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Discussion Starter #1
Hi guys,

So, after some help/ideas from this forum, I replaced my gearbox.
It had a ticking noise, even in neutral, when giving some rpms....
Difficult to get into gears in higher revs, only when almost standstill. Seemed like the notches and or guides were bad.

So I had a "spare" gearbox from the engine that suffered a broken camchain.
Put that one in, but kept the "original" clutch assembly.

After checking the Throttle Position Sensor, adjusting throttle cables, cleaning everything etc...
The bike ran buttery smooth, way better than before, especially out of slow corners.

Only, now it has a new problem, well, maybe 2 problems...

When in 5th gear (only in 5th gear!), when reaching 11000rpm, it tends to shoot instantly through the revs to 14500rpm and hit rev limiter.
Not always, but a lot of times. As long as I shift @ 11krpm, no problems, but if I wait to shift till like 13krpm, its a russian roulette.
You can imagine it's not fun having a bike bog down hard at those speeds, especially if its in a turn, hanging besides it.

Second thing is that I was quite a bit faster in acceleration compared to my mate's 2004 CBR600RR.
Now it only is just a fraction if any faster down the straight.
Seems like it's pulling fine until the upper rpms, which is where you're constantly at when going flatout... Like it's missing that final rush.


Does anyone have an idea what could be the issue?
I was thinking some bad sensor signal?
Like the bike "doesnt know" it's hitting high rpms and thus not giving right timing and fuel, resulting in less power, then above 11krpm, it sometimes gets a false +14krpm signal and activates the rev limiter?

To me, it doesnt sound like the bike mechanically goes through the clutch or so for example...



Thank you so much for your insights and efforts guys
 

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hmm..

not really understanding the issue clearly, are you saying it hits the rev limiter early or? hits 11500, shoots to 14500, then hit limiter?

not sure what the problem is?
 

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It it revving when you pull in the clutch, or is the clutch slipping?
Was the 'donor' motor the same as your current engine?
Did you determine what the problem was with the old gearset?
 

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Discussion Starter #4
Hi guys.

The bike seems to have a bit less HP in upper revs than it had last year.
In all gears.

But biggest problem is quite often, when it hits 11500, the rev gauge shoots to 14500 and offcourse, that activates the rev limiter

It's always on a "straight", where I need/tend to hit 13000 or even upshift to 6th...
So it happens under full throttle

Not when pulling the clutch

To me, it seems the clutch should slip in every gear at those rpms if that would be the case??? Or is the load in 5th bigger?


Problem with old gearbox was worn dogs and selection forks

Engines were exactly the same
 

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After it does that, if you back it down to 9k and get back on the gas, does it shoot through the revs only after 11k? What does it do in 6th? If it was a clutch issue, it'd slip just the same, but earlier in the band.
 

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Discussion Starter #6
Hi, it only shoots through the rev range AFTER 11500. Also if I back down, and get back on gas.

Saturday, I had no issues.
Sunday, I had no problems till last 2 runs. Then it happened like 6or7 out of 10 times at the end of the straight.

The 2 trackdays in Mai and June it happened constantly, like 8or9 out of 10 times all day, trackday in Juli though, it only happened like 3 times on a whole day (but I kinda rode around the problem all day by upshifting early)

I dont know what it does in 6th, since I dont reach those speeds on the tracks here.
Have been planning to put it on a dyno, to see whats wrong, but its just been so hectic over here, just dont find the time...




Like you said, I doubt its a clutch issue.
Every time I forgot to take my spare ECU with me, to swap out and compare. now i ve swapped them, might resolve the issue, but highly doubt it.

11sept is next trackday....
Hoped to be able to try something else before that
 

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this is still real vague description of the issue, is it "shooting" through the RPM,s with the clutch in, or clutch out?

if its with the clutch out I would suspect slipping clutch, you can get HD springs online..

they aren't the typical 5 spring set up like most they use these conical washers.. works..

so if you go to look up HD springs and you see these washers with splines that's it, maybe slap some new clutch plates and steels on there too..

at least inspect and spec everything out, all in the service manual, real straightforward

if the RPM's are shooting up with the clutch in that's normal.. shift later bout 500-800 before red line bout where power levels off

if the RPM's shoot and its not the clutch slipping you just have a fast bike....
 

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also the reason the clutch only slips in 5th gear is cuz that's when the bike is at speed where it takes a lot to push it through the wall of air, may not seem like it but up around 150mph it really takes all of that 125hp to push that bike through the air alone, so its like the engine wants to go but the bike doesn't,that wall of air is pushing back so hard any weakness in the clutch and its going to give in...

imagine putting the front tire up against a concrete walled building, then trying to go, either the tire spins, the clutch slips or the engine fails

you might be surprised but a lot of land speed bikes are doing 270 mph and the rear wheel is spinning as well, nuts, but that wall of air really pushes back at that speed and after around 198 mph the power needed to go faster through that wall of air is exponential, its something like 165 WHP will get you up to 190 mph, BUT to get just another 25 mph you almost need to double the WHP..

its crazy but that's how it works and if you ever go 190 barely put your finger outside the slipstream.. then if you ever go 225 do the same..

you can get more out of the HP if you make the bike more slippery, better aerodynamics, why the busa is shaped like that..

me thinks clutch slipping unless I am totally missing the issue altogether but you are fairly vague as to whats going on exactly?????
 

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Discussion Starter #9
Ok, sorry if its too vague, Im not native english, maybe thats the issue??
Maybe its difficult to explain?
To me, like i already said, it doesnt seem/hear like the ENGINE shoots to 14500, but the REV GAUGE does.

That should mean its not a clutch issue. Cause if the clutch slips, i should hear the engine scream harder suddenly?


I have the bike 5 years, I can tell you, as said earlier, it now is slower than last year, where I accelerated way faster than my mates cbr, but now its just barely as fast.

So, no its NOT just a very fast/powerfull bike issue.
The 2nd issue i have is actually the bike losing power in top rpms...




But back to problem 1:
The revs shoot when accelerating... that means I DONT TOUCH the clutch lever.
I dont see how thats vague...
I accelerate to 13000 in 5th, but a lot of times, the revs shoot instantly from 11500 to 14500 and engage the rev limiter.
But there are also times I can drive the bike to 13000rpm...
On the tracks here, I hardly ever reach 6th gear.
But 2years ago, I drove @SPA Francorchamps, and there it reached top speed in 6th without problems...


Maybe I didnt reassemble the clutch correctly... could be, but hardly doubt it.

I get what you re saying bout the hp vs airpressure.

I might try to put in the other clutch...
Hadnt any problems with that one either...
And check this clutch if the problem disappears...
 

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welp if the engine isn't revving up but the tac is then yea it could be the tac or the sending unit? wiring?

still don't get it, you don't pull the clutch in, it isn't slipping, but when you are accelerating and hit 11500 the revs shoot to 15000?

are you saying the engine revs up but the speed doesn't increase or are you saying you do not increase the throttle but the RPM's increase? all this but its slower than usual?

any way you can video the issue?
 

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Discussion Starter #11
Ok, so...

Hoped on a dry Assen trackday, so I could test the bike, but it wasnt meant to be.
Oncoming rain caused the others to drive hasty, resulting in a lot of crashes.
Later I saved a highsider, caused by worn out raintires (though still some tread, it was really slippery and unpredictable, the opposite of the rainy weekend a month earlier).
Tried to ride "around the tire", but I had to retire early... even at slow pace i got about 6 warnings per lap.
A bit too much for my taste.


BUT!!!!!
I replaced the ECU after the 1st session and it seems the bike regained its power and no problems in 5th anymore...

This was probably the last trackday of the year, so I'll have to see what the bike does next April.
 

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shame about the weather, never fun in the wet IMO, too much work and the hazard factor increases ten fold however Assen yea man I think I would run in the snow for a shot on that track.

what group do you rub with in the wet? :)

the extent of my premier track experiences are Miller and Laguna Seca. Miller was still very green I was one of the first bikes on it maybe the very first? I lost track of who got on first but the facility wasn't completed at that point, rather sharp surface and it shredded my Pirellis DSC's, lots of feathering, surface temps round 75, I upped the pressure and the feathering disappeared but the shredding continued, I knocked down what I could...

the front straight at Miller is ridiculous, 6th gear flat out for like 5 seconds at around 3/4 mile in length its crazy and you come smokin hot into a 1st gear lefty, man, lotta pucker factor on that track... lol

sounds like you might have it worked out?
 
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