Oh yeah thats what I forgot, the big torque curve. So what? I raced 4 Stroke twins for years. I like the challenge of keeping a proper race motor in the sweet spot and corner speeds high instead of being lazy and grunting off turns. Thats part of racing, right? Using skill to get the most out of your machine. It is for me anyway.
I think you're missing the point, really. He's building/developing a bike from ground up, so there will be growing pains. As a general rule, 4 strokes are more reliable [or have more of a "service life} than 2 strokes. Especially GP derived 2 strokes. I'd think that once a four stroke is built, it's at good for at least two seasons of racing. Not so with a 2 stroke. Keep mind that 250 crank is $1200. You can go out and buy another 4 storke single motor for that much, if you actually needed one after only one season of racing... Also, faster is not always better. Or more fun. Just because they're making these GP 250's "slower" doesn't mean they're any less fun. They're building these bikes to fit in a certain class, that the GP250's aren't allowed in. In closing, I love 2 stroke bikes and I wish I could run one. Fact of life is though, that I'd be allot closer to being able to afford running one of these hybrids, than running a 250GP bike, purely on the running costs of the thing.
i guess to answer the question of "why build one?" the answer would be for the fun of it. it's not to try to beat 250 gp bikes. you are right, this bike is / will be slower than stock tz. is there any question about that? i guess you have to have as much fun building it as you would racing it. my area of the country is know for dirt-biking. there are lots of dirt bike people around here. lots of resources for singles. in fact the guy who did my engine machine work does all of ty davis' work. so singles is a good fit for me. the guy who built my new pipe used to build pipes for muzzy (mark mcday 10 min. away). ron woods is 45 min. away. ty davis is 20 min. away. there are tons of flat-trackers around here. i took out my own valve train because of poor design (my own fault). but that's what i'm in this for, to do my OWN designing. some of my ideas may be good some bad. over in the uk they call it an engineers class http://www.supermono.co.uk/. it could just as easily be called a builders class. for me, that's what's fun about it. coming up with your own designs and testing them against other racers ideas / designs. it puts your knowledge and your riding skills to the test. update: changes: new stage II hot cam, re-surfaced rocker arms, new pipe, new oil tank, removed idle gear and kick start assy. weighs 245 # with oil and water but empty gas tank. had it out for it's maiden voyage at willow springs this past weekend. dyno'd at 60.6 hp. (only did hp pulls for jetting, don't know torque). saturday practice on 16 / 37 gearing. was on the rev limiter all day. got down to the 34's. i was pretty happy about it. changed gearing to 16/35 sat. night for sunday race. in morning practice got to the 34's really easy, was happy about that. ran great. never got over 80 c. in the formula singles race, had a real battle with the current fast guy - lloyd johnson. sunday morning i introduced myself to him and checked out his bike a little. '91 tz250 with xtz660 motor 280-290#. he asked me what my lap times were and i told him i got into the 34's and that got his attention. the month before he won the race doing 37's. he told me the fastest he has ever gone on his fs is the 32's. the bikes are very evenly matched. i have a little more accelaration but i think he has more top speed. i could pull on him and draft pass him but then he'd re-draft me and get even with me. that's what happened on the last lap. i draft passed him on the back straight, he re-drafted me and pulled along side. we were 2 wide in 8 and 9 but he had a better line so i had to pull out of it and get behind him at the apex of 9. i was going for a draft pass but when he went for a shift it caused me to close on him too quickly and i had to pull out of his draft before i wanted to. i came along side of him, then it was a flat out drag race to the finish line. i beat him by .050 sec. to win. he pounded his tank in discust! (as said by the anouncer). that race was one of the funnest races i have had. i'd say i am off to a pretty good start. now i need to sort out my suspension. in the race the bike got up to about 90 c. pics of the finished bike: edit: the noise level alowed at wsir is 108 db, front wheel is a marvic i found on ebay. added mylaps link http://mylaps.com/results/newResults.jsp?id=485118
where you guys racing these things? i need some other GP singles to beat up on. http://forums.13x.com/showthread.php?t=133748
Fair enough. Didn't set out to be a jerk or antagonistic with my comments and I wish you all the best with your efforts. The bike does look pretty cool and I'm sure you'll have a ball racing it. An old friend of mine used to tinker constantly with his hawk sometimes things worked most of the time they didn't, but he always had a good time trying even if he did DNF just about everything he entered. I always scratched my head at him because at the time all I did was work on bikes so that was the last thing I wanted to do at the track. He finally told me, "you know, I really just like fucking with the thing". If it works for you more power to you.
you have absolutely no idea what you are talking about. what kind of magic dependable TZ do you have that has double the service life of a modern 4 stroke single? my TZ weighs 5 lbs more than a stock TZ...full of fluids too. my WR450 motor with electric start, weighs EXACTLY the same as the TZ motor i removed. as previously stated, this isnt intended for competition against a standard TZ...although i have no problem beating them with mine, this bike is a neat alternative to the SV's and lightweight Ducs... open your mind mang.
Holy crap, Robert, that megaphone on the TZXR is ridiculous! I mean that in a good way, of course. Bad ass! If you ever make it up to run AFM, let me know. I'll load up the kid and come out to spectate.
what part of the country are you in? i'm in southern california and willow springs is one of my local tracks. wsmc has a race just for formula singles. unlimited frame, displacement, bodywork and fuel. only limitation is that it must be a 4-stroke single and meet the general motorcycle requirements such as 108 db measured from tech while you are on the track. i guess there used to be a lot more than there is now. ahrma has a local series too. i have thought about joining their club too. there are several other classes i can race the bike in but i think the only other competitive race would be formula twins light weight. that is for sv650's and ex650's with formula rules. i think that with enought time i can be competitive against the sv650. i was going to race the ftlw race last sunday but it was back to back with my fs race and i was tired and cooked my tires so i decided not to race it. i'll be doing wera west races too. f2, clubman, dsb
