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Modifying VTR250 motor to Spada spec

Discussion in 'Modifications and Projects' started by nate71c, Mar 19, 2009.

  1. Hi,

    Does anyone know the mechanical differences between the 88-89 VT250 Spada and the still current VTR250? Looking at the specs, I can see that the Spada runs 40HP vs 31HP in the VTR, the Spada redlines at 14,000rpm vs 11,500 in the VTR, and the Spada runs a 6 speed gearbox vs 5 speed in the VTR. So, am I right in assuming that the VTR was designed as a tamed down version of the Spada to appeal to a broader range of riders?

    I am interested in understanding if I can fit the different parts from a Spada spec motor to the VTR to achieve the 40HP. For instance, is it just a different profile pair of camshafts? If the bottom end is the same, will the VTR motor handle 14,000rpm? My VTR is still under warranty, so this is a "next year" project, but it's got me interested.

  2. Oh, and I forgot my other question, relating to free flowing exhausts and rejetting. The VTR250 is running a Neptune slipon, which has a very deep and quite loud note. I've fitted the baffle for commuting work, which seems to boost the low end torque a bit, but overall the bike feels very linear right through the rev range. Is this normal for a VTR250?

    I can only compare it to a 1989 Kawasaki GPX250 I owned 20 years ago, and the GPX seemed to be a fair bit quicker, with a real feeling of coming on the cams at 7,000rpm and pulling strongly all the way around to the 14,000rpm redline. The VTR doesn't rip to the redline, but makes strong power from quite low in the rev range.
  3. There is a performance difference between the Spada and Vtr250, you'd be lucky if it's more than a couple of bike lengths at best in a drag with equivalent riders up to illegal speeds. In day to day terms it's very little.

    To my knowlege, the Spada has double valve springs, different cams, different gearbox and perhaps different heads and jetting than the VTR250. Basically the VTR250 was tuned to operate at/develop similar levels of torque at 1500-2000rpm or so below the spada at any given engine speed and is geared to suit it. The extra power the Spada makes is essentially in the extra rpm it can pull and pushes the torque and power to a slightly higher points throughout the rpm range.

    The extra hp/RPM/gear does help a little at the top end, A Spada (on private road with a <80kg rider) will pull 160 on it's redline on a flat road eventually :-w , which I would consider near impossible on a vtr250 without some help (tailwind, cliff, fairing, gearing etc)......It doesn't mean anything though, at 100kph the VTR250 is cruising at lower rpm, although the Spada may have a tiny bit more response there, the easier cruise is probably worth the tradeoff.

    I think if you haven't ridden the GPX250 in many years you may have the rose tinted glasses on, I wouldn't consider the inline twin in the GPX/ZZR to be a sportier or more powerful engine than the Honda V-Twin, the honda is typical v-twin in it's delivery vs the inline's slightly more peaky power delivery. I would say the Spada is faster and the VTR is no slower than the GPX/ZZR

    The exhaust will make precious little difference to performance, and rejetting is unlikely to provide any benefit, The differences you feel are probably more perceived due to the sound.

    The v-twin is pretty linear in power delivery, if anything, the vtr actually trails off a little towards redline where the Spada is still pulling, although neither are peaky like an inline 4 or to a lesser extent the inline 2.

    It's worth noting all watercooled 4v multicylinder 250cc 4strokes are vaguely similar in outright performance on the road <80-90kph. Whether it be a gpx250 or a cbr250rr, the differences below 100kph (ie before the cbr250 can really stretch it's legs) are pretty small (couple of bike lengths at best). Ie they are all "slow" :)

    The gains from modifying a vtr250 engine to spada spec wouldn't be worth the cost especially if larger LAMs bikes are considered.
  4. you dont happen to park in the CBD around flinders st ish do you?
  5. No, I don't think honda thought to themselves 'gee this 250 is way too powerful we better slow it down a bit' :LOL:

    It is, zzr/gpx has a few more HP - but not where you want it. When I tried dan's vtr straight after getting off my zzr I was impressed by the low rpm grunt which easily trumps the zzr, you can feel a noticeable difference in torque in favour of the vtr, up until about 80 when it evens out again as the zzr is in its higher rev range.

    Sorry I don't know the difference between the vt/vtr though.
  6. I do work in the City, parking in and around Wakefield/Flinders/Gawler Place. I used to park my MadAss125 at the DECS bicycle racks on the paved area adjacent the plaza, and started doing the same with my VTR until wednesday when I got an expiation notice from Adelaide City Council. Since 3-4 other scooters & bikes had followed my lead, I think we all got done. However, the expiation notice was for stopping on a footpath which I challenged on the grounds that it's not a footpath. They cancelled my expiation notice because it is in fact a public space, not a footpath. If any other guys who got pinged are reading this, send an email to city@adelaidecitycouncil.com and plead your case.

    I've written a letter suggesting this bike rack become converted officially to motorbike and bicycle parking, since DECS now have a secure cage for pushbikes.

  7. While the parallel twin is virtually the same in the GPX and the ZZR250, the GPX is noticably perkier. All to do with weighing 25 kg less and having 2-3 HP more because the airbox in the GPX is supposedly less restricted. The even earlier 85-87 GPZ250R uses the same motor and is quicker again, being less than 130kg.

    I've been riding for over 20 years, so not restricted by LAMS. I just wanted a nimble but reasonably zippy commuter bike. Didn't want a fairing or useless forward mounted mirrors, so thought the VTR250 looked about spot-on. But I figured a 25% increase in power might be more noticeable. I'll talk to Honda World about Spada cams and see what they say.

  8. There you go. You have a PM. I work at decs too, and till recently had a blue scooter, just bought a VTR also :)

    I dont think you'll have luck with converting the racks. They will NOT set a precedent like that, and other people who dont work at DECS use the rack.
  9. Mm, peak power for the VTR250 is 10500rpm, just a whisker off of redline. Though the torque curve would be falling away some time before that.

    I tried to find a list of the differences between the Spada's motor and the VTR250's motor, but was unsuccessful... Heck, I can't even find a page specifying where peak torque occurs on the Spada. :?

    Anyhow... DTwo, your list of differences seems reasonable. :) At a minimum it'd have to be a different ignition computer to allow the bike to rev out to 14,000... Probably an upgraded valve train so it doesn't get valve bounce. Probably more aggressive camshafts to push peak power's appearance closer to 14k.

    Random thoughts:
    Not having a sixth gear actually saves a bit of weight (and rotational inertia), improving the VTR250's acceleration "all things being equal". You would have to weigh up the benefits of slightly closer gear ratios vs reducing rotational inertia and saving the time lost to due to an extra gear change. Much of a muchness, IMHO.

    Peak power coming in at 10,500 rather than 12, 13, 14k would suggest that the VTR250 would have a stronger low and midrange power delivery than the Spada, making it a "lazier"/easier bike to ride.

    I don't think it's worth trying to upgrade the VTR250 to Spada power levels. Motorcycle modifications rarely make economical sense, bang-for-buck.
  10. You're probably right. The VTR is perfectly fit-for-purpose taking me on my 42km round trip 5 days per week, rain or shine. My heart wanted a 2009 Kawasaki ER-6N, but I couldn't justify the extra $5k and additional fuel, rego, insurance and maintenance costs just to tootle around filtering through logjammed city traffic.

    Why don't Honda slip a 500cc V-twin into the VTR chassis and leave it otherwise untouched? Now that would be interesting. Or build a simple naked version of their VTR1000 Firestorm? All the Honda midsize bikes are 4 cylinders and that doesn't float my boat like it used to. Been there done that with all the ZZR-600, ZZR-1100, ZX-6R type stuff.

  11. Likely because that'd really start to piss of Ducati. Legally. Hold up a vtr 250 side shot to a monster 600 for a laugh.
  12. I think the VTR250 is lazier to ride, although frankly they are close enough it doesn't make that much difference, the spada pulls a little harder for a little longer, this image from the honda fact book spada page shows the spada's power and torque curves. It actually peaks at 40ps at 12,000 and 2.6kg/m at 9000rpm so there's not much reason to rev it over 12,000. It's interesting to note the Spada was detuned from the previous vt250f which is also on that image and looks very peaky for a vtwin, so the cams or whatever from that spec engine may be a better way to go....?


    The VTR250 is in the fact book too it's listed at 32ps/10500rpm and 2.4kgm/8500rpm so the differences are pretty small in some ways

    130oddkg dry for the gpx sounds suspiciously light for a faired bike, and would make it lighter than either the VTR or Spada......i guess quality will weight a little more though :LOL:
  13. Oh yeah. :LOL:

    Even the VTR250's instrument panel is somewhat familiar, if you squint a little.
  14. If I'm not mistaken, the VT250F uses a 4 valve head, wheras the VT250 Spada and the later VTR250 use a 2 valve head. 4 valves per cylinder tends to push peak power and torque up the rev range, and increase overall peak power compared to a 2 valve design, which is better for low and midrange response.

    So, upping the spec of my VTR to VT250F would definitely involve different heads, if they even fit on the block and the camdrive can be adapted to suit. That's just WAY further than I'm remotely considering going, especially since according to the dyno chart you posted, the extra power comes at the expense of having to carry 2000rpm more to achieve the same torque output as the Spada. There goes my primary reason for buying a v twin - i.e. good low down response for safe filtering through heavy traffic.
  15. Actually Honda thought 'this 250 is way too expensive to make and we can't sell it for much less than the cost of a 600 so we'd better lower the spec.' That's the reason it lost a gear and that lovely alloy frame.
  16. GPX250; 138kg dry
    ZZR250: 146kg dry

    You sir, need to go back to primary school maths class.
  17. I am sorry to have gotten the weight difference wrong. I was working from an almost 20 year old memory of the specs and hadn't looked them up. My reference was purely that the 3 or 4 GPX250s I've ridden have all been quicker than the 2 ZZR-250s I've ridden and I believed the specs explained this re slightly lower power and more weight for the ZZR. However, my main point was the GPX250 engine has a much more noticeable powerband than the VTR250, and pulls hard around to 14,000rpm.

  18. Just spent a few minutes at motorcyclespecs.co.za havign a browse. The GPX250R has 45HP as well as being 8kg lighter than the 40HP ZZR-250. That's enough to make the difference I noticed.

    Interestingly, the CBR250RR is 5kg heavier than a GPX250, and makes 5HP less than a GPX250, at a higher RPM.

    I suppose it's all academic these days with a broader range of LAMS approved bikes killing the highly tuned race rep 250 market in Australia. If you want to go fast, buy a 600 Supersport or a two stroke.
  19. 45hp for the GPX would seem very optimistic, certainly doesn't feel like 45hp :) ,

    The gpx250 service manual quotes 38ps at 11000 and 2.5kgm at 10000 those figures combined with the slightly less weight could make the GPX faster on paper then the Spada or vtr, Maybe when thinking of the GPXs i've ridden I have my Grey tinted glasses on :grin:
  20. I am pretty sure that the spada uses 4 valve per cylinder heads. The service manual shows 4 valves per cylinder as do the photos in this thread: https://netrider.net.au/forums/viewtopic.php?t=52150&postdays=0&postorder=asc