Starving for fuel?

N

nytrainer

Member
Visit site
2003 FZ, new to me. 17K miles. Ran perfectly for about 350 miles, now at 5000 RPMs engine cuts out until RPMs go under 5000, then runs fine.

Checked fuel line for kinks & removed the fuel filter...no change.

Starts & idles, runs fine under 5000 RPMs.

Any ideas?
 
It's been awhile since I had carb issues, but when I bought my FZ 600 it had sat for a long time unused and the carbs were gummed up. It would idle and start OK with the choke on, but run terrible (sputter and cut out) as soon as the RPMs were increased or the choke shut off. I am no expert, but as I understand it there are pilot, and main jets. If the mains are gummed up then you would be getting the sort of symptoms that you describe. You could run a good does of cleaner (like seafoam) through the system, but what I had to do was have the carbs torn down, cleaned and reassembled with a new gasket kit installed. The parts are not very expensive if you are up to the job yourself.

Now I'll let the Gen 1 boys chime in.
 
Oldschool said:
It's been awhile since I had carb issues, but when I bought my FZ 600 it had sat for a long time unused and the carbs were gummed up. It would idle and start OK with the choke on, but run terrible (sputter and cut out) as soon as the RPMs were increased or the choke shut off. I am no expert, but as I understand it there are pilot, and main jets. If the mains are gummed up then you would be getting the sort of symptoms that you describe. You could run a good does of cleaner (like seafoam) through the system, but what I had to do was have the carbs torn down, cleaned and reassembled with a new gasket kit installed. The parts are not very expensive if you are up to the job yourself.

Now I'll let the Gen 1 boys chime in.
Click to expand...

I agree...pilot jets would impact it at lower RPMs and the main jets at higher RPMs. It's weird that it ran fine and now it's acting up, but wont hurt to remove the float bowl covers and take a look at the jets. I'm curious if it will rev higher than 5k RPM in neutral.

Also verify that the EXUP valve is working and adjusted properly. I would also double check condition of the spark plugs and test the coils...
 
Still starving for fuel

I do not think it is a jetting issue.
It start & runs perfectly on the stand.
Yes, it will rev all the way up when on the stand, but under load, it cuts out at 5000RPMs.
When the RPMs drop it again runs fine until I get up to 5000.

???????????????????????
 
nytrainer said:
I do not think it is a jetting issue.
It start & runs perfectly on the stand.
Yes, it will rev all the way up when on the stand, but under load, it cuts out at 5000RPMs.
When the RPMs drop it again runs fine until I get up to 5000.

???????????????????????
Click to expand...

Hellgate said:
Coils good?

Sent from my LG-P925 using Tapatalk
Click to expand...

Well if that's the case then I suspect coils as well. When not under load they fire, but once under load over a certain RPM they can't keep up. Easy enough to check the resistance of the coils. Unfortunately I don't know what the specs are supposed to be for a Gen I bike.
 
Still starving...

When the problem began, I was almost home after a 100 mile ride (The bike ran fine the entire time) It began to sputter as I accelerated, ran OK when I slowed entering a 40MPH zone & pulled into my driveway.
I will get the multimeter out to check the coils, but my gut feeling is still a fuel issue.
 
nytrainer said:
When the problem began, I was almost home after a 100 mile ride (The bike ran fine the entire time) It began to sputter as I accelerated, ran OK when I slowed entering a 40MPH zone & pulled into my driveway.
I will get the multimeter out to check the coils, but my gut feeling is still a fuel issue.
Click to expand...

Just a thought, but have you checked the charging system? When my alternator quit on my FZ 600, I was out on a ride. It ran normal at lower rpm's and it wasn't until I really twisted on it that I noticed that something was wrong, and it was only running off the battery. One way to know for sure is flip on the high beams and turn signal while it is running. It won't have the juice to flash the signal and keep the plugs firing at the same time without running really rough.
 
I'am thinking this is a fuel flow issue. I would replace the filter and check the petcock. I don't know if the Gen I has a fuel pump but if it does check that as well. I thiink you are running out of fuel when volume is required.
 
Still starving...

Battery/charging is Ok, as I have repeatly started it up while trying to solve this problem. Flashers work fine with lights on.
I also thought about an electrical issue.
Fuel pump is the next suspect.
 
johnnyontherocks said:
I'am thinking this is a fuel flow issue. I would replace the filter and check the petcock. I don't know if the Gen I has a fuel pump but if it does check that as well. I thiink you are running out of fuel when volume is required.
Click to expand...

Gen I has a fuel pump. Easy enough to check it. Disconnect it at the carbs and point the hose into a container. Turn the key and see if the fuel flows...

I still think that it could be a bad spark plug or weak coil...I remember when Billy's Gen I had a spark plug with a cracked insulator and it idled fine, but as soon as any load was put on the engine it would run rough.
 
NJFZ1 said:
Gen I has a fuel pump. Easy enough to check it. Disconnect it at the carbs and point the hose into a container. Turn the key and see if the fuel flows...

I still think that it could be a bad spark plug or weak coil...I remember when Billy's Gen I had a spark plug with a cracked insulator and it idled fine, but as soon as any load was put on the engine it would run rough.
Click to expand...

Your absolutely right Tony. And just as his has done, in neutral, it would rev up with no problem. I would do the old "spray water on the headers" routine to make sure its firing on all cylinders.
 
Starving for fuel

I would check the tank venting. Then the next suspect is clogged main jets. When they are supposed to open up you run out of gas. Run some sea foam through it, before you clean the carbs.
 
Found the problem

When I pulled the air box cover, I discovered the padding that I had put on top of the battery had sucked into the snorkel & the K&N.
Thanks for all the help with what turned out to be simpls fix!
 
You must log in or register to reply here.
Back
Top