Common TBI bike issues

27MOTO cannot stress enough the need for a factory service manual. Either downloaded online or a physical paper manual, no other source was written just for your model of bike. It will tell you service procedures, torque specs, special tools and techniques to keep your bike running in top shape. Get one of E-bay or your local dealer, just get one.

We ride and work on the KTM Group TBI 2-strokes daily and are very familiar with the common issues that these bikes experience. Please read and share the information with other riders. And feel free to email us to share any issues you've found and solved. 

The "Burble" off idle: The single biggest issue that is common with the TBI 2-strokes is the hesitation or "Burble" off idle getting into the powerband. From 125's to the Enduro 300 models, it's a common complaint with riders. It's like the engine gets loaded up and needs to be cleaned out like a carb bike with high compression. Well, thru some mapping changes and running thru some basic settings the hesitation can be overcome.

First thing, it's not a 4-stroke!! It's a 2-stroke engine and needs to be opened up and ridden hard! Slowly rolling the throttle on like a 4-stroke makes the hesitation way worse. Yes, in some situations a steady throttle hand keeps constant traction but you're not riding your mom's Old Taraus wagon! If you give the throttle a whack you'll notice the hesitation isn't as present. The transition into the power valve opening is smoother and the engine can breathe and pull right away. The complaints are more present with the 300cc guys that do slow speed technical riding. The guys riding a 125cc bike don't really let the bike run at that low an RPM and don't really complain about it.

 So, what can we do about the hesitation? Let's run thru the basics first to get a solid baseline to start from and get rid of it. First, make sure you TPS is set correctly. This can be done with the Husqvarna Dealer Diagnostic Tool, a TSP ERM tuner or a digital multi meter (DMM). To start, back off both the Red (idle) and Yellow (cold start) throttle body knobs all the way out (counterclockwise). Next connect your chosen tool to the bike. With the DMM, you need to back probe the throttle position sensor wiring connector. Remove the cover on the TPS and loosen the retaining screws. Adjust the sensor to .400V with the throttle closed and both knobs backed out all the way. Secure the screws while watching the readings. Readjust if the reading has come off of .400v. 

After setting the base reading, you'll need to set the idle and cold idle settings. The factory settings for idle is in throttle position degrees, calling for 2.5-3.5. But a better way is thru setting the voltage reading. Most bikes will idle at .53v but the "normal" range we see at 27MOTO is .52-.60V. This is a personal preference to idle speed. Let the bike get some heat in it and double check the reading and your preference. The cold idle is usually set .62-.65V. Again, personal preference is key for where you want the bike.

The TPS value is usually not set correctly on the showroom floor. We've seen as low as .35V and as high as .692V on stock bikes! This is usually the culprit to the hesitation. 

Mapping, meaning fuel, ignition and power valve settings, are responsible for the hesitation as well. KTM has made changes every model year and have gotten better but the aftermarket has come in with a way to suit the delivery to your style. The TSP ERM is your best options for tailoring your bike to you. We have found that opening the PV earlier and adding ignition timing at low throttle inputs helps to iron out the hesitation at low throttle inputs with technical riding. Conversely, by delaying the PV down low, pulling fuel down low and retarding the ignition helps with a more aggressive "hit" out of a corner in MX applications.

 CCPS Issues: The factory Crank Case Pressure Sensor isn't sealed. Water, dirt and vibration can cause them to leak or break, giving the ECM false readings. This is the culprit for weird bogging and not wanting to rev in the TBI engines. Also, the small hose and holder connecting the sensor to the cylinder head can split and cause an air leak. 27MOTO seals the sensor with silicone before installing it. This will stop the false readings to the ECM and make the bike more consistent. PinIt Racing makes an aluminum CCPS holder that is a quality piece. This solves the split hose/holder problem as well. 

Chain Slack: The manual calls for 55-58mm of chain slack. The airbox on some bikes calls for 58-62mm. Both are too tight. Back in the day, "two fingers" of slack was good but the new chassis and geometry calls for 65-70mm of chain slack so it doesn't bind thru suspension travel. Too tight will also eat the chain guide pretty fast. The best way to check for your bike is to remove the shock and cycle the swingarm thru it's travel. Watch the chain for being taught and adjust the slack accordingly. You'll find that your bike will like 65-70mm. 

23'-24' Husqvarna Shock Cover: A bad design decision was made for shock access. It's handy to get to the adjusters but the small panel on the right side falls off too easily. Some dealers actually stopped putting them on new bikes! The secret is making sure the grommets and seated properly. We even put a dab of grease on them so they don't hang up when removing the panel. The best solution? 2025 and up plastics fit the 23'-24' models and get rid of the small panel for good.

Fouling Spark Plugs: Spark plugs are a maintenance item, just like a fuel filter and gear oil. We recommend replacing the plug every 10 hours to keep the bike crisp. But guys foul plugs because they're not warming up the bike properly. Dead cold start and then whacking the throttle a few times doesn't cut it with the TBI engines. The ECM has to learn the conditions of the day and will run better with a little more warm up time. Our warm up procedure: Set the cold start knob in, fire the bike and don't touch the throttle. Let the bike run at high idle with no throttle input until 100* on the digital fan display or you can feel heat in the pipe after the expansion chamber. You can also feel the end of the silencer for heat as well. Blip the throttle a couple times to turn off the high idle and ride moderately for the first few minutes. Then have fun. 

Air Leaks from the Crank Seals: Some bikes, mostly 23' models, came with "suspect" crank seals. This will cause an air leak and cause different issues with riding/idling. Replace them with the newest updated part number KTM offers. 

Running Out Of Fuel: With the new fuel pump pickup location in the tank on the 2.25 gallon tanks, the bike will run out of fuel with fuel still visible in the lower left of the tank. It's a design flaw between the tank and the pickup. There is a new fuel pickup on the market that is solving the issue. 27MOTO has not tested it yet but will soon. Our solution? First, don't run the bike that low! Second, if you raise the front of the bike, fuel will find its way out of the corner and into the fuel pickup area. Pull a wheelie, climb a steep hill or actually lift the front wheel off the ground high enough. You can add a bigger tank for range if you need more fuel capacity as well. 

Blink Codes: A lot of riders and customers also ask about the factory trouble or "Blink" codes that flash in the hour meter when there's an issue. We've listed the codes below i order to help you guys out. The Factory Service Tool or a TSP ERM is almost mandatory in this situation because many codes, 50 for example, have one flash code for 9 separate conditions within the Exhaust Control Actuator. The TSP ERM is a great tuner/tool and is worth the expense to tune your motorcycle.

Solid Light:  MIL light lights up                                  

                   Tilt sensor-input signal too low

                   Tilt sensor- input signal too high  

02: MIL light 2 short flashes 2

                   Crankshaft speed sensor-synchronization faulty

                   Crankcase speed sensor- signal implausible  

06: MIL light 6 short flashes

                    Throttle valve position sensor circuit A- input signal too low.

                    Throttle valve position sensor circuit A- input signal too high

09: MIL light 9 short flashes

                    Crankcase pressure sensor- short circuit to ground

                   Crankcase pressure sensor- open/short circuit to positive

                    Ambient air pressure sensor- short circuit to ground

                   Ambient air pressure sensor- open/short circuit to positive

12: MIL light 1 long and 2 short flashes

                     Coolant temp sensor- input signal too low

                     Coolant temp sensor- input signal too high

13: MIL light 1 long and 3 short flashes

                     Intake air temp sensor- input signal too low

                     Intake air temp sensor- input signal too high

14: MIL light 1 long and 4 short flashes

                     Crankcase pressure sensor- difference too high between sensor and engine                         control unit

21: MIL light 2 long and 1 short flashes

                     Battery voltage- input voltage too low

                     Battery voltage- input voltage too high

33: MIL light 3 long and 3 short flashes

                     Injection valve 1, cylinder 1- input signal too low

                     Injection valve 1, cylinder1- input signal too high

34: MIL light 3 long and 4 short flashes

                     Injection valve 2, cylinder 1- input signal too low

                     Injection valve 2, cylinder 1- input signal too high

37: MIL light 3 long and 7 short flashes

                      Ignition coil- circuit fault

50: MIL light 5 long flashes

                       Exhaust control actuator- no signal

                       Exhaust control actuator- no signal

                       Exhaust control actuator- temp too high

                       Exhaust control actuator- incorrect setting

                       Exhaust control actuator- setpoint value signal faulty

                       Exhaust control actuator- input signal too low

                       Exhaust control actuator- input signal too high

                       Exhaust control actuator- mechanical error in the lower position

                       Exhaust control actuator- mechanical error in the upper position

                       Exhaust control actuator- mechanical error

53: MIL light 5 long and 3 short flashes

                       Sensor voltage 1- open circuit/short circuit to ground

                       Sensor voltage 1- short circuit to positive

54: MIL light 5 long and 4 short flashes

                       Sensor voltage 2- open circuit/short to ground

                       Sensor voltage 2- short circuit to positive.

 

Rear Brake Line Rubbing: Almost every TBI chassis bike we've seen brand new has the rear brake line rubbing against either the shock or the swingarm! And unchecked it will rub a hole in the hose and you'll lose brakes. But it's easy to fix. And you don't have to bleed the brakes to fix it. Take a wrench that fits the indexing on the line or some plyers and gently turn the fitting away from the shock. It will roll away and stay out of the way very easily.

 

Clutch Noises: We hear this one all the time as well. A slight tapping or clunking noise that changes with the clutch being pulled in. Some describe it as a knocking noise as well. The TBI 2-strokes do normally make a little noise at idle and most of the time it's nothing to worry about. With that said, the OEM clutch dampers need to be checked or replaced quite often, usually 20-30 hours. These are usually the cause of more noise complaints than anything we see here at the shop. Changing the gear oil at 5-10 hours also matters, as fresh oil is the best thing for your transmission and clutch pack. The KTM clutch is pretty stout and will tolerate a lot of abuse. The baskets usually don't notch like a Japanese bike, which can cause noise. It's not uncommon to see a 70-hour clutch pack in decent shape still. But proper maintenance is still key to keeping the bike alive.

 

Silencer Spooge: Another common question we get at the shop, how much is too much "spooge" from the silencer? Well, it depends! I know that's what most people don't want to hear but it's a variable question. Exhaust drool or "spooge" depends on a few factors. Engine size, fuel/oil ratio, engine mapping, riding style, outside temperature and how old the silencer is all determine how much drool is present. Smaller engine sizes will not present as much drool at the end of a ride, a 300 will show more. Fuel/oil ratio is important, as too rich of mixture will obviously put more oil into/out of the engine. Stock bikes should follow the OE recommendations for ratio mixing, modified bikes should follow the tuners recommendations. Engine mapping will play a part just like fuel ratio and the OE tunes are rich to save the bike. Get a solid tuner, your choice here, to remap the ECM to your modifications and riding style. Riding style will affect the drool most dramatically. If you lug the bike around in 1st gear all day the silencer will never really get warm and move the oil from the packing, it will build up and come out of the end, onto the bike eventually. You don't have to wring the bike out but running thru the gears and getting moving will reduce the drool. Cold temps are worse for drool, just like idling the bike or keeping low RPM's all day. A hotter day will show less drool from the silencer. And finally, the age of the silencer has an effect on the drool. Over time, the packing on any silencer will get saturated with fuel/oil and will have the bike smoking more and drooling more than a new silencer. Also, an aftermarket silencer will drool less because of the less restrictive design. A brand-new silencer ran on a MX track will not have any drool at the end of the day because of all the factors above. 

Silencers can be cleaned. There are a few methods out there, a quick Google search will find them. We recommend replacing the packing on a silencer every 20-30 hours to stop the oil buildup. Or replace the silencer entirely. Like a pipe or the gear oil, silencers are a maintenance item on a 2-stroke. 

 

Fork seal leaks: This is not specific to the TBI bikes but it can definitely happen. To avoid fork seal leaks, you must stay after the maintenance. Remove the fork guards, drop the dust caps and clean out the fork seals with a quality tool. Motion Pro and Risk Racing make good tools for the job. Pull the dirt and grime from the fork seal and clean the fork legs with contact cleaner, finish with glass cleaner. Check the fork legs for any knicks are dents. Small knicks can be lightly sanded out but dents mean replacing the leg. Reinstall the fork guards and you're ready to rock. 

 

 

                   

More issues/solutions to come!!