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Discussion Starter #1
Hey all, I'm working on attempting to eliminate an off idle stumble that my 14 XC is suffering from. This is not a "blip the throttle" stumble, although you can make it do that too. This happens periodically (no really set pattern) once the engine is hot. I'll pull up to a light and wait for a bit, and when I ease into the throttle to clutch out in first hear, the bike will hesitate and *almost* stall. This happens when the bike is hot, and not very often, but enough to be annoying.

My mods are as follows:

Stock ECU (no stage 1 flash)
Vic performance filter
Witchdoctor baffle muscle mufflers
PCV with AT


Now, just so you all know, it was doing this *before* the PCV and AT. Now that I have the PC, I am looking for a way to tune that issue out. I have played with several different AFR tables (a couple from members here), but for simplicity sake, I'm currently running the bit too rich dynojet AFR tables. This allows me to compare to my friends 13 XC with a PCV and AT. He doesn't seem to have this issue, but he started with a stage one flash *before* he went PCV and AT.

The PCV and AT took care of all of the low RPM and low speed lean surges that the stock ECU suffered from, so I am happy in that regard. Right now I am just trying to learn more about the PCV and AT to see if I can correct that issue. So far what I have done, which seemed to help, was input AFR's into the 0 throttle column from 500 RPM to about 1750 RPM, and I also put AFR's into the 750 RMP row up to about 20% throttle. This seems to have helped, but didn't eliminate it entirely. In checking the trims I don't see much activity in those cells, so I'm not sure if that is the real issue.

What I am trying to figure out is what actually causes the stumble? Is it caused from being too rich at one point and then leaning down too fast when throttle is applied, or is it the other way around?

I'm looking for anyone who has just a PCV or a PCV with AT who is familiar with this issue and was able to solve it.
 

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Discussion Starter #3
^^ Frustrating...ain't it. :)

The thing is, this isn't new, I had the issue pre PCV as well. It just seems to be *more* intermittent now.
 

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Why dont you post your tables and i can take a look at them.
 

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bskouby

where do you live?

If it were me I would write Rylan at the vic shop and ask for a truly good program. Even if he charges for it that stop all the frustration.
Rylan only does thousands of dyno tunes and is very helpful man.

[email protected]
515.339.4313
 

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Mine does the same still and I have a timing wheel at +4.
 

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Discussion Starter #10
I'm in Southern Illinois. I'm a fairly good clip from a tuner, so I wasn't planning on a dyno yet...until I finally solidify all of my mods.

I do not yet have a timing wheel, that is probably the next mod time/money allowing. I might just reach out to Rylan and see what he would say. He is in Iowa, which is about an 8 hour trip for me.

As for the maps, I have played with three different AFR tables. One is the stock dyno jet table that comes with map M19-009-006, one is AFR table is from the other forum and was posted by dtml, and the final was a AFR table given to me by Drew Miller. I don't want to post that on here without his permission.

That being said, with the dtml table and the miller table I started with a zero map and built from there. They both had the off idle stumble. I then went with the dynojet map with the richer AFR's, and I based it off of the 006 map which was closest to my setup. This seems to run pretty good, less stumbling off idle, but still not great.

I attached the dtml ARF table I used to build a map. I only ran this for a very short time, so I don't have a good map to share. I felt that this setup was a bit too lean and I didn't like how the bike ran.

I also attached the most recent AT build of the dynojet map/AFR table I am using. I added the low RPM AFR's to try to calm down the off idle stumble. It helped, just didn't eliminate it.
 

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hmm wonder if the dtmmil and Drew Miller guy could be the same guy? haha. sorry you are having issues with the map. i dont have the stumble, i will look to see if theres something i have different

the chart you posted is a really old one of mine
 

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You could try this.

Wrap some masking tape around the throttle up by the throttle housing. Like this:


Before putting the throttle position marks on it hook up to your PCV to your laptop and use the power commander program's throttle position read out to put the lines on. That way you will know that your marks correspond to the correct cells in the PC-V.

Take the bike out and make it reproduce the stumble a bunch of times and figure out about what rpm and throttle position it occurs at.
Change those cells and the cells immediately around those cells to 12.8 afr and see if you get a further improvement.
 

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Discussion Starter #16
hmm wonder if the dtmmil and Drew Miller guy could be the same guy? haha. sorry you are having issues with the map. i dont have the stumble, i will look to see if theres something i have different

the chart you posted is a really old one of mine
D'oh...I guess I didn't put two and two together. :)

No wonder I didn't like the old map as much as your newer map. Other than the stumble, it seemed to run really well. I'm just trying to understand exactly why it does it. It really got to have something to do with the drop from rich to lean, or the reverse.
 

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Discussion Starter #17
You could try this.

Wrap some masking tape around the throttle up by the throttle housing. Like this:


Before putting the throttle position marks on it hook up to your PCV to your laptop and use the power commander program's throttle position read out to put the lines on. That way you will know that your marks correspond to the correct cells in the PC-V.

Take the bike out and make it reproduce the stumble a bunch of times and figure out about what rpm and throttle position it occurs at.
Change those cells and the cells immediately around those cells to 12.8 afr and see if you get a further improvement.
I know where the stumble occurs at, it is when you roll on from 0% to about 2% - 5%. If I hit it harder off of idle (which I don't always want to do), she won't stumble.

Basically a 12.8 AFR would really richen the mixture up at idle. Right now I have 13.6 with the dyno jet map in and around those cells, and with Drew Miller's AFR, I believe I was at 13.2.

That might be worth a go...I haven't heavily richened the mixture at those RPMs/Throttle Positions.
 

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I'll vouch for Drews maps. My scoot never ran better...............until I had it cammed and tuned by the doctor.......
The adjustable timing wheel should sort you out though
The red line is my bike with Drews map, thrush mod mufflers, a k&n modded filter and adjustable timing wheel at +5 , the blue line is from Kevinx and his magic fingers
ImageUploadedByMO Free1434417681.376774.jpg


Sent from Motorcycle.com Free App
 

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Discussion Starter #19
I'll vouch for Drews maps. My scoot never ran better...............until I had it cammed and tuned by the doctor.......
The adjustable timing wheel should sort you out though
The red line is my bike with Drews map, thrush mod mufflers, a k&n modded filter and adjustable timing wheel at +5 , the blue line is from Kevinx and his magic fingers
View attachment 140649


Sent from Motorcycle.com Free App
No doubt, Drew's maps are good. I like the one he sent to me...just if I could get rid of that pesky stumble. There were several issues that I wanted to fix with the PCV and all have been addressed except for the stumble.
 

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I'll vouch for Drews maps. My scoot never ran better...............until I had it cammed and tuned by the doctor.......
The adjustable timing wheel should sort you out though
The red line is my bike with Drews map, thrush mod mufflers, a k&n modded filter and adjustable timing wheel at +5 , the blue line is from Kevinx and his magic fingers
View attachment 140649


Sent from Motorcycle.com Free App

what i like about your before chart vs the after is look where the red line starts to peak vs the blue line, wish the cams would keep that line there!! im running the same af chart with cams now on my auto tuner, one of these days im going to the local dyno for some pulls to see where its at.
 
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