1998 GSX-R 750 SRAD difficulty starting | GTAMotorcycle.com

1998 GSX-R 750 SRAD difficulty starting

N

Neutronflux

Member
Hi all,

Model: 1998 GSX-R 750 W SRAD (fuel injected)
Mileage: ~53,000 Km
Issue: Engine often doesn't start

I bought this bike from a friend who hadn't ridden it in a couple of years. We've been working on it to get it running smoothly, but there is one big issue that we weren't able to completely fix: the starting of the bike. At first, it just didn't start. We have managed to get it to start, but only sometimes.

I put in the key, turn it on, dash turns on and I hear the fuel pump priming. Toggle the kill switch. Press the ignition. The starter motor turns. However, at this point the engine will either start, almost start (I hear a split second of the combustion or pop) or most likely I just hear the starter motor turning, but no engine. And I will try maybe a dozen times until the battery is drained, but still nothing. If it does start, it seems to run fine (I can ride it highway speeds, doesn't bog, don't notice any knocking). Chances of success seem a bit higher right off the tender, but a bit lower after riding it around and the engine is hot. Using a car to jump the motorcycle seems to be effective.

Some additional details about the motorcycle:
  • the exhaust is most likely an aftermarket, although I don't know if it's a full exhaust or a slip on
  • my friend was not the first owner, but he did ride a lot before he stopped (got married) and doesn't remember this issue
  • it gets very hot (>110C) if it's a hot day and I'm below 50Km/h for a couple of minutes, and continues to climb even with the fan on
  • gas is usually Costco premium (manual says 87+, but mechanic that did safety says use premium), tried regular once and didn't notice a difference

This is what we've tried (we have a shop manual):
  • Changed out the oil, coolant, made sure air filter was clean and other general PM; OK
  • Played around with the Power Commander II maps; nothing worked well, currently bypassed the PCII
  • Adjusted idle knob; seemed to help a bit with the odds of starting, but very finicky
  • Checked the stator and rectifier with a multi-meter as per manual; OK
  • Checked voltage on the battery as per manual (3 month old Canadian Tire); OK
  • Replaced the CT battery with a new Yuasa battery just in case and then checked voltage; OK, slightly better chances of starting
  • Replaced spark plugs, gapped as per manual and checked to make sure they all spark; OK
  • Checked air lines to see if there are any leaks; OK
  • Opened up starter motor to clean, assembled and tested; OK
  • Took apart fuel assembly and checked for any leaks or clogs, checked fuel pump is pumping, checked fuel injectors are clean; OK
  • Ran some fuel injector cleaner through the system; no change

Things I haven't tried yet or other people have mentioned:
  • I haven't tried taking anything apart past the fuel injectors (ie. cylinders and beyond).
  • I have heard people mention that if the fuel/air mixture is too lean, the bike might have trouble starting or getting hot, but I'm not sure how to change that since it's EFI, and none of the PCII fuel maps I've tried seemed to improve the bike's ability to start (the PCII LED always says lean).
  • A few random strangers have put their hand behind my exhaust during ignition and say they don't smell the gasoline coming through.
  • I haven't had the chance to figure out how to check fuel pressure.
  • I've tried carrying a lithium jump starter, but it never helps. A car with it's engine running will jump start the bike very easily.

If anyone has any ideas on what else I should check or what else I can try, I would really appreciate it. Let me know if any additional details would help.
 
Try this: when you turn on the key and hear the fuel pump running, hit the starter button before it stops running instead of after.
 
Neutronflux said:
...
If it does start, it seems to run fine (I can ride it highway speeds, doesn't bog, don't notice any knocking). Chances of success seem a bit higher right off the tender, but a bit lower after riding it around and the engine is hot. Using a car to jump the motorcycle seems to be effective.
...
  • I've tried carrying a lithium jump starter, but it never helps. A car with it's engine running will jump start the bike very easily.
Click to expand...

Based on these comments, if jump starting it with a car is always successful, then it sounds to me like an electrical problem:
- grounding
- wiring between the battery and starter
- possibly starter solenoid

By the way, have you tried jump starting off the car with it NOT running, and any difference? I don't like jumping a bike with a car that's running, just use its battery. Hopefully it's as simple as a bad ground since the only difference between a car and bike battery is the cranking amps, and they're easy to locate/check if you have the shop manual. You can also check the voltage between the battery and the starter while cranking it in the various scenarios (onboard battery/lithium jump pack/car) and then also compare the voltage between the battery and all the points in between to see if there's a loss.
 
Great post OP

When you say " I just hear the starter motor turning, but no engine ", do you mean that just the electric motor is spinning and not the mechanical motor, or do you mean the mechanical motor is spinning but not firing?
 
  • the exhaust is most likely an aftermarket, although I don't know if it's a full exhaust or a slip on
Original exhaust will have a whole bunch of writing stamped on it to say it is the correct and emission compliant exhaust system for that specific model motorcycle. Been like that for years and years.
 
Trials said:
  • the exhaust is most likely an aftermarket, although I don't know if it's a full exhaust or a slip on
Original exhaust will have a whole bunch of writing stamped on it to say it is the correct and emission compliant exhaust system for that specific model motorcycle. Been like that for years and years.
Click to expand...
I've seen that on the muffler, but not further up. You're probably right that the headers are marked somewhere but whether you can see the marks without removing (or if they even exist after decades of corrossion) is always a question.
 
GreyGhost said:
I've seen that on the muffler, but not further up. You're probably right that the headers are marked somewhere but whether you can see the marks without removing (or if they even exist after decades of corrossion) is always a question.
Click to expand...
Should be on the muffler and it should look very much like this:
1598031597097.jpeg
 
Chances are if OP posts pics of the system, someone might be able to identify it. For that vintage, I think the main contenders were just Yosh, Hindle, Supertrapp, or Vance and Hines. Possibly Muzzy? Not a lot or European or Chinese brands that I can recall.
 
Have you done a cylinder compression test?
See no mention of valve clearance adjustment, that can make a motor harder to start. 1998, absolutely past due for a check if it has never been looked at. You've got lots of them to look at.
 
Did you try this yet?
Trials said:
Try this: when you turn on the key and hear the fuel pump running, hit the starter button before it stops running instead of after.
Click to expand...
My reasoning is that your fuel pressure might be low.
 
Wow, thanks for all the quick and supportive responses! This is my first time doing this level of work on a vehicle, especially with electrical stuff, so I apologize if there's a lot I might not understand and need to ask for more clarification.

Trials said:
Try this: when you turn on the key and hear the fuel pump running, hit the starter button before it stops running instead of after.
Click to expand...
I've tried this every now and then, but it doesn't seem to make a difference as far as I can tell.
Relax said:
Based on these comments, if jump starting it with a car is always successful, then it sounds to me like an electrical problem:
- grounding
- wiring between the battery and starter
- possibly starter solenoid

By the way, have you tried jump starting off the car with it NOT running, and any difference? I don't like jumping a bike with a car that's running, just use its battery. Hopefully it's as simple as a bad ground since the only difference between a car and bike battery is the cranking amps, and they're easy to locate/check if you have the shop manual. You can also check the voltage between the battery and the starter while cranking it in the various scenarios (onboard battery/lithium jump pack/car) and then also compare the voltage between the battery and all the points in between to see if there's a loss.
Click to expand...
I think I might have tried jumping without the car running, in which case it probably didn't work. But I'll double-check just in case and let you know.

I'm not too sure how/where to check the grounding since it doesn't look like they talk about it specifically in the service manual. Is it just from the electrical schematics?

I will check the voltage from the battery to the starter. Can that be done with just a basic multi-meter?

It would definitely be nice if it's just a faulty connection somewhere that's easy to fix.
GreyGhost said:
Great post OP

When you say " I just hear the starter motor turning, but no engine ", do you mean that just the electric motor is spinning and not the mechanical motor, or do you mean the mechanical motor is spinning but not firing?
Click to expand...
From what I've observed, I'm inclined to say the mechanical motor is spinning, but not firing.
Trials said:
  • the exhaust is most likely an aftermarket, although I don't know if it's a full exhaust or a slip on
Original exhaust will have a whole bunch of writing stamped on it to say it is the correct and emission compliant exhaust system for that specific model motorcycle. Been like that for years and years.
Click to expand...
The muffler says Arrow on it, so that part should be aftermarket. I'll see if I can find the stamping somewhere else on the exhaust.
Trials said:
Have you done a cylinder compression test?
See no mention of valve clearance adjustment, that can make a motor harder to start. 1998, absolutely past due for a check if it has never been looked at. You've got lots of them to look at.
Click to expand...
I haven't done a cylinder compression test. It seems to require a compression tester gauge. Are these pretty generic, or is there a specific kind I should be looking for with fuel injected motorcycle?

Thanks again for everyone's help! My bike is currently in my condo underground garage, so I'll try out the simple stuff for now and report back. If those don't work, I'll have to see if I can borrow my friend's garage again to do some of the messier stuff.
 
Exhaust system is a wild goose chase. Won't affect starting.

Valve clearances. When's the last time they've been checked?
 
Brian P said:
Exhaust system is a wild goose chase. Won't affect starting.

Valve clearances. When's the last time they've been checked?
Click to expand...

Agree on the exhaust, we were just trying to help OP identify what it was as a sidebar.

As for the valves, could that be the cause if It starts consistently when jumped by the car?

OP, yes a regular voltage or multi-meter is all you need to test.
 
Relax said:
Agree on the exhaust, we were just trying to help OP identify what it was as a sidebar.

As for the valves, could that be the cause if It starts consistently when jumped by the car?

OP, yes a regular voltage or multi-meter is all you need to test.
Click to expand...
Spinning faster can overcome marginal compression caused by mal-adjusted valves.
 
Compression testers are relatively generic other then the size of the spark plug hole they need to fit into. There's not much to it, you bung the pressure gauge into a spark plug hole and spin the engine over, the gauge displays 160psi or whatever your engine should output, if you get low or different readings between the cylinders you definitely have a problem.

You mention inspecting the air filter :/ if it's an original paper filter I don't even bother looking at them if the bike is not running right and you don't know when it was replaced, just replace it, it's a consumable part.

Arrow exhaust is aftermarket for sure. I think your bike is old enough that it never had a catalytic converter or O2 sensors or anything like that to deal with.

... I've seen bikes that required modifications to the airbox intake when a less restrictive exhaust was fitted, you might want to see if that is a thing or not.
 
The exhaust doesn't matter. It won't effect the starting unless it's clogged.
Boosting from a running car is a red herring. The electrical pixies don't know or care if the car is running or not

Is the thing coded?
By the sounds of what you are saying I'd be looking at fuel pressure.
 
bitzz said:
The exhaust doesn't matter. It won't effect the starting unless it's clogged.
Boosting from a running car is a red herring. The electrical pixies don't know or care if the car is running or not

Is the thing coded?
By the sounds of what you are saying I'd be looking at fuel pressure.
Click to expand...
If it's running, the pixies are much angrier (14.7 instead of 12.7 volts).
 
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