2019 mt07 rpm fluctuation at idle

[nozeitgeist1800]

i have a tune from 2wdw which has been great, but ive noticed that since i got the tune the rpms fluctuate by anywhere from 1 to 3 bars (i think 200 to 600 rpm) while idling. everything else seems fine - no noticeable power loss while actually riding, but idle has me concerned. anyone have any insights or advice? i was thinking of getting in touch with them but thought id ask here first in case its something dumb on my end that ive missed or done wrong.

akra ti exhaust, pulled snorkel, i think everything else engine-wise is stock. ecu flash was done with ftecu with file emailed from 2wdw. 

any help is appreciated, im not the brightest tool in the race, and im certainly not terribly mechanically inclined, so i dont even know where to start with troubleshooting.

[M. Hausknecht]

I suppose it is possible the tune got corrupted in some fashion but first check the functioning of the IAC (be sure it is plugged in, at least) and I'd also sync the throttle bodies (especially important at idle and low throttle openings).

[nozeitgeist1800]

awesome, ill check those out, they dont seem to be too hard to check. i appreciate the help, nice to have a place to start

[klx678]

If cam timing was ever altered that could cause the fluctuation.  I just spent the weekend at the Columbus Goodguys Street Rod show, and saw that with all the supercharged cars running the blowers with high lift cams with longer overlap.  They'd be constantly going up and down in idle probably a thousand rpm, that "rump-rump-rump" kind of thing, lurching a bit if rolling clutch engaged.  

Probably not the situation with yours, but still a thought if you got it used.  I've not read where anyone is doing anything like that with the 700.  I do know it is one of the tricks to pick up power in a broad part of the mid-range of the Kaw KLX250, narrowing the cam LCA (lobe centerline angle) to give more intake-exhaust overlap.  Did it with mine.  I learned more about LCA reading an article in Hot Rod magazine, then seeing the supporting Motortrend channel video on TV.  It used to be posted on Youtube, but is gone now.  Interesting and informative, after all a four stroke is a four stroke.

[Triple Jim]

46 minutes ago, klx678 said:

...and saw that with all the supercharged cars running the blowers with high lift cams with longer overlap.

I don't think blower surge is nozeitgeist1800's problem.

[M. Hausknecht]

36 minutes ago, klx678 said:

If cam timing was ever altered that could cause the fluctuation.  I just spent the weekend at the Columbus Goodguys Street Rod show, and saw that with all the supercharged cars running the blowers with high lift cams with longer overlap.  They'd be constantly going up and down in idle probably a thousand rpm, that "rump-rump-rump" kind of thing, lurching a bit if rolling clutch engaged.  

Probably not the situation with yours, but still a thought if you got it used.  I've not read where anyone is doing anything like that with the 700.  I do know it is one of the tricks to pick up power in a broad part of the mid-range of the Kaw KLX250, narrowing the cam LCA (lobe centerline angle) to give more intake-exhaust overlap.  Did it with mine.  I learned more about LCA reading an article in Hot Rod magazine, then seeing the supporting Motortrend channel video on TV.  It used to be posted on Youtube, but is gone now.  Interesting and informative, after all a four stroke is a four stroke.

I gave a lot of thought to retiming the stock cams on the CP2 a few years ago when I was waiting (over 6 months) for cams from Web Cams. I decided not to bother because the stock cams have relatively little duration (and lift), so that adding overlap would narrow the powerband without adding much on top or to mid-range. Twenty-thirty years ago, moving from stock 114 degree lob centers to 104-105, as an example, would make a noticeable increase in mid-range and power up top but cam durations were longer in those days when emissions requirements weren't so challenging.    

[nozeitgeist1800]

17 hours ago, klx678 said:

If cam timing was ever altered that could cause the fluctuation.  I just spent the weekend at the Columbus Goodguys Street Rod show, and saw that with all the supercharged cars running the blowers with high lift cams with longer overlap.  They'd be constantly going up and down in idle probably a thousand rpm, that "rump-rump-rump" kind of thing, lurching a bit if rolling clutch engaged.  

Probably not the situation with yours, but still a thought if you got it used.  I've not read where anyone is doing anything like that with the 700.  I do know it is one of the tricks to pick up power in a broad part of the mid-range of the Kaw KLX250, narrowing the cam LCA (lobe centerline angle) to give more intake-exhaust overlap.  Did it with mine.  I learned more about LCA reading an article in Hot Rod magazine, then seeing the supporting Motortrend channel video on TV.  It used to be posted on Youtube, but is gone now.  Interesting and informative, after all a four stroke is a four stroke.

i did buy it used, but it only had 200 miles on it when i bought it, so im doubtful this is my issue. i still havent had a chance to check either of M. Hausknecht's suggestions, but i should be able to get around to it this weekend if all  goes well. i also plan on checking the battery, as ive seen similar posts where that ended up being the culprit. will report on what i find, though, in case anyone else ends up with similar symptoms

[klx678]

23 hours ago, Triple Jim said:

I don't think blower surge is nozeitgeist1800's problem.

It is the cam timing that I am talking about, not blower surge.  Blower surge is caused by cams.  Otherwise all supercharged cars would have it.   

I doubt the cam lobe angle is the issue, but knowing how it is done and the end result at idle was why I mention it.   It will give a lumpy idle, blower or not.  I don't know if it has been done on the 700s before, but knowing we who have the lowly KLX250s have done it. 

23 hours ago, M. Hausknecht said:

I gave a lot of thought to retiming the stock cams on the CP2 a few years ago when I was waiting (over 6 months) for cams from Web Cams. I decided not to bother because the stock cams have relatively little duration (and lift), so that adding overlap would narrow the powerband without adding much on top or to mid-range. Twenty-thirty years ago, moving from stock 114 degree lob centers to 104-105, as an example, would make a noticeable increase in mid-range and power up top but cam durations were longer in those days when emissions requirements weren't so challenging.    

Oddly enough with some minor tuning, changing the overlap gave the 20 hp 250 a boost to around 25 hp.  In that case it was a simple change that cost nothing but time.  Seems changing the intake cam sprocket to be bolted on at the EXH holes and the exhaust cam at the INT holes, then moving them two teeth in the proper direction altered the LCA to give a noticeable boost from around 3000 up to 8600 and those who put the bikes on dynos before and after the change had it showing said boost.  The interesting thing was that the bikes idle high enough and are seldom ridden at truly low rpm that the lumpy idle that might have resulted wasn't noticed.  In fact people were saying, incorrectly, that the change boosted bottom end.  No one rides a 250 at anything close to "bottom end".  

The Engine Masters show and articles were using a naturally aspirated engine, not overly built and what I have mentioned about characteristics was talked about, the difference at idle.  The wide LCA, like is used on production cars, gave a smooth idle due to less overlap, the narrow gave the lumpy idle like the street rod guys like.  They tested using identical ground cams altering only the LCA with 106°, 112°, and 118°.  I would venture to say the rpm they are calling idle and low would be in the 600-800 rpm range, not the higher range of a motorcycle engine.  The KLX idles at 1250 rpm normal, I forget what the 700 idles at.  

One other thing I learned with the KLX was that the redline didn't significantly change, apparently being more dependent on lift and duration.  That was pretty much true with the Engine Masters results too.  Highest horsepower within a hundred or so rpm.  

Edited July 16 by klx678