idle to 3000rpm missfire

Ton up · Post by **Ton up** » Sat Jul 31, 2004 2:47 am

I've posted this elsewhere, but I want to make sure it gets seen. Oh, and this time I checked it with a spull chocka<img src=http://www.ezboard.com/images/emoticons/wink.gif ALT=";)"> This one is interesting, I would appreciate some input from you guys. OK. As I have said before, my FZR1000 has a problem from idle to 3000rpm. Most of you seem to have a flat spot. Mine is a serious stuttering misfire. Recently I found a bike shop I was unaware of that has a new dynojet 250i with a gas analyser, so I booked it in. The very first run showed that the fuel metering was nigh on perfect at all revs (with a new BMC airfilter- no need to rejet mine with standard can). At low revs where the misfire happens (and it did it every time on the dyno) it was running slightly LEAN. Hmmm... The rpm vs time curve wobbled around at low revs, showing a misfire. He had the lead hooked to the ECU, so it was the signal from the ECU that was the problem, either caused by faulty connections, bad battery, bad pickup coil or bad ECU. Or so we thought. These all checked out fine. He did a compression test- all excellent; around 190psi He reset the EXUP valve, and tried altering it either way. No good. He checked the plugs. I think he also checked that all the plugs were firing when the miss happens. He balanced the carbs, and found that 3 and 4 were badly out of balance. Then he noticed something weird- when the misfire happens, there is no vacuum in the carbs! We know it's not poorly set exhaust valve clearances, as the compression is good. We know it's not cam timing, as the first run with badly balanced carbs saw 125hp at just over 10K rpm and 70 something ft/lbs of torque at just over 8K rpm. Plus the fuel/air curve is sweet. The slides in the CV carbs seem to be working fine. He did a run after doing all of this, he richened the mixture and the miss went away- temporarily. The next morning he put it back together and the miss had returned, and there's still no vacuum at low revs. He is not a happy boy! He's spent a few hours on this, but won't charge me for them all! (phew!) The guy is a very good mechanic, he has worked in GP, World Superbikes and AMA superbikes, so I think he will eventually figure it out. I'm just hoping there's someone here who has seen this before and can help us out. So, any takers? What the hell is going on? Maybe air is getting in between the carbs and the engine? When the missfire happens the EXUP servo wobbles around. Is it possible that it is closing off too much, pressurising the headers and preventing new air from being sucked into the cylinders? Edited by: <A HREF=http://p072.ezboard.com/bexupbrotherhoo ... =tonup>Ton up</A> at: 7/31/04 12:55 am

mintclint · Post by **mintclint** » Sat Jul 31, 2004 3:39 am

I'm assuming the diaphragms im the carbs are fine? Not quite the same issue, however, I once had a miss down low along with a problem balancing my carbs and found I had a leak in the fuel delivery rail. Solution, replaced all 16(?) o-rings in the rail and no more problems. (NB - I used the orings from an early GPZ750 as they were $2.40each AUD not $16.50<img src=http://www.ezboard.com/images/emoticons/eek.gif ALT=":eek"> ). Might be a long shot and/or totally irrellevant but you never know.......it might help too<img src=http://www.ezboard.com/images/emoticons/wink.gif ALT=";)"> Hi, my names Tim and I'm a postaholic. *clapping* Welcome Tim.

dragracer1951 · Post by **dragracer1951** » Sat Jul 31, 2004 9:37 am

I'm thinking that if there is no vacuume at idle then the thing with the orings may be one direction to go.....diaphrams may be another...or the little oring at the vacuume tap at the OD of the diaphram....or th eplastic insert may be VERY worn.... Vacuume is a function of gas velocity (sp?) and there are TWO things to trip the air speed in a diaphram carb....slide and butterfly....butterfly should drive slide ....So, If both of those components are OK, Look for leaks Jim

Post by **jjs777** » Sat Jul 31, 2004 6:02 pm

Long shot but easy to test. Are the spark plug wires old? Either way...startup the bike when all is dark and disconnect the headlights. Now inspect the spark plug wires to ensure no arcing is going on anywhere. It'd be easy to tell since all else is dark and the arcing would be easily visible. I found this to be the problem once before with odd running behavior. -John

Ton up · Post by **Ton up** » Sun Aug 01, 2004 2:00 am

Cool, this has given me a few things to suggest in the morning. The o-ring thing is especially good, as when all this first started I had just completed a big ride. I filled up with fuel, and the next morning the misfire started. I had accidentaly filled up with 96 unleaded instead of 91. When 96 was first released here it caused heaps of trouble with bikes- it used to wreck the seals, o-rings etc. I seem to remember that Kawasaki's were the worst affected, and if Kwaka orings are interchangeable....... Not sure if the 96 still causes this problem, but then pretty much no biker uses it now as it also burns very dirty- our fuel is crap! Thanks heaps guy's, this is brilliant! I will report back. Edited by: <A HREF=http://p072.ezboard.com/bexupbrotherhoo ... =tonup>Ton up</A> at: 8/1/04 12:02 am

Ton up · Post by **Ton up** » Sun Aug 01, 2004 3:36 pm

Just rang the shop to suggest the ideas you guy's put foward. Apparently it's fixed! For some reason the slides were opening too much, reducing the velocity of the incoming air and therefore reducing the vacuum and fuel flow. He found that putting his finger over one of the holes in the slides cured the problem. So now each slide has one hole blocked off, and it works fine, apparently. I have yet to ride it and see for myself. It seems a bit dodgy, but I guess if it works, and keeps working, then who cares, right? Hmmmm...

Post by **jjs777** » Sun Aug 01, 2004 3:51 pm

I bet the problem reoccurs - not too be pestimistic but...please keep us updated but good luck nonetheless -John

Ton up · Post by **Ton up** » Sun Aug 01, 2004 3:55 pm

You and me both John. It seems to me that the thing should work as designed. If it doesn't, then something must be wrong inside the carbs. I'm picking it up at lunch time, so we'll see. I'll report back in about three hours.

Post by **jjs777** » Sun Aug 01, 2004 6:33 pm

My 0-3000 rpm issue on my original fzr with the now 1040 motor is oddly similar. It was a problem that used to occur but it seemed as though it only occurred when it was ?damp? and/or rainy / washing the bike. It would stumble and almost backfire but then it would go away as suddenly as it occurred - when revved past lets say 4k rpms it would be fine. Since I had always attributed it to wetness I never researched it. But now it's doing it 100% on my bike. You may recall this is my bike without the exup - but this issue IS NOT the stumble - which I am very familiar with. -John

Ton up · Post by **Ton up** » Sun Aug 01, 2004 7:05 pm

OK, I picked it up. It certainly seems to have worked, but then I noticed a bit of a stumble as I pulled up the drive into work.<img src=http://www.ezboard.com/images/emoticons/mad.gif ALT=">:"> Will see what it's like on the way home. It's cold with high humidty here today. Maybe the electrical connections are part of the problem? Your bike has no EXUP valve, so it can't be that.

Ton up · Post by **Ton up** » Mon Aug 02, 2004 3:08 am

Misfired a few times on the way home. Again, cold with high humidity. The area where I live is generally warmer than the rest of Christchurch, when I was riding up my street I tried dropping the revs to 1500 and then rolling on smoothly and quickly- no misfire. Hopefully it's just running lean in the cold air. Hopefully! In general it's much better, smoother with more punch in the midrange, so all the things he did trying to locate the problem have improved the way it runs. I'm just frustrated to have spent all of my 'play' money without a clear result...

flyingcircus68 · Post by **flyingcircus68** » Tue Aug 03, 2004 6:00 am

it sounds to me like it might be an ignition problem. check you wiring for corrosion on the low voltage side to the igniter box. You should know that the coils are being supplied voltage from the battery all the time and the ground is switched on/off by the igniter. Check coil resistance on the low and high tension side to make sure that it's in spec. check the resistance of the caps to make sure they are still good. check your caps and high tension wires for any cracks or splits. leave the lower fairings off and park it somewhere dark, unplug the head lights and parking lights to keep it dark. Start the bike and look for arcing. Give it quick blip of throttle to load the motor and check for arcing. Check your plugs to see their condition. Is there carbon on the porcelain? Does it appear to cover up near the tip, or down at the root of the plug? Carbon deposits definitely will cause a misfire, especially under load when a higher voltage is required. What's your system voltage when the bike is running? Low voltage, corrosion, or a weak battery can cause ignition problems. Check the following voltage readings when running at around 2k: battery main fuse ignition fuse 12v supply at coils You should have 13 - 14 volts at the battery. The rest of the readings show you the voltage drop as the circuit fans out. If it appears that the voltage at the coils drops more than 2v under the battery voltage, try running a fused jumper wire from the battery to the coils to see if it solves the problem. The above might point out that you have a corroded ignition switch or corrosion elsewhere in the harness. A good way to check if the ignition is weak is to put new plugs in and set the gap smaller than the stock. This will require a lower voltage to to spark for a given condition and will usually eliminate a problem, at least temporarily.

Ton up · Post by **Ton up** » Tue Aug 03, 2004 2:01 pm

Thanks. Thats given me plenty to go on with. I'll report back when I get the time to try it all- I'm pretty sure the mechanic did most of it. He spent a lot of hours on it. But I'll try it myself anyway. John, have you ever tried swapping the battery from one of your FZR's that runs well to the one that doesn't? Waht about swapping the ECU? Edited by: <A HREF=http://p072.ezboard.com/bexupbrotherhoo ... =tonup>Ton up</A> at: 8/5/04 12:44 pm

Post by **jjs777** » Thu Sep 16, 2004 8:49 pm

I wrote earlier My 0-3000 rpm issue on my original fzr with the now 1040 motor is oddly similar. It was a problem that used to occur but it seemed as though it only occurred when it was ?damp? and/or rainy / washing the bike. It would stumble and almost backfire but then it would go away as suddenly as it occurred - when revved past lets say 4k rpms it would be fine. Since I had always attributed it to wetness I never researched it. But now it's doing it 100% on my bike. You may recall this is my bike without the exup - but this issue IS NOT the stumble - which I am very familiar with. tonup wrote John, have you ever tried swapping the battery from one of your FZR's that runs well to the one that doesn't? Waht about swapping the ECU? I did swap out the ignitor cdi black box with a known good V&H powerpak unit...and no noticable difference on the 1040 bike - never swapped batteries at all. I did respond back to you on my issue somewhere else I guess. Tonup...this probably won't help you...I kept riding my bike w/the newly installed 1040 and all the issues worked themselves out - after I changed gas and verified plugs etc. So I can only assume the bad running was caused soley by the carbs and/or bad gas since nothing else was changed. Been driving it since no serious issues to speak of. ANd I have since taken the bike...in poor tune...the one with the 1040 and ran at the dragstrip and ended up running almost the exact same mph numbers as my mostly stock bikes. So my next thing due to be arrive next week is a factory 10 jet kit. It will be installed on my 95 fzr carbs...and I will use those carbs to swap back and forth and run at the track to see if there is any improvement in the 1040 bike w/the carbs and jet kit installed. If it runs mildly better mph wise...then I will go ahead and attempt the factory 30 jet kit and fiddle with the airbox on the 1040 bike. -John 95 FZR1000 90 FZR1000Edited by: <A HREF=http://p072.ezboard.com/bexupbrotherhoo ... >jjs777</A> <IMG HEIGHT=10 WIDTH=10 SRC="http://home.comcast.net/~john.stempien/ ... larger.gif" BORDER=0> at: 9/16/04 6:52 pm

flyingcircus68 · Post by **flyingcircus68** » Fri Sep 17, 2004 6:05 am

JJS, If you're having a problem with poor running when the bike is damp, I would check the plug caps, and the resistance on the high tension side. Also, make sure that you are running the non-resistive plugs. Use silicone grease on the wire junctions and the caps to keep moisture from creeping in. I would also suspect a weak spark and check voltage supply and ground as I mentioned earlier. As far as hp is concerned, You need to look at a dyno curve for a stock bike. The stock curves reach peak hp and start to drop off toward redline. This tells you that the limitation is volumetric efficiency, so adding displacement will shift the peak hp to a lower rpm and make it more torquey. You need to help it breath to maximize benefits on the added displacement.

Post by **jjs777** » Fri Sep 17, 2004 5:49 pm

I don't want to go off topic too much...but has anyone EVER just removed the top snorkel of the airbox to see if any gains could be had with a 1040 or 1070? I have search myself on the airbox mods and I believe I understand why Yamaha used a smaller snorkel...to increase velocity...but given the increased volume of the cylinders from my 1040 I wonder...well at least I am defintiely gonna head up to the drags and compare. I may even drill some holes as I saw mentioned...but no one ever quantified their results with drag strip numbers. I can say...that my 1040 did almost 102mph in the 1/8th mile (660 feet) so that was on par with my other bikes...then she felt like it was flat in the upper rpm's - possibly having depleted the airbox volume. I think it was you circus that has the best handle...at least in putting it down in writing as to this rocket science. I'll look fwd to reading any follows to this post. -John 95 FZR1000 90 FZR1000

cvhjkdis · Post by **cvhjkdis** » Fri Sep 17, 2004 7:46 pm

First to stay on topic - For the idle-missfire I have one and only one suggestion - ( this has been covered masterfully so far ) - Check the connectors that go to the low voltage side of the ignition coils under the airbox. I had problems with mine when finishing up the 1070 project. They had started to corrode, for various different reasons, one of which being the heated enviroment they live in. I like the idea of running the bike at night to spot arcing, but if the connectors have high resistance from corrosion, they may not show any arcing. They can however reduce the coils saturation efficiency by allowing lower voltage to the primary windings when it's most needed. If this is reducing the secondary KV at peak demand, which will be with lean mixtures, it could cause a missfire. The low vaccum ( this is a stretch ) might be resulting from inefficient combustion just before missfire, as a result of the somewhat weaker spark. A leaner mixture is just less conductive, and even a good 25 KV system ( which I believe the FZR is ) is going to be taxed to perform at lean mixtures. (Those connectors will also be affected by moisture). A quick side note is to consider the 50+KV GM HEI systems, They started using these when mandatory emissions laws forced them to lean out mixtures at all ranges. I wonder if blocking one of the slide ports in Tony's bike was covering the symptom by keeping the mixture within ignition systems working range, voltage-wise. If the problem can't be traced to anything else, I would say take another at the coils and primary wiring. Whew, ok, I'll shut up on that. Onto the air box now, <blockquote>Quote:<hr>I don't want to go off topic too much...but has anyone EVER just removed the top snorkel of the airbox to see if any gains could be had with a 1040 or 1070? <hr></blockquote> Yes I'm running mine without the snorkle, Just the air filter set in place, and a couple strips of duct tape front and back, No ill affects are discernable. Light stumble at low rev's, but it 'aint down there often. I do hope this helps! I'll get off the soap box now, good luck, Bob.<img src=http://img.photobucket.com/albums/v209/ ... oapbox.gif ALT=":soap"> I approved this messageEdited by: <A HREF=http://p072.ezboard.com/bexupbrotherhoo ... FZRDude</A> <IMG HEIGHT=10 WIDTH=10 SRC="http://img.photobucket.com/albums/v209/ ... snoopy.gif" BORDER=0> at: 9/17/04 7:11 pm

flyingcircus68 · Post by **flyingcircus68** » Fri Sep 17, 2004 9:40 pm

I think I might have mentioned this before, so forgive me if it's familiar. We all like music and are familiar with sound equipment, so I'll use that as an analogy. There are different speakers on the market and I would like to cover two specific types since the way they function is very intuitive and similar to an air box. You've all seen the speaker box that has a woofer and a false speaker that vibrates to augment the bass output. That false woofer is being excited to vibrate at its natural frequency by the vibrations within the speaker box, kind of like a wine glass chimes when you rub your finger around the rim. This false woofer can be thought of as a weight attached to a spring. If you pulled on the weight, it would bob up and down at its natural frequency, whatever that might be. If you exchanged the weight for a heavier one, it would bob up and down at a lower frequency. If you use less weight the opposite happens. If you use a stiffer spring with the same weight, it will bob faster and if you use a weaker spring, it will bob slower. I know these details can get boring, but they are fundamental and need to be understood to visualize the abstract concepts to follow. The second type of speaker box I would like to cover is called a 'bass reflex' or 'ported'. This type of speaker uses the port to augment the bass output. It looks very different from the speaker system described earlier, but it functions very similar. The air in the port acts like the weight that bobs back and forth and the air within the speaker box acts like the spring. the smaller the box is, the stiffer it is as a spring. The air in the port is the mass, so the longer the port is, the greater it's mass, and the slower it vibrates. That part is easy to understand, but the diameter of the port has a surprising affect on the vibrating air mass: the smaller the port, the heavier the equivalent mass. Why is that the case? It has to do with velocity. Fast moving air tends to recruit air around it to move also. You could test this very easily by slowly covering the port on a speaker and listening to the result. So lets list these explanations as rules of thumb: 1. the smaller the box, the stiffer the spring 2. the longer the air duct, the greater the mass of air it moves 3. the smaller the diameter of the air duct, the greater the mass it moves. 4. stiff spring/light mass vibrates at a high frequency 5. light spring/heavy mass vibrates at a low frequency The air box functions in the same manner as the 'bass reflex' speaker mentioned. The snorkel augments the vibrations induced by the engines intake pulses. When the speed of the engine is such that the intake pulses match the natural frequency of the air box, it creates positive pressure pulses during the intake cycle and helps pack the cylinders. If you shortened your snorkel, you would tune that supercharge effect to a higher rpm. Increasing the cross sectional area would have the same tuning affect, but would also make the snorkel less restrictive to air flow. If you remove the snorkel from the air box you are effectively shortening the air duct and increasing its cross sectional area. This tunes its natural frequency to a much higher rpm, and also, reduces it restriction at peak air demand. The effect is twofold: you get a hole in the rpm range where it used to be tuned (~3k rpm) and you end up really lean on top. You will also be running rich at 3k because it was jetted fatter to accommodate the higher than ambient pressure from the pulses. No doubt, you would get more peak hp by removing the snorkel and jetting for it. Its up to you if you want a hole at the bottom. I wouldn't go swiss cheesing the snorkel, you're not likely to get much beyond ugly looks<img src=http://www.ezboard.com/images/emoticons/nerd.gif ALT="8o">

flyingcircus68 · Post by **flyingcircus68** » Fri Sep 17, 2004 9:50 pm

I would just like to comment on CVH...'s explanation on sparks: the explanation is accurate and masterfully crafted<img src=http://img.photobucket.com/albums/v209/ ... ock_On.gif ALT=":rock">

cvhjkdis · Post by **cvhjkdis** » Fri Sep 17, 2004 10:36 pm

Thanks Paul, I hope something there will help with the bike quandary. I went back and re-read you'r post, and I believe we were getting at the same thing. I just didn't see at first. Ok, dead horse that. The air box harmonics are something Iv'e been working on with or around for some time now. I'm NOT an engineer, and will be up-front about that. I do however read up on the how and why of things as much as I can. So the speaker analogy was perfect. I did put a four into one Yosh system on the bike a few years ago, and in one way or another have been trying to jet/tune/work around it's shortfalls ever since. The jury's still out on weather or not Iv'e been successful. I did read a book by Kevin Cameron of moto mag fame from a few years back, and he covered the tuned air box phenomenon better than I had ever seen before. Since then, Iv'e also talked with people who vehemently disagree with him. I will say this, after jetting my carbs into a state of complete un-ride-ability, I read his book. He covered everything I had just done to the letter. Then explained why I was wrong. Using this information, I went back through what I had done making the suggested changes. So far it's been good info. Interesting read if you come across a copy. ( This thread has now been officially hi-jacked)<img src=http://www.ezboard.com/images/emoticons/wink.gif ALT=";)"> I approved this message

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idle to 3000rpm missfire

idle to 3000rpm missfire

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