                          '07 S3 - WHEEEEE!

                          Comment


                            #14
                            Was wondering about the handle bars? If I use stock bars do I need to turn the out so they don't hit the tank when it's on?
                            Rob
                            88 Street Hawk
                            F2 tank, Aztec8 dual 4", Duc seat and CF cowl, Stage 3 jet, Uni Pods, M4 stubby, SV650 clips, controls & fuel pump, GSXR front mc and CFB1000 front caliper, F3 forks upper and internals, Penske 8983, Gino RCR, rear jump plates & R6 pegs and Vapor gauge...
                            04 CRF50 pit bike and stunt runner...
                            91 Suzuki GSF400 Bandit (she's a runner now...)

                            Comment


                              #15
                              What year seat

                              So winter is setting in and it's time to do some mods.
                              The monster seat mod is on my list.

                              A few questions.

                              What years Monster seat will work?

                              Same with the tailight housing?


                              Thanks

                              Andrew
                              ARRH Don't mind me, that's just the scurvy talkin!

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