2019 YZ250F Decel Pop

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6/18/2019 3:01 PM

Using TP map, T4 fuel...getting lots of decel pop. Guessing this may be a TPS issue? If so I was thinking about ordering the tool from TPS tool to adjust. Can somebody share more info about this condition and what was done to correct it? If you found it to be TPS related what was the setting used? Thx!

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"A rule is a rule and without rules, there is Chaos"....Cosmo Kramer

6/18/2019 4:38 PM

Its almost always tps related. Could be a header pipe issue too tho - but unlikely on a 2019. .62v is the sweet spot for most bikes.

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6/18/2019 7:32 PM

Using 100% T4 leans my bike out too much. No problems mixing it 50/50

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6/18/2019 8:18 PM
Edited Date/Time: 6/18/2019 8:21 PM

Has it always done it? Is it more noticeable with changing conditions like temperature or altitude shifts? Check the obvious likes headpipe connections and stuff first. Otherwise yeah I would try a different fuel first or adjust the amount as mentioned before to see if it improves before testing TPS and everything. Troubleshoot the easy stuff first. It could be as simple as a loose header bolt or connection and letting cold outside air sneak into the pipe and mixing with the hot exhaust gases and causing a pop pop when the pressure builds in the pipe on deceleration

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6/18/2019 8:29 PM

If the pipe was ever removed for any reason, then it may be the exhaust gasket at the head.
I feel that the new map and T4 may be the issue as it would be too lean. The TPS adjustment may not take care of this.
What if you try using straight 93 pump gas for a ride and see it the pop get better?

Paw Paw

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6/19/2019 4:37 AM

Pipe has never been removed. I'll try changing the fuel this wkd.

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"A rule is a rule and without rules, there is Chaos"....Cosmo Kramer

6/19/2019 6:39 AM

The T4 is likely the culprit then, being that it’s oxygenated and I don’t know anything about the TP map but it prab pulled fuel out to have better snap, so now your a little lean with the combination. Mixing some good pump fuel with it should do the trick.

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6/19/2019 11:46 AM

whole point of oxygenated fuel is to make more power, why cut it 50:50 when you can just increase fuel across the board? dont you have the wifi app on the 19 250f?

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Too many bikes not enough asses

6/19/2019 12:02 PM

GCBC wrote:

whole point of oxygenated fuel is to make more power, why cut it 50:50 when you can just increase fuel across the board? dont you have the wifi app on the 19 250f?

Increasing fuel across the board may help his decel pop issues but will more than likely affect the feel of his map as it will no longer be the TP map. Could lose a little power feel here or there with a richer setting. It’s unknown if he’s running the T4 for “more power” or for a more controlled cleaner burning fuel than roll of the dice pump fuel. You can definitely add some fuel to test if the decel goes away to rule out a TPS issue then play with what you want your map to look like for best performance and ride ability. At this point the OP is trying to figure if it’s fuel related or TPS? Checking the troubleshooting boxes of fuel is much easier first.

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6/19/2019 12:36 PM

The question is, is the TP map hes using made for that gas?

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6/20/2019 5:11 AM
Edited Date/Time: 6/25/2019 4:25 AM

kb228 wrote:

The question is, is the TP map hes using made for that gas?

Im curious about this. I want to run T4 just to have reliable and clean fuel but I’ve heard it can lean the bike out. I am running the TP map.

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6/20/2019 1:33 PM

Okay so I'm riding Southwick Saturday..I have filled up with straight Non-Ethanol 91. I'll report back. FYI..I ran straight T4 in my 18' YZ250F and never had this issue.

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"A rule is a rule and without rules, there is Chaos"....Cosmo Kramer

6/21/2019 2:34 PM

kb228 wrote:

Its almost always tps related. Could be a header pipe issue too tho - but unlikely on a 2019. .62v is the sweet spot for most bikes.

.62...was this tried on this bike? If not has anyone been successful with any other settings?

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"A rule is a rule and without rules, there is Chaos"....Cosmo Kramer

6/21/2019 3:39 PM

Paw Paw 271 wrote:

If the pipe was ever removed for any reason, then it may be the exhaust gasket at the head.
I feel that the new map and T4 may be the issue as it would be too lean. The TPS adjustment may not take care of this.
What if you try using straight 93 pump gas for a ride and see it the pop get better?

Paw Paw

I also have decel pop on my 18 KX250F and know it's a common issue, mapping issue maybe?
Will 98 fuel be better than 95? (Europe).

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6/21/2019 6:13 PM

Paw Paw 271 wrote:

If the pipe was ever removed for any reason, then it may be the exhaust gasket at the head.
I feel that the new map and T4 may be the issue as it would be too lean. The TPS adjustment may not take care of this.
What if you try using straight 93 pump gas for a ride and see it the pop get better?

Paw Paw

Titan777 wrote:

I also have decel pop on my 18 KX250F and know it's a common issue, mapping issue maybe?
Will 98 fuel be better than 95? (Europe).

Make sure the tps voltage is correct before doing mapping changes... starting to sound like a broken record lol

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6/21/2019 6:44 PM

kb228 wrote:

Make sure the tps voltage is correct before doing mapping changes... starting to sound like a broken record lol

0.57 - too low I assume.
Don't have the tools to adjust it. I don't need that Kawi harness thing? (can't find a 5V power supply).

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6/22/2019 1:58 PM

Ok, so back from the track using straight 91 Non Ethanol only with the TP map there was a significant decrease in decel pop..almost completely gone. So apparently using T4 with the TP map was too lean. I still would like to know if anyone has the best TPS setting for this bike. Thks to all...#57

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"A rule is a rule and without rules, there is Chaos"....Cosmo Kramer

6/23/2019 1:09 AM

Vet57 wrote:

Ok, so back from the track using straight 91 Non Ethanol only with the TP map there was a significant decrease in decel pop..almost completely gone. So apparently using T4 with the TP map was too lean. I still would like to know if anyone has the best TPS setting for this bike. Thks to all...#57

Good to know. Maybe add two points to the whole fuel map would be about right?

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6/23/2019 1:11 AM

Vet57 wrote:

Ok, so back from the track using straight 91 Non Ethanol only with the TP map there was a significant decrease in decel pop..almost completely gone. So apparently using T4 with the TP map was too lean. I still would like to know if anyone has the best TPS setting for this bike. Thks to all...#57

Good to know. Maybe adding two points to the whole fuel map would be about right?

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6/23/2019 1:39 PM

kb228 wrote:

The question is, is the TP map hes using made for that gas?

sandtrack315 wrote:

Im curious about this. I want to run T4 just to have reliable and clean fuel but I’ve heard it can lean the bike out. I am running the TP map.

this is not the TP map, you have not changed the r/min values! sry if someone mentioned before

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6/23/2019 6:17 PM

Hrzk75 wrote:

this is not the TP map, you have not changed the r/min values! sry if someone mentioned before

Yup , this is the correct one with proper “position “ settings

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6/23/2019 6:55 PM

I sent Kris Keefer an email, asking if he had a special map for VP T4 fuel. He said he uses his map and richen it up 3% on the top end.

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6/23/2019 7:27 PM

sesker15 wrote:

I sent Kris Keefer an email, asking if he had a special map for VP T4 fuel. He said he uses his map and richen it up 3% on the top end.

I do the same using the tp map/Yamaha Connected Response map.

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6/23/2019 7:57 PM

swtwtwtw wrote:

I do the same using the tp map/Yamaha Connected Response map.

Can you post screen shots of those maps please? Thanks

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6/23/2019 9:21 PM

sesker15 wrote:

I sent Kris Keefer an email, asking if he had a special map for VP T4 fuel. He said he uses his map and richen it up 3% on the top end.

swtwtwtw wrote:

I do the same using the tp map/Yamaha Connected Response map.

sesker15 wrote:

Can you post screen shots of those maps please? Thanks

They are the same map. On Yamaha website it’s called “Connected response “.

As far as richening, I just add 1 to every value on the fuel side only. Leave the ignition alone.

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6/24/2019 5:36 AM

Hrzk75 wrote:

this is not the TP map, you have not changed the r/min values! sry if someone mentioned before

Oh damn thanks for noticing! Hopefully this is correct:


So add 1 to all the fuel sides on this for T4?

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6/24/2019 6:51 AM

sandtrack315 wrote:

Oh damn thanks for noticing! Hopefully this is correct:


So add 1 to all the fuel sides on this for T4?

Yup. It works better for me. Also, not fuel related, I put a 49 rear sprocket on, per a conversation I had with keeferinc at the track (I was going to go up a tooth to a 51) and wow a noticeable positive difference.

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6/24/2019 7:36 AM

swtwtwtw wrote:

They are the same map. On Yamaha website it’s called “Connected response “.

As far as richening, I just add 1 to every value on the fuel side only. Leave the ignition alone.

So they would look like this richening them.

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6/24/2019 7:57 AM

sesker15 wrote:

Can you post screen shots of those maps please? Thanks

swtwtwtw wrote:

They are the same map. On Yamaha website it’s called “Connected response “.

As far as richening, I just add 1 to every value on the fuel side only. Leave the ignition alone.

sesker15 wrote:

So they would look like this richening them.

Change the position for the TP map.

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6/24/2019 8:43 AM

sandtrack315 wrote:

Change the position for the TP map.

Good eye. I fixed it! Here is the TP map with me just richening the fuel side only.

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