Hi Guys. I have an old first generation Sv 650 that I borrowed to a buddy for his first track day. The bike ran good in the morning then as the day went on it started to miss at high rpm. With each session the miss would start sooner and sooner, till buy the end of the day it wouldnt pull past 6,000 rpm. Not sure if i should be looking for a spark problem or a carb problem. It still has the original cv carbs. Any help would be appreciated.
could be many things. First check the low voltage wires to the front coil, they often get knocked loose or oiled. Then check rear coil. Check plug wires are not loose. Then pull the carbs and clean the main and pilot jets. Then pull the tank and clean the fuel filter. Then install an inline filter in the fuel line.
After pulling the carbs apart and cleaning everything out (didn't pull out the pilot jets, will try that as well) and put everything back together, it ran much better, idled better, no misses when revved up, then i looked closer and realized the front carb wasn't seated quite right in the boot. After pushing it in all the way and tightening everything up it was back to running the same way again. So is it getting too much fuel or not enough air or a combination of both? Am going to check the jetting to find out what kind of pilots and mains are in the carbs but seems very odd it ran better when it was sucking a little bit of extra air. Any suggestions would be appreciated.
You are on the right track, start basic. Ensure those pilots and mains are the same in both carbs. Ensure the needles are both set the same. Ensure the vacum diaphragms in the top of the carbs are not deteriorated or holed in any way. Oh, make sure the mixture/enrichment screw is set the same on both carbs as well.
Apples to oranges, but I rode a second gen SV that had a flat battery and exhibited the exact same symptoms. Would not pull RPM's above 6k. Check your charging system and battery, you may have a weak system causing minor headaches.
Battery is good, checked that when we first started noticing the problem. Going to pull the plugs and check as well but the fact that it ran so much better and smoother with the carb mis-seated would lead me to believe its an air/fuel problem (either not enough air or too much fuel). Waiting to get home to pull the carbs apart again and check the above mentioned problems and then will let you know the results.
Look for two things. ONE, there is a blockage in fuel line, or main. Don't worry about main jet size or pilot jet size, that is not the problem. Either you have a major fuel BLOCKAGE or an electrical problem. Again, look at fuel filter in tank, pull main jets and look for blockage, check needles to be sure they are not loose ( They should move about 1/4" up and down) and then check electrical. Dont waste your time rejetting. If it ran before it is fine, or at least good enough. 6k rpm means a major fuel blockage OR electrical problem
