Bike bogging/slowing at rev limiter

[riddleofsteel]

Hey guys, new to my 98 FZS600 (and carby bikes in general) so apologies if this is something simple/covered already.
I noticed today when pinning it in first/second, that when the bike hits the rev limiter, it doesn’t just bounce off it until I change gears, it seems like there’s a sudden loss of power and the bike slows/bogs and drops revs.
Is this normal? Or indicative of a problem?
Also, not sure if it’s related, but I’m getting a lot of popping in the exhaust, particular under deceleration/engine braking.
Cheers!

[fazersharp]

I noticed today when pinning it in first/second, that when the bike hits the rev limiter, it doesn’t just bounce off it until I change gears,

,are you deliberately trying to destroy it. Yes these bikes can be "screemers" but in 1st or 2nd gear 

[Gnasher]

I noticed today when pinning it in first/second, that when the bike hits the rev limiter, it doesn’t just bounce off it until I change gears, it seems like there’s a sudden loss of power and the bike slows/bogs and drops revs.
Is this normal? Or indicative of a problem?

When you say rev limit, do you mean on the rev counter? 

Also, not sure if it’s related, but I’m getting a lot of popping in the exhaust, particular under deceleration/engine braking.
Cheers!

Your fuelling is all to cock, either an air leak somewhere or some ones been playing with, needles/jets, airbox/filters and or end cans.

Does the bike have a AM endcan/exhaust, is there an air box i.e. is there rubbers at the back of the carbs going into an air box or just filters on the back on the carbs?

[riddleofsteel]

I noticed today when pinning it in first/second, that when the bike hits the rev limiter, it doesn’t just bounce off it until I change gears, it seems like there’s a sudden loss of power and the bike slows/bogs and drops revs.
Is this normal? Or indicative of a problem?

When you say rev limit, do you mean on the rev counter? 

Also, not sure if it’s related, but I’m getting a lot of popping in the exhaust, particular under deceleration/engine braking.
Cheers!

Your fuelling is all to cock, either an air leak somewhere or some ones been playing with, needles/jets, airbox/filters and or end cans.

Does the bike have a AM endcan/exhaust, is there an air box i.e. is there rubbers at the back of the carbs going into an air box or just filters on the back on the carbs?

I mean when I hit the bike’s maximum rpm on the tacho.


There is an aftermarket exhaust, the air box and filter are still in place. Does the popping suggest a lean condition over rich? I’ve suspected there may be some leaks around the rubber carb joints, a bit of carb cleaner sprayed around them at idle does change the rpm a bit

[darrsi]

Air leaks do cause bogging down, i had it once before when a carb rubber wasn't refitted properly.
The fact that yours is doing it at very high revs means it could be an air leak, but could also point to a dirty air filter as well.
Have you tightened all the jubilee clips around the rubbers for starters?


I've found that a carb balance clears up exhaust popping BUT before even considering doing that, everything else has to be in good order beforehand.
As in no air leaks, clean air filter, good plugs, TPS in good nick and correct position, etc.

[vinnyb]

 Surely if it's losing power when it hits the rev limiter, it is doing what it's supposed to do. You're way past peak power by the time you get to those revs anyway and all you're doing is risking potentially catastrophic damage to the engine.
  I have never felt the need to redline mine, never mind bounce it off the rev limiter but I assume the ECU cuts the spark so if the carbs are still chucking fuel into the engine, wouldn't that mean unburnt fuel in the exhaust when the spark starts again maybe that could explain the popping. Just a thought, I'm no expert.

[darrsi]

 Surely if it's losing power when it hits the rev limiter, it is doing what it's supposed to do. You're way past peak power by the time you get to those revs anyway and all you're doing is risking potentially catastrophic damage to the engine.
  I have never felt the need to redline mine, never mind bounce it off the rev limiter but I assume the ECU cuts the spark so if the carbs are still chucking fuel into the engine, wouldn't that mean unburnt fuel in the exhaust when the spark starts again maybe that could explain the popping. Just a thought, I'm no expert.

It shouldn't bog down when maxed out, it just won't go any faster.
Popping happens when you shut off the throttle with the bike still moving.

[Gnasher]

It shouldn't bog down when maxed out, it just won't go any faster.
Popping happens when you shut off the throttle with the bike still moving.

No, it should lose power. Speed limiters do what you describe.

[Gnasher]

Surely if it's losing power when it hits the rev limiter, it is doing what it's supposed to do. You're way past peak power by the time you get to those revs anyway and all you're doing is risking potentially catastrophic damage to the engine.

Yes, correct to a point, they are limited to stop them destroying themselves so taking it to the rev limiter won't cause any damage.  In fact part of tuning (race) is to move the rev limiter on occasion.

 
  I have never felt the need to redline mine, never mind bounce it off the rev limiter but I assume the ECU cuts the spark so if the carbs are still chucking fuel into the engine, wouldn't that mean unburnt fuel in the exhaust when the spark starts again maybe that could explain the popping. Just a thought, I'm no expert.

The rev limiter is way over the red line, so yes you're correct it's a waste of time in road tune.   The bike doesn't have an ECU as such, it has a basic set of engine ignition maps, which is what the TPS is all about. 

[Gnasher]

I mean when I hit the bike’s maximum rpm on the tacho.

The rev limiter is way into the red, if yours is losing power as you hit the red zone, it's not the limiter.

There is an aftermarket exhaust, the air box and filter are still in place.

What make is it, what about the filter?

Does the popping suggest a lean condition over rich? I’ve suspected there may be some leaks around the rubber carb joints, a bit of carb cleaner sprayed around them at idle does change the rpm a bit

Yes, it normally does, but you can have popping when the mixture is leaning off (losing power) and as it dies the mixture picks up again e.g. popping. Does it only pop when you lose power or when you shut the throttle, overrunning?

If the bike gains revs when you spray carb cleaning around them, would be an indication of a leak, but that could well be one or more of the intake rubber aren't fitted correctly, very common.

How long have toy had the bike, whats the mileage?

[BBROWN1664]

Hey guys, new to my 98 FZS600 (and carby bikes in general) so apologies if this is something simple/covered already.
I noticed today when pinning it in first/second, that when the bike hits the rev limiter, it doesn’t just bounce off it until I change gears, it seems like there’s a sudden loss of power and the bike slows/bogs and drops revs.

Essential riding during this time - Fine
Riding like a focwit at a time when the NHS does not need any more tw@ts to practice their sewing skills on - Thread closed.

Any more I spot like this will result in bans