Hideous Accelerator Jumping

[TommyT]

Hi all! Hope everybody had a good christmas and new year - really hoping for some help here:

Bike operates fine under all conditons, no faults to report anywhere at anytime, apart from the following:

If I pin the throttle (not sure if any particular gear) the bike will accelerate like a beast, as normal, but suddenly jump, as if the rear wheel is losing traction (it’s not) or there is a tooth missing on a sprocket (there isn’t).

It is worth noting that if I DON’T pin the throttle and accelerate gently through the same gear/rpm/speed this does not happen.

I have new-ish tyres, tested in the dry aswell. I’ve inspected both sprockets and nothing is missing or hooked. Chain is of adequate tension and well oiled. What the hell is going on? I’m worried about this happening in the wet or on a corner. Obviously something is wrong...

2006 FZ6-N

Thanks in advance for any help offered.

 

[Motogiro]

Clutch slipping is what first comes to my mind. During acceleration the engine comes into it's power rpm range where it produces more torque and that's may be where the clutch begins to slip. Has the clutch been recently worked on? Check the external return spring on the clutch lever at the motor. Also check that the cable is free and allowing full clutch release. the FZ6 clutch cable is made up using 2 cables with a union between the frame and the airbox. (left side) The FZ6 is more likely to have a cable issue than an actual clutch problem so check for full smooth operation. You should also have 1/8 inch play on your clutch lever on the bar.
It would also be smart to check your front sprocket and chain condition. The front sprocket has a spline mount so insure the sprocket and nut are secure. I would do the sprocket check asap as if there is a problem with the spline you don't completely ruin it.

 

[TommyT]

Thanks mate, will check out the spline asap. Would the clutch issue present itself only when ragging it? It just seems strange to me that normal riding doesn't show any problems whatsoever.

 

[Gary in NJ]

Slipping clutch or worn sprocket(s). Can you post a photo of both sprockets to review?

 

[FinalImpact]

Can you elaborate on ..."suddenly jump"....?
If it is somewhat repeatable you might set up a camera OR look down at the tachometer. If the clutch is slipping the RPMs will climb while the speed does not.

Keep in mind that 1st, 2nd, make less power than 3rd gear and 4th. Adding to that, the mechanical advantage 1st and 2nd have is much less load than all other gears.

If your problem begins in 3rd or 4th while ragging on it could be a slipping clutch if the rpm climb but the speed doesn't.

Also, smell the engine oil, does it smell burned?

 

[TownsendsFJR1300]

It would also be smart to check your front sprocket and chain condition. The front sprocket has a spline mount so insure the sprocket and nut are secure. I would do the sprocket check asap as if there is a problem with the spline you don't completely ruin it.

This, ^^^^.

I wouldn't ride it until THIS is checked...

I'd remove the sprocket and visually inspect splines and the sprocket if NOT obviously loose..


Clutch slip would be constant with high RPM's and no increase in speed.

If the sprocket/ output shaft are ok, you need to pay attention to what gear your in when this happens.
Should it be a specific gear, it's very possible you have a transmission gear "DOG" likely worn and jumping in and out of gear. Worn shifter forks could as well be an issue if NOT fully in gear.

*Your exact issue is becoming common on older FJRs, in the lower gears when nailed. The dogs, get the edges worn, the notches in the gear they engage is also buggered up*.. Usually just two gears BUT an entire gear box tear down.

BTW, just for S&G's, lube the heck out of the adjustable shifter linkage (left side of bike). It's possible your NOT fully engaging into a certain gear(s)

 

[Motogiro]

The engines power is different at different rpms with throttle, as is the resistance at different gearing ratio through the transmission. At some point the clutch plates may begin to slip under that work load and you experience the rpm rise with loss of power to the rear wheel.

As FinalImpact states, engine oil condition is also a consideration as the clutch is bathed in this oil and the oil must be motorcycle specific oil without friction modifiers to prevent clutch slippage.
Is there a possibility standard motor oil has been introduced?
As TownsendsFJR1300 suggests, Check that front sprocket spline first before any further used because it would prevent further expensive damage to the out put shaft of the engine or possible serious injury to you.

 

[TommyT]

thanks to everyone for all of your thoughts, i've been mad busy with work here so i haven't had a chance to look at anything - i finish earlier tomorrow so i should be able to get a good look after work. i'll update some pics as soon as i've done that. i just spent 800 on re-boring my cylinder head after #2 spark plug was fired out during a ride.. i really don't want to go back to the garage already :banghead: haha!

 

[TownsendsFJR1300]

The sprocket cover is just 3 bolts (Allan heads actually)....

Just make sure, when re-installing, you DON'T pinch the TWO wires at the rear of the stator cover-VERY EASY for those to get jambed in there..


Just curious, How did they bore out your head? Do you mean re-thread the spark plug threads?

 

[TownsendsFJR1300]

Any updates??

 

[TommyT]

Any updates??

Hey guys I’m literally in my garage right now. Managed to get the back wheel off nice and easy, upon inspection I can’t see anything to write home about, but for the life of me I can’t get the front sprocket off. Tried the pinning method (snapped the screwdriver) and also with an allen key for a more snug fix, one kept falling out and the other just bent. Also tried a pole though the swingarm & wheel (wrapped in carpet) but the damn thing just bent haha (the pole that is). I guess i need some stronger screwdrivers or poles right? Surely this isn’t the standard way to do this...

I’ve attached a pic of the wheel off so you can get a look at the sprocket. I’m using an 18” breaker bar so surely there is enough force on my end...

 

[TownsendsFJR1300]

The rear sprocket looks good from here.

If you can't get the ft sprocket off (too tight) it's likely fine. When the nut comes loose, it's gone and the sprocket is flopping around under the cover.

When re-installing the rear wheel, make sure the below pictured part is installed CORRECTLY with the swingarm:
REALLY, REALLY IMPORTANT!




IMO, at this point, your going to have to ride it some more, pin point what gear (If a specific gear) it's happening in

 

[TommyT]

The rear sprocket looks good from here.

If you can't get the ft sprocket off (too tight) it's likely fine. When the nut comes loose, it's gone and the sprocket is flopping around under the cover.

When re-installing the rear wheel, make sure the below pictured part is installed CORRECTLY with the swingarm:
REALLY, REALLY IMPORTANT!




IMO, at this point, your going to have to ride it some more, pin point what gear (If a specific gear) it's happening in

Is this a sign that the spline underneath is also fine? I mean this thing is really going nowhere lol. I’m waiting ror dry days to come and then I’ll get the gopro out and try and not die while i recreate this for you guys. Duly noted on the fitment of the brake, i can imagine that would be alot of fun if one were to miss this out...

In answer to your earlier question about the spark plug - I had one fire out of the top of the cylinder head not too long ago. The garage i took it to bored out the stripped thread, re-tapped it and put a threaded insert in, making the hole the original size and thread pitch once again. Lovely bit of spending over the Christmas and New Year period......

Also in answer to an earlier question, the likelyhood of regular motor oil being introduced is very low, normally I do that myself and get the oil from a motorcycle-only shop so to get the wrong vehicle type is not likely. The garage whom repaired the cylinder head did not replace any oil to my knowledge, but in any case this problem was occurring before I took it there anyway.

 

[TownsendsFJR1300]

Is this a sign that the spline underneath is also fine? YES...I mean this thing is really going nowhere lol. I’m waiting ror dry days to come and then I’ll get the gopro out and try and not die while i recreate this for you guys. YOU CAN STILL REMOVE THE FT SPROCKET TO CHECK, (HOW YOUR DOING IT IS HOW I DO IT). JUST MAKE SURE YOUR IN NEUTRAL, CHAIN ATTACHED-REGULAR THREADS. IF YOU HAVE AN AIR GUN, THAT SHOULD ZIP OFF THE NUT.VERY LIKELY, ITS OK..Duly noted on the fitment of the brake, i can imagine that would be alot of fun if one were to miss this out... NOT REALLY, BUT FOLKS HAVE BENT THAT BRACKET (NOT IN THE SLOT) CAUSING MAJOR BRAKE / BRAKE DRAGGING / WHEEL ABOUT LOCKED UP ISSUES

In answer to your earlier question about the spark plug - I had one fire out of the top of the cylinder head not too long ago. The garage i took it to bored out the stripped thread, re-tapped it and put a threaded insert in, making the hole the original size and thread pitch once again. Lovely bit of spending over the Christmas and New Year period...… SOMEONE DIDN'T TIGHTEN IT ENOUGH INITIALLY AND GETTING TO IT ALONE, IS A JOB..

Also in answer to an earlier question, the likelyhood of regular motor oil being introduced is very low, normally I do that myself and get the oil from a motorcycle-only shop so to get the wrong vehicle type is not likely. The garage whom repaired the cylinder head did not replace any oil to my knowledge, but in any case this problem was occurring before I took it there anyway.CLUTCH SLIPPAGE, NOT A SKIP, WOULD BE A RESULT OF THE WRONG OIL AND I SERIOULSY DOUBT IS YOUR ISSUE

I don't think you need a go-pro, just need to pay attention to what gear or gears this is happening in, maybe the RPMs as well.

**Also, make sure when you move the shifter lever, NONE of the linkage is hitting the frame. If it's adjusted too low, it WILL contact the frame and NOT allow FULL ENGAUGEMENT of the transmission gear cogs.

I gather you have NOT changed to a different style riding shoe / boot and the issue started after that?

 

[TommyT]

I don't think you need a go-pro, just need to pay attention to what gear or gears this is happening in, maybe the RPMs as well.

**Also, make sure when you move the shifter lever, NONE of the linkage is hitting the frame. If it's adjusted too low, it WILL contact the frame and NOT allow FULL ENGAUGEMENT of the transmission gear cogs.

I gather you have NOT changed to a different style riding shoe / boot and the issue started after that?

Correct on the boot - actually I’m still wearing the same boots I passed my test in :Flash::Flash:

I’ll get back to tou guys as soon as I can, hopefully the weather dries up a bit, recreating this will be VERY sketchy in the wet!

 

[TommyT]

just a quick update to close this thread - the problem has been solved!

my magical solution was to get T-boned by a car and have the bike written off. RIP to my FZ6 lucky for me i had all my gear on and i don't have a single scratch on me.

incredibly sad as i really loved that bike. really gutted. peace out y'all and thanks for all the help everyone has provided over my couple of threads.

 

[FinalImpact]

just a quick update to close this thread - the problem has been solved!

my magical solution was to get T-boned by a car and have the bike written off. RIP to my FZ6 lucky for me i had all my gear on and i don't have a single scratch on me.

incredibly sad as i really loved that bike. really gutted. peace out y'all and thanks for all the help everyone has provided over my couple of threads.

Dang dude, that's a tough ending. How many miles have you ridden and how long ago did you get your license?
We try to educate people here. Perhaps you can share what happened so others can learn.

Glad you are OK.

 

[Motogiro]

Glad you're okay!

 

[TommyT]

Dang dude, that's a tough ending. How many miles have you ridden and how long ago did you get your license?
We try to educate people here. Perhaps you can share what happened so others can learn.

Glad you are OK.

I’ve had my license for over 3 years, but ridden 125s and stuff like that for many years prior - as for miles i couldn’t hazard a guess... but alot.

1. Learn how to fall. Sounds silly but i always rehearsed in my head how I would fall, tucking my hands into fists and into my chest, rather than sticking them out in front of me, to avoid breaking any bones. that is, if you have time to do all of that. lucky for me, i got away unscathed despite it being well over 40mph.

2. Good gear is good gear. I was all kitted up, PMJ Legend Jeans, Alpine SMX 6 boots, Alpine gauntet gloves, Apline Balck shadow Jacket and Shoei NXR helmet. absolutely brilliant. very little damage. the jeans don’t have a mark on them despite me sliding down the road for a good few seconds. never felt so comfortable sliding down the road i have to say. I owe my avoidance of injury to the quality of the gear i was wearing.

3. never trust what a car driver is doing. ever.

4. always get fully comprehensive insurance.

5. know the law! the police tried walking away from the scene without breathalysing anyone. we both blew 0.0 after i pestered them to get it done (‘we havent got one in the car, are you sure you want to do that? we’ll have to call another car out to bring one down) but imagine this guy was over the limit and got away with it?

badically this guy slowed down and pulled over to the left in a blatant move to let me past. so i accelerated past him and he threw a 90degree right turn into a side road sending me flying. fantastic. lots of contradictory information in the highway code alluding to who’s at fault but let’s not turn this into a blame game thread - everyone please just exercise care on the roads.