Engine Stutters and low rpms - Suzuki GSX-R Motorcycle Forums Gixxer.com

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post #1 of 38 (permalink) Old 06-27-2018, 10:09 PM Thread Starter
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Engine Stutters and low rpms

Recently my bike has been acting really weird. When I go to start it, it starts up without an issue, but it idles pretty choppy like it’s starving for gas or something. When I’m riding it, during low rpms it’s very choppy and studders. The sound of the engine sounds like it’s carbed or something. The second I hit higher rpms, the sound goes back to normal and it the bike accelerates like now. This issue only happens at low rpms though.
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post #2 of 38 (permalink) Old 06-28-2018, 04:24 AM
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Re: Engine Stutters and low rpms

Also try disconnecting the IAP sensor, i.e. disconnect its electrical connector and see if that helps. How did this develop?
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post #3 of 38 (permalink) Old 06-28-2018, 03:33 PM Thread Starter
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Originally Posted by Samantha750 View Post
I would suggest checking that the TPS is properly adjusted for starters. What is the bike idling at? Should be 1,300 +/- 100 RPM's.
I checked the TPS and it’s right where it should be. Also my bike is idling right at 1,309 RPMs.
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post #4 of 38 (permalink) Old 06-28-2018, 03:44 PM Thread Starter
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Also try disconnecting the IAP sensor, i.e. disconnect its electrical connector and see if that helps. How did this develop?
I actually tried that this morning but no luck. Last Thursday, I noticed there was a grinding noise coming from my stator, didn’t think too much of it so I rode the bike all day. In my mind,I just assumed that once the bike warmed up and the oil was flowing, it was stop the noise. Well went I went to ride the bike back home, it cut off on me right at a traffic light. When I went to start it, it wouldn’t turn over. After letting it sit for 10-15 minuets, it would start at all. Luckily it cut off right in front of a motorcycle repair shop, so I was able to push it there. I had the guys take a look at it and was told that the screw holding the stator broke off and that caused the stator to come loose. He was able to clean the area and screw the stator back with a new screw. After that fix, the bike rode fine all day. I went to fill up my tank and drove it about 20 miles to my friend’s house. I parked my bike outside and the next morning went to drive back home. The bike started without any issues but when I was roughly 5 miles from my house, that’s when it started acting the way it is now. I thought it might have been bad gas, so I went out and bought Seafoam to add to my tank. Almost at a half tank now and still having the issues. I’m not sure if this could be something caused by the stator? I would think that isn’t the case, because it starts up okay without any issues.
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post #5 of 38 (permalink) Old 06-29-2018, 04:10 AM
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Re: Engine Stutters and low rpms

Try going through the charging system inspection section of the service manual, especially checking the voltage at the battery, at idle and at higher engine speeds. Perhaps the incident with the stator compromised it in some way.
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post #6 of 38 (permalink) Old 07-01-2018, 08:10 AM Thread Starter
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Try going through the charging system inspection section of the service manual, especially checking the voltage at the battery, at idle and at higher engine speeds. Perhaps the incident with the stator compromised it in some way.
So this morning I lifted the gas tank again to try and adjust the tps and noticed that the hoes going from the top of the air box to some part of the engine was not connected at the air box. Could this be the reason why? I connected it but haven’t had a chance to ride it yet.
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post #7 of 38 (permalink) Old 07-02-2018, 04:03 AM
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Re: Engine Stutters and low rpms

Your description makes me suspect you're not sure what the hose is for and therefore where it's supposed to go. Get a service manual and look up the hose routing in the service information chapter. Let us know if you find which hose we're talking about.
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post #8 of 38 (permalink) Old 07-03-2018, 10:38 AM Thread Starter
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Your description makes me suspect you're not sure what the hose is for and therefore where it's supposed to go. Get a service manual and look up the hose routing in the service information chapter. Let us know if you find which hose we're talking about.
The hose goes from the top of the air box to the crankcase breather cover. The part that was connected at the airbox was off. Not sure if this could cause any issues?
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File Type: jpeg B404833A-D9ED-4252-9301-4927676C0BDF_1530651116087.jpeg (784.9 KB, 10 views)
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post #9 of 38 (permalink) Old 07-04-2018, 04:18 AM
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Re: Engine Stutters and low rpms

I can't see the attached image, but if it's the crankcase breather hose, I can't see how it can be causing any running issues, although it would allow crankcase fumes, which are pretty toxic, into the environment and might also allow ingestion of debris into the crankcase, both of which are bad. I'd still advise double-checking with the routing diagrams in the service manual, to make sure the routing is correct, unless you have reason to be sure.
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post #10 of 38 (permalink) Old 07-04-2018, 07:18 AM Thread Starter
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I can't see the attached image, but if it's the crankcase breather hose, I can't see how it can be causing any running issues, although it would allow crankcase fumes, which are pretty toxic, into the environment and might also allow ingestion of debris into the crankcase, both of which are bad. I'd still advise double-checking with the routing diagrams in the service manual, to make sure the routing is correct, unless you have reason to be sure.
I’m 100% sure it’s th crankcase breather hose. What I don’t get is how this just happened over night. I rode th bike all day without any issues. Next morning, went to ride and almost made it home and then this starts. I took in consideration what someone said about the charging mechanism possibly being comprised and put the bike on a tether so that the battery would be completely full, but still having the same issues. Idk, after getting gas the previous night, that’s when I noticed the issue. My tank is almost on empty, so I’m going to run seafoam in it again with another fresh tank of premium gas and cross my fingers. It’s really weird because on low RMPs is where the issue is. Once I get into the higher RPMs everything is back to normal. When it idles, it sounds like it’s carbed and not jetted if that makes sense.
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post #11 of 38 (permalink) Old 07-04-2018, 02:35 PM Thread Starter
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Originally Posted by dpapavas View Post
I can't see the attached image, but if it's the crankcase breather hose, I can't see how it can be causing any running issues, although it would allow crankcase fumes, which are pretty toxic, into the environment and might also allow ingestion of debris into the crankcase, both of which are bad. I'd still advise double-checking with the routing diagrams in the service manual, to make sure the routing is correct, unless you have reason to be sure.

Thank you!!! So that hose attached to the top of the airbox, but for some reason when I went to check Monday it wasn’t attached. Since then I’ve attached it, but still not sure if that could have started the issue.
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post #12 of 38 (permalink) Old 07-05-2018, 04:09 AM
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Re: Engine Stutters and low rpms

Thanks for reposting the photo Samantha. As I've said, I don't think the breather hose being unplugged had something to do with your problem. I find it strange that the engine operates fine under higher loads. That would imply some problem with fueling, that is specific to low-load operation and the only things that come to mind are the IAPS, which you have tested and perhaps the primary injectors (although I've no idea if clogged primary injectors for instance, would allow the engine to run fine just because the secondaries have kicked in).

How and when does it transition from running badly to running fine? (Always at the same engine speed? Is the transition gradual or sudden, etc.)
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post #13 of 38 (permalink) Old 07-05-2018, 10:07 PM Thread Starter
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Originally Posted by dpapavas View Post
Thanks for reposting the photo Samantha. As I've said, I don't think the breather hose being unplugged had something to do with your problem. I find it strange that the engine operates fine under higher loads. That would imply some problem with fueling, that is specific to low-load operation and the only things that come to mind are the IAPS, which you have tested and perhaps the primary injectors (although I've no idea if clogged primary injectors for instance, would allow the engine to run fine just because the secondaries have kicked in).

How and when does it transition from running badly to running fine? (Always at the same engine speed? Is the transition gradual or sudden, etc.)
It’s really all about the rpms. When I let it idle, it sounds rough. It seems the second I go past 4K rpms it instantly goes from sound like shit, to normal. It happens suddenly. I’ve been running seafoam through the gas take like crazy. Is there something I can do it clean the injectors?
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post #14 of 38 (permalink) Old 07-06-2018, 04:17 AM
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Re: Engine Stutters and low rpms

I generally am suspicious of Seafoam and similar products. They seem to me to border or fall into the snake oil category, but I may be wrong. I also find it curious, that your problems happened to start right after your stator trouble, but perhaps it is just a coincidence. I can't imagine how they would be related. You can take your injectors to a shop to have them cleaned, or, if you want to do it yourself, I'm sure you'll find plenty of methods on the Internet, although I can't comment on how effective they'll be.

I still find it hard to believe that the primary injectors will be clogged up enough to prevent idling (which takes very little fuel) but this doesn't affect engine operation at higher loads at all. Does it always clear up when crossing 4k rpms, irrespective of the throttle? I wonder if your model has some other subsystem, which gets switched based on engine speed. You don't see FI flashing on the dash, do you?
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post #15 of 38 (permalink) Old 07-06-2018, 07:14 AM Thread Starter
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I generally am suspicious of Seafoam and similar products. They seem to me to border or fall into the snake oil category, but I may be wrong. I also find it curious, that your problems happened to start right after your stator trouble, but perhaps it is just a coincidence. I can't imagine how they would be related. You can take your injectors to a shop to have them cleaned, or, if you want to do it yourself, I'm sure you'll find plenty of methods on the Internet, although I can't comment on how effective they'll be.

I still find it hard to believe that the primary injectors will be clogged up enough to prevent idling (which takes very little fuel) but this doesn't affect engine operation at higher loads at all. Does it always clear up when crossing 4k rpms, irrespective of the throttle? I wonder if your model has some other subsystem, which gets switched based on engine speed. You don't see FI flashing on the dash, do you?
No FI code at all. This morning, I figured I would give disconnecting the IAP one more time to see if it would help. Only difference is that I actually ran the bike with it disconnected and of course that threw a code out. I powered the bike off and reconnected the IAP and the bike actually sounded normal. The throttle response was back to normal and I thought it was fixed. After letting it run for a couple minutes, I powered it off again to so that I could run upstairs to grab my gear and take it for a test drive. When I came back downstairs and powered it back on, the problem seemed to have come back. This time it’s not as bad as it was before, but it’s still there. I think I’m just going to bite the bullet and take it into the shop.
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post #16 of 38 (permalink) Old 07-06-2018, 07:43 AM
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Re: Engine Stutters and low rpms

So, to make sure I understand you correctly, with the IAP disconnected electrically, the bike run badly like before, with choppy idle, but when you reconnected the IAPS, then it ran fine for a while?
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post #17 of 38 (permalink) Old 07-06-2018, 07:44 AM Thread Starter
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So, to make sure I understand you correctly, with the IAP disconnected electrically, the bike run badly like before, with choppy idle, but when you reconnected the IAPS, then it ran fine for a while?
Yes, that is correct. To further clarify, the bike idles right at 1300 rpms. It just sounds like it’s starving for gas or air at low rpms. While cruising under 4/5k rpms it sounds horrible, but the instant in crosses into higher rmps it’s right back to sounding normal. I was able to get a video while riding, but can’t seem to figure out how to post it on here.
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post #18 of 38 (permalink) Old 07-06-2018, 10:57 AM
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Re: Engine Stutters and low rpms

Try uploading it to YouTube, or some similar service and posting the link.
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post #19 of 38 (permalink) Old 07-08-2018, 06:33 AM Thread Starter
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Try uploading it to YouTube, or some similar service and posting the link.
I’ve added the video link below. I’m not sure if you can hear it or not, but right at the 4 second mark, you can hear the engine rev right back to normal.

https://youtu.be/vkLq4r0oEew

This is the video of it idiling rough as well.

https://youtu.be/RxXAp6PfKvE
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post #20 of 38 (permalink) Old 07-09-2018, 04:20 AM
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Re: Engine Stutters and low rpms

It sounds like it's not firing on all four, both when idling and when under 4k rpm, but then again, if it didn't, I wouldn't expect it to idle at the proper speed, at least not if the K6/7 doesn't have an ISC valve, which I think is the case. Given that it suddenly starter running properly at idle, after you reconnected the ISC, I suppose it's not the injectors, at least not a case of the primaries being gummed up, as they wouldn't be likely to clear up for a few minutes only. This leaves some sort of control failure as the most likely cause, only you're not getting any codes thrown and it's not the IAP.

Have you checked your charging system, or at least checked your voltage at idle and at 5000rpm? Perhaps it's struggling to keep up at lower speeds due to your recent incident. Low system voltage, can cause all sorts of weirdness.
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