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Hey guys, picked up my first SV, an '08 SV650S with 9k miles little over 2 weeks ago. I've put a little over 1k miles on it so far, changed all the fluids, brake pads, and did a throttle body alignment.

Everything about it has been incredible so far, except for the one issue of riding when it's "cold" (I live in Tucson AZ so cold has a different definition here lol). Whenever it's below ~70° F out the bike throttle lag is unimaginably awful, it's sputtery in the low RPMs and the RPMs take forever to move.

Just this morning I went to run some errands it was about 50° F degrees out coming out from the low 40's ° F the night before, it started right up on the about the third crank (usually starts on the first or second crank but not a big deal) and idles just fine. I started to ride and it was a little laggy/jittery until the engine got to temp where it improved a little bit but didn't last long. I'll try my best to describe the symptoms.

No matter what gear I'm in, I can turn the throttle as little or as much as I want and you can hear the engine rev up a little bit but the RPMs absolutely crawl up. I was going 50 MPH in third gear and threw the throttle wide, it took 2 seconds before anything even happened and at least a solid 6 seconds for the RPMs to go from 5k to 10K and to go from 50 MPH to 60 MPH. No matter where I'm at RPM wise this will happen. Sometimes after a few seconds of open the throttle the engine feels like it finally "catches" and it yanks me forward for a second or two until I hit 7-8k RPMs and it starts crawling again. It happens all throughout the reve range but 7-8k RPMs seems to be the worst. Sometimes the it'll just stop at 8k and I can't go any higher.

This never happens when it's above ~75° F which is really strange since that shouldn't impact engine operation once it's up to temp, especially since the coolant temp is the same ~170 F regardless of the ambient temperature. I'm running Rotella T6 15W-40, I know it recommends 10W-40 but figured shouldn't make a difference, especially since it'll barely ever even drop below freezing here and at operating temp should be idenentical.

There have been days where I would go to church in the morning when it would be pretty cold out and it would have these issues, let it sit out in the sun for little over an hour and on the way home when it was 10-15° warmer would run perfectly. I'm gonna check the battery this afternoon because I've heard the SV's can do some funky things when the battery starts to go bad and ambient temperature can impact battery performance regardless of engine operating temp, beyond that I'm at a loss, any ideas or help would be greatly appreciated! Thank you!
 

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very big dumb
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that's... beyond fucking weird.
no codes on the cluster? are all the sensors plugged in on the airbox?
tps adjusted?
does it have a power commander? (if yes, try unplugging it)
about the only thing i can think of is some sensor freaking out but even then this makes no sense...
 

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Discussion Starter #3
No power commander, everything seems to be plugged in, no codes, nothing. You're right it really doesn't make any sense, I was thinking that there might possibly be some sort of sensor error but I would have no idea what/what could be impacted by cold air temp. The first couple times I thought it could be a coincidence but its happened too many times now for it to be so. As soon as I can I'll take her out and try to get a video.
Actually I haven't adjusted the tps I just got the security bit and was gonna do that today.
 

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Take the airbox off and check your secondary throttle plates. Kind of sounds like they are sticking shut.
 

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Sounds like carburetor icing... but your bike is injected. Could be sticking secondaries, as golden chicken suggests.
 

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Discussion Starter #6
Thanks for the responses guys...I'll take a look at the secondary throttle plates tomorrow. I was able to take a video, I'm sorry for the lowsy quality and the youtube upload certainly didn't help...anyways the time stamps are in the descriptions. Things don't seem nearly as bad in the video but in the first few times stamps you can see the RPMs crawl through 7-8k range and it taking longer to go from 45-55 than it normally does to go 0-60. The next big symptom is at the 1:11 mark where you can see it takes 5 seconds to go through 1st gear with the throttle pinned, until ~9k where the revs move (and sound) normal again. And lastly at the end I literally had the throttle open half way and nothing happens for about 4 seconds.


I tried the tps but it seemed like a previous owner must've already adjusted it, however the fuel injector line was triggering at about 1,250 (which is low) it was idling lower than it usually does, usually idles at 1,300. I tried adjusting the sensor clockwise as I read online counter-clockwise is to lower the RPM point at which the trigger occurs, and at fully clockwise it was still triggering at 1,300-1,400 which seems strange...🤷‍♂️ Thank you all!
 

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Do you get a clear indication of priming from the fuel pump when you turn on the ignition?

Is the tank free of rust on the inside? When temps fluctuate you can get condensation in the tank if the level is low. If there is any question that's a possibility, draining and filling the tank with fresh gas may be needed. Running a tank with Techron (1oz per gal) once per season isn't a bad idea either.

I've had olld dirt bike that did a similar thing (wouldn't rev) and it was old gas or water in the gas. Fresh gas and it was fine.

Make sure you have a good battery. Test before and during cranking.

When you synced the TB, did you have to make any large adjustments? Did it start running poorly after you worked on it?
 

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Discussion Starter #9
I do get good priming when I turn the ignition, the tank does however have a little bit of rust build-up on the gas cap...so possibly some in the tank. Tested battery cold and while running and it seemed to be running perfect based on other walkthroughs. I made a decent adjustment for the TB since they were really out of sync, however the sync is screw is one turn from coming out, basically had to make it as short as possible without risking it falling out.

But having condesation seems like could possibly be at as it would be temp. dependent. I've run a decent amount of tanks through already but never fully empty and I don't know the exact mechanics of how that would occur. Definitely worth a shot though!
 

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I do get good priming when I turn the ignition, the tank does however have a little bit of rust build-up on the gas cap...so possibly some in the tank. Tested battery cold and while running and it seemed to be running perfect based on other walkthroughs. I made a decent adjustment for the TB since they were really out of sync, however the sync is screw is one turn from coming out, basically had to make it as short as possible without risking it falling out.

But having condesation seems like could possibly be at as it would be temp. dependent. I've run a decent amount of tanks through already but never fully empty and I don't know the exact mechanics of how that would occur. Definitely worth a shot though!
You need to test the battery before and during cranking to really know its condition.

I'm thinking the TB sync may have gone wrong given the need for significant adjustment. I'd recheck it for sure. I think it would be unusual to need to go that far with the adjustment screw.

Draining the tank completely and making sure it, and the pump screen, are clean may be a good idea.
 

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Discussion Starter #11
Gotcha, I'll give that a look as well. Im thinking of checking the battery whole cranking then taking the tank off and clean it as if its rusty, and inspect the pump and screen. While I'm at it im gonna take off the throttle bodies and give them a clean. After going to resync them and readjust the tps, I'll update once everything is finished. Thanks for everything so far!
 

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Two things just happened in the Tucson area in the past couple days.

1. It rained. Did you get rain in your part of Tucson? Do you park your bike outside? You could have water in your tank.

2. It just got “cold”. Last week it was still warm, but now it’s cold. Check your temp sender for the ecm . If it’s failing or not hooked up, the computer may not realize that it’s cold outside and needs to richen up the mixture.

3. check to make sure the throttle bodies are secure in their intake boots. One could not be seated all the way and the rubber may be allowing an air leak behind the tb which is causing it to run lean.
 

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Discussion Starter #14
Update: The rust in my tank was worse than I thought. (Bottom half of tank is being soaked in distilled white vinegar). Mesh filter had a only a little bit of sediment and I'm gonna check the high pressure filter as well. The vinegar seems to be working very well and I'm going to use a chain as well to try to get as much out as possible, will seal with kerosene to prevent flash rust.

@casual_observer
1. Parked outside but under and an overhang so didn't even get wet, I did leave it in the rain a couple weeks ago and there was no issues from that.
2. That's exactly what I was looking for, I was beginning to think the bike didn't have something like that because every article I could find was about engine temperature but makes sense why it would have one. If after the work I'm doing now it isn't fixed I'm definitely going to try replacing that especially being such a cheap part.
3. They were seated well but I'll make sure I seat them fully when I put everything back together.
As well as the TB sync and tps.

I'm feeling hopeful, thank you all!
 

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Honestly that rust doesnt look that bad.. You may just want to put fresh gas in it, since you've already drained it and that may resolve it. Scenario 1 was about water getting into the tank, and the evidence of rust in the tank indicates that may be the case.

Here is a link to disassembling the high pressure filter: How to clean the high pressure Fuel filter


And for getting rid of rust out of a fuel tank, check this stuff out. I've used it with an SV650 (from Tucson no less) and it did a great job of getting rid of rust. Its about $20 and usually on the shelf at Home Depot.

 

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Discussion Starter #16
You're right, after seeing more pics of others gas tanks the rust isn't that bad however figured might as well fix it as it can only get worse yanno. Gonna let it soak until Saturday (used white vinegar, for $2.50 a gallon figured absolute worst case I'm out $10).

And after spending an hour on the fuel pump, if it wasn't the main culprit it most certainly wasn't helping. After pumping the gas through the high pressure filter, I filtered the gas back into the gas tank through paper towels and that's what I've gotten out so far! I'm not even done yet, just needed a break from the fumes lol. Either gonna find somewhere to dispose of the gas or just put it in my car depending on how much nasties made it through the paper towel.
 

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Update: over the past couple days while I was letting my tank soak I checked the battery and it's good, cleaned the throttle bodies, took apart the fuel pump and cleaned both filters. The high pressure filter took hours of pumping gas through as there was so much junk in there it wouldn't stop coming out. I completely de-rusted my tank and put everything back together. After letting the fuel pump prime a few times, to my pleasure it started right up only after the third or fourth crank. It was idling great and was definitely running much better than before. I realigned the throttle bodies and ended up tightening the adjustment screw at least an entire turn inwards. I tightened the throttle cables and the TPS seemed good, no codes.

Feeling good I decided to take her for a spin. For the first minute or two it felt amazing, much snappier and more powerful than before which was very surprising, that may also be partly since I tightened my chain. Although after those couple minutes it started to get worse and worse. After about 15 minutes in I'm struggling to even get it moving from a stop. The revs wouldn't hold and immediately die down. If I twisted the throttle with any sort of speed literally nothing would happen for ~4 seconds before the RPMs spiked and if I tried to start moving from there they'd die back down almost instantly. Once I was moving it was a tiny bit better, but the RPMs would not go past 7k unless the clutch was in. The same symptoms as before but honestly worse.

Once I realized how difficult it was to start rolling I headed home because it became a danger to even ride. I had to limp home and when I made it to my apartment complex I could barely even keep it rolling the, RPMs just wouldn't go up. At idle it the RPMs began to dip below 1k and stall. I'm at a loss at this point, I'm thinking of looking at the fuel pump again but it starts right up on the first crank everytime so I'm not sure if that's the issue. Do you guys have any other ideas of things to check for next?

With the throttle bodies off I could see there was a ton of black buildup on the top of the valves, not sure how much much is normal. I'm going to do some looking around other forum posts but I figured I'd give an update of my work so far. If any more videos would be helpful I can take some whenever. I'm in college so Id like to avoid having to go to a shop since money isn't of the most abundance at the moment lol
 

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My first thought is a failed fuel filter. Kinda seems like it could be falling apart and blocking flow.
 

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I'm thinking the fuel pump is bad.

Once you get it runnning again, run a tank or 2 with Techron Concentrate (1oz per gal). It will clean the injectors, valves, and combustion chamber of deposits.
 
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