Relax
Well-known member
It consistently starts when jumped, meaning the higher voltage and cranking amps of the car’s battery and/or alternator is overcoming an underlying problem, such as wiring, or valves as mentioned above.
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1998 GSX-R 750 SRAD difficulty starting
- Thread starter Neutronflux
- Start date
It consistently starts when jumped, meaning the higher voltage and cranking amps of the car’s battery and/or alternator is overcoming an underlying problem, such as wiring, or valves as mentioned above.
Neutronflux
Member
I asked my friend and it sounds like he did check valve clearance not too long ago (assuming we're not counting when the bike was just sitting in storage).
Great, that will make things a lot easier. The service manual mentions all kinds of devices such as pocket meters, multi-circuit meters, peak voltage adapters, etc, so it was getting a little overwhelming. I will try this out once I get a multi-meter.
The compression test sounds simple enough to do from how you explained it. I will try that once I get a gauge. My bike uses the CR9E, which I think has a 10mm thread, so would I get a kit with the 10mm adapter?
The air filter is one of those reusable K&N filters. I can try getting a new paper filter if that might help.
If the catalytic converter or O2 sensor is for the California air quality thing, my friend thinks it might already be modified from a previous owner.
When you say coded, do you mean the error codes that show up on the dash by shorting one of the plugs? If so, then yes. I think it was just c00 though, which means no defective part.
I will investigate on how to measure the fuel pressure.
Haha, that would certainly be really bad luck if both batteries were bad... worse yet, the CT battery was replaced twice through warranty before getting the Yuasa battery, so it's actually more like 4 batteries.
I've done a rough inspection of the connectors and don't see anything that looks uncoupled so far. But I'll check some more, especially once I get a multi-meter. I also feel like a loss in voltage is a pretty likely cause, considering how easy it is to start with a bigger battery.
Also, in response to an earlier question on whether I can start the bike using just the car battery without the car running, it looks like I am able to do that after all. Also for some reason, the bike was also happy to start with its own battery when I tried today.
Neutronflux
Member
I wish it was as simple as that. Unfortunately there are many times where the bike doesn't start even with the battery topped up with the tender. And in today's case, the battery has been sitting for a few weeks in the bike and I'm pretty sure isn't full, since I had tried to start it last week.
Also one more thing I've noticed is it does feel like the bike has a harder time starting when it's hot. I've found myself able to start the bike more often when the bike is cold, but it's much more difficult when the engine is hot. I thought maybe my battery wasn't charging enough from riding, so one time I brought a battery tender with me. I rode to my parents' place and hooked up the battery, so it was full by the time I was ready to leave. But the engine was still around 65-70°C according to the dash and didn't want to start.
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Neutronflux
Member
I've checked for spark and that the fuel pump was providing gas when I got stuck at my parents'. I also try just turning off and on the bike, with kill switch and all. Twisting the throttle (I'm told it squirts more gas in). Ignition while the fuel pump is still pumping. I've attempted to bump start, but I'm terrible at it. I've tried using a lithium jump starter. That's the stuff so can think of for now, none of which work.
Usually the only way to get it going is to jump from a car. One time, a car mechanic neighbor also managed to get it to start somehow by spraying some WD40 into the air intake while pressing the ignition.
Trials
Well-known member
Your engine needs air/fuel intake, compression and ignition to fire, plus exhaust to let more fuel air mix in and repeat the cycle. You also need all these things to happen at the right moment.
Mechanic manually added fuel (spray WD40), which would support a fuel delivery problem, he introduced atomized raw fuel into your engines air intake, briefly bypassing the requirement for fuel delivery via the normal injection process.
A hot start problem potentially indicates valve clearance issues, valve stems elongate when they are hot and that is why you need a valve clearance to be set when the engine is cold. The valve clearance becomes smaller with engine wear. When cold clearances are too small, the valves don't hold compression and it cranks over very freely on the starter. Your compression test numbers will typically be lower then expected when this happens.
If the motor becomes very tight when it's hot and the starter motor is having to work very hard to turn it over :/ that's a very bad scenario as it can indicate something seizing when it gets hot, such as piston, rings or valve train parts. That's kind of a worse case scenario, for your sake you want it to be a valve clearance adjustment issue or a dirty air filter or something less catastrophic.
"Twisting the throttle (I'm told it squirts more gas in)" Only if you had a carburetor fitted with a throttle linkage fuel pump, aka accelerator pump,
never happens on a fuel injected motor. On a fuel injected motor the amount of fuel delivered is controlled by time, the ECU (electronic control unit) controls the duration of the fuel injection cycle. When it needs more fuel it keeps the injector open a little longer, if it needs less it reduces the duration that the injector opens.
Excess fuel under pressure is vented back to the fuel tank so the electric fuel pump can keep running, which is also why fuel injected motors heat the fuel in your tank when it's running.
Relax
Well-known member
Don't forget to hold the throttle wide open while cranking. This was the only kit I could find locally that includes the 10mm adapter:
Depending on where you're located, I might be willing to drop by with my compression tester (same as above) so you don't need to buy one.
That said, I still think it's electrical...
I have that one. The spring in the valve core failed very early on in it's life (making the gauge useless). You cannot use a tire valve core as that spring is far too stiff. You have to buy compression tester valve cores to replace it. Not exactly an item that is sitting on the shelf in most stores.
Trials
Well-known member
For the benefit of the OP to understand the process; The compression tester needs to have its needle stop and remain at the highest pressure reading that has been applied to it so you can take a reading. There is a pressure release button to release the pressure inside the instrument and take the next test reading.
Relax
Well-known member
Mine's 10+ years old, but I probably only use it a few times a year. Will have to keep an eye on that valve.
boyoboy
Well-known member
or...
always starts well with a boost ! states OP.
maybe the battery is simply tired and pooched.
always starts good with a boost...Im stumped shrug
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Trials
Well-known member
Depending on where they connected the ground cable, starts good with a boost could also make bad ground cable a possibility. But a bad ground cable should have shown when it was meter tested, or you could just hook a jumper cable from your battery negative to the motor and now you know you have a 100% good ground.
"sounds like he did check valve clearance not too long ago"
I'd be doing that check first hand.
Personally I have never had any luck just checking the screw type adjusters, I just back them off and then reset them. Maybe with bucket and shim adjusters I can see just checking them as adequate. Then there is the issue of; how good are you at using a feeler gauge. You can use a micrometer to test your ability to use a feeler gauge. Sometimes it is a really good idea to do that just before you start setting or checking valve clearances ?
... riding was awesome today
it can't get much better then this.
"sounds like he did check valve clearance not too long ago"
I'd be doing that check first hand.
Personally I have never had any luck just checking the screw type adjusters, I just back them off and then reset them. Maybe with bucket and shim adjusters I can see just checking them as adequate. Then there is the issue of; how good are you at using a feeler gauge. You can use a micrometer to test your ability to use a feeler gauge. Sometimes it is a really good idea to do that just before you start setting or checking valve clearances ?
... riding was awesome today
it can't get much better then this.
GVH
Well-known member
I have the same one. Many years old still working good. What area is OP in.
Roadghost
Well-known member
Meh, you've got a fuel pressure problem. Check the psi on the pump. You'll need a fuel psi gauge (they used to sell them at Princess Auto). On those fuelly bikes the starting psi is usually around 50psi. If it's below 40psi your pump is junk. You have to be realistic, this is a 22 year old bike and the components will be brittle. Expect a few more things to go once you get it running well.
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