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Fuel Tap and Rev Range?

Discussion in 'Technical and Troubleshooting Torque' started by presti, Apr 23, 2010.

  1. Hey guys, im new to the forum so sorry if this is in the wrong area.

    MOD: Moved to troubleshooting

    I have a 1993 Kawasaki ZXR250 and i had just a quick couple of questions.

    Firstly, the fuel tap. Know i know to turn it to reserve when it runs out and stuff, but how do i turn the fuel off when its parked for the night? Does anyone who has had a ninja know or anything? It doesn't have an 'OFF' position but i know you are meant to turn it off. 8-[ sorry thats a really nooby question but yeah..

    And secondly, what RPM range should i be cruising in for the ZXR250? The bloke in the shop that i bought it from mentioned that you can kill the spark plugs if ridden in too low RPM's but i dont wanna use up heaps of fuel holding high rpm's. I do alot of 80kph riding and i usually sit around 8000rpm which feels comfortable, but anything lower and it feels like the bike doesn't appreciate it. Any help would be great, i can always go back to the shop that sold me it and ask but its quiet embarrasing.

    Thanks guys,

  2. Generally speaking you'll have a good feel for when an engine is running too slowly and labouring. If it feels like it needs to be kicked down a gear, kick it down and vice versa.

    8,000 is a few rpm but I haven't ridden a ZXR250 and they're total screamers no? Probably fair enough.
  3. Hi mate, I think your fuel tap is a vacuum operated one, ie it's normally closed until you start the engine, then it opens automatically.

    If it is, it will have three positions: On, prime, & reserve.

    As to the RPM, check out a dyno graph of where your bike makes power, you'll want to be sitting below the redline, but above the flat bits, if that makes sense.

    Doing a quick google search, it looks like the make 45 BHP at 16K rpm, so it's probably only just starting to make useable power round 6-8K rpm.

    You probably won't notice a lot of difference in regards to fuel consumption if you rev it more. Do what feels comfortable for you. You'll eventually get a feel for it.
  4. i don't ever turn my fuel tap to off position, but bikes ridden 2 or 3 times a day (neccesity, i have no car)...perhaps you would for longer term storage.

    if it runs out of fuel the engine just stops (obviously!!)... but you"ll know when it's getting close, because it"ll run rough, like it's starved of fuel.. and have a few seconds to turn the tap over... just have to learn how to find it without looking and which way to turn it... if not, you"ll just coast along...but if that happens you just pull the clutch in and fire her up again, preferably select a gear to match your speed... it won't lock up and throw you off or anything crazy (i think haha, never owned a 2fiddy ninja).

    80kph on a 2fiddy 6 speed... could either do it in 4th,5th or 6th i'd say... but if the engine is lugging change down a gear... 6th would be your highway gear, so you'd get better economy of a long stretch of road.. also the tallest gear so flexible for cruising...
    if you were in heavy traffic doing 80kph you may opt for 5th or even 4th, so as you've got quicker acceleration available instantly if you need it (or deceleration via engine braking)... but generally i'd think you'd change into 5th around 80kph on a 2fiddy if you intend to maintain that speed for a bit... or leave in in 4th if you anticipate you're likely to have to slow down shortly....or chuck in in 6th if you've got a long stretch ahead at 80kph on the flat or a downward grade, might need to change to 5th on an upward grade.
  5. thanks for all the help guys i really appreciate it :) the RPM was worrying me abit but you guys seem to have heaps of knowledge on it all. I turned the fuel tap abit because i could smell fuel and afaik (i had the garage door open) but i couldn't smell any fuel. Ill have to remember to turn it tho haha.

    Thanks again guys,

  6. I had a '91 of the same bike on my L's. I always kept it above 8k as it simply doesnt develop power until then. Ideal was about 9 or 10 (or usually about 12 upwards hehe)
  7. yeah i can feel how it doesn't produce heaps of power down low (below 8) i just wasn't sure. But around 12 it just lights up and goes for it lol thats how you gotta overtake ;) hehe

    thanks guys
  8. One thing I've found on most vehicles I drive/ride.. the (almost) optimum rpm to shift up a gear for economy purposes will be with the tacho needle pointing straight up.
    Obviously unless you're in top gear and already past that in which case just use what you got
    Mine cruises the highway on around 8 grand at 120km/h indicated (actual 112 ish) and its a V-Twin

    Plus with bikes being built the way they are, you should be able to hit redline every single gear change for several years without hurting it. Shouldn't use that much more fuel either
    I get about 5L/100 highway, 6L/100 when fanging it around mountains or short trips

  9. 8000rpm is bang on what you'd be cruising around at.
  10. Throttle position, not RPM usually dictates fuel consumption, especially on a smaller bike. Don't worry about the high RPM. That's the trade off we get for lower engine life compared to a car.

    EDIT: by throttle position, I mean whether you pin it in all gears or go easy up to cruising speed. My Daytona 675 uses similar amounts of fuel in 3rd and 6th at 110km/h.