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Discussion Starter · #1 ·
Hi all, I have a 2005 R6 5sl that just doesn't sound smooth in the low rpm's.

It initially had a rough idle and would sometimes die on me at the lights. I had the blown rectifier plug which I have now replaced with beefier cables which has stopped the bike dying, and have changed the spark plugs and ignition coils with new ones which have solved the rough idle, I just have this choppy exhaust note that smoothens out and disappears at above around 5k rpm's.

Here's a video, you can hear it towards the end.

05 Yamaha R6 choppy exhaust note

Any ideas what could be causing it?

I have tried cleaning the TPS and putting in seafoam / redex / premium fuel but it has not fixed it.

It happens only when opening the throttle ever so slightly when cruising at low rpm's
 

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Hi all, I have a 2005 R6 5sl that just doesn't sound smooth in the low rpm's.

It initially had a rough idle and would sometimes die on me at the lights. I had the blown rectifier plug which I have now replaced with beefier cables which has stopped the bike dying, and have changed the spark plugs and ignition coils with new ones which have solved the rough idle, I just have this choppy exhaust note that smoothens out and disappears at above around 5k rpm's.

Here's a video, you can hear it towards the end.

05 Yamaha R6 choppy exhaust note

Any ideas what could be causing it?

I have tried cleaning the TPS and putting in seafoam / redex / premium fuel but it has not fixed it.

It happens only when opening the throttle ever so slightly when cruising at low rpm's
Hi this sound like a carburetor problem. Air and fuel is not mixing right. Carbs & jets must be the cause of the issue. I had the same problem with my 99 R6. It’s a big job taking carbs out cleaning and rebuilding completely but it’s worth the outcome. Best of luck!
 

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Discussion Starter · #5 ·
Hi all,

yes this bike is fuel injected so no carbs, but could it be the fuel injectors?

I went into diagnostics mode, went to the right number, hit the kill switch off and on and listened for the 5 solenoid clicks from each injector for each cylinder and they sounded fine, no delays in the clicking or missing clicks.

I have not got around to doing compression or throttle body sync, but as I said the bike runs really smooth over 5K, its just under that it has this strange jittery noise.

This bike has a Lextek exhaust (with the baffle still in) and K&N filter on it, not sure if that would contribute to the problem. When I pulled the old spark plugs out I expected them to look white with those mods as I had thought the bike would be running lean, but the plugs actually looked more towards a black fouled condition.

There is no power commander on this bike and I doubt the ECU has been tuned but not sure how I would ever know that.

I have been riding it like this for the past two months and the issue is still there..
 

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Sounds odd, but I was fouling plugs because I was too lean. I'd stick a fresh set in there and it would have those fouled within a tank's worth of fuel. Couldn't figure it out. Mechanically did nearly everything. Valve lash didn't need adjustment, despite having never been done with over 40k on it. Vacuuum readings were spot on. My Brother built and tuned his own racing car looked at the plugs and knew. HOW TO: Hidden Air Fuel Ratio Adjustment Enriched the mixture and the results were instant. Didn't make sense to me cause I was look'n at the same plugs and thought they were rich. Didn't occur to me that they were fouling due to lean. There were other symptoms such as cold hard-starts. (warm starts were fine) The colder it was the crappier it ran on cold start. If you tried to give it throttle on a hard cold start that would actually kill it. Had no power until it got up around 150F. I eventually added an AFR gauge (in my sig) to help with tweak/tuning. The Winter / Summer fuel blends require different settings and didn't want to keep running back to a tuner when I could do this on my own.
 

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Discussion Starter · #7 ·
I looked into that post and what I got from it was that for stock street bikes the C numbers are for each cylinder and are used to adjust the fuel air mix at idle only, for people that had bought a track ECU it adjusts the fuel air mix mimicking how you would on a bike with carbs ( what throttle position you are in). If this is the case I don't think this will help but will play around with it and see what happens.
 

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Standard bikes without the race package allow you to adjust fuel-enrichment only. Timing and other parameters are not available. Guess I need to clean that up. (I'll get around to it.)
 

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Discussion Starter · #9 ·
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Ok so I played around with the Co numbers, mine originally were C1: 1, C2:-2, C3: -3, C4: 1, I changed them all to zero, no change to the sputtering noise, I then set them all to 3, still no change to the sputtering noise. I put them all back to default numbers. I also throttled the bike at a standstill to 4000rpm and can here the sputtering noise. While riding it also happens in any gear. Here are some pics of my old plugs before I replaced them for new ones (and before messing with the Co values), I initially thought these were rich looking but let me know what you guys think.
 

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Adjust your idle using this procedure: R6 2005 - Idle RPM increases as engine heats up It seems that an idle that's too high for the given engine temp may seem "choppy"; I suspect because the ECU is trying to idle down but the air (which 2nd-Gen ECU has no direct control over) isn't where it needs it to be. 3rd-Gen bike ECUs have control over air.

Keep in mind that fouled plugs will keep you from making the necessary adjustments. You may have to run hotter plugs until the appropriate settings can be pinned down. Though the bike comes with CR10EK, the manual says you can use CR9EK. (boost octane if you go hotter than spec)

Be sure to verify vacuum via throttle-body sync procedure or you could be hunting down "choppy idle" forever.

Re fuel-enrichment adjustments:
Changes seem to represent small increments. Think of it as the electronic version of jetting. After much experimentation I began making changes in increments of 10~20. Then smaller changes once the results were close. EDIT: Be conservative when adjusting toward lean. You can be aggressive when adjusting toward rich.
 

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Discussion Starter · #11 ·
Ok so it has been awhile but thought I would update on this as I still have the choppy throttle issue. As my idle was fine, playing with the C numbers didn't fix my choppy exhaust problem. I put in a stock air filter and stock exhaust, and decided to see if I needed to do the valve clearances, cracked the bike open, here is what I found: the new plugs I had put in all looked good:
Finger Nickel Household hardware Gas Auto part


Here are the valve clearances, I measured three times for each valve, each time was after turning the crank rather than measuring 3 times at the same time. I did this as it's hard to guage how tight the feeler guage needs to be. For the larger readings it was tight but the feeler guage went through and the next size up would not go in at all. For some of the lower readings you could feel the drag on the feeler but it wasn't tight.
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Long story short some are right on the limit but still all in spec. So I decided not to do an adjustment.

Here is another video of the issue, towards the end you can hear it clearly from the stock exhaust.


Recently I have also noticed that the bike does not do this when it is cold or warming up but more so when it has fully warmed up like in the video. I have also noticed a very slight rattle or ticking at around the hottest temps (~100C) that come and go with an rpm change that I don't hear when it's cold. The bike however runs fine at these temps, does not die or anything, but stays hot fluctuating from 88 - 101C. I changed the oil (10w40) and coolant both with yamalube stuff and still have this exhaust note.
 

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Wow does a video help. Sounds great. THought it was an idle problem. 35 second mark - nothing to worry about. Load the engine and you won't get that. Perfectly normal. Ride safe and enjoy. Fully stock it'll power wheelie at high RPM in first gear and depending on body weight, winds, elevation, top-out between the high 140s and low 150s per GPS on track. Stock speedometer will read 8% fast so it'll look like it's at/near the claimed top speed.

THey're going to be "some timey" about the idle and finnicky about fuel. Even when it's perfect for awhile, it won't stay that way. There will be periods where it sounds like a wet dream and stretches where it sounds like a tortured lion. Avoid over-analyzing it. Idle needle will "wonder" a little; more rarely will it stay perfectly stable.
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Discussion Starter · #13 ·
Ok thanks for the update Intuit, I was concerned that this was not normal as I never had this issue with an sv650s I own, however that is a Vtwin that can cruise smoothly below 4k rpm and keep relatively steady temps under 100c at low speeds where as this inline 4 feels like it's a lot happier above 4k rpm's and at high speeds to keep her nice and cool
 

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The ones on the lower limit are probably your issue. Particularly since it is doing this when hot. Valve clearances “wear” tight, not loose. The “wear” mechanism is the valve beating itself into the valve seat, not friction between the cam and valve stem bucket. As the bike gets hot, the valve stem grows and takes up the clearance. If the clearance is too small, it will go to 0 and hold the valve open just slightly giving you the choppy idle you are experiencing. It will only get worse.

I always set valve clearances on the loose end of the spec.
 

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Discussion Starter · #15 ·
Wait I'm a little confused now, none of the clearances for the intake or exhaust are on the bottom tolerance, the ones on the limit are for the top tolerances (largest clearance spec), in any case if they are still all within spec would this still happen? The choppy idle was a lot choppier until I changed out the plugs and coils, the idle isn't perfect now but clearly does not fluctuate as much as it used too. My main concern was the 35s mark on the second video I posted, that distinct exhaust note at around 4k rpm. I think the biggest regret I have was not doing a compression test when I had it stripped down, I don't have a garage so the whole job had to be done during an evening on my driveway..
 

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Our confusion was based around the idea of an idle problem. Your video doesn't show one... at all. The choppiness being most pronounced at the 35 second mark, is perfectly normal. Has to do with the way the engine is cammed + the way it manages RPM. There's a specific term for the way it manages but don't recall what it is.
 
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