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Looking forward to next season of miniGP.

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  • Looking forward to next season of miniGP.

    I know a few of you in the chatbox are probably already tired of hearing about it, but I figured I'd do a post for the progress of getting ready for next season. Last year, I prepped a small bike I bought/built and took it to a miniGP open practice day. It was tons of fun, and highlighted a couple areas where I needed to improve the bike. I did those improvements, but never did make it to a sprint race with that bike. I did, however, manage to practice most Sundays throughout the summer. I got a LOT better than I had been at riding in general, and it has taught me many lessons on cornering at the limits of traction, and a few times at just past the limits of traction. I eventually did a 4 hour endurance race with my friend, but my bike wasn't quite big enough to fit in a real race class for the endurance race. So, I recently purchased this ...

    It was already setup just as you see it in this picture, including the 17" excel wheels and slicks. I have already tweaked the suspension a little, including pulling the forks off, popping them open, and setting the oil level correctly. One was a bit overfilled. The rear shock has been rebuilt by Hlebo Brothers and revalved. Stiffer springs all the way around. I imagine it would be quite good, if I was riding a motocross course and doing jumps, but it feels a bit harsh. Really, the Kat with all the RaceTech springs and emulators and gold valve and tweaking feels better and better the more bikes I ride.

    Anyway, I'm still formulating a plan for that. Other issues I've already taken care of, replaced the torn grips, put on hand guards to protect the levers for when I go down while practicing, made a breather for the crankcase, replaced the lightly cracked fuel line, and rebuilt the front brake caliper.

    Here it is as it stands now, complete with flashlight for testing after I get home.

    At this point, I am seriously done with winter, and I am impatiently wanting to start seeing what it can really do.

    Oh, and for how it's been built before I bought it, there's a big cam, valve work, seems like higher compression, upgraded CDI or "revbox", a very free flowing exhaust, a 28mm Mikuni Flat Slide carb with K&N filter, and a renthal chain and sprocket kit to use a 428 chain. When trying to keep up with my neighbor's 250, I found out that it's fairly wheelie happy shifting into 2nd and 3rd. It's supposedly putting down 18.5hp on a dyno, which is approaching double it's stock hp.

  • #2
    Pretty sweet and if ur tired of winter move to tx im looking forward to my sunny 70 degree ride here today in the great state haha we havnt even started winter
    I just wanna ride my bike
    2001 katana 600


    • #3
      Originally posted by Jar3d200 View Post
      Pretty sweet and if ur tired of winter move to tx im looking forward to my sunny 70 degree ride here today in the great state haha we havnt even started winter

      Hrm... ride all year long on flat, long, straight, boring roads with hot/warm temps... or ride here, on amazingly curvy and scenic roads with a few months of colder weather....

      Think I'll stay here.

      93 750 Kat

      Modified Swingarm, 5.5 GSXR Rear with 180/55 and 520 Chain, 750 to 600 Tail conversion, more to come. Long Term Project build thread

      "I've done this a thousand times before. What could possibly go wron.... Ooops!"


      • #4
        Originally posted by Kreylyn View Post
        Hrm... ride all year long on flat, long, straight, boring roads with hot/warm temps... or ride here, on amazingly curvy and scenic roads with a few months of colder weather....

        Think I'll stay here.

        I'm with you Krey, Given the opportunity I would move to your area in a heartbeat
        2002 750 Kat
        2013 Polaris 850 XP LE(wrecked)
        2002 Ski-Doo MXZ 800
        2002 Ski-Doo MXZ 800 X-package
        1999 Ski-Doo MXZ 670 H.O.
        2009 Kawasaki KX250F(SOLD)


        • #5
          Theres some good scenic and curvy roads here lol. I do wish we had some mountains though
          I just wanna ride my bike
          2001 katana 600


          • #6
            Okay, so I'm doing a bit of work to get this bike ready for the big time, in ... uh ... the mini gp. *Ahem* Anyway, this bike had the suspension already upgraded with BBR springs, because that's the standard upgrade. They put gear oil in the forks, because they probably read about it somewhere. The work was done by monkeys. These bikes are known for front end chatter, and aside from how horrible the forks were due to gear oil, I can now see why they are prone otherwise. From the measurements I did, the fork springs were just a touch on the soft side, but was close for proper sag. The rear isn't close, but I'll address that later. I'm tackling the forks for now.

            These forks have been well used. I mean, really well used. The fork tubes had an interesting pattern on them.

            I spent some time polishing the tubes, for good effect. Used 600 grit paper, followed up by 2000 grit.

            I'm putting in the RaceTech emulators. Apparently the emulators they make fit many different forks of the same diameter, with various types of dampening rods. In the directions, they mentioned that sometimes circlips were used for locating the emulators on the top of the dampening rod. On my dampening rods, the emulators were a little loose, and could shift enough to stick out further than the side of the dampening rod cup, so I measured carefully, and then made my own circlips out of .030 stainless welding wire.

            The instructions did say that the circlip was not for sealing, just for locating the emulators. I figured then that the top edge of the cup would seal against the bottom of the emulator. I took the time to lap that surface on the dampening rod.

            Now, because this bike is for racing, I want adjustability, and I don't really care how ghetto it looks. The fork caps on this bike are simple aluminum, largely hollow, with just a 17mm hex portion on the top to unscrew them. I removed the o-ring, cleaned them with solvent, roughed up the inside portion with a dremel, and filled them with JB weld, just to help reinforce. After giving that plenty of time to cure, I drilled down through the cap and JB Weld, and tapped it. I welded some washers to a couple bolts, and made my own hacked together external preload adjusters.

            Don't worry, the washers are mostly held on by filling the central hole with welding. The tacks on the outer edge were just for getting things held in place at first. I'm also using another washer between those and the springs.

            I also cut the fork springs by 2 inches, and then reclosed the end coils where I cut them and ground them flat. Didn't take pics of that. In the end, I couldn't finish one of the forks yet, because the previous owner had apparently taken the forks apart at some point, and left one of the oil lock pieces out. I was wondering why there was such a difference in height with the springs between the two forks. So, that part is ordered, all the mods are done, and all I have to do is put it together when I get that part. Previous Owners, what a forking shame.



            • #7

              Thanks for sharing!
              1998 Katana 750
              1992 Katana 1100
              2006 Ninja 250

              2006 Katana 600 RIP - 130k miles


              • #8
                Time for another update!

                I got the parts! I popped the oil lock piece on the end of the dampening rod, stuck it all together, and put the forks on the bike. Before tightening everything down, I mounted the new Pirelli Diablo Rosso II 110/70/17 on the front 2.5" wheel. I keep my house at 64 degrees in the winter when I'm home, cause heating oil is expensive. Those beads just didn't wanna pop! I turned on both electric heaters in my bathroom, shut the door, and let the tire heat soak in there. That and some diluted dish soap did the trick.

                Before testing any of that, as long as I had the bike on blocks, I pulled the rear wheel and swapped the old tire for a Pirelli track day take off tire I had that I didn't use for the Kat last year. It was a front tire, perfect for the rear of the CRF. I'm still trying to figure out a real solution for the rear shock, but figured I should at least get proper sag, even if the heavy duty BBR spring is too soft. So, I ordered a rather cheap aluminum shaft collar that fit around the adjusting collar on the shock.

                To keep the spring centered, I shaved enough off to create a ridge around the inner edge. Worked perfect!

                Got it all put back together!

                Did the front suspension bounce to make sure everything was straight and settled, then torqued everything down. Adjusted the sag!

                How she sits right now.

                It never really got above freezing today, the road looks like it's covered in gravel due to all the salt and cinders, and there is still small patches of ice on the road, and big patches on my driveway, so of course I took it out! It really is too cold to tell much about how the suspension is doing for bumps. What I could tell is that it still felt nicer. After it was all warmed up, I found that it loves to power wheelie in first. Brake dive didn't feel excessive. It did want to do a stoppie kind of easily when I was headed down a steep grade on my driveway, but what should I really expect when headed downhill without pushing myself as far back on the seat as possible?

                All in all, it is much better than it was. I think at this point, even if I don't get a better spring/shock for the rear, it's pretty well set to go. Only things I really need/want now is a better catch can than the crushed aluminum energy drink can zip tied to the frame, and maybe the oversized front brake rotor and caliper relocation bracket. The bike will stoppie now, but with endurance races, fighting brake fade and reducing effort to fight fatigue is where it's at!


                • #9
                  Okay, it's been a while. I've had issues with the engine in this bike. It's been irritating. I believe I had a problem with a stretched timing chain, and possibly a tired old cam chain tensioner. I've swapped to a mcct, and have ended up rebuilding almost everything in the motor. It's taken a few times of things breaking to finally go this route. I've cracked open the cases, replaced nearly every bearing, cleaned everything really well, had the valve seats cut at a machine shop, new valves, high tension valve springs, new cam chain. I'm hoping it stays together at this point, because it's getting very frustrating. I've done mechanical wonders before with never an issue, but this motor has been one problem after another and is starting to make me doubt myself. THIS is why I like to buy brand new bikes, instead of buying problems from other people.

                  Anyway, with a little testing I've gotten to do, the suspension is doing awesome. I did tweak the front emulators a little, making it slightly softer. It's really well balanced, and steers like a dream.

                  The last time I was testing and this bike stopped, I got in some good practice on a ttr-90. Yep, it's under powered, only a 3 speed, no clutch, and nearly no brakes. I started a policy of downshifting from 3rd to 1st to slow down for turns, and started getting really good at sliding sideways into the turns. It was a blast, and I was laughing so hard while doing it. It was just comical how tall I am, 190 pounds, on such a tiny bike and sliding it sideways almost to full steering lock with countersteering. It was fun, and I learned a lot about getting comfy with sliding a bike sideways.

                  This last weekend, I didn't have one last part for the crf, so I did the training with the DRZ. I started out really tentative on it. It just feels different, has a softer suspension, more torque. I ended up having to do some basic drills like emergency braking and turning tighter and tighter circles, then figure eights, just to get more comfy. I soon started getting faster on it though. Even started getting comfy on a new track setup with only one sharp turn, sliding it into that turn under braking and downshifting to 1st. Wasn't getting it anywhere near as sideways as that ttr-90 though. I'm still learning. Anyway, I've melted the front tire a little bit, and really wore the rear down. I've got just over 1000 miles on it, and I'm almost down to the wear bars on the rear tire. I also feel like a truck hit me. It's hard work making these bikes go fast, especially the drz400sm, as it wants to launch out from under me when coming out of a turn in 1st and whacking the throttle open.

                  I should have the crf together very soon, and hopefully it stays together.


                  • #10
                    The CRF lives! It's healthy! Mostly!


                    So I did some training this last Sunday. The bike ran great and held together well. By the end of the day, dirt had gotten into the carb and plugged up the pilot circuit, but I'm considering this a very minor thing. It ran great!

                    So, I've got this video. It was the second session, and I was still getting used to sliding the bike sideways into turns. I had gotten pretty good by the end of the day, but didn't capture it well on the camera. It was my first good day with this bike, and my first day trying out the camera. I later tried helmet mount, which was pointed too low, and front fender mount which shakes way too much. I'll get more creative next time.

                    In this video, I'm the guy in front.



                    • #11
                      More updates, more pictures

                      Okay, I finally have time for a real update.

                      I mentioned that I split the cases and replaced all the bearings and stuff. I like the mechanical simplicity in this design. The bearings had steel races in the aluminum cases that held the bearings.

                      Putting it all together again.

                      I had ported the exhaust side of the head for better flow. It was really tiny. As most people know, there are always tradeoffs in doing this. Sacrifice low end torque for high end horsepower. In one of the iterations where I had more parts break, I had done this porting on the exhaust. The motor really did love high rpms, but lost quite a bit of the low end. There is apparently a ratio of intake to exhaust that keeps the motor more balanced, but the problem with porting the intake is losing the velocity of the incoming air. Air is compressible, so as the piston starts sucking it in, the air "stretches", gains velocity, and then sort of "bounces" as the piston nears the bottom of it's travel. The higher the velocity, the more air/fuel you can get into the chamber especially towards the end of this cycle. That's also how you can modify the flow of an engine that runs fine on 87 octane, and end up having enough compression to get pinging and needing to either up the octane or retard the ignition timing. So, I wanted to get closer to that ratio, with having the ported exhaust, but without slowing the velocity of the intake by porting it. My solution was to give a back cut, and an under cut to the intake valve. I did this with the metal lathe at work. Wahoo!

                      I'm happy to report that it works! The intake trick, that is. I don't have any dyno figures, but I did lose a tiny amount of bottem end torque. The massive gain in upper end HP and useable rpm range was definitely worth it though! Now that the bike is holding together, I'm able to actually spend time practicing and learning.

                      I've mostly had sportbike related riding experience up until these crf miniGP adventures, so I'm finally learning about real supermoto style riding. That's why I've been learning to slide into turns. Admittedly, I wanted to learn because it looks cool. I've gotten comfortable enough to start leaning into the upcoming turn while sliding, and it's such a rush doing it. Naturally, it feels way more dramatic than it looks with my nonprofessional camera touch.


                      Now, having started getting used to sliding, I can report on the amazing benefits of doing it on very sharp turns. What seemed obvious to me when first watching youtube videos was that you get the bike part of the way turned into the apex before getting there, so you can naturally take the corner a little faster. What wasn't obvious at first is how insanely late you can brake going into the turn. When braking in a straight line, you can eventually brake so hard you lift the rear tire, so it can't help with any braking at that point. When sliding sideways, leaning into the turn, and counter steering, you are effectively keeping the front tire upright and traveling straight, so you can brake really hard with the front, but since the rear tire is sliding sideways with weight on it, it's helping slow the bike as well. If you've ever done a track day and practiced late braking, you likely know how it takes a bit of retraining your brain as to what acceptable braking distances are. Learning to slide into turns just takes that to a whole new level. When I start getting in the zone while riding, it makes me way more confident going into turns, knowing I can point the bike where I need, brake as hard as I need, and modify lines to suit changing conditions.

                      In the video, I'm getting valuable feedback about my riding position as well. It felt like I was leaning off the bike more. I am doing so more than the video makes it look, but not nearly as much as it felt like. I'm only just beginning to be able to combine that with not braking too early, being in the right gear, making a smooth transition to steering into the turn and getting on the throttle, and not killing myself. I'm starting to get comfortable enough to start worrying about body position. I have a lot left to learn about doing it right, and a long way to go, but it feels like I've made leaps and bounds of progress in training in the last 3 days that I've gotten to.

                      Oh, and don't start trying to slide a Katana into a turn. This bike is about 300 pounds lighter, and I'm not on the street!

                      I almost forgot to mention, I did almost highside the bike pretty bad once. This isn't an undertaking to be done without considering the consequences. I wear full race gear whenever I'm training. I was lucky, and managed to steer the bike back under me as I was in the air and landed on the seat again.
                      Last edited by ygolohcysp; 06-15-2015, 08:01 PM. Reason: Adding info about the highside.


                      • #12
                        Well, it's been a while since I've updated this. I did lots of practice last year, but consistently had problems with the engine. I eventually found that it was actually the fault of the oil cooler the previous owner put on. It was done incorrectly, and was robbing oil from the passage going to the crankshaft, and dropping the pressure so much the top of the motor would starve for oil.

                        I got that sorted, and then had issues with BBR valve springs breaking, twice. Luckily no other damage from that. I ended up with lighter Kwibblewhite racing valve springs with titanium retainers. No more playing.

                        I also decided to up the game by lightening the flywheel and crankshaft.

                        Here's the flywheel. The original in the back, lightened one I'm holding. Sorry it's blurry, I had oil on my hands which got on the camera lense on my phone.

                        The final build is a high compression piston, ported head, bigger cam, and lightened crankshaft and flywheel. The response is greatly improved, with much better low end torque, and a pretty good top end HP. This bike wheelies with ease now. A few friends have ridden it, and they were amazed with how instant the response is from the motor. I personally like the improved engine braking as well.

                        I've recently decided to get a little more serious about making parts for it, so I have plans for replacing the fork caps that I modified before. They function great, but I got some tools to do a better job, so I'm making adjustable fork caps just to learn my way around the tools a little better.

                        Started by cutting to length, and then milling the hex to be able to use a wrench.

                        Then I turned down the area for the o-ring, turned down the extra part that's going to provide the length for the internal threads, and then cut the threads so it can thread into the fork tube.

                        That's about as far as I got with it for tonight. Cheers!


                        • #13
                          You suck...... I truly am impressed... How much weight did you shed?
                          "I'm sorry, I didn't mean to upset you when I called you stupid. I thought you already knew..."
                          spammer police
                          USAF veteran
                          If your a veteran, join the KR veterans group


                          • #14
                            It was around 14oz total, so nearly a full pound off the rotating mass of the engine. Not too shabby.


                            • #15
                              Yeah, that's pretty good....
                              "I'm sorry, I didn't mean to upset you when I called you stupid. I thought you already knew..."
                              spammer police
                              USAF veteran
                              If your a veteran, join the KR veterans group