Weird ignition help
2003 Suzuki SV650S
Hey! I'm currently dealing with quite a specific problem with ignition and am running out of ideas. In the video, the bike is idling with me revving it to 3k RPM at the end. Any advice would be greatly appreciated.
TL:DR version:
Since getting my bike (K3 SV650S - already with EFI), it is misfiring quite noticeably, mostly when hot. There are new spark plugs, I've adjusted the idle speed to 1300 RPM and ignition coils are new as well. I'm currently considering the following options: throttle body sync, throttle position sensor check (but it's been ok when last checked), or trying to find a gremlin in the wiring upstream from the ignition coil.
Longer version:
It's 2nd gen SV so it already has EFI. It's in quite good condition with no signs of rust. I've bought the bike as my first "big bike" last October. I've already had some experience with servicing motorcycles so I'm doing all the work myself.
I started noticing the issue after taking the bike out after winter, but it may have been present before without me noticing.
When riding at around 4k RPM with warm engine, the bike misfires and the unburnt fuel sometimes catches on fire in the exhaust and makes the bike jolt forward. The misfire is quite frequent, but the jolts not as much. It occurs throught the whole rev range, but more in the lower RPMs (under 4k). The fuel exploding in the exhaust sound seems to come from the front cylinder, but I'm not certain.
There are new iridium spark plugs on the bike and because my first suspect were ignition coils, I've already replaced the rear one. After finding out nothing improved, I tested the rear coil for the front cylinder and it is still the same - so I've ruled the coils out as well.
I've started noticing that it got worse over the past two weeks. Lately the bike started occasionally dying after revved in neutral. Also, when spinning it up to stable 6k RPM (again in neutral), it runs smoothly, but with audible cuts. The bike is restricted from factory via an ECU to 25kW, but it's been doing the same thing with a full power ECU as well.
I figured the following options to do next (not in order):
- synchronizing the throttle bodies
- trying to find a bad contact in the cables that power to the ignition coil
- checking the throttle position sensor
- the SVs were suffering from water reaching the front spark plug, so possibly something with that, but I've never ridden it in the wet.
What do you guys reckon? I'm getting quite desperate, so I really am thankful for any advice. Also, some of my observations may be wrong as I don't have that much experience. Feel free to ask for any extra info :D