Stutter/no acceleration/power loss when hot

[Fizlam]

Hello,
First time poster.

I recently inherited a 2008 FZ6 with 11k miles. The bike sat for a few years before i got it. It was in good shape... this is what i did before getting it going.
-Replaced the battery
-Changed fluids (oil, coolant, brake)
-Drained and replaced old gas and thoroughly cleaned out the tank
-TPS checked and all within spec
-Warmed-up idle set to about 1200rpms

The bike fired right up with new/clean gas, I did a number of short initial rides and the bike ran good, but stalled out a couple times (always fired back up). Turns out the fuel pump was bad, would intermittently stop... so I swapped it with a new Fuel Pump Factory replacement and OEM O-ring. I completely cleaned the gas tank out again before putting the new pump in. Never stalled again after that.

The only other thing I replaced was the ignition coils... because I noticed that it had a bit of a misfire/rough idle.
I came to that conclusion after forum and Youtube searches. I got some used ones off eBay, replaced the plugs at the same time, and it seemed to idle/run perfect after that.

I did quite a few more short (10-15mi rides) and the bike seemed flawless. Smooth acceleration in every gear, all the way to redline, smooth idle. Went thru a full tank of gas on short rides with no problems. Always got the bike up to temp on these rides.

Anyways, I finally did a longer ride yesterday (about 50mi). Functioned awesome throughout the entire powerband in every gear, all the way until the last 3 miles or so.

Right at the end of the ride (going up a hill), the bike would hit a brick wall around 4-6k rpms when accelerating in any gear. It wouldn't completely die.. and when i backed off the throttle the lower-end (idle to 4k rpms) it ran fine.
If i tried to keep accelerating beyond 4-6K, it would practically die. Theres plenty of gas left in the tank.

Avg operating temps on that ride was like 180-200F (got higher when stopped). It was a pretty warm day (mid 70s)

Do you think the used coils i got off eBay might be failing when the bike gets hot?

I'm kinda ruling out a fuel delivery problem at this point, because the fuel pump is new, the filter screen is clean. I ran Seafoam and the bike still accelerates perfectly to redline when cold/warm... so i doubt the injectors are obstructed/clogged. I haven't gone on another longer ride since, so i haven't been able to make the symptom happen again. It didn't repeat the problem on a 10mi ride i just did (tried to get the bike as hot as i could).

thanks for any guidance and responses.

-Fizzle

 

[PauliusD]

Hey there, sad to hear that you're having issues. Did you have any chance to measure the primary and secondary coil resistances after buying them and putting them in your bike?

Also how is your fuel line that goes from the tank to the throtthle body? Are there any kinks in it that might restric fuel flow? Does sound a bit like not enough fuel is getting in under a load

Edit: don't rule out a fueling issue yet. As this is a non return fuel system the ECU controls the fuel pump (just checked the FSM) If there's a restriction between the fuel pump and the injectors it very might well behave the way your bike is behaving. The fuel pump pushes more fuel with more speed and load, but if it can't get to the injectors it won't rev past certain RPMs. There would not be enough fuel to increase engine speed.
Also it does not behave like that while stationary as there's no speed/load on the engine so going to redline requires much less fuel where the restriction is not yet kicking in

 

[TownsendsFJR1300]

Make sure the two vent lines, attached to the underside of the tank, are not kinked.

When ever the tank is raised and then set back down, those hoses will kink.
(Possibly causing the tank to not vent-running out of fuel with full tank)

The fuller the tank, the worse it would be.

Just reach in, from the right side and gently tug the lines on the end, (near the right side foot peg).

One line is actually a vent, the other allows excess fuel, spilled in the gas cap area, to drain out...

 

[tuning-forks]

Do you think the used coils i got off eBay might be failing when the bike gets hot?

I'm kinda ruling out a fuel delivery problem at this point, because the fuel pump is new, the filter screen is clean.

Yes it is possible the used coils are failing when hot. But did the pump kit you bought include the pressure regulator?

 

[Fizlam]

Thanks for the responses everyone.

I did not test the used coils before I installed them. I’ll double-check that the fuel line isn’t kinked!

I assume the fuel pump does have the pressure regulator, as it looks nearly identical to the oem unit.

I will check the vent lines too, to make sure they aren’t pinched.

I’m going to take the bike out again on a longer ride to see if I can duplicate the symptom.

What was weird was that it starting having the problem right at the end of the ride… it had run so well up to that point. This is kinda making me think the coils might be the culprit.

Will update this post after I take it out again.

Appreciate the input!!

 

[PauliusD]

One good way to check the went line is to disconnect it from the tank and try pouring some water down it and seeing if anything comes out the other end. I usually blow into it, but not everyone is comfortable with sticking bike hoses in their mouth

 

[tuning-forks]

I assume the fuel pump does have the pressure regulator, as it looks nearly identical to the oem unit.

The regulator does not mount in the pump motor, and is not included when you buy the pump motor, unless you ask for it. It mounts in the plastic housing assembly, as shown here:

Also, there is sometimes an issue with the o-ring that goes between the 2 halves of the housing assy., which you can read about here: https://www.600riders.com/threads/bogging-and-not-running-right.60611/post-656088

 

[Fizlam]

Quick follow-up here. I haven't taken the bike out on a long ride yet, but i just checked the fuel line, and 2 vent tubes.

It looks like i might've routed the fuel line so that it was resting on top of one of the vent tubes, instead of having the factory pre-bend wrap around it. I think i corrected it and have it routed the right way now... not sure if that was enough cause my issue. I 'blew out' one of the vent tubes, and it was clear.

Also, looks like i unfortunately have the CA version of this bike... so there's a rollover valve (part no. 5RB-24180-00-00) leading to a canister (part no. 5VX-24170-00-00) connected to the other vent tube.

Do you guys know if either of these parts can get clogged or go bad, leading to problems like the one i'm having? Maybe i can just run a straight tube and bypass it? Or would that confuse the ECU?

Last thing, on the aftermarket fuel pump i got, it looks like there's a cap where the pressure regulator would go... not sure if it's removable or not. Hoping i can just run this pump as-is and not have to pull it again.

http://[URL][URL]https://www.fuelpu...0-5vx-13907-02-00-5vx-13907-01-00?keyword=fz6

[/URL][/URL]

Not trying to over-complicate things... just trying to get full confidence with this bike before finalizing my decision on whether i want to keep it or not.

Thanks for your help.

 

[tuning-forks]

Last thing, on the aftermarket fuel pump i got, it looks like there's a cap where the pressure regulator would go... not sure if it's removable or not. Hoping i can just run this pump as-is and not have to pull it again.

http://[URL][URL]https://www.fuelpu...0-5vx-13907-02-00-5vx-13907-01-00?keyword=fz6

[/URL][/URL]

Did you see the image in post #7? The regulator is not in the pump motor.
Here I have circled the regulator (metal) in the photo of the unit you bought:

 

[Fizlam]

Did you see the image in post #7? The regulator is not in the pump motor.
Here I have circled the regulator (metal) in the photo of the unit you bought:
View attachment 93941

Right. So can I remove that cap and pop in the regulator?

 

[tuning-forks]

You can't see that bit of metal like they show in their photo? That would be ridiculous if they expect you to take it apart and put your old regulator in there!
If they are selling a complete pump assy., it should be complete. I would contact them about it and ask why it does not include the regulator that is clearly shown in the photo.

(P.S. the photo in post #7 shows the regulator with it's plastic cover removed)

 

[Fizlam]

**UPDATE** So i got it out on a longer ride today and the same thing happened after the same amount of time (about 1hr). This time i was on the freeway, noticed a slight drop in power at 7500rpms, stayed on the throttle and the bike died.

Fired up and then had the same power loss (around 4k) limping back home (which got worse going uphill).

I think you guys were right about it being a fuel pump issue, because i could almost feel a surge and then pause when the engine was getting and not getting fuel.

The fuel line and one vent tube were clear, the other vent tube leads to a roll over valve and canister.

My options right now are:
Warranty replacement or refund on the new fuel pump (maybe it's bad)
Trying to add a new fuel pressure regulator to this one (assuming it's possible)
Disconnect the vent tube from the roll over valve/canister and run a straight tube and see if that might be where there's an obstruction

Anything other suggestions would be way appreciated. Thanks.

 

[Gary in NJ]

Have you checked the fuel pressure with a gauge? Seems like a first step when the fuel pressure is suspected to be low. Otherwise you’re just guessing and throwing parts at a problem hoping for the best.

 

[Fizlam]

Have you checked the fuel pressure with a gauge? Seems like a first step when the fuel pressure is suspected to be low. Otherwise you’re just guessing and throwing parts at a problem hoping for the best.

Your 100% right NJGary... my only problem is that it only has this symptom after running for an hour, plus it has to be under load.
Thanks, this is right way to troubleshoot fuel pressure issues. Just difficult for me to make it happen while riding it while the problem happens.

It doesn't do it when the bike is stationary, and when cold/warm.

Also, i don't have the adapter on my fuel gauge to connect it to the factory fuel line.

I'm thinking i can bypass the vent tube that goes to the CA-only roll over valve and canister. Hopefully the ECU isn't preset/calibrated with it being hooked up.

At least that way i can rule out a restriction/blockage there. The vent tube from the gas cap is confirmed clear... both in the tank and rubber tube that goes to the footpeg.

Doubt it's the coils, since the chance of 2 going out at the same time simultaneously is nearly impossible. No check engine lights go on when it happens.

I hate throwing parts at problems. What makes it hard is that it runs good the rest of the time.

This is my first injected bike, seems some aspects are awesome... but it's making my street-legal 2stroke supermoto KTM seem like more my cup of tea-- fewer parts and variables, things that can fail.

 

[tuning-forks]

Doubt it's the coils, since the chance of 2 going out at the same time simultaneously is nearly impossible. No check engine lights go on when it happens.

The 2 coils still get there power from the same place, and that goes through the kill switch, which is a known problem for these bikes.
I would try a kill switch bypass before changing any more parts. By that I mean locating the connector from the kill switch and putting a jumper across the 2 wires from the switch.
There are a couple other switches that the coil power is routed through, but the kill switch is a known issue, so that is the best place to start.

I have an old truck that shows the same issues, sometimes bogs or dies under heavy load, like up a steep hill or when I really tromp it. Every time it starts to do this, I clean up the power lead at the coil and that fixes it. I never thought that the coil primary current would be load dependent, but it is. This is also why the old spark plug testers used air pressure to simulate loading. More load requires more/better spark, which requires more primary current to the coils.

 

[Gary in NJ]

If you have low fuel pressure it is there all of the time. It manifests into a poorly running engine only when the demand exceeds available flow/pressure. It is easy to pipe-in the gauge adaptor and temporary connect the gauge to the bike.

 

[Fizlam]

The 2 coils still get there power from the same place, and that goes through the kill switch, which is a known problem for these bikes.
I would try a kill switch bypass before changing any more parts. By that I mean locating the connector from the kill switch and putting a jumper across the 2 wires from the switch.
There are a couple other switches that the coil power is routed through, but the kill switch is a known issue, so that is the best place to start.

I have an old truck that shows the same issues, sometimes bogs or dies under heavy load, like up a steep hill or when I really tromp it. Every time it starts to do this, I clean up the power lead at the coil and that fixes it. I never thought that the coil primary current would be load dependent, but it is. This is also why the old spark plug testers used air pressure to simulate loading. More load requires more/better spark, which requires more primary current to the coils.

Thanks, great tip! I saw threads earlier about potential with this issue being the kill-switch. I'll try to track down the kill switch connector and bypassing it (any clues on where it is? Is it at the switch on the handlebar/perch?)...I never use it anyways. And in an emergency, i can attempt to just turn the key.

Appreciate your feedback TFork.

 

[Fizlam]

If you have low fuel pressure it is there all of the time. It manifests into a poorly running engine only when the demand exceeds available flow/pressure. It is easy to pipe-in the gauge adaptor and temporary connect the gauge to the bike.

Thanks Gary. I haven't tested but the only time this problem happens is when i've been running/riding the bike for like an hour. The fuel pressure seems normal all the way til that point. I'm looking at making my fuel pressure gauge connections match as I'm typing this.

 

[grahammarsden]

Thanks, great tip! I saw threads earlier about potential with this issue being the kill-switch. I'll try to track down the kill switch connector and bypassing it (any clues on where it is? Is it at the switch on the handlebar/perch?)...I never use it anyways. And in an emergency, i can attempt to just turn the key.

You need to remove the right handlebar switch gear.

There's two Allen bolts underneath, remove them (note that one's longer than the other), then open up the switch gear and you'll find the Kill Switch and the wires that connect to it.

Check the KS components for corrosion and clean them up if needed. If they were dirty, try riding the bike again and see if you still have the problems. If not, bridge across the connector and then try riding it.

 

[Fizlam]

You need to remove the right handlebar switch gear.

There's two Allen bolts underneath, remove them (note that one's longer than the other), then open up the switch gear and you'll find the Kill Switch and the wires that connect to it.

Check the KS components for corrosion and clean them up if needed. If they were dirty, try riding the bike again and see if you still have the problems. If not, bridge across the connector and then try riding it.

Got it. When i got the bike the throttle handle was corroded and stuck, so I'm familiar with what that area. So to "jump it", i just merge the two wires together right?

I'll give it a shot, take it for a long ride and see if the problems happens again.

Thanks.