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Suzuki Across - To tune? 'Normal' characteristics?

Discussion in 'Technical and Troubleshooting Torque' at netrider.net.au started by TassieRider, May 4, 2009.

  1. Hello all,

    I have a 1996 Across and basically would like to know whether it is worth getting it tuned. I would appreciate any advice that you can give me based on the following:

    - I am aware that it is a 4 cyl 250cc and as such is, and should be, slow.

    - It has been regularly serviced but never had the carbys tuned that I am aware of.

    - With an even mix of spirited riding and commuting it has returned around 5.5 L/100km, perhaps a touch high?

    - I have pulled it apart and the carby slides are healthy, needles in stock position, and that's about the limit of my carby knowledge.

    - It is my first bike and the only one I have ever ridden properly, hence I'm not really sure whether it is as quick as it should be...

    - It feels 'gruntiest' from about 7k to 11k rpm, and above that feels quite flat, although it will rev out to around 16k. Is this normal? If so is it worth changing air filter/exhaust and retuning to free up the top end? Or is that just the way it is and always will be?

    - As you can probably tell I would like it to be a bit faster, but am unsure whether I will be able to gain anymore power by modifying/tuning.

    If you think that all of that sounds like a normal, healthy Across then at least my curiosity will be satisfied and I can harden up and deal with it until I'm off my restrictions.

    As an aside, it has arrow max's on it... can anyone recommend a more sporty tyre? If I can't go any faster in a straight line, at least I can go faster around corners!

    Also worth mentioning, if I ride it every day it starts straight away with a bit of choke. If I don't ride it for a week, it's a real bastard to start, taking a long time and a lot of cranking to get it going, doubly if it's cold. Could this be a leaky fuel tap slowly flooding it? Or s that normal as well?

    Apologies for the lengthy post, any insight would be welcomed.

    Thanks in advance.
  2. Hi mate, I doubt you will get much performance advantage, but getting the carbs synced & tuned will make it run smoother & your fuel efficiency will be slightly better. (Slightly)

    Everything else seems fairly normal, most people don't bother doing any mods to 250's, unless you want to keep it for a commuter or whatever, I wouldn't bother, your performance gains will be negligible (& probably not cheap) & I doubt you will add anything to the resale value.

    Save you money for a bigger bike, then mod the crap out of it! :grin:

    Tyres: Dunlop BT45's are good for the ZZR (IMO), I can't imagine an Across being too different.
  3. Aha. Chengaleng's Across does the same thing. It's not normal - if you ride another Across you'll feel power build all the way to the redline.

    I believe the power has been limited. Somebody once told me that ours was probably a Japanese import and that in Japan they were limited to 30hp or something like that. So you get power that builds up to about 11k, and then is completely flat up to the redline.

    I don't know how to fix it - it could be in the ECU, or it could be a mechanical restriction. The fact that it happens at a specific RPM leads me to guess that it's more likely to be in the ECU than mechanical. In fact I've been kinda wanting to grab a stock Aussie ECU from a bike that I know goes like it should, and plug it in to see if it fixes it - but now I've streetfightered Cheng's bike and the ECU is jammed into a tiny hole in the frame and I doubt I can get the buggering thing out to try.

    I suggest you have a crack at that before trying anything else. And please let me know how you go, if it's an easy fix, or your mechanic works out how to derestrict it mechanically, I'd love to do the same.

    Oh - and yes, get Bridgestones. Arrowmax are shite.
  4. You could always get a performance silencer and K&N air filter, then tune the carbs to match. This will mean that you'll have to set the needle a step or two richer, and probably get an upsized main jet(s). Not very hard, but you'll be getting the best from your bike with the stock setup.

    Other mods start getting expensive and focussing on internal work. If you're really keen, you could order an ultra thin cylinder gasket to bump the compression ratio up a small amount. Fair bit of spannering involved to do it yourself, and not worth the cost to send it to the shop.

    I say do the silencer, filter and carbies. It'll be relatively cheap and easy. It won't let you keep up with litre bikes by any means, but it should give you a slight, yet noticable, improvement. Hell, I'm working a 125...and why? Because I enjoy tinkering and like the improvements I'm seeing already.

    You could go crazy and put the bike on a race diet; stripping components where they aren't needed. Pillion seat and footpegs, replace battery with 10,000 mF capacitor, ditch electric start for kick, run minimalist lighting, replace the subframe with a lighter alloy one and the wheels with cast magnesium items... Crazy stuff, of course.

    But fun :)

    Cheers - boingk
  5. Hmm, not sure about that number. :)

    The power limit for 250ccs in Japan was 40ps, but prior to the limit was brought in the Across made 45ps. Post-limit models should be making 40ps.
  6. Fair enough Spots - but I can tell you having ridden several Acrosses back to back with Cheng's, the restriction makes a much bigger difference than 5hp would suggest. It's absolutely strangled just where a normal Across starts to take off.
  7. my across pulled 6.5-7.5l/100km and there are allot that pull simmilar to that.

    i did ride spiritedly and that was mainly city use. still its an old heavy 250 4. it will use some fuel.

    for comparo my 600 uses about 5.3-5.5 l/100km but i dont have to ring it as hard

    if you want better economy and power buy something newer.

    but hey my 300 uses closer to 10l/100km in the tight single track

    and my fairlane uses 22l/100km

    so take your 5.5 and be happy :p
  8. even with an across in good condition, at this age it will still be out of puff at 15krpm, max power is more likely to be around 14k

    on highways i have to ascend inclines at 14k in 4th gear :shock:

    will not go past that so i believe max power to be there
  9. Thanks for all the great replies guys, sounds like I've got 90+% of the power that I'm ever going to screw out of the little motor already, although when I get it serviced I'll mention the restriction idea to the mechanic, see if he can see anything. I'll get some sportier tyres and if I get really bored I'll do the airfilter and can and get a tune... otherwise are there any other across riders out there interested in a group buy on gixxer 750 motors and some custom mounts? :twisted: I'm happy to put on a tech day at my place to do the installs... free beer to any grease monkeys who can assist :grin:
  10. Geeze, you'd have run out of petrol at what.. 150km? That sounds like a VERY worn engine. Even with lots of stop-start traffic, I wouldn't hit 5L/100km.

    Sounds like they all need a tune and maybe a few carbie seals replaced.
  11. What other ways are there to restrict an engine mechanically other than restriction plates in the carbies? My across has nothing above 11k, I only ride it above there for the noise :grin:
    I'd love to look into derestricting it, since I think I'll have it for a while.
  12. Another way it could be restricted is with the ignition timing. They may have backed off the ignition timing at high rpm to deliberately neuter performance.

    Mmm, what else.. They may have changed the camshafts or advanced/retarded the camshafts to push the peak torque rpm down, giving the engine stronger low-rpm power and weaker high-rpm power.

    Different length intake and exhaust headers mebbe...

    Lots of possibilities. Though neutering the ignition timing is the easiest/cheapest way they could have done it.
  13. Hehe me too. Sounds like a little F1 car, and anyone who can't see you would think you were going reeeeeally fast. Anyone who could see you would just chuckle to themselves.
  14. It sounds like it is just retarded ignition timings. The drop in performance is very fairly abrupt, and the engine feels very linear (if that makes sense), the engine feels pretty much the same from 12k to 16k rpm. Sounds like a lot of the mechanical restrictions would choke the engine differently at different rpm.