spacemonkey Posted April 1, 2009 Report Share Posted April 1, 2009 just to add, i dont think the 125's are especially light. alright compared to a big 1ltr 4 stroke but my nsr125 felt heavier than my kr1s race bike!! prob making 4-5 times the power in restricted form it makes sense to buy a nice 250 and spend the change on tyres/suspension and pattern bodywork. the prilla is miles better than the nsr in terms of spec id imagine but still suffer the fate of haveing rubbish forks regardless of how pretty the frame/swingarm are or how fast the motor is compared to other 125's. if your hooked on the idea of a 125 get a superteenm bike as it will be soprted and have 30 odd hp. those bikes are well capable of seriosly quick laps considering there a road based 125. i say rgv/kr1s/nsr or tzr and have it prepped to cope with track day hammer. You are probably right there! The 250's are built for people who want a light bike with good performance. The 125's are built for the learners that are restricted to 125cc bikes but want to look the part. Low price is the main goal here. Even the frame on my RS125 is shite. It's all cast instead of being fabricated from Extruded aluminium and castings like the old AF1 frame I have. The swingarm is similar. They look nice but they aren't designed to be light. Link to comment Share on other sites More sharing options...
wavydavy Posted April 1, 2009 Report Share Posted April 1, 2009 Anyone remember a late 80s/early 90s PB photo-special on GP bikes? One of the pics was Schwantz' Pepsi RGV500 being carried, sideways, into the pit box by two mechanics - the caption read something along the lines of "RGV500, weighs less than an NSR125, but with 180bhp". I think the NSR was the latest, lightest, hot-poop 12bhp 125 at the time... It's the same law of improving returns with 4Ts as well - look at the power/weight of a GS500 vs a GSXR1000. Jesus I *have* to get the NSRVF finished for this summer - I'm hoping to keep below 150kg dry (which, given the basis bike(s) is hoping for a lot!) and a quick refresh on the motor shoould, I hope give 70+ at the rear wheel. Nowt like a 'modern' bike (160kg dry, 112bhp at the wheel 600s, anyone?), but it's a "peaky" stroker and that's what counts, innit? Dave Link to comment Share on other sites More sharing options...
mgtkr1 Posted April 1, 2009 Report Share Posted April 1, 2009 150kg shouldnt be outta the question with some careful forethought regards to bracketry ect. trick wheels is worth its weight in gold for saving unsprung mass. irc a 1kg saving unsprung is worth something like 4kg of sprung weight!! with pipes i dont think 70hp should be ruled out either, from a healthy ns400r. think theyt can make serious power with pipes/cr barrels/carbs ect. seen the special been built on the rgv site?? practiclly a gp bike with a wet clutch!! gorgeous thing. Link to comment Share on other sites More sharing options...
wavydavy Posted April 1, 2009 Report Share Posted April 1, 2009 150kg shouldnt be outta the question with some careful forethought regards to bracketry ect. trick wheels is worth its weight in gold for saving unsprung mass. irc a 1kg saving unsprung is worth something like 4kg of sprung weight!! with pipes i dont think 70hp should be ruled out either, from a healthy ns400r. think theyt can make serious power with pipes/cr barrels/carbs ect. seen the special been built on the rgv site?? practiclly a gp bike with a wet clutch!! gorgeous thing. Gotta get the thing back on the road after the NK Racing nightmare..... The 500 Terry Shep kit is reputed in the state mine is to be more than 70, but it feels like 70ish to me. Jolly Motos save a lot of weight and revs are 2k higher, but that's serious short engine life territory.... From a std 387, I'd be shocked to see 50 at the wheel...... 72 was claimed, but 40-is is normal NS RWbhp... There are many nice trick NSs and more than one using CR125 barrels and heads... I've not seen one running yet, but they all look bloody great and I envy the patience/expertise of all the guys who do that. Dave Link to comment Share on other sites More sharing options...
fontyyy Posted April 1, 2009 Report Share Posted April 1, 2009 I'm hoping to keep below 150kg dry (which, given the basis bike(s) is hoping for a lot!) and a quick refresh on the motor shoould, I hope give 70+ at the rear wheel. Picked up a 1996 RS250 (a real one, i.e. a Honda one) from the Isle of Wight for a friend of mine yesterday, it felt light even next to my NSR250 racebike, quick flick through the manual revealed 102 kg "semi wet" (which I guess is all other fluids, no fuel?). Proper tool, I'll race the proddy 250 this year I think then maybe move along to a real one Link to comment Share on other sites More sharing options...
spacemonkey Posted April 2, 2009 Report Share Posted April 2, 2009 Picked up a 1996 RS250 (a real one, i.e. a Honda one) from the Isle of Wight for a friend of mine yesterday, it felt light even next to my NSR250 racebike, quick flick through the manual revealed 102 kg "semi wet" (which I guess is all other fluids, no fuel?). Proper tool, I'll race the proddy 250 this year I think then maybe move along to a real one I wonder if the proper race bikes would be too delicate for the road? It'd be cool to put one on the road, maybe even with a road motor in so you don't have to spend all your time and money on changing engine parts! Some of the TZ's use road bike crankcases don't they? Link to comment Share on other sites More sharing options...
wavydavy Posted April 2, 2009 Report Share Posted April 2, 2009 I wonder if the proper race bikes would be too delicate for the road? It'll be fine! After all "Sameshoz"'s 131mph RS125 doesn't have any reported reliability issues.... Dave Link to comment Share on other sites More sharing options...
spacemonkey Posted April 2, 2009 Report Share Posted April 2, 2009 It'll be fine! After all "Sameshoz"'s 131mph RS125 doesn't have any reported reliability issues.... Dave Yeah, but that was 'well specced up, innit! - Or somink or nofink.' Link to comment Share on other sites More sharing options...
wavydavy Posted April 2, 2009 Report Share Posted April 2, 2009 Yeah, but that was 'well specced up, innit! - Or somink or nofink.' u no its trick cuz wen u choon em the speedo swaps from the 'm' for 'mormal' to a 'k' for 'kwik' Dave Link to comment Share on other sites More sharing options...
Cris Posted April 2, 2009 Report Share Posted April 2, 2009 Just for clarification, spacemonkey and fontyy, trackday addict was quting someone called "Sameshoz" and didn't claim the speed himself - I'll agree that Sameshoz sounds like a , though, and I bet he knows the fella I used to know who had a 150mph X7 and once got 125 mph out of a GSX250 twin..... As for it maybe being all down to gearing, how much run up does a "highly tuned" RS125 road bike need to get to that kid of speed? If it's just a case of finding a 27 mile straight then the bike ain't going to be much use for racing/track days. If it's any help back in the day my mate had a de-restricted Mito (seven gears and all). On it's tod it would get close to 100 with my mate riding (he was a little ahem slimmer than me). With him drafting me on my RGV about 3 inches from my rear wheel (me bolt upright) we saw 105mph (based on my speedo over reading by 10% which was about right). This was in seventh on the Mito with the engine running well above the red-line. Link to comment Share on other sites More sharing options...
spacemonkey Posted April 2, 2009 Report Share Posted April 2, 2009 If it's any help back in the day my mate had a de-restricted Mito (seven gears and all). On it's tod it would get close to 100 with my mate riding (he was a little ahem slimmer than me). With him drafting me on my RGV about 3 inches from my rear wheel (me bolt upright) we saw 105mph (based on my speedo over reading by 10% which was about right). This was in seventh on the Mito with the engine running well above the red-line. Must have been a 'mormal' speed reading! It was really doing 150 at least! Link to comment Share on other sites More sharing options...
trackday addict- Posted April 2, 2009 Report Share Posted April 2, 2009 LOL... yeah i didnt really believe him myself, he also said it was with a standard carb soo i myself know that the bigger 34 is better like i say iv only experianced 108 on sat nav with my bike and its not exactly standard, standard gearing but with renthal sprokets aswell and a double bubble which all helps at the end of the day. Id say get a 125 im 31 and have my gixxer for going fast and my rs for twistys. Link to comment Share on other sites More sharing options...
mgtkr1 Posted April 4, 2009 Report Share Posted April 4, 2009 for serious track use look at the honda rs125 or tz. the later the better but your budget should see you get a quality older model poss with spares if you shop around and are patient. inc little bikes on a par with a fast 250 prod bike in terms of straight line speed i would imagine, certainly faster than anything else were corner speed is concerned. more national kart than motorbike if you get my drift. if your quite light then the 40hp should be more than ample to give you a good impression of speed/acceleration. best learn the technique of clutch slipping then!! Link to comment Share on other sites More sharing options...
SamB Posted April 4, 2009 Author Report Share Posted April 4, 2009 Thanks for the advice - lots of good info here. I think a little 125 might be a bad idea now. I was attracted to the rs125 because the frame and swingarm look really well made- I understand this is largely cosmetic? Looking around, the RS250 seems to been the most numerous 250 out there. Might buy a scruffy one and put track fairings on it. Link to comment Share on other sites More sharing options...
spacemonkey Posted April 4, 2009 Report Share Posted April 4, 2009 LOL... yeah i didnt really believe him myself, he also said it was with a standard carb soo i myself know that the bigger 34 is better like i say iv only experianced 108 on sat nav with my bike and its not exactly standard, standard gearing but with renthal sprokets aswell and a double bubble which all helps at the end of the day. Id say get a 125 im 31 and have my gixxer for going fast and my rs for twistys. Yep, it is pretty on the outside, but take a look on the inside surfaces... Link to comment Share on other sites More sharing options...
trackday addict- Posted April 4, 2009 Report Share Posted April 4, 2009 Sorry but the rs frame is really strong, i had a 50 mph crash on a old CBR and the frame bent, had a 60 mph crash on the the rs and the frame was fine with no crash bungs. Did need new fairings though. Link to comment Share on other sites More sharing options...
spacemonkey Posted April 4, 2009 Report Share Posted April 4, 2009 Sorry but the rs frame is really strong, i had a 50 mph crash on a old CBR and the frame bent, had a 60 mph crash on the the rs and the frame was fine with no crash bungs. Did need new fairings though. Don't be sorry. I wasn't trying to suggest that the RS frame was weak. I was saying that it was shite quality. Anyone who takes a close look at one will see what I mean. Stiffness and weight are usually the main issues with motorcycle frame design. If they are stiff then they are generally strong enough in any case. Resisting crashes is not normally a priority in frame design, so you wouldn't call it a rubbish frame just because it doesn't survive accidents well. They are normally meant to be as stiff as possible and as light as possible at the price. The RS frame is made from cheapo, cast shite so they had to make it very heavy. Most aluminium bike frames are made from couple of castings (on fancy frames these would be billets) welded to extruded beams. - Much better stiffness to weight ratio but surely more expensive to produce. Take a look at an Af1 frame (the earlier Aprilia 125) and you'll find it is far nicer and far lighter. I would be willing to be the stiffness to weight ratio is far, far better on the old AF1. Are you suggesting that the speed of each crash is a sensible way to judge the strength of the frame? For all we know, the 60mph crash was a lowside on grass and the 50mph crash was a highside into orbit, landing on spikes and then getting run over by a truck. For example you could possibly graze a fairing at 120mph or totally destroy a bike at 30mph depending on the individual accident. It can be the same story for the rider too. Link to comment Share on other sites More sharing options...
beerat Posted April 4, 2009 Report Share Posted April 4, 2009 Hi All Here is my opinion for what it's worth , I have riden and crashed (too many times) both my TZ125 and TZ250 and while all the cosmetic stuff seems to destroy itself quite easily ie bars, footpegs etc the frames on both have taken some heavy impact's and other than a few scratches have remained straight and true all the time . The thing with both RS and TZ they are true race bikes not road going so have more strength in the headstock and frame spar's than normal . I have seen FZR 400 frames snap the headstock off after a lighter impact crash . For your hard earned cash try and get a RS or TZ of either cc they are built to race/crash and the the most fun you will ever have , Corner speed is better than going fast in a straight line Chris Link to comment Share on other sites More sharing options...
trackday addict- Posted April 4, 2009 Report Share Posted April 4, 2009 Hmmm i actually agree with you on the quality of the frame my GSXR's is far superior, i only relised this after i polished my frame today and notices all the shite welds. Still aslong as it stays together lol. Link to comment Share on other sites More sharing options...
spacemonkey Posted April 4, 2009 Report Share Posted April 4, 2009 Hmmm i actually agree with you on the quality of the frame my GSXR's is far superior, i only relised this after i polished my frame today and notices all the shite welds. Still aslong as it stays together lol. It'll be fine for it's purpose... Just not the highest quality item, not as stiff/light as it could be. Link to comment Share on other sites More sharing options...
beerat Posted April 4, 2009 Report Share Posted April 4, 2009 Hmmm i actually agree with you on the quality of the frame my GSXR's is far superior, i only relised this after i polished my frame today and notices all the shite welds. Still aslong as it stays together lol. Sorry I'm NOT knocking standard road bike frame's or the quality of the factory weld , But they are what they are road bikes . It is in the interest of the factory to make a frame strong enough to use as a "road bike" but not to use as a race bike . Why do you think the factory race frames are so much stronger and lighter than the road going ones ???? All i was pointing out was that TZ and RS bikes are true GP race bikes and thus stronger / lighter in therir build Only my opinion Chris Link to comment Share on other sites More sharing options...
intra Posted April 5, 2009 Report Share Posted April 5, 2009 Get yourself a 10 year old Honda RS250. They aren't too expensive and it will blow you the fuck away. Fuck dicking around with street-legal 125cc bullshit-bikes. Link to comment Share on other sites More sharing options...
gregtrx Posted April 5, 2009 Report Share Posted April 5, 2009 Surely on the stokers the engine isn't a stressed member so the frame itself has to be stiffer/stronger? Link to comment Share on other sites More sharing options...
Kayla Posted April 5, 2009 Report Share Posted April 5, 2009 I think they were/are on the later models. Link to comment Share on other sites More sharing options...
spacemonkey Posted April 5, 2009 Report Share Posted April 5, 2009 I think they were/are on the later models. AF1's have a loop that goes right under the engine, connected to the main frame at the front and rear. RS125's have a couple of bars that go down from the headstock to the front, lower engine mounts. It's also bolted in at the back and on the barrel. Link to comment Share on other sites More sharing options...
mgtkr1 Posted April 15, 2009 Report Share Posted April 15, 2009 above as joshmolloy(any relation to adam??) posted is the way into trackdays/racing/2 strokes. they aint perfect but with the huge amount of aftermarket parts they can be made reliable and tuned highly with not a great deal of effort. loads of suspension options, brakes ect and best of all theres mega potentiol to be had from the motor. from kit gaskets/the col mod to dave coopers p'vs/heads/inserts to ignitions programmable ect. also new 1st/2nd gear option that gives closer ratio's and eliminates the notoriously fickle gearbox issue with 2nd gear. imo, the vj21 with 17' wheels/usd forks is the nicest, race orientated rgv other than the unobtainable/pricy 23. 60hp is easy, 65hp is still not too hard and 70hp plus is quite normal for top level f250 bikes. 65hp is the usual though but trust me, its plenty. good pipes and careful setup with (most importantly) suspension work/tyres and weight saving should see that people arent using you as a chicane on trackdays with enough practice at all but the fastest tracks. the kr1s is a similar prospect but not as much off the shelf tuning gear. a bit specialist if your serious although one of the best 250 engines in f250 ironiclly. also see rs250 prilla. a bit on the expensive side though compared to a battle scarred vj21 and not really a great deal quicker/better if you sort the bike out personally/have k tech/maxton revalver your forks/shock ect. at trackday level, what more do you need? i suggest you look up the rgv site. Link to comment Share on other sites More sharing options...
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