98 CBR900RR “running out of gas” problem
 

Hi there! I am the new proud owner of a 98 CBR900rr. I picked it up about a week ago and it was(and is) in almost show room condition. I checked all the fluids and all, everything looked good with about 15,000 miles on the clock. I have now put on about 800-900 miles in the last week-2 weeks.

I can across the problem when, rather embarrassingly I was going about 130 and then at 150 (I know i shouldn’t be going those speeds anyway but I promise it was in a safe environment on an empty 4 lane highway.) When I was doing that’s runs however both times it cut out as if it had a speed limiter. Would sputter and wouldn’t let me rev until I dropped back down to about 120 both times. Forgave it as a fluke as it happened at 2 different speeds.

However on the way back about 3-4 hours later on the same highway I was cruising around 80-90 when it started cutting out and sputtering as if out of gas. I pulled in the right lane and switch to reserve and it went back to normal. I was about 80 miles into the tank but I assumed with how hard I had been pushing it before I had simply run out of gas. However once I found a gas station and filled up I saw I still had about half a tank.

After filling I up got back on the highway and about 20-30 minutes later it happened again and I pulled over and let it idle. (to note it never fully shut off at any of these encounters) I did a full check of fluids and let it idle for a good while, didn’t see any suspects.

It’s been about 4-5 days since this happened and I haven’t encountered any of these issues again on short rides or long rides. I plan on taking the bike apart and doing an oil change and a once over everything next week. Just asking for any advice or if anyone has encountered this before. The only thing I suspect atm is something with the carbs? Or I noticed the choke likes to back out 1/4 of the way while riding for more than 10-15 minutes however like I said I only experienced this issue that one day but the choke issue happens every day.

I do apologize for the grammar I wrote this is a hurry at work! Thank you for any and all responses, happy riding!
https://cimg9.ibsrv.net/gimg/cbrforu...f3145efd5.jpeg

I would check that the tank breather isn’t blocked, if it’s blocked it can cause a vacuum in the petrol tank and that stops fuel leaving the tank, as you ride the fuel level drops in the tank, if air can’t get in through the breather into the tank that’s when a vacuum forms, I think the Fireblade tank breathes through the petrol cap so give it a good blast through with carb cleaner then WD40 then air.
A good check is to ride the bike until it starts cutting out, then stop as quickly as possible and immediately open the fuel cap, if you hear a rush of air that’s a good sign that it’s a blocked breather, also if you set off again straight away and the bike runs normally it’s also a good sign that you had a vacuum in the tank.

edit, looks like there’s breather tubes, so check the tank breather tube so check the tank breather tube for kinks and blockages.

yes, make sure petrol flows from tank easily. Do you ever hear whistling or whining sounds from tank? Filter-screen on petcock may be clogged. Or petcock needs rebuild. Test petcock according to manual. Then repeat test with tank-cap open.

https://drive.google.com/uc?export=d...p7RqzgHG0PGlxr

As far as I can tell it hasn’t ever whistled or whined, however as stated I’m very new to the bike so all the sounds are very new to me. I will keep and ear out for it and I do plan on rebuilding the carbs soon which would including cleaning the petcock as well. Keep you updated on that.

Thank you, i’ll give it a look. Do you know though if a breather blockage would cause it so randomly though? It seems to me a breather issue would arise more often.

You don’t necessarily have a complete or constant blockage, also it’s likely that a small amount of air can get in past the Petrol cap, high revs will drain the tank quicker, therefore if you ride slowly it’s possible that enough air leaks into the tank to keep it from forming a vacuum when not riding hard, or that a kink in the breather partially opens allowing the bike to run normally, there are many possible variables, it’s such a simple thing to check out though, all your having to do is confirm the tank is getting air through the breather, so have a go at this before you start pulling parts of the bike off.

Well after months of being too busy and putting it off I did a rebuild and discovered my issue. It was a carb issue. Turns out due to my inexperience I failed to notice that the bike was missing and I wrote it off for the carbs being rough. Turns out the previous owner had messed with the carb and put 120 jets on two of the carbs a 122 on the other two. That along side a ton of other details (missing washers and incorrect fuel/air adjustments) caused the cylinder 1 plug to foul.

I did the viking mod, air box, jets and all changed and an ignition advancer. After all this it now feels like a completely different bike, not gonna lie scared the **** out of me when I felt the real power of a Fireblade!

Goes to show never hurts to clean the carbs!