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Review of L2 GSX-R750 and a potentially complex issue

3491 Views 53 Replies 7 Participants Last post by  craigfer63, 
Donutninja
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)

Automotive tire Automotive wheel system Gas Auto part Pipe


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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Donutninja
craigfer63 said:
You have to get your sport bike to a track day.
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100%. I need new front and rear tyres plus some equipment to change the tyres myself (~$500 total inc. tyres). But I have other financial commitments right now. I plan on going for a track day around January 2022.

craigfer63 said:
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 !
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Does the rear feel unstable when you do this (like it is slightly swerving from side to side)? Or does it track straight under heavy braking and rear just feels "lighter"? I'm still trying to figure this out myself as I personally don't think I'm supposed to feel the rear becoming unstable. I'm going to install some stainless steel braided lines in a couple of days. This will give me the chance to flush and bleed the lines with new fluid. I'll test out the brakes (in a safe way) to see if I still get the unstable feeling. If that doesn't work, my next guess is tyres. Then I might also look at suspension, though I don't think the suspension is at fault as I've put it all back to factory settings as per the service manual.

I want certainty that when I'm braking for dear life that I don't have to worry about if the bike will slide out from under me or not. Especially for street riding.
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craigfer63
Yes, you can see this watching Moto GP races. Of course these guys are pros and work very hard to keep the bike straight and settled.
The physics is obvious, under braking the rear is lightened and with the rear wheel off the ground, the rear of the bike wants to overtake the front.
As all bikers know when you lock the rear wheel on a slippery surface, the rear comes out, then the rider automatically corrects the slide with steering and body movement.
Sitting up and moving your weight to the rear can settle the rear.
Just before you come off the front brake, use your forward inertia to move into position forward for the turn.
There are lots of youtube vids on this.
Oh and yes, having only two wheels means the bike will slide out from under you sooner or later ! For me in my old age this means the race track insures I wont hit any foreign objects, cars, trucks, trees, barriers, with my head. (y)
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Donutninja
craigfer63 said:
The physics is obvious, under braking the rear is lightened and with the rear wheel off the ground, the rear of the bike wants to overtake the front.
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I actually just remembered something. Before I purchased the Gixxer I had a go on my mates 2017 CBR1000RR. I braked hard with that bike as well and the rear became unsettled (just like the feeling I'm getting now with the Gixxer). So I'm starting to think it's normal for the bike to do this. I just find it strange that the ZX6R never did this 🤷🏻‍♂️ Now I just have to learn to control my braking better to help keep it under control.

That was a good video. I think I may have seen it a few times on my YouTube feed but never bothered to watch it. There was lots to learn in that video. Thanks 😁
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xtremsiege2
Donutninja said:
I actually just remembered something. Before I purchased the Gixxer I had a go on my mates 2017 CBR1000RR. I braked hard with that bike as well and the rear became unsettled (just like the feeling I'm getting now with the Gixxer). So I'm starting to think it's normal for the bike to do this. I just find it strange that the ZX6R never did this 🤷🏻‍♂️ Now I just have to learn to control my braking better to help keep it under control.

That was a good video. I think I may have seen it a few times on my YouTube feed but never bothered to watch it. There was lots to learn in that video. Thanks 😁
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I think its normal..have the same brakes and at the end of straits stock everything i feel that front end clamping down and rear becoming a little unsettling..but never a feeling of losing the rear in any way possible. Had the same feeling on an s1000rr hard braking and that had SS lines and better master. Think you're just mentally still thinking of the zx6r like the last girl you put some miles on..

Just get those new tires and hit the track, tires for a new or experienced track rider will change the game.EDIT-theres a Bridgestone tire rebate going on now. Can pick up some RS10-RS11 or S22's which will work well on and off track for around $220 US, whatever that equates to for you..
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Donutninja
xtremsiege2 said:
I think its normal..have the same brakes and at the end of straits stock everything i feel that front end clamping down and rear becoming a little unsettling..but never a feeling of losing the rear in any way possible.
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Good to know :) If it's normal I can have a little more confidence in what to expect and try to better control my braking. I currently have rubber hoses on there which I will be replacing with HEL SS lines front and rear tomorrow. New SS lines and new brake fluid would definitely make a huge improvement in braking performance.

xtremsiege2 said:
Think you're just mentally still thinking of the zx6r like the last girl you put some miles on..
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You are probably right about this. Perhaps I wasn't as hard on the brakes with that bike as I thought I was, even though I had SS lines in that bike as well.
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craigfer63
The situation / feeling you are getting, from the rear wheel under braking, can be caused / fixed by suspension setting. Assuming you have your ride height and sag set, there is lots of info on this, search.
And your suspension is set to standard, (which Suzuki went to a lot of testing to find this)
Try adding some Rebound to the rear shock. Go 1 click in (harder) at a time, do not go past 5 clicks in.
Make a log book of what your doing and how your bike feels with each change. (y)
.
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craigfer63
Changing your own tires is hard core ! I have been changing my own tires since I was 10, on pushbikes and dirt bikes.
I have every tire lever, spoon and device known to man but it is still a battle of whit's, 😡🤬 So attempting to gouge my way through my Gixxer rims, I'm reluctant. 😆
Let us know how you go.
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Donutninja
craigfer63 said:
Let us know how you go.
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Won't be for a couple of months as I still have some life left in the current tyres (~1.8mm above wear indicator). But will update when I do get it done (y)
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Donutninja
ARRRGHH!! Another issue now 🤬 This is beyond me. So I changed the front brake lines to SS lines just now.

Here's how I did it. I used a vacuum brake bleeding pump to suck out all the fluid from the reservoir. Then I connected it to the furthest bleed nipple on the caliper (left side) and sucked out all the fluid. - easy

I removed the banjo bolts from left caliper, then right caliper, then master cylinder (and of course the tab which runs over the front fender). - easy

Installed the SS lines. I started by installing onto the calipers first, then finished off with the master cylinder. I got the "race" style lines so 2 banjos at the master and 1 line to each caliper. Installation wasn't overly difficult, just a bit fussy with routing. - easy

Now here is where I got stuck. I fill up the brake fluid reservoir with brake fluid, go the vacuum pump at the right caliper. Pump for ages but only get a trickle of fluid. Huh? Then tried the other side. Same thing. Then I tried pumping the lever. It stays soft and never firms up. No fluid is being sucked into the lines. Connected a hose to the master bleed nipple, cracked it open and pumped the levers. Nothing. No fluid is flowing even into the master cylinder.

The only thing I did was change the lines. I did not touch the master cylinder at all and I made sure nothing was being squeezed or pinched. What could be the issue? HELP! 😩
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craigfer63
Patience is the answer. when there is air in the system it will be in multiple places. so the master cylinder piston is pushing against air.
This is what is driving you crazy. 😆
A simple analogy is when you put the garden hose on the tap. When you turn the tap on, the water starts coming out in a broken flow, until there is a solid flow.
A simple way to bleed brakes is the gravity method. Keep the reservoir full at all times.
Open all bleed nipples and watch brake fluid running out. When there is a solid flow from all nipples, the system is full.
Of-course this would get brake fluid everywhere but you get the idea.
Using your bleeding hose on the further est nipple, watch the fluid run out, the air will be coming out here, but under gravity it will be slow and had to see. Let a reservoir full through, then to each closer nipple in turn. Good luck.
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Donutninja
craigfer63 said:
Patience is the answer. when there is air in the system it will be in multiple places. so the master cylinder piston is pushing against air.
Click to expand...
Went back to the bike today. It's all good now. I zip tied the lever to the handlebar overnight to draw out some air (according to internet wisdom), this didn't work.

What I did was try the vacuum bleeder on the master nipple. I wanted to see if there was any blockage or if it was still drawing air. Fortunately fluid started to flow after a minute or so but it was still drawing air. To make double sure it wasn't just luck, I started using the tried and ture method of pumping the brake lever, cracking open the nipple and closing it again. This worked and fluid started to flow. I made sure no air bubbles were present then moved on to the calipers. After bleeding the calipers I went back to the master cylinder.

Then I installed the rear lines and bled the system by pumping the pedal.

Cleaned up the bike and test rode a little bit to make sure brakes were fine. Inspected the lines for leaks (there were none). Now I'm all good to go :)

The only minor thing is after installing the front banjos at the master, I can't angle the brake lever down like it was prior to the fitment as the line hits the fork. Only after I finally bled the system I realised this. Now I can't be f__ked draining the fluid again to fix this up. I'll adjust it again the next time I bleed the system.
Automotive tire Hood Motor vehicle Steering part Steering wheel


Here are some pics of the installation.
Tire Wheel Bicycle tire Automotive tire Motor vehicle
Tire Wheel Automotive tire Automotive lighting Bicycle tire
Motor vehicle Automotive tire Hood Automotive design Synthetic rubber
Bicycle Automotive tire Bicycle tire Bicycles--Equipment and supplies Bicycle frame


Things I have learned.
1. A vacuum brake bleeding kit is only good for emptying the system and it more useless than tits on a bull when it comes to filling up the system again with fluid.
2. Gravity bleeding and traditional bleeding methods have stuck around for a reason. They work.
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Donutninja said:
Went back to the bike today. It's all good now. I zip tied the lever to the handlebar overnight to draw out some air (according to internet wisdom), this didn't work.

What I did was try the vacuum bleeder on the master nipple. I wanted to see if there was any blockage or if it was still drawing air. Fortunately fluid started to flow after a minute or so but it was still drawing air. To make double sure it wasn't just luck, I started using the tried and ture method of pumping the brake lever, cracking open the nipple and closing it again. This worked and fluid started to flow. I made sure no air bubbles were present then moved on to the calipers. After bleeding the calipers I went back to the master cylinder.

Then I installed the rear lines and bled the system by pumping the pedal.

Cleaned up the bike and test rode a little bit to make sure brakes were fine. Inspected the lines for leaks (there were none). Now I'm all good to go :)

The only minor thing is after installing the front banjos at the master, I can't angle the brake lever down like it was prior to the fitment as the line hits the fork. Only after I finally bled the system I realised this. Now I can't be f__ked draining the fluid again to fix this up. I'll adjust it again the next time I bleed the system.
View attachment 579030

Here are some pics of the installation.
View attachment 579027 View attachment 579028 View attachment 579031 View attachment 579029

Things I have learned.
1. A vacuum brake bleeding kit is only good for emptying the system and it more useless than tits on a bull when it comes to filling up the system again with fluid.
2. Gravity bleeding and traditional bleeding methods have stuck around for a reason. They work.
Click to expand...
The problem is you completely evacuated the system of fluid so it only contained air.
A vacuum bleeder needs fluid to pull, not air.

I have had a similar problem and had to use a syringe filled with new fluid attached to the bleeder nipple on the caliper to actually push fluid in and "reverse bleed" it to get the air out of the system.

Sent from my LG-H700 using Tapatalk
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Donutninja
Advmgm said:
A vacuum bleeder needs fluid to pull, not air.
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This makes sense actually and probably the reason why I became stuck. I just assumed i could fill up the reservoir the start sucking.

I’ve never tried the reverse bleed method, and I can’t be bothered to buy yet another piece of equipment for something I’ll only do once a year or two haha.
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craigfer63
Thanks for good pics.
Once a year minimum. Racers will bleed brakes every meeting. I would bleed mine every 4 track days. Noted in log book, date and Km's.
I have a cheap syringe (fleabay) that I use to remove old fluid /crud from reservoir before I start bleeding. No use pushing that shit through the system.
Mark your Brake fluid bottles with date, 1 year, bin it.

RACING BRAKE FLUID 600 | Penrite Oil

RACING BRAKE FLUID is a premium full synthetic, non silicone, Super Dot 4 Plus brake fluid for superior performance in severe braking conditions. Application RACING BRAKE FLUID is designed for use in hydraulic brake and clutch systems in all types of competition - cars, trucks, motorcycles...
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Mark where your Master Cylinder Banjos are now, with a white marker. So when you undo them to move them you will have a starting point.
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