So I have bought a totaled cbr f2, 94. had the frame checked and its straight, fixed everything about it, 100% cleaned crarbs, adjusted them, and synced carbs. Put a lot of time and money into this bike. It looks like a street fighter because I don't want to buy fairings and gauges till I'm really good at wheelies. The bike runs 100% around town, and for short rides on the highway, but if I'm on the higihway for 45+ minutes she will randomly lose all power all of a sudden, no matter where I have the RPMS and no I'm not loading the motor, and I have to struggle to keep her alive. Ive learned the only way to keep her going is to pull over, play with the throttle an slowly keep it alive till I can let it sit around idle, and after she idles for a few miuntes she runs 100% again but Ill go riding and it will do the same again in 5 minutes. If I let her die then she wont start for about 10 minutes. Ive checked the fuel lines, the vent ports on the tank, she is not overheating. I'm stumped. Also the Vacuum ports on the intake are well plugged. Any thoughts are appreciated.

Side note: she is getting fuel because when she loses all power, if I give it moe gas she has a deeper tone to her bad sounding exhaust and I actually decel with more fuel. motor has about 30k on it, royal purple oil, new NGK plugs

 

Hi Miguel, welcome to the forum.

From your description, it does sound like a fuelling problem.

Have you tried cracking the filler cap with your ear next to it, so you can listen for a vacuum? I know, you have checked the tank vents, but it's worth a try.

The only other thing I can think of is a blocked fuel filter, there is normally one incorporated into the pet-****.

 

Thank you for your input, much apprieciated. Ill check it out here in a few hours. Why do you think it would occur only after long highway rides. Thats what blows my mind.

 

It might be a blocked breather, run the bike with the fuel cap slightly open and see if it makes a difference, if so, take the tank off and run a length of wire up the breather pipe.

 

If there is a vacuum in the tank, it may be building up slowly because the tank is not completely sealed (breather not completely blocked).

Once the bike starts to loose power the revs die and fuel is no longer being drawn from the tank at the same rate, allowing air to leak back into the tank, especially if you let her idle for a few minutes.

Starting to ride normally again increases the vacuum again, so you get a repeat of the problem.

I might be completely wrong, but it's a theory

 

Really appreciate the replies, I'm going out to the shop tonight with redbull and beer. Lots gets done that way. Ill take off the breather hoses and see if I can blow anything out and also check on the tank, I will let you guys know. I think once before on the highway when she ran bad I opened the gas tank before and tried riding with no difference. But that could be bad memory

 

Good luck Miguel, got my fingers crossed for you, hope it's that simple.