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Discussion Starter #1 (Edited)
After making it through the summer with the bike running pretty much like a top, within the last few days performance started dwindling. Nothing new has been done to the bike to cause performance to change. No new fuel, no other modifications to the bike. Bike is running on Citgo 90 octane ethanol free fuel. I noticed much less power off the line and acceleration not up to par - not even when I get it above 10,000 RPMs.
Temperature out this morning is about 58°, I took my grill thermometer and mounted the probes on my exhaust pipes as evenly as I could across the pipes. I started the bike up and right soon after I started what turned out to be a 5 minute video showing the bike heating up the pipes heating up and hopefully the sound of the bike. I stopped the video once the engine reached 150°. I'm hoping someone can give me some information that will help on what to check. The top temperature on the gauge is the left side of the bike the bottom one is the right side. I'm not sure if it's the probes or not but the temperatures don't heat up exactly the same. I include a shot of the probes to show you exactly where I mounted them. one thing I do notice is there a there is a little bit of a hesitation if that's what you call it around 4,000 RPMs the idle isn't as smooth as it is at other RPMs.
if someone can tell me how to post a five minute video or tell me how to send it to them via email or Facebook messenger I'd be glad to send the video I think it will help.
The 2006 bike has just over 18,000 mi on it. With an indicated engine temperature of 150°, the left pipe was at 318. The next one over was at 243, the next one was 286 and the pipe on the right side was at 354.
Thanks.
 

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Discussion Starter #3
I'll post again after riding the bike this afternoon. Once in awhile if it's not running great at lower RPMs once it hits at least 150 degrees or I've run the gears up past 10,000 to shift from say second to third, third to Fourth, the bike seems to run better. Not sure if it's a coincidence or not.
Thanks. In the video I took the engine almost sounds like there's a tapping noise, but it was filmed on my cell phone. When I put my ear to the sides of the engine it just sounds like a regular inline four to me.
 

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Discussion Starter #4
even though the temperatures were in the upper 40s this morning the bike seemed to run okay once it got up to around 150° or so and also after I had been on the throttle just a little bit. Is there any chance that since this is intermittent that maybe the secondary throttle valves are sticking a little bit and once I get on the gas a few times it frees them up? I'm not sure what RPM they kick in. The temporary lack of performance starts at roughly 4,000 through 6,000+ RPMs at least probably a little bit higher. Once this clears up I have smooth acceleration all the way up to red line which I never go to anyway.
 

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If it was anything to do with the secondaries, the self-diagnostic would see it and you'd be getting an FI warning.
 

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Discussion Starter #6
That's what I figured. Since the problem just recently came back but seems to clear up after a short time, I'm still wondering if It could be the main fuel filter in the pump. When the engine isn't performing like it should, it never stutters or backfires like bad gas or something. It just acts like someone turned the power/acceleration way down. Once the engine is warm enough I feel I can safely get on the gas a few times, the problem usually goes away.
 

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Discussion Starter #8 (Edited)
I have. Fuel flow was perfect, so was pressure.
I could probably keep my pressure gauge ready to go and if I start out on a ride and the bike is running restricted, come straight home while it's acting like that and hook up the gauge. That would be tedious but it might tell me something.
 

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Discussion Starter #10
I would have changed them in the winter while it was in my basement 2018 to 2019 so this was the second summer on the new plugs. Oil is always changed before I store the bike for the winter and at the same time I did the plugs I would have replaced the air filter.
I still have no codes and if I flip my homemade switch into dealer mode I get c00 with the dash right in the middle at idle so it seems to me like everything is fine that way.
 

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Might need a compression/leakdown test. Could be that the oil and heat are helping seal things back up.
 

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Discussion Starter #12
I'm not sure if I can post say a two minute video of the engine starting from cold but if I can, would that tell anyone anything?? It is about 65° out here today. also I know I should get a code but when I did a video last Summer of the secondary throttle bodies they go through what looks like a normal cycle before the bike starts but mine go almost completely closed and stay there during warm up the video and pictures I've seen of where they're supposed to be during that time is partially open could that have anything to do with loss of power until the bikes warmed up? Still it doesn't happen all the time. It didn't act up all summer and it doesn't do it every time I ride now.
 

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Discussion Starter #15
I assume that means a compression/leak-down test isn't warranted yet? If that was the problem it wouldn't be occasional, and you (more experienced than I) would have heard something in the warm-up? I believe the tapping noise I hear is the typical online four engine sound? Last two times I have been back out the bike ran like a top again.
Power picks up around 5-6K and then hold on tight from around 9k+😀😀😀
 

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It's really hard using videos. The microphones just don't pick up everything and are usually overwhelmed by the volume. Intermittent issues are the most difficult to troubleshoot. As an example, my bike had an issue where it would rev high pulling up to a stop, or sometimes right at start-up. About a year and a half of troubleshooting I found a really tiny split in the intake air pressure sensor hose. Basically a tiny vacuum leak caused me months of frustration.
 

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GSXR engines are notoriously noisy, but a tapping could be the need for a valve adjustment. The past requirements for GSXR engines was 15k for a valve adjustment however I have done them at 30k and found almost no wear (just depends on the oil and how hard the bike was run). Other then that Chuckster's recommendation for compression then leak down test is accurate.

If you have never done a compression test or leak down test be sure to research them, also I suggest checking the tolerances before the compression test so you know if there is a tight or loose valve problem.
 

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Discussion Starter #18
Thanks for the help. I have never done a compression test or checked / replaced valve shims. I have the service manual downloaded and would attempt something like that while the bike is in my basement for the winter. I'll need help from you folks as well when I have questions.
This is my third summer on the bike. RPMs have only occasionally been run above 12K when shifting, usually from second to third. I never cruise with RPMs above 8K, and considering that these are race engines, do not believe I run the engine hard at all.
Oil and filter are changed before each winter with Rotella T6 and genuine Suzuki oil filter. I hot the bike with around 14 on it and am at just over 18 k miles now. Oil was slightly above the full line when I bought the bike, and after about three months when I started to notice performance issues I found an oily dirty air filter. Not long after that same Fall I changed a dirty fuel filter (Sock pre-filter).
When valves are checked do I need to have any fresh gaskets on hand? I've read that sometimes you can get away with swapping shims around and don't always need an extra supply???
 

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You need some silicone and you can re-use the valve cover gasket. But, if the gasket is damaged during removal, you'll need a new one. But, at 18k miles, your valve lash is probably fine. When they're too tight the valve train gets quieter, so I don't see any evidence that's your issue.
 

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Discussion Starter #20
👍👍👍
If you watched the full video it sounds like the engine warms up fine to me. Never a problem starting, and no detonation or anything when I shut it down. Enging cuts out immediately.
 
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