Took my street bike ('99 SV650) to the track at the end of June. Ran great on days 1 and 2 but on the last day I noticed that it started falling flat at around 7000 RPM. Didn't want to rev beyond that. No obvious misfiring or jerkiness. Most noticeable in 4-6 gears, from what I recall. Don't think it's a clutch issue because starts from a stop weren't a problem, but it's certainly one thing to check. Air filter was checked and cleaned before I went to the track. I'm going to start looking into it this week, my current suspects would be a vacuum leak or electrical (coil/wire). Thoughts?
Not sure if this applies to your particular SV, but check the foam that is stuck on the bottom of the fuel tank. If the foam is loose it gets sucked down onto the airbox opening at higher RPM's and kills airflow. This could kill the engine completely or just reduce performance depending on how badly restricted the airflow becomes. This issue drove me nuts for awhile on a customer bike.
Yep. 1st Gen has foam on the underside of the tank. Sounds like it could be a fuel supply shortage, like it has enough fuel for high load, up until the bowls empty. Make sure the fuel tank vent is clear. These have a vacuum-operated petcock. Make sure that is properly functioning and has a solid vacuum. Pull the fuel pickup out of the bottom of the tank and make sure it’s clear. As side checks, make sure all the vacuum lines tightly fit and are free of cracks. Check the carb boots are tightly clamped and free of cracks, as well.
Given the age of this bike, it wouldn't surprise me if some of the vacuum lines or carb boots are failing. Good idea on the fuel supply - will check those things while I'm in there.
There you have it OP. Get rid of it and get a 2nd or 3rd Gen SV… on that note, my first LWT bike was a ‘99 SV with flat slides and boy was that thing sweet. Made beautiful sounds and had a ton of torque.
ha! if they don't blow, they suck... This is my street bike that I drafted into track service because running my GP bikes for track days has gotten expensive. I plan on replacing it with something more touring-capable in the future, so maybe it has realized that and is acting up on purpose.
Foam is loose under the tank and torn in one spot - I’m guessing enough to partially obstruct the intake on the air box I’m guessing this is there for attenuating the intake noise (?). Options are to reattach - and if so, what glue to use - or just remove it. Thoughts? What did IrocRob wind up doing?
I don’t think that’s your problem. If the whole thing was loose where it would block the air box opening, then, I could see it.
Point taken - I plan on inspecting the vacuum lines, petcock, etc. while I've got things apart. It's hard to see from this photo, but it is also loose along the center of the foam right above the location of the intake - I can easily pull the foam away from the tank in that location.
Aaah! That could be it. There might be 1/4” between that foam and the airbox lid. Such a small gap is why many run spacers under the front of the tank; it allows more airflow.
Update: This weekend I pulled off the tank and got to work removing the old torn and loose foam. Worst part was getting off the adhesive, but eventually got it clean and installed a new piece of heat shield (photo below). Checked vacuum lines and other bits for cracks and leaks - everything looked okay. Also tested petcock and it functioned normally. For good measure, I cleaned and reoiled the air filter. Took the bike out for a ride this evening and it ran smoothly up to 9000 RPM, so I'd say the problem was the loose foam. Thanks to IrocRob for the helpful tip. Noticed that I'm burning some oil - oil level in sight glass was below the L mark and it was just below the upper mark before the three track days. I guess it's to be expected from a motor with 60,000 + miles on it.
The harder you run something, the more oil it’ll burn. Don’t forget to flush the brake fluid. It’s probably due, as well.
