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Discussion Starter · #1 ·
Preface: I am not mechanically inclined whatsoever. Also hi, I've been lurking for months :D

I've recently purchased an 03 sv650s from a private seller. The bike has 14k miles and I thought it was in pretty good condition, but I'm having issues with the throttle getting really weak and the engine choking up whenever it gets hot.
It seems to run perfectly fine as soon as I start it up, but then the hotter it gets then the worse it performs. If I start giving it too much throttle then it seems like the engine isn't getting any fuel, then the bike starts jerking around due to engine braking, and its just a rough ride. The throttle is also really weak when this starts happening.
The amount of throttle I can give it before it starts choking up just gets smaller and smaller until I'm going 5 mph, and then the engine eventually cuts out on me. The engine has no problem starting afterwards, though. I just have to let the bike sit for a few minutes and then its good to go another few miles. The temp gauge has never really gone over 225 in heavy traffic so I'm lost.

It feels like a fuel system issue but I'm not really sure where heat would come into play. I've opened the gas tank after this happens and there's never any hissing or anything...seems to be venting properly. I've used a bottle of fuel injector cleaner and a bottle of total fuel system cleaner. I just replaced the spark plugs. The bike has a brand new battery. Using 93 octane gas now. Nothing has seemed to help at all.

Probably going to take it to the shop when I can, but I'd at least like to have a clue as to what the problem is. Any ideas?

pic related:
 

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Discussion Starter · #2 ·
also:

I'm just holding the throttle still...this is after leaving the bike out in direct sunlight during a summer in florida for 5 hours and then riding it in heavy traffic for 2 miles.
 

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Adjust your TPS and get an ATRE, that should take care of some roughness.

As far as the heat goes, mine got up to 215 yesterday in lighter stop and go traffic. When was the coolant changed last? You might try Redline Water Wetter or something like that.

The 93 octane is not going to do a thing for you, it is made to combust at higher compression, which the SV does not have.
 

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Discussion Starter · #4 · (Edited)
Waiting on the TRE to get here and I was actually going to do the tps adjustment tonight.

I'll try flushing the coolant and adding water wetter, but it normally operates at around 190 which is normal afaik...but it wont hurt anything.

My 1 friend that actually owns a motorcycle suggested the 93 octane fuel...I'll just trust the internet from now on.

Thanks.
 

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The internet is no more trustworthy than a friend when it comes to advice. Higher octane fuel is also used in engines that run hot, such as a Harley aircooled twin. Not just for higher compression engines. No need to run fuel higher than 87 in the SV. You use the lowest grade that will not produce pinging or engine knock. There are riders who run higher octane fuel and swear their mpgs are higher and the motor runs better. May have nothing to do with the octane but rather a company's fuel additives. A very debatable subject. Owning a motorcycle doesn't make the owner an expert on motorcycles. Listen and read as much as you can, then make your own decision and test.
 

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Just for giggles, have you pulled the air filter and checked the air box for critters?

I had similar symptoms with my '03 and found a nice mouse nest in the airbox...
 

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Why "trust the internet". The Suzuki manual will tell you to run 87 octane in it, but what do they know :)
Doesn't it say 'at least 87 octane'? All fuels are NOT created equal.:)

The TPS adjustment is something that everybody should make sure to check and adjust if needed, but won't cause the bike to lose power like the OP is experiencing. I'm thinking fuel pump as many times they will work OK until they've run a while then start dying out. There is a way to T-in a fuel pressure gauge to watch while riding.....which would positively show the pump if it IS the culprit.
 

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Discussion Starter · #11 ·
Spent the last 2 days on my bike. I flushed the coolant and threw in some water wetter, used a bottle of fuel system cleaner and refilled with 87 octane gas, did the TPS adjustment, removed the air box snorkel, and then just removed the top of the air box altogether. My bike doesn't go over 190F now, and it feels way better thanks to the TPS/air box mods, but nothing is helping my issue at hand.
I took it for about a 45 min ride down some back roads and the same thing popped up.
0-15 mins - Amazing...very responsive and very powerful. Was a blast to ride.
15-25 mins - Gradually losing power on the throttle. Small hiccups at high rpms accompanies with a pop from the exhaust sometimes
25-35 mins - Throttle is really weak, when trying to go over 7k rpms the bike just seizes up on me and engine brakes, then a pop from the exhaust.
35-40 mins - Final countdown. Bike is crawling home....cant give it gas without the engine dying.

I don't even know what else I can try. I'm probably just gonna take it into the shop next week and let people who know what they're doing take a look at it. Thanks for the suggestions.
 

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Have you tried checking the voltage at the battery terminals when it sputters?

I heard Suzuki's have rectifier problems. Sounds like it may be heating up and not providing enough voltage.

Maybe also check all the vacuum lines from the gas tank and make sure fuel is flowing. I had a similar problem on an old bike, there was enough air in the tank for the fuel to flow, but when there was no more air in the tank fuel would not flow properly and would gradually die.
 

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That sounds like slow fuel starvation to me. Maybe the gas cap vent is clogged. I know you said that there's no "hissing" sound when you open the cap, but there is all the symptoms of fuel starvation somewhere.
 

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Hmmm...only other thing I can think of is clogged fuel filter. Used to happen on my other bike and cars...too much junk in the filter, but not enough to stop it completely...then as you ride, more junk gets sucked in till it slows flow and affects engine. When you turn it off, the junk is no longer held in the filter by suction and it backfeeds back into tank ready to be sucked in again when you restart it. It only seems like it's heat related because it takes so long for it to reclog. I'd check your filter. It does sound like a fuel starvation problem or venting problem, but if you just filled the tank, it would happen sooner because it wouldn't take as long for poor venting to cause the issue since there's more fuel in the tank. Hope you figure it out.
 

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JollyGQ, you may have nailed it. I'll bet there's debris in the bottom of the tank. Fuel filters probably almost full. Possibly rust.
 

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Discussion Starter · #19 ·
I'll look into those suggestions when I get some time. I was replacing the turn signals yesterday and the bike sat out in the sun when it was 100 degrees out...rode it around the parking lot and it started dying on me within a minute.

External conditions play a big part in how the bike runs. Friend says "And what it probably actualy is, is vapor lock. So hot that the fuel in the lines is turning from liquid to a gas. Check the bike shop and ask if then have any sleeves for the fuel lines to prevent vapor lock also maybe one for the tank itself."

Sounds legit to me. Maybe not vapor lock in the tank but the gas lines themselves...would explain why it has issues in hot weather and after the engine has been running for awhile. I'll let you know how it turns out.
 

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Just an observation, two constant things during this problem have been time and heat. The failure seems to happen only after one or both of these have occurred.

Speaking from an electronics engineering background, it sounds more like an electrical component problem. Something like Rider808 referred to. There are times in my work lab where we will get an electronic device that operates fine under normal conditions, for a fixed amount of time. Over time the device will fail because it will heat up, and sometimes we will purposely add heat to make it fail faster.

Would be nice if you could borrow a rectifier, replace yours, and see if that solves the problem.

I also had a similar problem, but it turned out to be a pinched wire on the ignition coil. At times it would short out and I would lose one of the cylinders.

HTH and doesn't confuse things....
 
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