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Looking forward to next season of miniGP.

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  • #16
    Awesome thread...keeping an eye on this one. That bike is super fun. Its the bike I got to ride for two days straight doing my MSF course. So light and nimble. Looks like a blast with slicks on her and drifting out the ass end to make the sharp corners. Good on ya!!

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    • #17
      Well, I've gone a little off the deep end with this bike. I did some testing, and was spinning the rear tire coming out of turns. I've been using Pirelli Diablo Supercorsa V2 120 front tires for the rear on this. They slide great, but that front tire profile is wrong for the rear. So, I finally tried the Pirelli Diablo Superbike slicks that came with the bike. One of them is a 125/70/17 that's actually made as a rear tire.

      Woohooo! Damn, that tire stuck like glue! I started dragging footpegs doing the foot out style, and dragging knees while leaning out. But it really made me think. Leaning off on this bike is half-assed at best, just because of how far forward the foot pegs are, and how high and wide the bars are. That's when I came up with a crazy idea. My friend had given me a set of stock R6 rearsets when I was doing so much R&D on the pocket bike, just in case I could use them. I still had them sitting around. I mocked them up with wire ties, and couldn't believe how well they fit. So, here they are. I did have to make the linkage piece, but everything else is stock R6 rearset, with just some coupling nuts welded to the frame. Easy to go back to stock.


      That gives me the upside down GP-shift pattern. I haven't taken a pic further away with them done like in that previous picture, but here is further out in the mock up phase. It shows the difference between them and the stock pegs anyway.


      Now, I didn't want to just have pegs in a different spot, but still have the high and wide bars of a dirt bike, so ...


      Yes, I have clip-ons and rearsets on a CRF150F that's definitely putting out well over 20hp. And wow, that bike rips. I'm not as good with downshifting the GP-shift pattern, so I haven't been sliding it sideways into turns like this. But what I can do is carry a LOT more corner speed. In previously 2nd gear turns, I'm carrying 3rd in the power band, dragging my knee, with my upper body hanging off the side as well. I've had to learn to get on the throttle for maintenance throttle before being fully leaned over, because this bike has so much instant torque, it upsets the chassis if I don't have the slack of the chain taken up already. And, since it's still setup like a supermoto (with a stiffer suspension) otherwise, this bike has incredible ground clearance. No worry about dragging hard parts. I can lean completely off, drag my knee through the turn, and as soon as I hit the apex, just keep adding throttle until the rear tire just starts to edge sideways. It's a rush.

      And finally, I finished one of the fork cap adjusters. I ended up only making it to have 1" of adjustment instead of 1.5". Figured that was good enough. But that also meant that that the one I made was .5" too long. So, I've started making more that are shorter. Don't have any pics of those yet, but here is the longer one finished.

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      • #18
        Man, that 150F build is sick. I'm working on an open class (formula 3) XR100 for Herrin Compound. I've just been running stock XR for about a year now and I'm having a blast with it.

        I'll post a few more details of my bikes and my builds later on this week. Cool to find someone else on KR that likes mini racing too.

        "We are not all beautiful unique flowers. Some of us have bad ideas and bad taste and the things we do come out awful, no matter how much work we put in."

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        • #19
          Originally posted by 1FSTKAT View Post
          Man, that 150F build is sick. I'm working on an open class (formula 3) XR100 for Herrin Compound. I've just been running stock XR for about a year now and I'm having a blast with it.

          I'll post a few more details of my bikes and my builds later on this week. Cool to find someone else on KR that likes mini racing too.
          Dude, that's cool! I like the pic. I sometimes wish I'd gone with a 100 because of the frame size. It takes a lot to get this 150F leaned over far enough to drag knee, at least when setup as supermoto, which it is again now. The suspension is stiff enough that it handles very well on pavement, and I don't suffer from low ground clearance on the right foot peg mount like these bikes typically have.

          I have a few more pics and mods now. First up, here are the actual size fork adjusters I made, which are now installed with the springs cut for them and fork oil level adjusted.


          Compared with my friend's, my front brake was a bit lacking. We both had the same stock master cylinder (1/2" piston), so I figured out he had a caliper with larger pistons that came stock on other Honda's, giving him closer to the ideal master to caliper piston area ratio. I didn't have another caliper, but I did have an 11mm master that I had tested on my pocket bike. Perfect! So I had that on the last weekend that we tested, and holy crap I could brake! We were also using his gps data logger, so I know for a fact that I braking from 55mph to 18mph for a hairpin turn. I was doing that in approximately 40 feet, sliding sideways. Over a week later, my thumbs still hurt from the G-force of my hands on the bars. I'm now playing with the handlebar angle to better suit my hands. I did however have a new braking problem. Only during that one particular braking zone, I was braking hard enough that the caliper would flex enough to allow the brake pad pin to contact the outer edge of the oversize rotor, even with the relocation bracket. I have decided that it might just be due to the deflection allowed by the rubber bushing for this alignment pin.


          So, I got some 1/2" bronze, and made a bushing to replace the rubber. It took longer to make than I had hoped, due to the inner bore not matching anything in a numbered/lettered/indexed drill bit set. But still, here it is, press fit into the caliper. I'm hoping I get more positive brake engagement, smoother operation, better brake feel, and less caliper deflection. I've machined the bore just oversized enough that I'm not worried about binding. DO NOT TRY THIS AT HOME, ESPECIALLY ON THE STREET!!! I'm experimenting in a closed course.


          Finally, I got sick of tubes, and I'm now in the process of making all my spoked wheels tubeless. All of mine are 17" with the tire bead shoulders inside the wheel. I'm smoothing out the bead area using JB Weld, applying stickers that frankly don't really stick to the spoke nipples (so I can adjust the spokes without breaking the seal), and then applying a specialized 3M tape over the spokes and adding a 90* valve stem. No more tubes! I've done 2 wheels so far, and both are holding steady without dropping a single PSI that isn't due to temperature variance. Freaking astounding!





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          • #20
            Hooray bike porn!
            Thanks for the update, was wondering how this was going.
            1998 Katana 750
            1992 Katana 1100
            2006 Ninja 250

            2006 Katana 600 RIP - 130k miles

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            • #21
              That tubeless set up is genius. I've seen tubeless conversions on mountain bikes before but for some reason it never dawned on me to do it on a dirtbike.

              This was the first of the couple of race bikes I built over the past two years.



              (Had to post the album link, the photo size is massive)

              unfortunately I blew up the transmission last december and never got around to reassembling it. Hence my newer red bike in the previous photo.

              Word on the street is that Herrin Compound in conjunction with Amish Racing/Trackapalooza is offering a $2000 prize purse for this weekends races. Going to make my best effort to get up there.
              "We are not all beautiful unique flowers. Some of us have bad ideas and bad taste and the things we do come out awful, no matter how much work we put in."

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              • #22
                Dude, that's awesome! I have the BT-45's on my bike now. Just now trying them out for the first time. Put them on when I made the wheels tubeless. All 5 wheels still holding air so far. I did mess up the sticker over one spoke nipple on one of my drz400sm wheels. Oh well. As for the tires, because I was spinning the rear on turn exit, with 3-5 year old tires (likely the reason), I got the 130/70/17 rear tire for my 3.5" rear wheel. It fits, barely, but I had to add two extra chain links and move the rear axle back for it to clear the weld on the right side of the swingarm. If it was a steel swingarm, I'd modify it, but it's aluminum, and I haven't welded aluminum yet. I like the tires, but I'm not sold on the 130 rear with the axle moved back. It does feel stable, and the bike isn't as wheelie prone with the same gearing, but it does turn a little slower. That said, testing on Sunday, I scrubbed in the whole rear, edge to edge, and never had it slip. It doesn't even like sliding when downshifting two gears. Going down 3 provides predictable results.

                For the rally last year, I almost brought the crf150f with me, with the intention of maybe taking one day and going to the Herrin compound. Thought about taking the 150f on the dragon. Instead, I took my pocket bike and rode it on the dragon, in the pouring rain. The Harley guys didn't wave back, and I passed a mini-van.

                My brake mod worked perfectly. Not sure there was really that much improvement other than not the pin not contacting the rotor at all, but there were no downsides at all. The tubeless wheels will take some getting used to, and playing with air pressures.

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                • #23
                  I went out with a couple of friends to a local Kart track on Labor day and made this video. Buddy in front of me has a TB120cc kit, i'm all stock.

                  Track is super fun, way less technical and demanding than Josh's place. Also only about an hour away instead of five.

                  Enjoy the videos and music you love, upload original content, and share it all with friends, family, and the world on YouTube.
                  "We are not all beautiful unique flowers. Some of us have bad ideas and bad taste and the things we do come out awful, no matter how much work we put in."

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                  • #24
                    Okay, time to update once again. I've suffered another engine failure, this time not as significant. Another issue that was hindering my engine longevity was the cam. Apparently, the powroll cam was produced by a company called web, which is known by a few people to produce cams for these engines that are too aggressive, and don't have a ramp on the back side to slow the closing of the valves. I noticed it myself this time by wear finally showing up on the cam lobes, but being suspiciously absent on the closing side of the lobes. It was the cam that came in the bike. This time, it broke the top of the valve off, so the valve dropped, got bent, broke the valve guide, and aside from little scarring, left the head and piston in tact.

                    I purchased a smaller lift cam from a known good company, but as always, decided to play a bit with the rebuild. I found an intake valve from a brand, Psychic, that was black oxide coated for reduced friction and already undercut with the head shape changed for better flow. That meant I didn't have to try doing that part myself, which I had planned.


                    In the time since my last update, I upgraded mills as well. The one I got is old and used, but it's a full size Bridgeport with a 9"x42" table. All I can say is wow, that mill runs nice. I haven't touched the small one since I got the full size. Anyway, the mill comes with with the head. There was small scaring around the edge of the head that provides the squish, so I decided to try my hand at milling the head down. I assembled the motor with clay on the piston, rotated through a couple cycles, and measured. I then milled the head and remeasured. I got the exhaust valve to piston clearance to .070". Perfect.



                    I also did more port work on the head, smoothing out the ridges where the valve seats stuck into the port. You know, the opposite end of the hardened material from where the valves sit. I also removed a fair bit more material from the intake side. Having tried it out since then, all I can say is WOW. The compression is definitely noticeable. I was already starting with a high compression piston. Now, the kick back on the kick starter is impressive when I get it wrong. In switching to a smaller lift cam, I managed to either hold the same power, or even increase it throughout the entire range. The porting work on the exhaust side also served to up the usable rpm limit quite a bit. Using GPS, I've clocked it at 63mph, and I ran out of road while the engine was still climbing. All in all, not bad for a 150 with a 5 speed.

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                    • #25
                      Thanks for the update, love seeing the pics with the mill. Super jealous, hope to someday have a workshop with something like that in it.
                      1998 Katana 750
                      1992 Katana 1100
                      2006 Ninja 250

                      2006 Katana 600 RIP - 130k miles

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                      • #26
                        Well, looks like I finally have a good reason to dump photobucket!

                        Windows 10 won't even let me get to the login page due to all the unsafe issues with their page and advertising. Maybe I'll eventually move the pictures somewhere else and redo the links for this thread. If anyone has any suggestions for hosting, let me know. Otherwise, I'll likely use imgur.com

                        On to other news, I finally got a cool new toy for making my practice a little more informative. A GPS lap timer! The software is a little buggy, but it does do a great job anyway. I can see what I'm doing where to save time, hit better speeds, where I brake to carry the most corner speed, etc. I've also learned how to merge the data with video, and finally learned the bare minimum of video editing. Just taking the raw video and merging the GPS data gives me a whole new perspective of where I'm shifting, where I can brake later, which turns I can take faster, etc. I'm just playing around with this.

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