Hello all, long time lurker, first time poster (because registration took weeks lol)

I have a 2012 GS500F and just rejetted it to go with a new filter and full exhaust.

K&N OEM replacement filter
Delkevic full exhaust system
Jetted to 20/62.5/142.5

Everything is fine in all rev ranges and throttle positions other than full throttle and high RPM where I get flat spots.

Any suggestions? Main too lean or too rich? Adjust mixture screw? Washer for the needle?

I need your help.

Quote from: mansonitefirefox on September 08, 2014, 07:38:22 AM
Hello all, long time lurker, first time poster (because registration took weeks lol)

I have a 2012 GS500F and just rejetted it to go with a new filter and full exhaust.

K&N OEM replacement filter
Delkevic full exhaust system
Jetted to 20/62.5/142.5

Everything is fine in all rev ranges and throttle positions other than full throttle and high RPM where I get flat spots.

Any suggestions? Main too lean or too rich? Adjust mixture screw? Washer for the needle?

I need your help.

I was going to say that there should be a flat spot between 5k and 6k rpm. But your config's far from stock, I'd say contact The Buddha (member here, I'm sure you know who I'm talking about if you're a long time lurker )

Quote from: mansonitefirefox on September 08, 2014, 07:38:22 AM
Hello all, long time lurker, first time poster (because registration took weeks lol)

I have a 2012 GS500F and just rejetted it to go with a new filter and full exhaust.

K&N OEM replacement filter
Delkevic full exhaust system
Jetted to 20/62.5/142.5

Everything is fine in all rev ranges and throttle positions other than full throttle and high RPM where I get flat spots.

Any suggestions? Main too lean or too rich? Adjust mixture screw? Washer for the needle?

I need your help.

You're likely too rich @ 3/4 throttle and up.
K&N in the airbox is somewhere around 135 mains with a 65 mid. You have 62.5, you may be 137.5 (or not, just more squarely 135 than the - Oh I wish they sold these main jets in unit increments so I can run a 133 or a 133.5 - ...

But answer these couple q's.

Does the flat spot go away if you start to close the throttle ?
If you open throttle quick does it fall on its face, but work better if you gradually open throttle ?

Those 2 indicate your slides are rising too fast. You may need to train your wrist to open at the right speed.

The next Q is the answer to the above 2 is no -
Is it worse @ steady throttle as in you've revved up and just staying @ that steady throttle setting - or worse when you're opening throttle and the revs are still rising.
If yes to the first part - its lean, yes to the second part - rich. Please dont say yes to both. I'd have no idea then.

Cool.
Buddha.

Quote from: The Buddha on September 08, 2014, 10:52:23 AM
You're likely too rich @ 3/4 throttle and up.
K&N in the airbox is somewhere around 135 mains with a 65 mid. You have 62.5, you may be 137.5 (or not, just more squarely 135 than the - Oh I wish they sold these main jets in unit increments so I can run a 133 or a 133.5 - ...

But answer these couple q's.

Does the flat spot go away if you start to close the throttle ?
If you open throttle quick does it fall on its face, but work better if you gradually open throttle ?

Those 2 indicate your slides are rising too fast. You may need to train your wrist to open at the right speed.

The next Q is the answer to the above 2 is no -
Is it worse @ steady throttle as in you've revved up and just staying @ that steady throttle setting - or worse when you're opening throttle and the revs are still rising.
If yes to the first part - its lean, yes to the second part - rich. Please dont say yes to both. I'd have no idea then.

Cool.
Buddha.

1. After more testing of the bike in a fully warmed up longer distance ride, its no longer a flat spot but a 'bog down', loss of power, accompanied by a crackle from the exhaust.
2. Only occurs on WOT as its climbing up the revs, only from 7000rpm+, particularly bad if it occurs at 9000rpm+
3. Doesn't occur at the same place in the rev range every time, sometimes never happens, sometimes happens twice.
4. Speed with which I open the throttle doesnt change anything. Fast or slow, never a problem until it starts climbing higher.
5. If I snap the throttle shut during a bog down I get a kick of power.
6. Any RPM and any throttle position is smooth and crispy, much better than stock. Other than WOT at high RPM of course.

I assume this means I am too rich on my main jet, what should I bring it down to? 140? 137.5?

Thanks Buddha

Need to read it slowly tomorow - you seem to be contradicting my assumptions on both sides.

OK WOT = Full throttle ? Or just open throttle ?
And dont snap the throttle shut - slowly close it a wee bit.

Cool.
buddha.

Quote from: The Buddha on September 08, 2014, 06:34:47 PM
Need to read it slowly tomorow - you seem to be contradicting my assumptions on both sides.

OK WOT = Full throttle ? Or just open throttle ?
And dont snap the throttle shut - slowly close it a wee bit.

Cool.
buddha.

WOT = Wide Open Throttle = full throttle.

And I mentioned snapping the throttle shut because if during a bog down I close it slowly or close it a little bit it doesn't do anything different. I only get a different reaction out of it if I snap it shut quickly and I get a jolt of power and then the revs start dropping as per usual.

OK sorry about the delay, but I had to read your post slowly and think, didn't get time till now LOL.

1. After more testing of the bike in a fully warmed up longer distance ride, its no longer a flat spot but a 'bog down', loss of power, accompanied by a crackle from the exhaust.
2. Only occurs on WOT as its climbing up the revs, only from 7000rpm+, particularly bad if it occurs at 9000rpm+
3. Doesn't occur at the same place in the rev range every time, sometimes never happens, sometimes happens twice.


Cause #1 semi explains these 3: I suspect you may be having the slide rise too quickly here - but I may be off. The single factor that can explain all 3 is that, but 4 and 5 contradict that. Though I can imagine cause #2 as dominating over this. Dont touch the slide till you get causes 2 and 3 into the right location.

4. Speed with which I open the throttle doesnt change anything. Fast or slow, never a problem until it starts climbing higher.


Rich on main jet - horribly rich. Easy to imagine (to me) this richness compensating for the leanness of the slide rising too fast, but at times failing ... See most people are barely 1 size rich - if that. The drop off in performance between correct and 1 size too big is so vast, you can easily tell. You may be 2-3 sizes over - so you may be in as yet uncharted territory.

5. If I snap the throttle shut during a bog down I get a kick of power.


This is likely a float being set high - or rich on the mains (I've seen a lightly modded 92 GSXR 1100 wheelie while closing the throttle cos its floats were set pretty high )

So 1 change at a time and make observations - 1. Easiest first - check your floats - change it to the correct height - the top of the float bowl and no more and make your test run again and post symptoms. If the floats are correct, or very very close, just get the mains down to 135 and make a test run. Those 2 should get rid of 5 of the 6 problems.

Cool.
Buddha.

Quote from: The Buddha on September 09, 2014, 01:16:07 PMSo 1 change at a time and make observations - 1. Easiest first - check your floats - change it to the correct height - the top of the float bowl and no more and make your test run again and post symptoms. If the floats are correct, or very very close, just get the mains down to 135 and make a test run. Those 2 should get rid of 5 of the 6 problems.

Cool.
Buddha.

Cheers Buddha, float height is set correctly as expected, this bike is only 10,000km old.

I can change the main out to 135, however, as an alternative because getting some 135 jets will take a while, is there any other combination of air filters that will work better with my 20/62.5/142.5 jetting? I can get a hold of a K&N lunch box filter or 2 independent K&N filters a lot faster, as in today, where as jets will take a month.

Well I just ran the bike from stone cold, to full temp and then ran around for another 10 minutes or so with no airfilters and no airbox and my issue appears to be all resolved (yes I paid special attention to not run through any dirt/sand/dust/water/anything). So it was simply unable to get enough air through the filter at high RPM WOT.

So I have got a lunchbox on its way, if that doesn't work then I will get a couple of twin race filters which are super un-restrictive and we should be golden.

Quote from: mansonitefirefox on September 10, 2014, 11:53:14 PM
Well I just ran the bike from stone cold, to full temp and then ran around for another 10 minutes or so with no airfilters and no airbox and my issue appears to be all resolved (yes I paid special attention to not run through any dirt/sand/dust/water/anything). So it was simply unable to get enough air through the filter at high RPM WOT.

So I have got a lunchbox on its way, if that doesn't work then I will get a couple of twin race filters which are super un-restrictive and we should be golden.

Or you can drop down to the 135 mains and put all the airbox and paper filter back in - and yea clean that paper filter before putting it back.

BTW K&N will need you to go to 147.5 - 140 not gonna cut it.

Cool.
Buddha.