Stutters in first and second? not higher gears?!! HELP!!

[Bretty]

Hi All,

I seem to have fixed a misfire on my bike but it now has a VIOLENT stutter during full throttle in 1st and 2nd but not in any of the other gears? What could do that? It only stutters in the wheelie/power zone. Fine on motorway at full chat and fine at low rev's.
It's like the whole bike shuts down.

It used to misfire and drop from 4 to 3 cylinders which made the bike change in power 75%/100%. I seemed to fixed that by changing the spark plug caps, spark plugs and cleaning the carbs. But now it stutters between 0%/100% power when on full throttle, full torque in 1st and 2nd gear.

some details:
2001 FZS600, 36,000miles
Had new rectifier and regulator 18mths ago
New spark plug caps
Carbs fully stripped and cleaned and in good order
Scorpion exhaust fitted (has ran fine for the last 3years)
K&N filer (a bit old but apparently good for 50,000miles?)
Coil resistances are fine.
Spark plugs were new 18months ago and I just replaced number 3
recent oil and filter change.
Carb/engine rubbers are in good condition - no holes

Battery seems to drain if sat for over 1 month. Fully charging it doesn't seem to change the problem.

No obvious fuelling restrictions, although I've not looked too closely at the filters as it runs fine at full chat in 3rd gear and up?!

Any suggestions greatly received? Or could you suggest a goo garage that is handy with Fazers in London?

thank you!

Brett

[Punkstig]

Just because k&n claim 50k without cleaning doesn't mean it's not worthwhile! Get it out and clean it!

[Frosties]

Hiya fella,
 
Does this stutter happen all the time i.e. when  its hot or cold.......after a good blast..........when filtering etc.
 
+1 for check the air filter and also have a look at your fuel filter.

[Bretty]

hi guys,

Thank you for your inputs!

It happens all the time hot or cold, straight away. it doesn't noticeably improve or get worse the more I ride it.

For diagnostic purposes is it worth taking the air filter out and giving it a short run to see if this solves the issue?

I may change the fuel filter anyway.

If the fuel filter and air filter are the problem, why does the bike run fine at full throttle in third gear throughout the rev range?

[Jules-C]

Checked the TPS?

[Bretty]

No.
The TPS is on my list of things to consider, but I don't understand how it works, what it does or how to test it... so have been putting it off.

The revs have been fluctuating a bit on tickover, but this improved by replacing a rusty looking spark plug number 3.

How should I test theTPS? (I have a multimeter and a Haynes manual)

Brett

[Deefer666]

Is it a stuttering in the power or in the drive chain? (I.E. Gearbox, sprockets, chain) A shuddering at 7K in first and second is an early symptom of gear selector failure.

[darrsi]

Had problems myself recently and checked my K&N filter, and it was filthy after 7000 miles from new.
Do the simple stuff first but only do one at a time, then see if it still happens, don't start doing 2 or 3 things at the same time because it's always a good learning curve to know exactly what was wrong so you can recognise the symptoms if it ever happens again.

[Deefer666]

If the motor can't breath it won't rev out at peak power in the rev range, so yeah I would check the air filter first.

[Bretty]

The bike runs fine on full throttle throughout the whole Rev range in 3rd gear and all higher gears.
This to me suggests the air filter and fueling are fine, no?!

I don't think the problem is the gearbox or drive chain. Although initially when it first started stuttering and only at peak torques I though the chain had come loose and was jumping a tooth on the front sprocket. It was that violent a jump in power.

I'll pull the air filter out this week.

[Fazerider]

An acceleration sensitive fault? Weird. Can you get it to stutter in 3rd if you're accelerating hard up a steep hill?
Does it backfire when it exhibits the fault? (Which would suggest sparks getting killed and unburnt fuel getting into the exhaust.)
If not, it points to fuelling... perhaps float heights are wrong, with a low level of fuel slopping to the back of the float chambers under acceleration you could be running into fuel starvation that doesn't show up under the lower acceleration you get in higher gears.
Most electrical problems are dodgy connections that would probably show up with bumps in the road rather than acceleration... the only possibility I can think of there is the tilt sensor, which IS designed to cut the ignition if the bike's on its side. Perhaps if that was misaligned or damaged in some way it might give the symptoms you describe.


Edit: Strike that last bit. No tilt sensor on the FZS600.

[maxzer1500]

I take it you mean you cured a missfire but still have a stutter directly after having the carbs apart? As the air filter is the easiest to do i would do that first, making sure to clean and re-oil it properly, not over oil and use proper k&n oil. Also that the refitting is correct as the k&n on mine seemed to sit a bit high for the lid to fit snug until i gave it a firm push. If that don't help i would check the fuel pipe is not kinked anywhere and that the tap is fully on. I think the thing here with it just in 1st and 2nd is the speed of the pickup of the revs demands max fuel flow more than the higher gears and especially at those revs. Fazerider has a good point about float levels.

[darrsi]

No.
The TPS is on my list of things to consider, but I don't understand how it works, what it does or how to test it... so have been putting it off.

The revs have been fluctuating a bit on tickover, but this improved by replacing a rusty looking spark plug number 3.

How should I test theTPS? (I have a multimeter and a Haynes manual)

Brett

Read CAREFULLY, it actually only takes seconds to do, but a moody or breaking down TPS can make the bike feel shit (technical term).


http://foc-u.co.uk/index.php/topic,13864.msg157056.html#msg157056

[Jules-C]

The TPS feeds into ignition system details on how far open/closed throttle is and how quickly it's being opened/closed. The ignition system also has a feed from the speedo to use in its calculation for the ignition timing.  That could explain why it's only a problem in first and second gears.

Haynes manual also has the checking/adjusting details in Chapter 5.  It only takes 5 minutes

[Bretty]

TPS is reading fine.

With throttle, resistance changes within the Haynes manual spec:
   1.7 - 5.5Kohms between terminals 1/2
   0.91 - 4.65Kohms between terminals 2/3

I tried to see if I could adjust it to get those readings the same but it didn't want to rotate from it's current position when I did the rev gauge 0-5000-10000rpm test.

Hmmm...  the saga continues. Air filter will come out over the weekend but I'm not holding out much help...
Going to take if for a quick run now to see if I can make it stutter in 3rd.. up a hill.

If never backfires, only on overrun which I like with the scorpion exhaust. :-)

[darrsi]

Are the carb rubbers all fitted back correctly, a mechanic I used years ago managed to refit my carbs with number 2 rubber folded in on itself, so it was letting air in, it would bog down on overtaking or hard throttle.
Couldn't figure it out until another mechanic spotted it by removing them and showing me.
Just a thought......

[darrsi]

You mention cleaning the carbs but not balancing them.


A combination of clogged up air filter and out of sync carbs will cause issues.

[Bretty]

Clutch slipping, Maybe?!

I think it might be, but it's not slipping smoothly it's jumping quite violently?! Would that happen? I would expect a slipping clutch to be like you're pulling the lever in a bit  and the engine to smoothly over rev but this is quite violent stutters. I had the nerve to watch the rev gauge on full throttle and it is jumping but hard to tell which way.

If I sit stationary with the brakes on in first and slowly let the clutch out the rev's smoothly reduce until it stalls.

No problems in 3rd at all only in 1st and 2nd.

I know the clutch got some abuse when it was misfiring as I had to over-rev it off the line to prevent it stalling.

Is this in my head or a possibility?