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Curious if anyone has had any issues with bogging regarding use of VP T4+ fuel.
I’ve been running it exclusively in my 25 KX250 and it started bogging the last 2 times I rode it, particularly when I went to give it a lot of throttle at once. Once as I was landing off a jump going into another jump, scaring the shit outta me.
Anyone have a fix? I mixed it with some 93 gas station fuel and it seems to have helped some, but last time I rode it it still did it like twice.
I have about 19 hours on the bike.
Also, I noticed on the OEM parts diagram for my fuel pump, I only see one seal to replace, and I’ve read some people recommending replacing the fuel pump “seals.”
Assuming your bike is mapped for pump fuel and not oxygenated fuel? If so could be just running lean and as ambient temp increases it's exacerbating the issue.
From here. Run regular pump gas only and see if the issues goes away. (It sounds like when you cut the t4 with pump gas you noticed less of an issue?)
If not, make sure there is no debris in the system. Replace fuel filter, clean injector, continue to use pump gas.
Still having issues, replace fuel pump continue to use pump gas.
When you read about fuel pump seal replacement, usually it's about fuel additives causing seals within the pump assembly to swell and restrict fuel flow (not the gasket seal that mates pump to the tank. )
Sorry I forgot to mention I have a Vortex CDI tuned by Twisted Development. Said I can run race gas and pump gas
Ok. As mentioned above check for debris in system/clean and then move to fuel pump replacement if needed.
There are bad batches of t4+ that damage fuel pump orings and cause issues.
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Is this the first time you've run the +? I ran it for the first time yesterday in my Husky with stock ECU mapped by Twisted and it was fine. Apparently T4 is phased out. Supposedly T4+ produced after October of 25 is good to go. It was cheaper for me this time than T4.
No, I purely ran T4+ since I bought the bike new. Went through 2 cans. This was my 3rd can, and when i started having issues with the random bogging.
Last time i rode I felt like it went away as the day went on and i mixed it with 93 ethanol free.
I have no idea how to clean the injector. And to be honest ill be absolutely livid if i have to replace the fuel pump as they are $450
I thought it was just regular T4 and that T4+ was supposed to be the fix to those issues
Alot of riders have been impacted with race fuel eating fuel pumps. Before buying a new pump outright, Id still recommending making sure debris isn't causing your issue.
There are plenty of how to videos on cleaning injectors.
Basically, you need current to run the injector and spray carb cleaner through the injector
Here's one from RMATV that uses a motion pro tool.
https://youtu.be/5LS9_MQWzd0?si=nSy8e7SdZBlgIQAj
T4 had disintegrating fuel can liners causing issues. T4+ was causing fuel pump problems due to some incompatibility with the seals.
A bad batch of T4+ caused the same issue last fall in my 24 KX450. VP sent me 2 new pails and those have been fine. I replaced my fuel pump anyway for peace of mind, as bogs on the face of a jump are not fun.
I’ve been running T4+ in that bike and my new 26 YZ250F without issues. I did just order 5 pails of RX96 to give a go instead of T4+. Hasn’t arrived yet so I don’t have any feedback.
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