A pic of Ian's Ns 2 1/2 with crosser barrells. Dyno chart + dyno chart of the 475. Makes intersting reading. The crosser barrelled 444 should be good also.
The 475 graph looks fantastic. Not that the other don't as well but that 475 looks really good. _________________ If I have to take the carbs off once more...
I'm going to get the 444 crosser engines pipes made to peak at 10500 rpm which is 800 rpm higher than the 475 (big bore standard barrel) engine. The crosser barrel gives better power & torque throughout the rev range than the standard engine so even with 33cc less at 444 should put out as much as the 475 engine, with the same sort of curve and the extra revs at the top end 90bhp should be achievable.
The 250 with the standard bore of 56mm makes 54bhp so add another cylinder + 27bhp equals an 81bhp 375cc engine so with another 69cc (+18% more cc) should give around 10% more power which would be 88 / 90bhp. The 250 engines barrels are very mildly tuned and the pipes are not custom made for the engine (damaged RGV250 race pipes off Ebay for £40) so custom pipes and a higher state of tune together with what I learnt whilst building the 250 engine should go in my favour, fingers crossed with the triple !
The 250 looks wicked! As it already looks so different to an NS, I'd almost be tempted to say fit some TYGA bodywork ad do as in a Kato replica, with the pipe exiting under the seat like that!
The guy you may be interested to talk to here, is Martin77. I bet he'd like to do a set of pipes for something interesting and unusual like this! He only does mild steel though, but they are all hydroformed, look fantastic, and work exceptionally well. They will certainly work better than adapted RGV pipes, anyway!
He mostly does Yamaha pipes, but did a few sets for my MC21, the best of which saw over 2hp on top of my million dollar Japanese Ethos pipes, but at the cost of the midrange. Another set were the same kind of power as my Jap pipes, but the midrange was better. I'm a tart though, so naturally I kept my Ethos pipes on! Martin's pipes are ready and waiting for a project one day though! _________________ Andy.
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NS500Racing wrote:
I'm going to get the 444 crosser engines pipes made to peak at 10500 rpm which is 800 rpm higher than the 475 (big bore standard barrel) engine.
I only ask as I am unused to a motor that peaks as "low" as the NS triple. I am comfortable with the majority of well set up NSRs peaking around 11,500 and revving to 12,000. It just feels natural to me. I guess it would after 18 years! _________________ Andy.
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Thanks for letting me know about the pipe chap, I'll no doubt contact him and see what he can do.
I've tried a few different sets of pipes on both the standard bore NS's, the 444 and 475 big bores and found out that a pipe that peaks at anything much over 10500 - 11000 rpm simply shifts the curve over to the right and makes not much more power than it would do at 1000rpm less with a lower peaking pipe, lower revs are also kinder to the crank. The NS front two cylinders fire at the same time so would struggle to spin up as fast as a 250 twin and the portings a little more old school than the NSR's.
A pipe that peaks at 10500 will rev on to 11000 and drop back in the power at 9500, (especially with programmable ignition fitted) the NS is also very torquey when bored out and even more so with the crosser barrels fitted as they are ported as standard for more low down grunt than a road race barrel.
The chap at the dyno I use still can't get his head round the 475 power curve, he said it looked more like a tuned SV650 and made as much torque as the tuned R6 he'd just set up, except that was reving to 16-17000rpm !
Yeah, the NSRs are similar in the torque department (although, not as much, obviously!), when compared to similar bikes and equivalent capacities.
The revs would be useful for a higher top-end on some circuits, I imagine, which is why I asked if the lower RPM and torque was suitable for pulling much taller gearing than stock to compensate for the higher revs.
Are such things as kit transmissions available for the 250 and/or 400? _________________ Andy.
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You can pull higher gearing with the bigger cc's and even if you find yourself in the wrong gear coming out of a corner just dip the clutch a little and away you go, back up into tractor pulling zone.
It's just a shame that PSB mag didn't give me more time to set the road bike up as it is now making 7bhp more (fueling right now and new clutch plates ) than when it was tested against the RG so I think would go over 145mph or a little more with taller gearing/sprockets.
I have had uprated gears made in the past and have some more on order together with taller 1st gears to make 1st and 2nd closer. There is also a company in Japan that makes close ratio boxes with dry clutches but they work out at around £4000 so it would probably be cheaper to have them made over in the UK but would many people want to pay that sort of money for a noisey clutch ? and no more power, probably not.
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