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1998 GSX-R 750 SRAD difficulty starting
- Thread starter Neutronflux
- Start date
Trials
Well-known member
But, but, I thought Japanese motorcycles are bulletproof and don't have any of the electronic issues the Italian bikes are reputed to have
TK4
Well-known member
After 22 years anything can break.But, but, I thought Japanese motorcycles are bulletproof and don't have any of the electronic issues the Italian bikes are reputed to have
boyoboy
Well-known member
this may very well be the problem, checking cleaning wiring/ground cables, test for fuel pressure, compression test and other no cost work should be done already or now.
ctc lends tools - including a fuel pressure gauge. I would try to make it work on the bike. possible?
how expensive is a tps sensor? at this bikes age it could be considered a maintenance item.
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TK4
Well-known member
Some bikes its just a matter of testing resistance at various openings. A shop manual would certainly help.
Roadghost
Well-known member
I can't tell for sure. On fuelly cars there is a valve, like a tire or A/C valve on the fuel rail that you screw the gauge onto to do the test. Never done it on a bike. My testing gauge is in both SAE and metric, but my fittings are all SAE. You'll have to ask the CT tech if they have one with your specific fitting (likely a 10m). The manual for your bike is online here:
Fi System Troubleshooting; Customer Complaint Analysis - Suzuki GSX-R750 Service Manual [Page 179]
Suzuki GSX-R750 Manual Online: fi system troubleshooting, Customer Complaint Analysis. Customer Complaint Analysis Record Details Of The Problem (Failure, Complaint) And How It Occurred As Described By The Customer. For This Purpose, Use Of Such An Inspection Form Such As Below Will...
www.manualslib.com
Go through the section on FI and it should tell you where they hide the valve (if there is one). Otherwise, it might be somewhere on the bike's fuel rail. Regardless, the manual will tell you how to do the test.
boyoboy
Well-known member
yes.
I would especially suspect the main ground cables, where they go to the frame and motor.
This would be my guess also. I believe you should check them every 15k.
Neutronflux
Member
Thank you everyone for all the suggestions and also the explanations on how the different systems work. For now, I've tried disconnecting all the connectors, cleaning them with contact cleaner, and putting them together, and this seems to have helped tremendously. It's at the point where I can get it started pretty consistently, although not always on the first try (or maybe I've tried starting too many times and the battery needs to be charged). I've also tried riding it around and I'm now able to start it again even when the engine is hot. I even tried switching to the Canadian Tire battery (Yuasa battery is back on the tender) and I'm able to start up regularly. Although it feels like it requires a bit more time cranking on cold start compared to the Yuasa (the CCA is higher on the Yuasa battery).
I think I will still try some of the other things such as checking the compression and the valve clearance, but I'd like to enjoy riding around a bit first before the season ends if my bike continues being able to start and run without any major issues. So I will come back later once I'm ready to do some of these other maintenance items. Again, thank you to everyone for teaching me and giving me advice!
I think I will still try some of the other things such as checking the compression and the valve clearance, but I'd like to enjoy riding around a bit first before the season ends if my bike continues being able to start and run without any major issues. So I will come back later once I'm ready to do some of these other maintenance items. Again, thank you to everyone for teaching me and giving me advice!
DownUnder
Well-known member
In that generation suzukis there was some issues with the starter relay wiring plug corroding and causing similar symptoms your experiencing. A lot of people at the time actually cut the plug and soldered the wires directly to the relay to fix it permanently, but cleaning it out and using die electric grease helped most of the time.
Neutronflux
Member
It's been a while, but I wanted to give another update, which will hopefully give people some ideas to try if they find themselves in a similar situation with their bike.
So since 2 years ago, my GSXR750 started getting more and more difficult to start again. Based on what DownUnder commented, I thought maybe there were some old, worn out wires. And I do think it's part of it. While cutting the relay plugs and hard-wiring them directly didn't seem to make any noticeable change, going back and cleaning up some of the other wires, spraying with contact cleaner and covering with dielectric grease did seem to help, but it was still taking a few tries to start the bike each time.
Since the bike was occasionally able to fire up, I assumed there should be fuel and air, even if they're not perfect. Sparks were still good. Battery still tested at the right voltage with the bike off/cranking/running. Alternator and rectifier were also still good.
So I started thinking about the starter motor again. It spun, but I wondered if it might be spinning too slow. So I took apart the motor thinking maybe it needs new brushes. Instead, I found one of the springs for the brushes was a little corroded and sticking. I cleaned it up a abit and used some WD-40 (not sure if there's something better I should be using inside an electric motor) so it was moving smoothly. Sanded the contacts a bit, cleaned everything up and put everything back together. I tried spinning the shaft by hand and found it seizing, so I realized I put the spacers back incorrectly. After taking it apart, putting the spacers in correctly and reassembling, this time the shaft was able to spin pretty easily. I put the motor back in my bike, charged my battery back up to full. So far, the bike has been starting up pretty much right away each time.
Now the only thing left is that the idle RPM's fluctuate a bit. I've found at least one source of an air leak, and will be trying to see if there's any others. If after fixing all the air leaks up and there's still some fluctuation, I'll have to see if there's an easy way to test my fuel injectors. But for now, I have my idle knob adjusted to allow me to ride without much issue.
So since 2 years ago, my GSXR750 started getting more and more difficult to start again. Based on what DownUnder commented, I thought maybe there were some old, worn out wires. And I do think it's part of it. While cutting the relay plugs and hard-wiring them directly didn't seem to make any noticeable change, going back and cleaning up some of the other wires, spraying with contact cleaner and covering with dielectric grease did seem to help, but it was still taking a few tries to start the bike each time.
Since the bike was occasionally able to fire up, I assumed there should be fuel and air, even if they're not perfect. Sparks were still good. Battery still tested at the right voltage with the bike off/cranking/running. Alternator and rectifier were also still good.
So I started thinking about the starter motor again. It spun, but I wondered if it might be spinning too slow. So I took apart the motor thinking maybe it needs new brushes. Instead, I found one of the springs for the brushes was a little corroded and sticking. I cleaned it up a abit and used some WD-40 (not sure if there's something better I should be using inside an electric motor) so it was moving smoothly. Sanded the contacts a bit, cleaned everything up and put everything back together. I tried spinning the shaft by hand and found it seizing, so I realized I put the spacers back incorrectly. After taking it apart, putting the spacers in correctly and reassembling, this time the shaft was able to spin pretty easily. I put the motor back in my bike, charged my battery back up to full. So far, the bike has been starting up pretty much right away each time.
Now the only thing left is that the idle RPM's fluctuate a bit. I've found at least one source of an air leak, and will be trying to see if there's any others. If after fixing all the air leaks up and there's still some fluctuation, I'll have to see if there's an easy way to test my fuel injectors. But for now, I have my idle knob adjusted to allow me to ride without much issue.
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