Hey,

I'm new around here, i used to be on cbrlist email but I guess that doesnt exist anymore. Havent been riding much but trying to get back in it but I'm having some problems with the bike. It is jetted (was totally against it but some mechanic convinced me, kind of regret it) but I had this bike for 10 years and it has always been super reliable.

It was sitting for a while so I

put in new gas
completely cleaned the carbs
replaced the fuel pump (seemed to not be working)
put in a new battery

So now it will start up and run great and idle with the choke on. I can even rev it to some high rpms and it wont hesitate. But after the engine warms up a bit it starts to hesitate and then it dies and stalls out. after that i cant start it again, i can hear some ignition but it wont turn over and carry itself.

I dont think it is
the plugs, or it would not run before stalling
not the battery
carb is clean
the bowls have fuel in them

Can it be an air vacuum issue? Not sure what to check next. it hurts me to see my baby sick like this this.

thanks in advance.

 

I would say double check all your vacuum lines. Got a manual?

 

I do have a manual for a 98 F3, should be good enough? Where shoudl i look though, I only see a vacuum tube to the carb for cali bikes, in the fuel section, which is not me.

 

ok, found one that come in the side of the carb, how exactly can I check it?

 

it sounds like fuel starvation to me. First thing I would check is to make sure you didn't kink the fuel line from the tank when you put the tank back on. Lift the tank, and then slowly lower it into position closely watching how the hose from the tank is laying.

Also, I would start the bike, let it warm up and as soon as it dies, open the gas cap. If you hear a woosh of air, your vent line is plugged on the tank.

The next step I would take is to check the petcock for proper operation, and also maybe consider taking the petcock off the bike and inspecting the screens. there will be one or two tube screens that can sometimes get plugged up.

I don't think its a warming up issue, its just a time issue. Your bike is running out of gas around the same time it takes to warm up. Just a guess though... without knowing more about the bike, thats my best guess.

One more thing, does it run with the choke off? If not, you may have the pilot jets adjusted too far in.

 

I went out and checked those things

No whoosh when i open the gas cap
The hose looks ok

However i do agree that it is a fuel starvation issue.

When it dies, if I turn the ignition key off and on 4 or 5 times, which causes the pump to pump regardless for a second and then start it it, it will do exactly the same cycle over again. I just did it 4 times, it runs fine then dies, play with the ignition, runs fine for 5 mins and then dies.

Any suggestions, the pump should pump to a certain pressure right? Then the bowls shoudl shut it off. I'm sure they are not getting stuck, i just cleaned them and certainly not all of them.

 

thats true, but its a really low pressure to begin with. Im sure of the exact figure, but its right around 2 psi, which you could stop with your finger over the hose. the fuel pump only acts as an asistant to the gravity feed of to the carbs. So, if its pumping up after a few cycles, I'd lean towards the fuel pump cavitating..... which means pump replacement, or there is an abstruction before the pump. Also, Im not sure how the fuel pump on your bike shuts off, but I imagine there is a check valve, and a pressure switch. If your pressure switch is not resetting, that could be the issue. But again, I think it would be internal to the fuel pump, which would mean replacement.

If it were me, I'd pull the line to the carbs, get a gas can and point the line towards the can. Turn on the key and see how well the fuel flows. There should be a constant flow of gas. It may pulsate a little, but if you have any periods of gas not pumping, there is something wrong between the tank and the pump. If for some reason the pump doesn't work at all, check the fuel pump fuse, and also check the fuel pump relay.

If you didn't check the screen inside the tank, that would be my next step if you have any fuel shutting off. I would also inspect and clean the petcock itself. You could also do a quick test by getting a hose, and a seperate gas can, run the hose from the gas can to the fuel pump and try to run the bike. If the bikes runs fine, you have nailed down an issue with your gas tank itself either the screens or petcock.. If it still runs bad, look closer at the fuel pump or carbs.

 

Checked the filter which goes into the tank and its clear. No kinks either and petcock ok.
Also ran the bike with the fuel into a jar, it only pumps when the ignition is intially turned on, it doesnt pump after that. I checked to see if the throttle sensor was not seated correctly but was ok, however I tried hooking up the 3 contacts to the voltmeter and didnt see any voltage.

 

I think i'll check the relay via the flowchart in the manual but its raining now