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TPI Common Questions & Troubleshooting

We have collected 10 of the most common questions that come up with the TPI bikes, please see the appropriate questions below:

How do they compare to a carby bike?

The TPI bikes are often considered to have slightly softer bottom end power delivery than the carby
bikes, but similar top end. The main reason for this is the TPis generally have softer ignition curves,
especially at part throttle, and this gives the feeling of a softer power delivery. There are also some
differences due to the location of the injectors and the reduced opportunity for fuel/air to mix
properly at low rpm, but this can be overcome with some basic mods as we’ll discuss later…
If we are talking about strictly unmodified bikes in 100% stock form then they both have their small
issues that most riders will end up improving at some stage… the 17-on carby bikes have terrible
jetting from the factory resulting in spluttery power and poor fuel economy plus a finicky Mikuni carb
which is extremely difficult to get running consistently, while the TPIs have softer power delivery and
some models have had issues with spluttery power delivery at low revs.
Both carby and TPI bikes respond very well to basic mods and once setup correctly both have very
similar power delivery. The cost to modify both bikes to this level is about the same … for the carby
bikes we would normally fit a TSP billet head and a Keihin PWK carb, and for the TPI bikes we would
fit a TSP Billet head, reflash the ECU and fit an idle bolt/spring. Doing these mods brings both bikes
up to a level where most riders wont feel the need for more power and will experience excellent
reliability.

Once setup properly the TPIs have a few distinct advantages over the carby bikes… no mixing of oil,
smoother power delivery and the fact that the ECU is self adjusting to changes in weather means
they are easier to live with in a wider range of conditions.

 

Rebuild intervals?

We suggest top end rebuilds every 80-100 hours maximum for a 250/300. Some riders in other
countries report longer intervals between rebuilds however in Australia its extremely rare to see a
bike with more than 100 hours on it that’s still in reasonable spec and does not display running issues
of some kind. Perhaps our riding conditions are harsher than other areas, or possibly we have more
dust during the hotter months, but whatever the reason we see most top ends well and truly worn
out by 100 hours.
The TPIs are also especially sensitive to top end wear as blow-by past the rings will begin to alter the
crank pressure readings sent to the ECU. This in turn causes the ECU to alter fueling, ignition and
oiling and as a result performance will drop, often to the point where the bike begins to run poorly
and doesn’t want to idle.
Doing regular top end rebuilds will lead to much better engine life overall and keep your bike running
to its maximum potential. Its better to view it a cheap insurance rather than wait for an expensive
failure.

Bottom ends are very reliable, as they are on the carby bikes. As long as the oil system is maintained
and you clean and mount your air filters properly you should see at least 250 hours from a bottom
end, and often up to 500 or more.

 

How reliable is a TPI bike?

Generally the TPI bikes are very reliable however there have been some issues that we have seen on
stock bikes over the years.
Its important to recognize that over the years between the 2 generations (18/19 and 20-on) of the
150, 250 and 300TPIs there have been a total of 17 different stock ECU maps released by the factory.
Some maps have had inherent reliability issues and others have been much better. Some give softer
power and others give stronger power. That’s why there are so many strong but differing views on
the TPIs on the internet… different owners have had very different experiences depending on which
generation/capacity/map they have owned.
Regardless of the generation or capacity all TPIs become extremely reliable once a few basic mods
are done. At an absolute minimum we suggest fitting an idle bolt (which allows separate tuning of
the air and idle settings on the throttle body) plus running the latest “extreme” stock maps as they
have a greater amount of oil in them. Ideally though we recommend fitting our TPI Power Kit, which
includes a reflash of your stock ECU, a new billet cylinder head with a more efficient combustion
chamber design, an idle bolt/spring and a new spark plug. This kit not only transforms the
performance and power delivery of your TPI but it also offers significantly increased oiling over stock,
making the engine even more reliable.

Below is a list of some of the most common reliability issues we have seen over the years. Don’t be
alarmed by the size of this list as we could easily create a similar list for just about any make/model.
Most TPI bikes wont experience any significant reliability issues in their lifetime but if they do
hopefully this list will help you diagnose the issue quickly and easily.

 

What are the oil related failures?

Probably the most significant issue has been failures due to a lack of oil. The overall number of bikes
this has happened to is actually quite low compared to the number of bikes sold but it has stood out
to us as one of the more significant and consistent issues we have seen on the KTM bikes over the
years. Oil related failures are very obvious because they result in significant wear up the back wall of
the cylinder, usually centered over the rear boost port. A quick check for this type of wear is to
remove your expansion chamber and look directly up the exhaust port at the back wall of the
cylinder. Any vertical black/grey marks at the rear of the cylinder are usually a sign that the engine
has suffered a lack of oil at some point and should be investigated further. The marks left on the
cylinder due to a lack of oil are very easy to distinguish from the wear left by other failures, such as a
cold seizure, dirt/dust through the engine, detonation, overheating, etc.
The reasons for the oil damage differs depending on the year and the riding conditions… for the
18/19 bikes they generally had a good amount of oil in the stock mapping (some were less than
others though) but the oil tank did not have a screen in it so any dirt that got in there tended to make
its way into the pump and reduce the output. With these models its critical to regularly clean the
tank and test the output of the pump. For the 2020 models a screen was fitted to the tank but then
for some reason the amount of oil in the stock maps was significantly reduced at the same time
leading to a high number of oil related failures on low hour bikes. The new “extreme” maps bring the
oil level back up to roughly what it was in the 2019 bikes and the addition of the screen in the oil tank
has made the system very reliable now.

 

Why do I keep fouling plugs on start-up?

This emerged as an issue on some of the 2020+ models. Even on brand new bikes in perfect
mechanical condition the plug will foul before the engine reaches operating temperature. A simple
bandaid for this is to always pull out the cold start knob on the side of the throttle body when
starting the bike cold (or just warm) and let it idle and build up heat for a few minutes before
touching the throttle. The cold start knob allows extra air to enter the throttle body, giving a higher
idle speed and leaning out the overly rich air fuel mixtures which the ECU gives when starting the
engine below operating temperature.
A more permanent fix is to update the ECU with more appropriate fuel maps. The ECU reflash that
we offer addresses this issue and virtually eliminates plug fouling.
If you are dealing with a bike that is consistently fouling plugs you can use the cheaper NGK BPR7ES
or BPR8ES plugs as they will still perform very well but only cost a fraction of the genuine plug to
replace.
Be aware that a bike that suddenly starts fouling plugs after not previously doing so can often be a
sign of another fault, such as a worn top end or a faulty crank pressure sensor (see the next section for more information)

 

Spluttery power delivery at low/mid revs?

Some of the earlier 18/19 bikes exhibited spluttering and unpredictable power delivery at part
throttle and low/mid revs due to issues with the stock mapping. For these bikes the only solution
available to completely fix the issue is to reflash the stock ECU with improved maps. TPI Power Kit
completely resolves this issue on bikes that are otherwise in good mechanical condition.
The other main causes of spluttery power delivery are a faulty Crankcase Pressure Sensor, an
incorrect Air Screw setting, low fuel pressure, or a worn top end. See below for more info.

1. Faulty Crankcase Pressure Sensor (CCPS):

The ECU uses the data provided by the CCP to determine the fuel, ignition and oil needs of the engine
according to the maps that its programmed with. It is reasonably common for the CCP to become
faulty or blocked and when this happens the most common symptom is spluttering and
weak/unpredictable power delivery at part throttle and low/mid revs. Often a bike with a faulty CCP
will still rev out fine and that’s because the ECU relies on the data from the CCP more heavily at lower
revs and lower throttle openings.

The simplest test for a faulty CCP is to swap it with the ambient pressure sensor… The 2 sensors are
identical and can be interchanged. If the bike suddenly runs better with the sensors swapped then it’s
a sure sign that the original CCP was faulty and needs to be replaced or cleaned. Generally a bike will

still run well enough with a faulty Ambient Pressure Sensor, but wont tolerate a faulty Crankcase
Pressure Sensor.

There are many other aftermarket pressure sensors that appear physically identical to the genuine
KTM CCP, however be aware that they don’t all operate the same… some will give very different data
to the ECU and cause the bike to run richer or leaner than intended. As the CCP is critical for the
reliable running of the engine (as its used to determine fuel, ignition and oil) we strongly suggest only
using genuine KTM sensors to avoid more problems.

2. Low Fuel pressure:

Low fuel pressure on the TPIs usually results in spluttery, jerky power delivery, the engine cutting out
when throttle is applied, or a general lack of torque. You may also notice common signs of lean
running such as overheating and a hanging idle. Its most commonly caused by either a faulty fuel
pump, or a split or blocked in-tank fuel filter. The small in-line fuel filter that’s found inside the fuel
hose very rarely gives any issues. The easiest check is to test fuel pressure with a gauge. It should give
approx. 52 psi at all times, regardless of how hard the throttle is opened.

3. Incorrect air screw setting:

The “Air Screw” is the large screw found on the left side of the throttle body. From the factory the Air
Screw is used to adjust the idle speed, however it actually has an impact on fueling all the way up to
mid revs. A far better way to tune the idle is to remove the stock grub screw which is hidden in the
throttle body and fit a longer bolt that can be adjusted by hand while the engine is running. This
separate control of the idle speed then allows you to use the Air Screw to adjust the fuel/air mixtures
richer or leaner depending on what your individual bike needs. It’s a very effective way of fine tuning
the TPI system and has a noticeable impact up to mid revs and part throttle. The vast majority of TPI
bikes will benefit significantly from fitting the idle bolt and then experimenting with adjusting the Air
Screw. The common issues it helps to resolve are: weak or hanging idle, spluttery power delivery and
poor throttle response.

4. Worn top end:

Even if your bike has been mechanically perfect without any issues sooner or later your top end will
wear to the point that the bike no longer runs properly. Don’t believe what you read on the internet
about people always getting 150-200 hours + out of a top end. Yes SOME bikes will get that far, but
in our experience most will need to be replaced much earlier than this, especially on the TPI bikes. We
suggest a normal interval of 80-100 hours between top end rebuilds on a stock or modified 250/300.
A TPI that doesn’t want to idle, suddenly starts fouling plugs or wants to stall is often a sign that your
top end is worn. We’ve seen countless bikes with extremely low hours with top end wear that causes
running problems. There can be many different causes for top end wear but one thing we have
noticed is that the TPI bikes don’t seem to tolerate top end wear as well as a carby bike… this is most
likely due to the fact that any blow-by or leakage past the rings due to a worn top end will alter the
pressures in the crankcase. These altered pressures will then be sent to the ECU via the Crankcase
Pressor Sensor and the ECU will adjust fuel, ignition and oil as it deems necessary, often resulting in a
bike that lacks power, splutters, doesn’t want to idle, and in some cases eventually seizes.

The best advice is to regularly rebuild your top end to avoid running problems, and if you do have a
bike that has started to have running issues don’t discount top end wear as a possibility just because
your bike has ‘low hours’… its not hard to check the condition of your top end and it may save a lot of
time and money down the track.

5. Corrosion of electrical connectors or relays:

Corrosion of electrical connectors or corrosion inside the main relays under the seat can cause several
different running issues. Usually, electrical issues like these will present some of the following
symptoms:
– Engine doesn’t want to start
– No spark
– Fuel pump wont prime, or primes randomly by itself
– Oil pump wont prime
– Dash wont light up when pressing the starter
– Switches/controls at the bars wont work
– Engine runs but breaks down, splutters or wont rev out
The only solution for these issues is to carefully check and clean each connection and re-test.

 

Do I need to replace the oil pump regularly?

Generally the oil pumps are very reliable UNLESS they get dirt or grit inside them, in which case they
will often continue to work but with reduced output. The 18/19 bikes don’t have a screen inside the
oil tank and are more susceptible to getting dirt into the tank and then down into he pump. The 20+
models have a screen which should stop dirt getting into he pump and make it very reliable. On an
18/19 model if you regularly test the output of the pump as well as remove and clean the oil tank you
shouldn’t have any pump issues.
We have a video on our website/facebook showing the process of checking the pump output.

 

How can the stock ECU maps be improved?

As mentioned earlier there have been 17 different stock ECU maps released by the factory so far
across all the generations and capacities of TPI bikes. Each stock map has different areas that can be
improved and the gains that can be had vary from one map to the other can vary. In general terms
when we reflash an ECU we are changing the amount of fuel injected into the engine, the ignition
curve, the amount of oil injected, the cold start sequence and a wide range of other variables. The
end result is a bike that makes more power, becomes more reliable, delivers its power in a much
smoother manner and is more enjoyable to ride in almost any conditions. We are very confident that
we can improve ANY of the stock maps for any of the TPI bikes.

 

Can you move the injectors?

Although moving the injectors to the front of the reed cage can give a degree of increased power due
to improved mixing of the fuel/air charge its not something that we recommend doing with the stock
ECU maps on the current TPI bikes. In particular, the fuel and oil needs of the engine change when
the injectors are moved and so in order to do this mod safely you should also reflash the ECU with an
appropriate map that’s designed to work properly with the new injector location.

Further, from what we have seen in our development work most of the gains in power due to the
improved mixing of fuel/air can be equally achieved with the stock injector location by fitting an
improved combustion chamber design that promotes higher turbulence prior to ignition. Plus,
changing the combustion chamber also brings other benefits such as increased detonation
resistance, improved efficiency and smoother power delivery that are not gained by moving the
injectors.

Our advice to customers with the 18-22 TPI bikes is to leave the injectors in the stock location and
increase power, smoothness and reliability by fitting one of our TPI Power Kits (ECU reflash, Billet
head, idle bolt and new spark plug) as this will give greater gains overall.
Assuming the rumours about the new 2023 bikes having the injectors in the throttle body are true
then we will also recommend owners of those new bikes to leave the injectors in their stock location
as well, and chase improvements in power, smoothness and reliability through changes to the ECU
and cylinder head as these yield the greatest results.

 

Can you add oil into your fuel?

This is a very contentious issue and many people have formed strong views based on very limited
information. The short answer is YES you can add oil to the fuel on your TPI bike… HOWEVER… if you
are going to do this you need to be aware that very little of the added oil will actually reach the
bottom end of the engine.

The current TPIs inject fuel into the transfer ports near the cylinder wall. The timing of the injection is
recalculated every revolution depending on a range of factors, in particular load and rpm. Under
some conditions of rpm and load the majority of fuel will go straight into the cylinder and not reach
the bottom end, while under other conditions of load and rpm injection begins much earlier, long
before the ports open, and as a result a large amount of the fuel will gather in the bottom end before
being drawn up into the cylinder. As a result, if you add oil to the fuel on a TPI the extra oil will
sometimes reach the bottom end, and sometimes go straight into the top end. The extra oil WILL
have a benefit, but just how much benefit it gives depends on how the bike is ridden. Usually the
benefit is only very small, but it is there. If you are going to add oil to the fuel do so only as a bandaid
to give the engine a small amount of extra protection in extreme conditions. A good example of this
was when the 2020 bikes were released and we started to see a larger number of oil related failures
due to the reduced oil in the stock ECU mapping. At this time we suggested customers riding stock
bikes (with stock ECU mapping) in extreme conditions (eg deep sand, high speed racing, etc) should
add between 150:1 and 200:1 oil into the fuel tank. Doing this virtually eliminated oil related issues in
bikes that had previously suffered top end seizures due to a lack of oil in the same conditions. The
small percentage of oil in the fuel was not enough to have a significant impact on air/fuel ratios but
the overall result was a noticeable improvement in reliability in these bikes.

Despite saying all this a FAR better solution is to increase the amount of oil in the ECU maps. Our TSP
maps have more oil in them than any of the stock factory maps, including the ‘extreme’ maps, and as
a result we virtually never have customers experience oil related seizures when running our TPI
Power Kit. If the ECU mapping has enough oil in it there is never a need to add extra oil into the fuel.

 

What are the minimum things a TPI owner should do to ensure reliability?

– Update to the latest “extreme” map (20+ models only) as they give more oil, or better yet
reflash the ECU with our TSP maps which ensure far better reliability and performance for all
year models.
– Regularly clean the oil tank (18/19 models)
– Fit an idle bolt/spring and spend some time finding the ideal Air Screw setting for your bike
– Improve the stock head design with a TSP Billet Head (better efficiency, less detonation risk,
smoother power delivery).
– Regularly check oil pump output
– Regularly check top end condition
– Run good quality TPI specific oil
– Use good quality 95-98 octane RON fuel
– Regularly clean your air filter and apply grease to the sealing surface
– Regularly clean your CCP

 

What are the best things a TPI owner can do to improve the performance of their TPI?

– Fit an idle bolt and tune the Air Screw
– Fit a new head with an improved shape eg TSP
– Reflash the ECU with improved maps