Hello everyone. This is is a doozy of a first post, but I was directed here to ask about a problem with my bike. I'll try to make it brief, but it seems to be rather complicated. I just purchased a race bike that was converted back to a street bike, says the previous owner. It's a 99 F4. It has been bored 3mm over, has HRC cams and valve springs, larger than stock valves, ported head and Keihins FCR 35mm flatslides. Settings for the carbs are as follows: 158 mains in and out, pilot is 50 (?), A/F screws 2 turns out and clips on needles are 5 from the top. This information was provided by the previous owner as well. The bike has a very noticable low end stumble, but that's not the biggest problem. The biggest problem I have is the bike is dying when I cruise. It has the symptoms of running out of gas (slows, bogs then quits running) even when the tank has gas in it. Even odder than that, is I can't repeat the problem when the revs are higher than the cruise range. The bike has quit running 3 times in 8 miles of 35 to 55 mph riding. Revs are usually around 5k to 6k. On the 4 mile trip from work this morning, I kept the revs at 9k for the entire trip minus stop signs, etc. and the bike seemed to run fine. I've worked on the stock carbs on my 2k F4, but have no experience with the Keihins and really don't know where to start to try to fix this problem. If anyone has any advice or can point me in a certain direction, I would certainly appreciate it. Thanks
check that the tank is vented crack the fuel cap open and see if it dies. The bog. you need dyno time float level is important low end richness is effected by float height. Low end could be due to a overadvanced ign. timming too.
Hey, thanks for the reply. I did get a logical tip from a local bike shop. The mechanic told me the pilot jets may be the culprit. He said they are responsible for the midrange or cruising rpms. I don't know how long the bike sat up before I bought it, so I will be tearing into it today and giving the carbs a good cleaning. What was baffling to me was the bike idles fine and at high revs it ran great, but when I cruised through town to work, it would die a slow death. If I find anything out worthwhile, I'll post up for future reference. Thanks again.
