Need help installing booster plug on my 2015 RC390

jm20

New Member
390 apart1.JPG

390 crack1.JPG

390 crack2.JPG

The surging on my RC390 seemed to be getting worse so I decided to try a booster plug. It arrived with instructions that were vague (as far as I am concerned, I am very familiar with jet skis but don't have a lot of experience working on motorcycles).

#1 on the install instruction sheet says "Locate the air intake temperature sensor in the airbox and unplug the cable connector."

That is as far as I got, pretty sad I know. I took off a few parts and opened the box that contains the air filter and there was no connector to be found. I tried tracing the wires in this region and looking for a connection that would fit the booster plug and found nothing.

I was hoping someone might be able to point me in the right direction. On some bikes the plug is not in the airbox (which seems to be the case here). I think it might be a connector in front of the air box on the right side of the bike and I'll attach a picture with a circle around this spot390 plug.JPG, or maybe it's under the gas tank?


When I was doing this I noticed that a plastic component appears to have a crack and it seems to be connected to the carburetor possibly. I'll attach a picture of that as well. I could epoxy it back together but I think that might be foolish and that I should probably take it into the shop and let them fix it with an OEM replacement part.

Thanks in advance for anyone who takes the time to read this and respond. I truly appreciate it.

BTW, I did a google search for the questions above and tried to figure this out on my own but there does not seem to be much out there regarding the installation of the booster plug on a 2015 RC390.

Thanks again!
 

Tom

New Member
Are you able to return the snake oil thinggy you bought? I would do that as quickly as possible.

Also, one of your pictures has what appears to be a bunch of fine particulate black plastic on your frame, and a cut in the air box (from what Im assuming to be a rotory tool). I would undo this as quickly as possible too.

These bikes run very lean from the factory. You have a pre '17 bike so you will be able to have what is known as the "Akra" ECU flash. This reflash was a factory upgrade that came with the Akrapovic full exhaust power part. I'm not aware of dealerships still offering this, but a fellow named Chad may be able to help you. He is one of the site's premiere gurus.

His site vendor forum is KTM Performance:
https://www.rc390-forum.com/forum/forum50/

His site username is cjwell:
https://www.rc390-forum.com/forum/members/cjwell/

And this is the site sponsored website:
Welcome to KTM Performance

The quickest way I have always gotten in touch with him is via the "Contact Us" page on their website. Just tell them you need to get an Akra reflash on your bike, and you should be good to go. Once you are ready to start really making power than I would advise you to get their Power Commander, as you will have access to Chad's maps. You can find a Power Commander for about $50 less elsewhere, but you will not have a map for it, and would need to spend much more than $50 for a custom tune.
 

jm20

New Member
Thank you for taking the time to reply and for the information. I got a laugh out of the snake oil reference. Not sure if I can return the booster plug or not. Might be easier to list it on ebay. I guess the lack of posts on this forum regarding the boosterplug speaks volumes. I read some positive reviews on the internet and figured it might be a quick easy and relatively inexpensive fix. I'll look into the Akra flash.

Also thanks for the information about the cut in the airbox (if that is still part of the airbox down there). Now that you mention it, that does look like the melting cut of a rotary tool. Not sure what the previous owner was up to but none of that was disclosed.

Again thanks for the information and your time.
 

DysfunktionAl

New Member
I had a BoosterPlug installed on my 2017 RC since new, when I replaced the exhaust with a decat Leo Vince system. No issues, no engine/warning lights or resets needed. On updated RC 390 models from 2017 and newer, you can access the AIT sensor on the left hand side of the bike, just below the tank. On Dukes I think it’s the right. For a 2015 I don’t know, but you can contact the seller/developer directly through his eBay site, just look up your BoosterPlug model year and hit “contact seller” with your question for your model/year bike. He will respond.
There is no “snake oil” here (lets be open to new ideas). I had my doubts so had an engineer and a mathematician check out his theory - they said both theory and numbers were sound and the idea ingeniously simple (tho the math is complex). He first developed this product for BMW bikes. For an inexpensive simple means of increasing your fuel/air mixture above stock it seemed to work for me. No issues. My 2 cents...
 
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Tom

New Member
If it can control the closed loop on our bikes, as well as bypass the ECU's o2 sensor input then great. Maybe our forum vendors should look into these. However, you'll have to excuse my skepticism that it actually does either of these things, at least not until the ECU figures out what's going on and compensates.
 

DysfunktionAl

New Member
I certainly make no claims of understanding any of the engineering, but you can check out the developers basic explanation and concept development here https://www.boosterplug.com/shop/cms-24.html (and no, I don’t work for or know any of them :)
It just adds another option to some great products that are already out there for us. And speaking of... I’m soon going to install and check out RapidBike for comparison.
 

ReidMcT

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For certain this device manipulates ONLY the intake air temperature reading that goess to the ECU. Whether - and to what extent - that has an effect once the engine enters closed-loop operations (essentially once it's warmed up), I do not know. I do know that the oxygen sensor is a major player in closed-loop operations; and it would surely read differently if the mixture were made richer by the Booster Plug. In any case, assuming it does what it claims, it is enrichening the mixture by some arbitrary amount that may or may not be a net improvement in the buyer's particular circumstances.

It strikes me as a product that costs half as much as a Power Commander, but delivers much less than half as much value.
 

DysfunktionAl

New Member
All true... it is a simple device that only manipulates the intake air temperature, and when a lower air temperature is read by the stock ecu, the stock unit is already programmed to increase the fuel mixture by as much as 6% (I asked the KTM mechanic). And I agree the unit doesn’t cover anything close to all the parameters that a PCV can provide, but simple is the idea - no maps, no downloads, no re-flash, no dyno. The reason I purchased it was economic, as I was waiting on the not yet available RapidBike Exclusive, but needed something immediate with the removal of the stock cat/exhaust. As you say, it was half the price and value, but IÂ’ve had no issues, no warning lights, no engine overheating. Now I’ll see what RabidBike brings to the performance table... should be in next week.
 
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