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Discussion Starter · #1 ·
For whatever reason my motorcycle doesn't want to go past 93 mph and it's acceleration is weak compared to when I first bought it used (I accelerate at about the rate of a standard 4 door car). I have full access to my rev range in neutral, with the clutch in, and in lower gears but it falls off as I approach higher speeds. For example, I can take 1st gear up until around 60 mph, very close to the red line no issues at all. But say if I'm in 4th gear, I can ride up to 93 mph and I can't get past that no matter how much throttle I give. The RPM will be stuck around 8k (unless I pull in the clutch) and if I shit up to 5th gear, the revs will drop but maintain a maximum speed of 93 mph, same story with shifting up to 6th gear, further RPM drop and I can't get past 93 mph. What are some of the things that could cause this issue?
 

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Im not sure if it would solve the issue or even be in a possibility of whats wrong but maybe some sort of "limp mode" you could try unplugging the computer and leave it unplugged for a day then go back and see if plugging it in works. im pretty sure limp mode cuts your rpm range even in neutral and you said yours isnt cut with clutch in or when in natural but i mean worth trying anything that is simple and doesnt cost a single dime
 

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Fuel system is clogged most likely. Pull the pump and inspect the inlet screen...you're going to find gunk on it. That's just a strainer while the actual filter is within the body of the pump housing and they're tiny and clog easily. If you look in the stickies there's info on bypassing the clogged filter and putting an external one on that'll fix you up. At least...this is the first thing to do as it's very common and when you have a limited amount of fuel being pumped...that limits how much power you can make and thus your speed. Good luck!
 

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Discussion Starter · #4 ·
I'm definitely going to look into that external fuel filter you mentioned. It seems like my power just isn't all there. I found that if I accelerate in lower gears to a higher speed, I can get past that initial 93 mph limit. For example, if I take 3rd gear to around 90 I can take 4th gear a bit over a hundred. But my acceleration is weak. Previously, if I rolled on the throttle it felt like the bike wanted to throw me off the back and now I can't come close to that type of acceleration at all.
 

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Im not sure if it would solve the issue or even be in a possibility of whats wrong but maybe some sort of "limp mode" you could try unplugging the computer and leave it unplugged for a day then go back and see if plugging it in works. im pretty sure limp mode cuts your rpm range even in neutral and you said yours isnt cut with clutch in or when in natural but i mean worth trying anything that is simple and doesnt cost a single dime
there is no limp mode on svs
 

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Discussion Starter · #7 ·
is it running on both cylinders?
it seems like both cylinders are running, just took the temperature right after a ride and they were about the same so I'm leaning towards a fuel issue. Maybe my TPS needs proper adjustment because when I last did that, I found out I didn't do it properly (didn't warm the bike up or have it running to watch for the change at 1400 RPMs.)
 

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it seems like both cylinders are running, just took the temperature right after a ride and they were about the same so I'm leaning towards a fuel issue. Maybe my TPS needs proper adjustment because when I last did that, I found out I didn't do it properly (didn't warm the bike up or have it running to watch for the change at 1400 RPMs.)
Hi! Did you sort out the problem?
 

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Discussion Starter · #9 ·
Hi! Did you sort out the problem?
Unfortunately I have not, I was wrong with the original problem of that speed limit, but it's a lack of power caused by a lack of compression
I did a compression test and both cylinders were at about 125 psi when they should be roughly 180. But whenI did a leak down test,both my cylinders showed very little leakage, like less than 3%. I'm gonna do the test again soon to double check butI know my issue is a lack of compression
 

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... I did a compression test and both cylinders were at about 125 psi when they should be roughly 180.
It is important to have a fully charged battery for fast cranking, engine warm, and throttle held wide open for proper compression test readings.

125 is low, but since both cylinders test similarly (good sign) there is a good chance this is just a testing error. It is rare to have compression problems on the SV.

As mentioned, there is a good chance this is a fuel problem. A good next step is do a fuel volume test.
 

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Discussion Starter · #11 ·
A while back I did a fuel pressure test and found that my fuel pressure was staying at a constant 44 psi. I did prepare everything to do the external fuel filter mod only to find out that one of the 2 previous owners actually drilled the hole in the pump but never installed an in line filter. When I saw that I put in an external filter myself and changed out the fuel injectors and saw no changes at all. I'm thinking about trying to get one of those cameras that go down the spark plug hole so I can see if my cylinders are scratched up at all.
My thought process for this is that if I have low compression but my leak down test shows a healthy engine that maybe the cylinder walls might have some issues. Since the leak down test only tests when the piston is at the top of the stroke I think that maybe if the walls have imperfections, that on the compression stroke air might be lost due to scratches. I'm skeptical about that because the compression numbers were so similar but that's the last thing I haven't really tested for compression. I've checked valves and they were all in spec too.
 

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When was the last time this bike was running well? A little history would be very helpful.

Does this bike have a Power Commander? Any other mods?

A compression issue is the rarest of problems on the SV. If the cylinders were bad enough to cause low power, this bike would be smoking like a chimney, and blow-by gas would be so bad the air box would be full of oil.

I know you checked already but maybe use an infrared thermometer to double check both cylinders are firing equally.

If that 43psi fuel pressure test was a while ago, maybe retest that also. This really does sound like a fuel problem.
 

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Cranking compression test on the SV1K can give weird results because the exhaust cams have a compression release feature to ease the strain on the starter. You can't get an accurate reading unless you have deactivated the comp release. 3% leakdown isn't terrible..but also not tremendous, but probably not your problem.
When I had the top end off of mine around 14,000 miles there was a shit-load of carbon on the piston and combustion chamber and I'll wager yours is the same. This in and by itself probably isn't causing the problem but is also not good. It's caused by them running super rich most of the time which the stock ECU tends to do.

When you did your fuel pressure test...did you run the bike at redline and WOT to verify that it was holding the 43 psi? Just checking it static isn't telling you how healthy anything but the pressure regulator are and the actual flow capacity could still be lacking for full power. Since my fuel filter clogged the first time I've had a pressure gauge permanently installed so I can monitor the system and feel better for it as a gradually failing pump can do exactly what yours is doing.

The cylinders are plated and VERY tough things....highly unlikely that they're scored or causing any problems, but if the rings are getting clogged with carbon it could cause some sealing issues.
 

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Discussion Starter · #14 ·
The bike ran well when I bought it back in January of this yeah and it ran strong for about a mo the or so. The issue first began on my way home from work. I had just gotten off the highway for about half a mile then it just got weaker.
First thing I did was change my spark plugs, no change. I did take an infrared thermometer to both cylinders and saw that both seemed to be firing with similar temps. The front was a few degrees cooler but I assume that's because it has more cool air around it. I also took the temps of the headers just to be sure and the temps checked out.
I checked fuel pressure, 43 whole running. (I don't believe I went all the way to red line, probably just to about 10k RPMs and it stays at that 43). Changed the fuel pump because I'm an idiot and didn't realize I was installing the wire connections badly and thought I broke it so I bought a new one.
The bike does have a power commander 5 installed so I removed it all just to see any type of change but that was stupid because while it was still weak, it was backfiring a heck of a lot (it does have yoshi pipes on it). So I reinstalled the power commander then hooked it up to the laptop to see if the map that's on the bike matches the set up for yoshi pipes based on the PCV website and it's an exact match. Maybe there some type of issue with the module itself but there's no indication based on the modules map or on the box itself which seems to have a status light for in the case that there would be an issue (the light is off so I assume that means there's no status issue)
Then I did the compression test, got those numbers so I went in and did a leak down and checked my valves. All valves were in spec, but I should probably check again after a couple thousand more as one was a bit closer to out of spec than the others.
After that is when I went back into the fuel pump to do the external pump mod and noticed that it was done but never had the actual in line filter installed so I changed the injectors.
The last thing I did was a compression test again just to be sure about the numbers.
That should be a history of everything I've tested myself, over the course of the past couple of months (haven't been in the biggest rush to fix it since I can get to and from work no problem)
 

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60mph in first gear but refusing continuing acceleration at 90 and above? Holly shyt! I have to get out of first well before 60mph. Have you looked at your sprocket sizes? At 77mph I'm doing 5500 rpm approx. in 6th. Something's eating a lot of HP. Your symptoms are so weird. I'm being to think something is rubbing, for lack of a better term. When I lowered my bike an inch, the S rear fairing fender cover would occasionally rub because the guy before me increased the tire size. I had to remove the fender and chain guard (same unit).
But now I have to go check out my bike for top end, but just a few months ago I was going around 110mph.
 

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Discussion Starter · #16 ·
I don't believe it would have anything to do with my sprockets. The issue began during a ride some. Like while I was riding the change happened. I was wrong in my initial assessment that I can only reach 93 mph. But my horsepower is limited. The more load, the weaker it gets. 1st and second gear I can max out the RPMs but my acceleration is still garbage. I would probably get beat in acceleration with a minivan at this point. If I get into 3rd gear and beyond I can no longer hit the redline no matter what I do. I can get to roughly 110 mph in 4th gear but it will take ages to get there unless I shift up when 3rd is around 10k RPM. But say I'm 4th gear going 105 mph, if I shift up to 5th gear, I will start to lose speed no matter how open the throttle is. Same with 6th gear. And no gear from 3rd and up can get to red line. The higher the gear the lower my revs can reach. Roughly as follows 3rd maxed at 11k, 4th @ 9k, 5th @ 7k, and 6th @ about 6.5k.
Thanks to recoilrob, I'm looking into the fuel some more. My fuel pressure should be fine but I suspect that maybe my power commander was causing issues and might not have the status light show up. I bought a newer one and I'm just waiting for myself to not be lazy so I can install that then I'll return with the results.
 

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Hi, I'm back! I can't stop thinking about your problem. I'm working on installing new throttle cables and am working on the throttle bodies.
Suzuki uses 2 throttles to help instantaneous acceleration. What would happen if the primary and secondaries were out of sync? I imagine a loose mechanism causing a partial throttle closing. There's electrical involved, springs, etc. Check it out if you haven't solved the problem. I'm just brainstorming so don't blame me for stupidity. Good luck!
 

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Discussion Starter · #18 ·
That's fair but I have checked that out. I did a throttle body sync maybe 2 months ago give or take a few weeks. So I don't think it will be the issue. I was actually trying to go out for a ride tonight but my bike decided to tell me that it's time to work on it because it wouldn't start anymore. It cranked normally, never caught and as I continued to crank it would get weaker and weaker. I never let it die but I did notice it weaken. If I flipped the kill switch off and on again the crank would be at max power again but then weaken after about 3 seconds of cranking. I took off the flywheel cover so I can finally check the magnets like I've been wanting to for a while. Thankfully they're intact with some movement so I'll sort that while I have the oil out, change the power commander, and finally reinstall my fuel level sensor once I fix that part shortly. But yeah idk why it wouldn't start, has fuel but maybe the fuel issue (if it's that) finally got to the point that it cant start now.
 

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If it cranks for even a second without firing...the plugs will be fuel fouled and it's not going to start. Weak cranking is just a waste of time...make sure the battery is fully charged so it cranks strongly which then delivers the hottest spark.

If you crank for a second and it doesn't light on its' own, open the throttles wide to give it more air and the ECU should go into 'flood mode' which turns off the injectors so you can clear the chambers and plugs. Be ready to let go of the throttle when it lights!! FI bikes with electronic ignition are not like old carbureted bikes using point type ignitions where they'll start even by kicking. Got to crank fast enough to make spark, and with slipped magnets your charging system hasn't been working properly...so sort them out, charge the battery, clean the plugs and it'll get running again. :)
 

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Discussion Starter · #20 ·
guess what yall, new issue cause of ignorance and negligence. I was doing my flywheel magnets and has almost cleaning the magnets. I dropped a magnet from off my thigh and the thing shattered. I had 3 of them stuck together on my thigh taking one at a time to clean and they fell off and one shattered. If anyone knows where I can get a magnet for the flywheel as I'd rather not shell out $400 for a whole flywheel assembly.
 
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