Stutter when accelerating hard 5000-8000 rpm range

[MeteorStorm]

Hi to all. First post on the forum though i've been reading it for 3 years.


I have a 2002 fzs1000. Bought it at 10k miles a year or 2 ago and it now has 20k miles. I'm Belgian but converted it for you . I bought it with a titanium akropovic exhaust but last year i went to the ground in a corner at around 80mph and slid some 140meters... so now i fitted a stock can.


My problem is this:


When i open the throttle hard and the rpm passes 5000-8000 rpm, i occasionally get a big stutter. Just 1, a fraction of a second. I never had it happen to me in first gear.
It feels quite violent. At first i thought it was my chain or something else locking up, so i changed the chain and sprocket, serviced the swingarm. However the problem remained.


Then i figured ok...the big stutter is just the acceleration dropping away and coming back on full in a fraction of a second. It feels as if for a moment somebody gives a very strong tug from behind.
Probably just losing power which comes right back on.
Last thing i did now is replace the fuel filter, because i figured maybe not enough fuel comes into the engine while accelerating hard for a moment...but unfortunately that also didn't make any difference. Any ideas as to what my problem could be? I've been searching the internetz quite a bit this last week but haven't found other people that have my problem. It's really 1 big tug that i get for a fraction of a second, then it keeps accelerating.


But i think if i were leaning in a corner far with open throttle and i get that kind of shock, i could actually loose the backwheel or something when riding on the edge. Though i'll probably never accelerate so hard when cornering.


Any thoughts as to what might be the problem? I didn't have the problem until like 10 days ago. I service it myself. Haven't done valve clearance check. I'm afraid that if it keeps happening and it's something in the engine, it might actually wreck the engine. Could it be the fuel mixture setup? I have to use choke to turn my engine on, even when it's like 20°c out. and i also have to give it a little bit of gass before it comes on. Is that normal? once it has run about 20 seconds i can drop choke and it will sit around 1000rpm and when the engine is warm it idles at 1100-1200 rpm. At a pretty constant rpm as well.


Greetz and thanks in advance !


Sebastiaan

[MeteorStorm]

Fuel mixture? Fuel feed problems? Fuel tank not letting air in? Spark plug? Cam chain ? Gearbox skipping teeth?  valve clearances out? The motorcycle runs fine for the rest except for that one problem.

[Kenyun]

You didn't mention it, but have you checked the Exup valve adjustment and TPS setting, they are very simple to check and adjust.

[unfazed]

Do you know if the carbs were Modified? Ivans Full Monty and Dynojet rejetting  could cause issues with the standard can being refitted. Neither setup was designed for use with the standard exhaust as it would be to restrictive.
Do you know if the  the Akropovic a road can or race can or what the code on the end of the Akropovic exhaust was?

[MeteorStorm]

I don't think there is an exup problem as it would indicate on the tacho if there would be right?


As for being Ivanized or jetted. I'm not sure. But the new stock can has been fitted some 10.000km ago and it ran fine up until 2 weeks ago.


After some more testing it appears it's only doing it in second gear....so now i'm actually guessing 2nd gear broke a tooth or something.
There's no easy way of fixing this right? Probably the easiest thing to do is a full engine swap? or is it cheaper to do the gears only. I might just ride it until it breaks fully. Just not gonna push second to the limit so it doesn't skip...


greetz

[Gnasher]

As for being Ivanized or jetted. I'm not sure.

Just pull off a carb top and check if the springs been cut to shorten it, it will be blatantly obvious.

After some more testing it appears it's only doing it in second gear....so now i'm actually guessing 2nd gear broke a tooth or something.

If second gear had failed you know about it all the time, not just while accelerating and it wouldn't go away.  From what you said, your problem is either fuel/air mixture, an air leak and or fueling is leaning off/being restricted or it's high tension circuit i.e. coil/lead/plug breaking down or leaking.  Changing the end can will not cause this, just bolting on any end can will have little effect to top end power.   

You keep mentioning pushing it to the limit, pushing a FZS1000 to the limit in second is probably why you had an 80mph off, if nothing else mate slow down or the bike possibly you are likely not to last very long on the road.     

[MeteorStorm]

As to me mentioning pushing the bike..
I don't often give it full stick in second but it happens. Like when you want to overtake quickly, or get on the highway...Or when you feel like just giving it some on a straight. The reason i mention 'pushing it to the limit' is because it only skips when i give it more or less full throttle. I agree with you that one shouldn't be pushing a bike too often to it's limits on the public road though. But sometimes lessons need to be learned.

I don't really find it hard to imagine when torque is at it's highest, the gears skip over a worn/damged/chipped tooth in second. I know this is simplified but it's what it comes down to right? Why would i feel that problem constantly?

Just pull off a carb top and check if the springs been cut to shorten it, it will be blatantly obvious.

I'll do that this evening.

From what you said, your problem is either fuel/air mixture, an air leak and or fueling is leaning off/being restricted or it's high tension circuit i.e. coil/lead/plug breaking down or leaking.

But why wouldn't i feel this in other gears. The bike runs perfectly for the rest of the time. It still goes 160mph+ on the speedometer (no flaming for testing this please).

[Gnasher]

 The bike runs perfectly for the rest of the time. It still goes 160mph+ on the speedometer (no flaming for testing this please).

Ok more information, if the bike pulls perfectly in 1st, 3rd, 4th etc to red line?  It's possible there is damage to the 2nd gear but normally you'd feel it at any speed, but it's possible.  Drop the oil and check for metal particles (magnet) in the oil, you may even had the odd tooth

The only real way of knowing for sure is split the cases and get the gear cluster out.

[MeteorStorm]

I already did an oil change since i had the problem. Didn't see any metal pieces.


I've been reading up in the meantime. I don't know anything about the gearing in a motorcycle...but by reading up the problem i'm getting could originate from "rounding the dogs on the gears".  [/size]This can be caused by bad shifting. I can imagine the previous owner doing tons of clutchless upshifts etc... and i did it on occasion. Though i haven't heard about this on this fazer forum or anywhere else about the fzs1000.

[/size]Think i'm just gonna keep riding it and avoid going full out in second. Guessing that if there's no metal pieces flying around in my oil...i'll still be able to do a ton of miles with it . At least that's what i hope .

[PieEater]

Don't know if it's been mentioned but make sure the is nothing under the seat that could possibly obstruct the airbox snorkle and also take off the airbox lid and make sure nothing has got sucked into the filter and is obstructing the air intake. I had a similar issue although in all gears. When I was riding the bike it would be fine until ~6000rpm but after then it would bog down and stutter.

When I bought the bike I asked the garage to fit an optimate charging lead under the seat which they did but they left on the large plastic instruction label which was near the air intake. When I accelerated the suction from the air intake pulled the label towards it and around 6000rpm there was sufficient suction that the label was flat against the intake and blocked most of the air getting to the carbs. Removing the label and making sure the airway was clear resolved the issue instantly.

[Gnasher]

Don't know if it's been mentioned but make sure the is nothing under the seat that could possibly obstruct the airbox snorkle and also take off the airbox lid and make sure nothing has got sucked into the filter and is obstructing the air intake. I had a similar issue although in all gears. When I was riding the bike it would be fine until ~6000rpm but after then it would bog down and stutter.

When I bought the bike I asked the garage to fit an optimate charging lead under the seat which they did but they left on the large plastic instruction label which was near the air intake. When I accelerated the suction from the air intake pulled the label towards it and around 6000rpm there was sufficient suction that the label was flat against the intake and blocked most of the air getting to the carbs. Removing the label and making sure the airway was clear resolved the issue instantly.

Very true mate, but it would do it in every gear, this chaps problem is only happening in second.

[Gnasher]

I already did an oil change since i had the problem. Didn't see any metal pieces.

I've been reading up in the meantime. I don't know anything about the gearing in a motorcycle...but by reading up the problem i'm getting could originate from "rounding the dogs on the gears".  This can be caused by bad shifting. I can imagine the previous owner doing tons of clutchless upshifts etc... and i did it on occasion. Though i haven't heard about this on this fazer forum or anywhere else about the fzs1000.

Think i'm just gonna keep riding it and avoid going full out in second. Guessing that if there's no metal pieces flying around in my oil...i'll still be able to do a ton of miles with it . At least that's what i hope .

I think you've got what is the fairly common 2nd gear fault on the early R1 motors suffered, which the FZS1000 is based on.  It was/is a driving dog wear/damage can effect 6th too. 

Look here https://www.r1-forum.com/threads/2nd-gear-problems.257319/

[PieEater]

Very true mate, but it would do it in every gear, this chaps problem is only happening in second.

I'm not saying it is the issue mate, I'm just mentioning that it would be worth checking, and it still is. There could be any number of reasons why a partial obstruction to airflow might be more noticeable or only evident in lower gears. You can't necessarily pin the throttle back in all gears, second is probably the one where you can, first will have you flipped off the bike, third will have you doing insta-ban speeds and potentially having to be more cautious of traffic and turns. The obstruction if it's on a wire / string / elastic like mine could be pulled through into the airbox whilst in second gear clearing the obstruction and then once the bike and suction stops it could be pulled back out again setting it up for the same thing to happen next time. You just don't know, so it's definitely worth checking, even if it's unlikely.

[MeteorStorm]

Thx for the reply Pieeater. I also replaced the air filter so nothing is obstructing the air flow.


As to 'replacing the gearbox' or gears. Do you reckon it's possible to do this? I mean, i have enough time to do it myself. Read somewhere the engine needs to go out. Most people recommend just replacing the entire engine block.


Can any new spare parts be bought somewhere to replace the damaged parts? Or do you recon an entire new gearbox or engine block must be bought second hand.


Greetz

[Gnasher]

Thx for the reply Pieeater. I also replaced the air filter so nothing is obstructing the air flow.

As to 'replacing the gearbox' or gears. Do you reckon it's possible to do this? I mean, i have enough time to do it myself. Read somewhere the engine needs to go out. Most people recommend just replacing the entire engine block.

Can any new spare parts be bought somewhere to replace the damaged parts? Or do you recon an entire new gearbox or engine block must be bought second hand.

Greetz

Yes it's a fairly straightforward repair, providing you know what you're doing that is and have all the tools.  First you need to confirm it is indeed the second gear driving dogs and to do that you've got to pull the engine out and split the cases.  From there you order the parts required and rebuild, i think there're modified gears available, but not certain you need to do some research. 

Or you just replace the whole motor,  quicker but more expensive maybe, choice is yours. 

Best of luck lets us know how you get on. 

[FazThou]

If i remember correctly when i done my old 99 r1 there are three bolts that are punched over that hold in the input shaft, make sure you get some new ones to replace the old ones in case you have to chisel them out.
Oh and some gasket sealant for between the crankcases.

Fowlers will do all the parts you need.

Good luck

[MeteorStorm]

Thanks guys!


I'll keep riding for now untill it starts skipping when giving it less then full throttle. I might actually replace them once it get worse. Just had a look in the haynes manual. I think i could do it when required. If and when i am to replace the gear, i'll make sure to follow up on this topic with pictures .


Greetz and again thanks for the help.

Details My fzs1000

My fzs1000

[MeteorStorm]

Been reading up. It looks like the fzs1000 had the shitty 2nd gear until 2002 production year. Used to be part 5jj1712100 which got upgraded to 5jj17121 from 2003 onwards.


https://www.japan-webike.be/ps/5JJ-17121-00/#!search&p.k=5JJ-17121-00


My question is. When splitting the block and going for my repair, any idea as to what parts will probably need to be replaced?

greetz

[FazThou]

Been reading up. It looks like the fzs1000 had the shitty 2nd gear until 2002 production year. Used to be part 5jj1712100 which got upgraded to 5jj17121 from 2003 onwards.


https://www.japan-webike.be/ps/5JJ-17121-00/#!search&p.k=5JJ-17121-00


My question is. When splitting the block and going for my repair, any idea as to what parts will probably need to be replaced?

greetz

Could be just the second gear cog
Could be second and sixth gear cogs, could be gear selector, could be selector forks etc etc
You wont know until you have split the cases and taken the gearing out and have a good look.


BTW you need to be pretty competent to tackle this.
Let us know when you attack it and im sure you will get some good tips