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That just happened
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Discussion Starter · #1 ·
Hey fellas I'm needing some advice on my motor. I've got a Hyosung GT650 (1st gen. Suzuki SV650 clone) the motor is a 649cc dual carbed V-Twin. Problems started about 2 weeks ago while I was cruising to work, everything was running just fine for about 20 miles then it felt like I lost a cylinder so I slowed down to turn around and head back the house and the bike just shut down as soon as I got of the throttle. I let it sit for a bit then started it back up on only 1 cylinder but didn't want to chance it so I hauled it back to the house and took the carbs off thinking that the needles might be gunked up or that maybe the bowls were glazed real bad since the bike had been sitting up for a bit. But when I got the carbs off and apart they looked brand freaking new inside. No particles, no glazing, no nothing. So then I took the plugs out and they looked a little worn but not that bad and replaced them anyways. After I got it all back together it fired right up and worked great.......for 2 days. Then today on my cruise back home from class I lost a cylinder again. Now I'm pretty mechanically inclined and can/have worked on just about anything with a motor, but this one is killing me. I mean motors aren't that hard: Air, Fuel, Fire. I've got air, and I know I've got good fire, so the only thing really left is fuel but the carbs are clean. This problem is just straight up driving me crazy so any input or ideas would be appreciated.

List of things to consider:
1. Plugs are less than a week old
2. Air filter is fairly new
3. Fuel filter is inside clear casing and I can see no particles inside
4. Carbs are clean
5. Coils firing just fine, did a ground out test
6. Choke/Throttle operating normally
7. Bike sat up all winter and beginning of summer
8. Bike ran normally for almost 2 months prior to problems
9. Have only lost power from one cylinder while in motion / after start up
 

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sickboy
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3,544 Posts
Take the spark plug wire off the GOOD cylinder. Try and start the bike while spraying some carb cleaner into the carb of the non firing cylinder. If the non firing cylinder suddenly fires its a fuel problem and time to take a closer look at that carb.
 

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That just happened
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Discussion Starter · #4 ·
Thanks for the reply RD but say I do that and the cylinder fires off, what do think needs to be checked in the carb?
Needle? Float? Jet? Butterfly?
When I took the carbs off last I removed the floats and even though everything looked priestine I scrubbed down the bowl, float, and needle with cleaner anyways (a "while I was there" deal). I mean as far as getting fuel to the cylinder theres really not much else that I could clean

I'll try that too Jmattsen appreciate the input, I know that it fired off fine in outside the cylinder but I'll still give it a shot.
 

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Wannabe
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Happened on the wife's SV. You might consider checking to make sure all of the connectors in the ignition circuit are tight. They can seem tight but still not let the cylinder fire.

Also, the front cylinder on first gen SV's has a bad habit of drowning... if you kick some water up into it off the front wheel, it can build up around the sparkplug and stop it from running. You need to put something in the way to stop water from getting kicked up into the sparkplug hole.
 

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That just happened
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Discussion Starter · #6 ·
Hmmmm, it did hit a little rain on the ride to class today, and the bike ran fine. Nothing really went wrong until the ride home. I'll double check the connections too. Thanks Sev
 

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That just happened
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Discussion Starter · #7 ·
SEV!! You mad genius! I googled the drowning front plug on SV's and found the drain hole that gets plugged up. So I went out there popped the boot off then cleared the drain hole with a skewer. I swear that entire hole must've been full of water. Gonna fire it up tomorrow, I don't think everyone at my apartment complex would like me firing off that no muffler v-twin at 1:30 AM. I'll put up a post about how it performs in the morning.
 

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That just happened
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Discussion Starter · #8 ·
Ok so it rained pretty heavy yesterday so I couldn't ride, but today it's been a great day so I took the bike to class. On start up the bike sounded like it was drowning almost so I looked at the tail pipe on start up and I had a massive amount of water spray out, but the motor fired off (could've simply been rain collected in the pipe from the rain before). It fired off on both cylinders but was only on one by the time I got out of the parking lot. I went on ahead and rode it the 2 miles to class and the entire ride consisted of running on one cylinder with the second kicking in every other 30 seconds or so. Got to school, parked it, came back an hour later, and had an identical ride home. Then I thought about what RD said and I hit the front carb with starting fluid but got nothing from it. The bike will still start up and idle but only on rear cylinder. Perhaps the coil or plug is damaged from water being trapped in the plug hole? Thoughts?

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The Hell You Say!!
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Sounds like either a bad wire or bad coil keeping you from getting spark. When is acting up swap your plug wires and if the front cylinder starts firing then change the coil out
 

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That just happened
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Discussion Starter · #10 ·
Good ideas, I keep thinking it's something particular to the bike and continue to overlook the basics. I'll get my hands dirty after work

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Pull the plug from the non-firing cylinder, leave it connected to the lead, and ground it. Disconnect the other plug to prevent it from starting, then crank it over. You want a bright blue spark... if the spark is orange-yellow, you have a weak coil that isn't putting out enough power to jump the gap under engine compression, or only doing so intermittently.

Or as mentioned swap coils and see if the dead cylinder follows the coil.

Run the bike in a dark room and look for any arcs coming off the wires to ground. To the head/valve cover is most common. Wiggle the wires (with an insulated tool) to see if you can provoke any arcing.

If the plug boots come off (some can unscrew, some are glued on), remove it and snip off the last like 1/2" of wire, and reinstall. Same at the coil end, if the wire comes out.

If all that checks out and still no go, check the coil's harness connectors for water. I've seen a LOT of electrical problems on the clone bikes due to poorly waterproofed connectors corroding.

The very last resort could be the ECU taking a dump, but that's pretty rare on modern bikes, even the clones.


Note that driving the motor on one cylinder is not very good for it. Balance is all fucked up. Our lawnmower fouled a plug on one cylinder and my dad didn't notice and ran it full tilt mowing for 2 hours on one cylinder, until the running cylinder tossed the rod.
 

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sickboy
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ya I agree with Jmartin, switch the wires and see what happens, could be that easy. If that doesnt do it and it still runs the same on that one cylinder id say its time to pop the top and make sure it hasent jumped time on that cylinder.
 

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That just happened
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Discussion Starter · #13 ·
Alright just to report in on what happened, got home from work and was gonna try to swap the wires and or coils but when I removed the wire from the front plug it was still soaking wet with water. So I removed the radiator so I could get a light down in the hole and low and behold there was still water in there. So I again jammed a skewer through the drain hole on the side of the cylinder while shining a flashlight down the hole but couldn't see it near the plug, so I simply applied more muscle and a freaking dirt dobber (Texas slang for a wasp that builds a nest from dirt) larva came out....seriously!?! :nuts:
Yea so after that all the water drained away, I cleaned the hole, the plug, and the wire and went for a test drive. She's running great now, I'll just have to remember to spray my bike down with bug killer next summer.

Stupid insects
 

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That just happened
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Discussion Starter · #14 ·
By the way I greatly appreciate all the help you guys threw my way. CF ROCKS!!:shocker:
 
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