GSXR400 SP race bike info

[Artifice]

http://www.400greybike.co.uk/
the guys here will have all the info you want in the forums.

mine is a 91 gsxr400 rr i think, frame is the gk76a.
it has an arrows exhaust and im only getting 13k/litre out of it on the hills.
cant seem to find my dyno chart for it.

[bugjuice]

http://www.400greybike.co.uk/
the guys here will have all the info you want in the forums.

mine is a 91 gsxr400 rr i think, frame is the gk76a.
it has an arrows exhaust and im only getting 13k/litre out of it on the hills.
cant seem to find my dyno chart for it.

the 'SP's have different carbs, designed to work better at higher rpm than 'regular' carbs, so the power band will be slightly different.. If yours isn't an SP, your bike might run out of steam quicker than Quasi's bike, but yours would be better at lower rpm and around town, sort of thing.. But the differences there would bearly be noticeable

[TwoSeven]

If you are running 13/47 tooth sprockets then I suspect you're way out of the ballpark.

I'm not familiar with the gsxr400 or what year bike you have but roughly plugging some numbers thru the calculator shows your only going to be getting about 150kph tops at 11k rpm with 13/47 final drive.

The bike was geared for roughly 180kph at 11k rpm (being a jap import they are all like that), so it would have to be geared stock 14/43 (or close to it). I suspect the SP model will probably be capabe of topping 220kph knowing the japanese.

They often design the bike with more power, then restrict it to 180kph, which is what its geared for stock, what this means is the torque which is minimum for its 220 top speed, becomes great for punching out of corners (what road bikes want).

My suggestion is go back to stock

If the bike is spitting at 11k rpm, whats the carb state of tune like - when was the last time it was stripped and cleaned. Do you have an aftermarket can on ?

[FROSTY:Me]

Quazi --thinking about ya problem im a frigging eejut Im sorry --Unless your bike has the rev limiter bipassed ya aint ever gonna get full speed outa the SP
Sorry for not remembering
It costs about $50 and plugs into ya rev counter Otherwise when ya get to 180-190km/h or high revs in top gear the limiter cuts in and causes a misfire.
Your gearing is way out but ya already knew that. I think ya should have a 14 tooth front.
again talk to slims partner about the gearing thats about right.
Gary can sort that out for ya.
5746688 is GP's phone number

[Artifice]

well i found the old dyno chart.

[bugjuice]

well i found the old dyno chart.

does it redline at 12,500?

[Quasievil]

Thanks for all this guys fuck I love this site !!!!!!!!!!!!!!!!!!

[Artifice]

it redlines at 15000

[Quasievil]

it redlines at 15000

Mines reds out at 14500 rpm I think

[TwoSeven]

Quazi --thinking about ya problem im a frigging eejut Im sorry --Unless your bike has the rev limiter bipassed ya aint ever gonna get full speed outa the SP
Sorry for not remembering
It costs about $50 and plugs into ya rev counter Otherwise when ya get to 180-190km/h or high revs in top gear the limiter cuts in and causes a misfire.
Your gearing is way out but ya already knew that. I think ya should have a 14 tooth front.
again talk to slims partner about the gearing thats about right.
Gary can sort that out for ya.
5746688 is GP's phone number

Thats not a rev limiter, its a speed limiter (unless we are talking at cross purposes - then sorry in advance) - the rev limiter turns off spark to stop pistons/rods/cams moving faster they were designed for - eg. 12000 rpm, 15000 rpm etc. Often they'll turn off spark to reduce heat as well. That gives a shudder when it kicks in and you'll see the rev needle bounce back slighlty.

Speed limiter on most japanese bikes is 180km/hr - if its a mechanical speedo, likely you will find a contact in the back that needs a slight bend in it or you can just put a resistor across the wires at the cdi as some require (I cant remember which to wires, so you'll have to look at the wiring diagram).

On a 400, I probably wouldnt de-restrict it unless your going to re-jet and change the zorst, because the power it makes at top end, wont be enough to deliver the maximum speed in the distance you have available - the whole bike will have been designed to peak at 180kph. Often you'll find the dif. between an SP and normal bike is that the design has been moved 40kph up the scale. Its pointless extending the rev limiter unless you change the zorst design to move peak power and torque up the rev limiter further, if you change the zorst, your likely to require a re-jet to cover the impact on lower speed stuff (oh the joys of tuning).

The bike seems like it has incorrect gearing and bad fueling. I'd sort those first before tweaking anything else.

After that, i'd calculate your shift points and change properly. Is likely that you need to short shift a couple of gears if its using a road gearbox (proper race bikes use linear gears), As a rule, i've found that odd numbered gears are accelleration and even numbers are driving (they have big overlap), so you could probably short shift those, to enable you to get the drive required to get you up to speed (changing to a higher speed sprocket will counter this effect, hence its probably not worth de-restricting the bike unless you've increased power). You can check your shift points by doing an all-gear run on a dyno.

Not sure if any of that made sense, but what I am trying to say, is set it back to stock and fix the fueling - thats the optimum for that bike unless you do some engine work to increase power/torque. Remember, once its at optimum, the tradeoff will always be - gain speed on the straight at expense of corner exit capability. Thats why you often see bikes getting passed on the long bits, making it back on the short bits.

If you intend to ride at multiple tracks, then buy a few more rear sprockets, do the math and work out which combinations give the best results for each circuit and certainly consider a 520 chain - its worth a few ft-lbs of drive over a 425.

The last thing on changing sprockets is to remember that the angle of the chain/swingarm changes depending on the suspension compression - most bikes can only cope with 1-2 tooth difference before the chain loses drive or rubs against the swingarm (bad if the front sprocket is too small). So while the math might say 4 teeth difference on the rear, check the bike can actually take it

[FROSTY:Me]

well aint it interesting -all the fancy theories flying around and ol frosty was right. --If he wants to I'll let quazi fill ya in on the exact details.
suffice it to say that quazi's bike will be a fair bit faster next time at pukie

[Quasievil]

well aint it interesting -all the fancy theories flying around and ol frosty was right. --If he wants to I'll let quazi fill ya in on the exact details.
suffice it to say that quazi's bike will be a fair bit faster next time at pukie

Okay good one ol frosty.

The Bike has been at GP Trading all week for a bit of attention, heres what they found
1/ Plugs needed to be replaced
2/ Needles needed to be adjusted as well as the jets
3/ They put in a Cam from a CBR600 ? I dont understand that one
4/ The bike had 3 speed restrictors in it, this would be why I was going so slow on the straights
5/ The engine was running lean down low and rich up top so theyve corrected it
6/ They gave it a good going over and tuned it on the dyno and got me another 3 HP and a engine which is running alot better

They did a bunch of other stuff as well to get it into race shape and have already suggested further mods and improvements for getting more grunt outta it.

Watch out Frost now I will be on youre Arse !!

[Artifice]

so, can you post your dyno chart? i think mine is just a little down on power.

[TwoSeven]

So they fixed the fueling - did they do the gearing as well ?. Also what year cibby cam(s) did they use - was it just inlet or exhaust as well ?

Not sure where the third restrictor was unless it was inlet (fuel) related, but I'd be interested in seeing if you beat 180 on the speed gun

[Quasievil]

so, can you post your dyno chart? i think mine is just a little down on power.

Yeah I will, the bike is still in Tauranga I pick it up On Tuesday so will post it then mate