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Review of L2 GSX-R750 and a potentially complex issue

3492 Views 53 Replies 7 Participants Last post by  craigfer63
Hi everyone. As you all know I'm new to the forum and I would like to post a little review of the limited time I've had with the bike so far.

A little about me. I've been riding for about 15 years now. But haven't been to the racetrack yet (planning on that within the next 6 months). I also haven't owned many bikes but I started off on a Kawasaki ZZR250, then upgraded to a 1999 Yamaha R6, then a 2013 ZX6R (new) and now a 2012 GSX-R 750. I've had small rides on a 2013 Triumph Daytona 675, 2015 Yamaha MT-09 and a 2018 Honda CBR1000RR. Again, I've mostly ridden street but I am fairly confident in handling the bikes at high speed and through corners (as far as street riding goes). I also like working on my own motorcycles because I just don't trust the dealers unless I can't fix something due to lack of resources.

With that out of the way let's move on to my small review. Five days ago I went for an inspection of the bike it looked clean and seemed well taken care of, hence I purchased it. It has the following mods on there:
-Full Yoshimura R77 (??) exhaust
-ECU and dyno tune (130hp apparently)
-Aftermarket grips
-Bonamici Racing brake and clutch levers
-Clutch switch mod for clutchless start (throws an FI light but more on this later)
-Techspec tank pads
-Fender eliminator

I've since ridden the gixxer 750 only 3 times since then, including riding it home from the inspection. Today I went for the longest ride (about 40 minutes) with my wife on the back. It feels great to ride and it's not an overly aggressive body position. I can actually flat foot the bike which is neat. I've changed the shift pattern to GP shift as that is what I had on the ZX6R, which helped solve an issue I had with the gear lever placement as I was riding today. It goes well but I find the power is lacking which must be due to the clutch switch issue I've been reading about on this forum. Brakes feel good for the street and stop really well. Handles corners well enough but I think after changing to new tyres, it might be better at this. Overall a great bike and not many complaints.

Now comes the issue I'm having. From what I understand, removing the clutch switch forces the bike to use a neutral map and therefore it loses power. According to the guy I bought it from it has been tuned, but the throttle still feels choppy, almost the same as if it was from the factory. Because of the aftermarket levers, there doesn't seem to be a mounting point on the bike for the clutch switch. But it has been zip tied to a harness with 2 wires connecting to it (see picture)

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I want to fix this up and put the clutch switch back where it belongs so that the bike can run as it was intended. I really don't care that I have to pull in the clutch to start the bike. That FI light annoys me (I don't have the dealer switch to pull the code) and I feel the lack of power is due to this issue. So the problem for me is two fold. 1. improve the bikes performance and 2. get rid of the FI light. The issue I'm having is where can I mount the switch and which wires do I connect to the switch?

Now to be clear, the bike runs smoothly and without issue despite the FI light coming on. I could leave it as is but I feel like I'd be gaining so much more if I could resolve this issue.

Any help would be greatly appreciated. Thanks for reading :)
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Clutch Switch is an on / off momentary switch. So you are saying with this switch depressed the bike works well ?
What readings are you getting when you test the Gear Position Switch, as per the workshop manual ?
Yes. It seems to run and perform better when the switch is depressed.

I haven't tested the GPS. I don't actually have a multimeter to test it. I do see how useful a multimeter can be so I'll buy one and see what reading comes up. Are there any concerns with having the clutch switch constantly depressed? I figured it's just similar to having a quickshifter, where the clutch is not involved.
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I have jumped it in the past.. I always get this wrong, if it affects mapping paper clipped I dunno? far as if it's left activated, will it remain in a neutral map? 1st gear map? not sure but I have done it on both FI and carbed SRADs, bike starts, runs and rides? my guess is taping the switch is same as jumping it with paper clip and taping it up?

HOWEVER the bike doesn't behave normally as in starts in gear so careful there, but if I do remember right the 98 carbed SRAD works funky anyways? I don't need to pull clutch in to start unless stand is down which I believe is wrong, we just went over this a month ago and I cannot remember exactly but the Busa needs the clutch in every start no matter what? I believe that's standard for all SRADs as well? not 100%

haven't tried to start the FI bike in years but I know I just put a new controls on it and clutch sensor could have sworn I put a new one on the 600 too and now I think of it just now I am wondering if I connected it backwards?

the 98 600 just has 2 leads with thin factory L plugs, like a brake light, they are separate and the same size so they can plug in either way.. I might go switch those around today see it that makes a difference with the no clutch starts?

everything works like a charm on that one save the intermittent fuel light always blinking cuz there is a poor job of repairing a break in the lead off the fuel pump lead bout 4" down from base.. my pizz poor job.. I really din't know how I wanted to attack it so I pinched and taped, Imma cut the insulation at the break, twist wire the newfangled way solder then a couple 3 layers of heat shrink, really like to do all new leads on that pump but I dunno how to remove those funky sealed up connections on the base of the pump where they go through into the tank, is that leaded?

for whatever reason all 4 leads are hard, no flex at all, more than likely what broke the one wire lifting tank and sich? eventually other wires will break by lifting tank for tunes ups, vibration what not, leave me stranded.. should source a faulty pump with good soft leads and connector, the racer who ran it before me busted the latch on the connector so I zip tie that, a new pump would solve that as well.. thinkin bout that zip ties it may have dislodged a connector as I had to scootch over the leads to get the tie in between them to cinch it down?

as good as that bike runs its still very difficult for me to get motivated to do this small fix, draining the tank, yadda yadda, praying to every God in the universe it seals back up.. all that stuff is brand new, don't really wanna budge it, leave well enough alone... lol

I'll switch those clutch sensor leads around when I get a minute here soon and get back to this thread, that very well may be why that 600 does what it does, start without clutch engaged? could it be jumped being connected backwards? one would think not as it wouldn't start with clutch in if that were the case? gonna switch em anyways..worth a shot, I can also paper clip it and see how it behaves, need to get it out on the street anyways circulates fluids so forth, I should raise that tank and at least solder that light lead as well..

wanna take that Fox race shock off and have it rebuilt or something, its very hard and won't dial out, slap a good 750 stocker on there call it good, I see em for $20+ bucks on the auction site..
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I'll switch those clutch sensor leads around when I get a minute here soon and get back to this thread, that very well may be why that 600 does what it does, start without clutch engaged? could it be jumped being connected backwards? one would think not as it wouldn't start with clutch in if that were the case? gonna switch em anyways..worth a shot, I can also paper clip it and see how it behaves, need to get it out on the street anyways circulates fluids so forth, I should raise that tank and at least solder that light lead as well..
welp, this is weird, so I went to flip the wires around as the racer clipped the connector and I soldered on little terminals to slide over the pins in the clutch sensor.. welp one must have been jammed in and making contact against the side cuz when I soldered on the connector the solder went all teh way down no way to go over the pin..

I fixed that and connected them both ways, flipped the two clutch sensor leads around both ways and it ran either way and neither way do I have to pull in the clutch, so I din't have em backwards..

the weird thing is it will turn over with these leads disconnected but it wont run, get spark, the pump primes and everything acts like normal but it wont start, no spark? then when I plug the leads back into the clutch sensor either direction it fires up but I still do not have to pull in the clutch?

WTF?

anyone have any ideas WTH is going on here, this bike was prepped for supersport in the day but I am confident I have everything put back on the bike in OEM off the floor?

I am wondering if they didn't get into the ECU and do something, the clutch and side stand sensors are brand new.. weird
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That’s very weird indeed. Unfortunately I would be of no help as you seem to be much more knowledgeable about this stuff than me 😅 But at least it works.
I'm thinking maybe it is working how its should? non FI, it wont start in gear stand down and that's the big one so it won't do anything potentially dangerous..

if I start it in gear stand down the moment I release clutch it kills it, impossible to start it in gear, wont turn over in gear stand up without clutch, so I think it may be a carbed bike thing been so long I had one I forget, or they tweeked the ECU so it doesn't need it for everything start like my Busa does, it wont start in neutral, stand down without clutch engaged, soon as it starts you can release it and it stays running, just wont turn over...
Update: I ended up installing an on/off toggle switch in place of the clutch switch that was on the bike. It’s much easier to use now. Flick the switch one way, start the bike, flick it back then ride. Far easier than fiddling with the cable tie to keep the old switch depressed.
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redid mine yesterday too, one of the connectors was soldered closed no way for the pin to slip in, clearly it was pushed against the prong making contact.. got that sorted, still doesn't need clutch to start in neutral tho, but works as intended will not start in gear stand down, or in gear without clutch in, busa needs clutch no matter what, prolly carbed vs FI?
Mine will start without clutch in neutral. Mine is FI obviously lol. I haven’t tried starting in gear or with the side stand up/down. I should probably go and check those as well. Just to make sure everything is covered.
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hmm, could it be the Busa is off then? have to pull the clutch in, even with stand down, in neutral.. seriously, release and it stays running, it just wont turn over without clutch in period
Just wanted to add a couple of pictures to show what I had done. Wires are still exposed but I'll need to wait until lockdown is over so I can go and get some female spade connectors from my parents. At the very least I was able to cable tie it securely to the harness. Once I'm able to crimp some connectors on and insulated them with heatshrink and/or electrical tape this FI light issue will be over :giggle:

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hmm, could it be the Busa is off then? have to pull the clutch in, even with stand down, in neutral.. seriously, release and it stays running, it just wont turn over without clutch in period
Would it help if you wired the clutch switch the same way I have done?
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On all the wiring diagrams I can find these Clutch Switch wires are Black / yellow and Black / White. Is this correct ?
My first impression of your problem was dodgy wiring, and it still looks like this ?
Have you traced these 2 blue wires back to the harness ? What does their other end look like ? They just don't look like Suzuki wiring.
I haven't traced the blue wires back to which colour wiring they are connected to yet. I will in the future but as of now it works as I want it to so there's no rush for me to do this. I will be cleaning up the wiring connections to the toggle switch pins as soon as I can.

Next issue:
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As you can see from the picture, the shift lights light up during start up. However, they do not activate when they are supposed to when engine rpm's are at the top end. I also cannot set the shift light parameters either. I've searched the service manual and there doesn't seem to be any mention of how to fix this. Does anyone have any ideas?
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go back and inspect all that wiring, all of it
go back and inspect all that wiring, all of it
Will do. I should be able to do this within the next couple of weeks.

Update: I have finally solved the "issue" I had with the shift light. Turns out it was set to "off" 😅 🤦‍♂️ I followed the instructions on this thread, which helped me realise that you could actually turn off the shift light (I didn't know that was a thing).

Now, other than needing to clean up the wiring of the toggle switch (and tracing the blue wires back inside the harness), everything is how I want it . I reset the front and rear suspension settings to factory defaults (preload, rebound and compression) and adjusted tyre pressures (36psi front and 40psi rear). When I have the time and some mates free, I plan on setting sag and playing around with the suspension for a better ride. But for now I think it is fine the way it is.

I still have a rough idle on cold start up though and I will be investigating this further. Once the bike starts to warm up to around 70 degrees C, it does start to stabilise. Not sure if this is because of the aftermarket air filter and full exhaust that is causing this or if there is something else which might be doing it.

I think the bike is about 95% where I think it should be for me. Thanks everyone on this thread for all your help! 😁
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I managed to heatshrink and wrap up the toggle switch so now it looks clean. I've installed a chain guard (took me about an hour to get the rear brake pads back in and fit the caliper to the brake disc as I had to remove the rear wheel to install it 🤦‍♂️), rim tape and GSXR decal to the bike. I'm loving it even more now! It looks like a completely different bike.
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I finally had the chance to take the bike for a real hard ride today. Not sure where to start with how I felt. I guess in one word...incredible. The feedback I get from the front tyres in a turn is amazing, I love how stable it is in the corners, the tyres (Michelin Pilot Power) has less than 2mm tread left but I never felt any loss of traction and gave me so much confidence in the corners. Compared to my old 2013 ZX6R 636, the GSX-R750 just feels better. It truly is a confidence inspiring motorcycle.

The only thing I didn't like was the brakes. At one point I hit the front brakes hard and it felt like the bike was becoming unstable, not a feeling I'm used to nor do I know if this is how it's meant to behave. It feels like the rear wheel was sliding around (and no I didn't touch the rear brake). Other than that I'm really happy with bike and it's performance.

The only thing I have left to do is to install the SS braided lines (HEL yellow with black banjos). Then the bike will be complete with all the mods I want. Next step is to take it to the track and start gaining some real skills 😉

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I thought if the switch is depressed- that would be when the clutch lever is NOT pulled in? So the clutch is NOT engaged.
When you pull the clutch in, the little switch pops out, right? As in the clutch is engaged. At least I thought on mine it had a little rod that gets pushed in when the lever is not pulled towards the handlebar.

You can still skid the wheel WITH a slipper clutch! It's just doesn't do it as much or as often. Sounds like you're not using your brakes well?
What is the purpose of bypassing the clutch switch anyways? ASFAIK, it only keeps the starter from engaging unless you pull the clutch in, right? You can still 'push start' it when needed, etc.
WHY do it at all?
'The only thing I didn't like was the brakes. At one point I hit the front brakes hard and it felt like the bike was becoming unstable, not a feeling I'm used to nor do I know if this is how it's meant to behave. It feels like the rear wheel was sliding around (and no I didn't touch the rear brake). Other than that I'm really happy with bike and it's performance'

Really? If you apply the front brake to a greater degree, and you go to 1st or second like you said before, what happens on the back end? If it's touching the ground at all, it's REALLY light back there, not much traction. You think this is a front brake thing?

How much, what type of riding have you done again?

Hint #1- RARELY ever use the rear brakes- rarely ever!
Hint #2- if you had a scale on the under the rear wheel while you're applying the front brake anywhere near max, the scale would go to at or near zero. Or even come off the ground. Not much traction there on that already small patch of tire is there?
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What is the purpose of bypassing the clutch switch anyways? ASFAIK, it only keeps the starter from engaging unless you pull the clutch in, right? You can still 'push start' it when needed, etc.
WHY do it at all?
The bike already had aftermarket levers when I bought it and there was a modified clutch switch that was wired up to allow the bike to start clutchless anyway. The clutch switch was not attached to the clutch lever, it was lightly cable tied around the wiring harness. It was not a decision I made to remove it as it was already like that when I bought it. I just had to figure out a way to stop the FI light from coming on because it was making the bike perform poorly. That's why I replaced the clutch switch with a toggle switch.

Really? If you apply the front brake to a greater degree, and you go to 1st or second like you said before, what happens on the back end? If it's touching the ground at all, it's REALLY light back there, not much traction. You think this is a front brake thing?
Perhaps you misunderstood what I was saying. Under hard front braking (I don't touch the rear brakes) I never changed gears. I understand how motorcycle geometry works and perhaps the rear was lifting as you say. That's what I'm trying to figure out but I don't feel like I'm applying the brakes hard enough for that to occur. I don't grab a load of brakes, I progressively squeeze the lever. My point was the rear sliding feeling didn't happen with the 2013 ZX6R I owned no matter how hard I applied the front brakes. That bike was always stable and straight. Again, if this is normal for the gixxer then that's fine, but as far as my experience goes it is not normal.

I had a moment where the slipper clutch actually did it's job recently (though that was unintentional lol) so I know how that works now.

How much, what type of riding have you done again?
Been riding for 15 years. Always had sport bikes. Not yet tracked but I do aggressive riding in the corners (not afraid to get my knee down). I'm probably above average for the street.

Edit: I should add the ZX6R had traction control. So not sure if that was the reason it felt more stable under heavy braking.
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You have to get your sport bike to a track day. If you have access to a Race Track. It is like night and day. The sport bike is designed to do this. It is like riding from your house to the end of your street at 100 mph. (170 k) In 3rd gear !
I'm still using the rear brake, in braking area, at least when the rear tire touches, it grabs a little. I'm trying everything to get me stopped !
Front brake hard, rear brake full, body sitting up straight in the air stream, matching down changes hard with revs low. MOUTH OPEN 😯 fingers crossed 😁 Turn in, trailing off front brake, last.
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