Updated March 2015
In November of 2010 I bought my first fuel injected dirt bike! I was excited! Buttery-smooth power delivery, no more messing with carburetors. No worries about the choke, or altitude. This was going to be great!
Did I have a few surprises coming!
Fuel injection has been the standard of the industry for automobiles for many years. Long gone are the days of vapor lock. How hard could it be to get a reliable fuel injection system on a dirt bike?
The more I read posts from fellow Husaberg owners, the more I began to panic about failing fuel pumps, clogged injectors, etc. So, I started taking some preventative measures that in the end caused more problems than they solved.
I now have almost 5 years of experience with fuel injected bikes. I currently own the Husaberg FE450 and two KTM 350s. I am by no means an expert, but hopefully this blog posting will help others as they transition from a carburetor to a fuel injected bike.
If you don’t want to know all of the details, this summary should give you the most important things you need to know.
1) Always use high quality gasoline.
2) Use fuel additives if you will be storing your bike for more than a few weeks.
3) Make sure your bike and your work environment is very clean when you work on the fuel system.
4) Clean or replace your fuel filters on a regular basis.
Now let’s review how fuel injection really works. A dirt bike fuel injection is similar to that used in an automobile. Here is a basic diagram:
Basically, the system works like this;
- The fuel pump pressurizes the fuel so that it will properly spray out of the injector.
- A pressure regulator ensures that the proper pressure (usually about 50 psi) is provided at the injector.
- For easy of service, a quick disconnect is provided between the fuel tank and the injector.
A typical system will include two fuel filters; a coarse filter that prevents large particles from damaging or clogging the fuel pump, and a fine grained filter (usually 10 or 20 microns – which is very small) that protects the injector.
Here is an illustration of an injector:
Notice that the spray tip is much smaller than the pressurized fuel intake port. Herein lies one potential problem. If particles somehow get past the filter, it can clog the injector.
Also note the fuel filter inside the injector. According to “melk-man” on KTMtalk, this is a 35 micron filter. He also says; “It’s usually not particles that clog a fuel injector, but rather a build up of hard varnishy gunk that builds up over time and is made worse if it sits for long periods of time. But no doubt, if there was no filtration, and large particles could pass to the injector unchecked, the injector would surely fail. The multi-ports on the bottom of the keihn bike injector (that make the spray) are very small”
If the injector is partially clogged, your bike will run lean – and hot. Trust me, I know. If it gets totally clogged, your bike will not run at all.
The injector is difficult to replace, and I would not want to attempt it out on the trail. It is therefore essential that you take adequate precautions to keep it clean.
As I see it, there are five ways for gunk to clog the injector:
1) Dirty gas. Always try to buy gas from a reputable source. I try to avoid gas stations that have very little traffic and therefore may have old and stale gas. I also try to avoid a station that has just been refilled by a tanker since that action can stir up the debris in the bottom of their storage tank.
2) Gas that has gone bad. Gasoline goes bad over time – especially gasoline with Ethanol. Ethanol has a very short shelf life – only a few weeks. As it ages, it absorbs moisture from the air and forms water particles that collect in the bottom of the tank (near the fuel pump intake) and leaves behind white crystal deposits that can damage your system. If your bike will be sitting for more than a few weeks, always add some stabilizer or Star Tron and keep your tank full.
3) Dirt can enter from the quick disconnect when you open it up for service. So always make sure you clean your bike thoroughly and work in a clean environment. Try to avoid opening up the system while out on the trail.
4) Mechanical failure or breakdown of components such as the in-tank filter. Replace components as they age.
5) Fuel residue that builds up over time. This is normal, which is why the manufacturer recommends periodic cleaning or replacing of the injector.
For most people the stock system with its two filters is probably adequate. But if you ride in harsh environments, or ride a long ways from help, or if you just want to be extra safe, there are a few things you can do to improve the system. Two common enhancements are the addition of a tank sock to catch any large particles from entering the fuel tank in the first place, and a fine grained filter at or behind the quick disconnect.
Keep in mind that the tank sock is a coarse filter – it will help prevent gunk from entering your fuel system, but it will NOT prevent small particles that could clog your injector. This filter cannot be as fine as those used on the pressurized line because they would not allow unpressurized fuel to flow into the tank quickly enough. A tank sock is a good option to add, but it is not sufficient to protect the injector. I bought my filter from Profill Australia. They offer very affordable shipping to the United States. But there are probably other good sources as well.
There are several choices for adding external filters to the system. Some people use a CanAm filter, others prefer Golan or other similar products. Basically any 10-20 micron fuel injection rated filter can be used. I prefer the Zip-Ty Racing filter that replaces the quick disconnect.
The Zip-Ty Racing filter replaces one half of the quick disconnect, so it is very easy to install. It contains a large, cleanable 10 micron filter and a small disposable 20 micron filter.
Some people choose to leave out the 20 micron filter, but I prefer to leave it in. As I see it, the small 20 micron filter is likely to be the first filter to clog up and it is the only filter that is easily removed or replaced while out on the trail. If my bike starts running lean, I can easily replace or remove this filter and see if the bike runs better. Essentially it is my early warning sign that my filters need servicing.
If you bike starts running lean (gets hot, looses power, or pops on deceleration), that may be an indication that one of your filters is getting clogged – or perhaps the injector.
My plan is replace the small in-line 20 micron filter about every 50 hours and clean or replace the other filters every 100 hours.
Here is what my stock in-tank filter looked like at 115 hours (1.5 years), compared with a brand new filter.
And here is the coarse fuel pump filter at 115 hours. Note how much cleaner it was than my Husaberg filter when I got it from the dealer with the Ethanol crystals.
When you open up the quick disconnect, be sure to install the fuel caps to prevent dirt entering the fuel lines. Keep in mind that particles much smaller than you can see without a microscope are capable of clogging your injector.
The first few times I replaced an Oetiker one-ear clamp I found it to be a very frustrating experience. But then I learned the trick to easily removing the clamp. Here are the tools you will need; a small pair of dikes, a larger pair of dikes or pliers, and a pair of Oetiker crimping pliers. I have heard that a ceramic tile nipping tool can also be used.
To remove a clamp carefully grip one corner of the clamp and one of the locking tabs with the small dikes.
Squeeze just enough to bend up the corner of the clamp. Then use your stronger dikes or pliers to bend the clamp outward until the locking tabs give way.
Once all of the locking tabs are free, just bend the clamp until it can be removed from the hose. This technique is very fast and easy.
Use the Oetiker pliers to crimp the ear on the replacement clamp. I find these clamps to be very secure and reliable if installed correctly.
If you choose not to use Oetiker clamps, be sure to use fuel injection rated clamps – not regular pipe clamps.
I had a few fuel injection related problems with my Husaberg during the first year. As with many others, I got one of the faulty fuel pumps that began failing at about 35 hours. This was eventually replaced under warranty. One easy way to tell if your fuel pump is cycling is to momentarily blip the start button just long enough for the ECU to power up the system. You should hear the fuel pump cycle for 2-3 seconds while it pressurizes the fuel line. If you don’t hear that, you either have an electrical problem or a faulty fuel pump.
I think all of my other fuel related issues were a result of my messing with the system. I think the stock filters would have been just fine (for me) – if I didn’t mess with it. Every time I pulled the system apart, I took a risk of introducing junk into the system.
Before Zip-Ty Racing introduced their quick disconnect filter I tried using a CanAm filter. The way I installed it caused a kink in my fuel line that eventually ruptured and I had to get towed 10 miles back to the truck.
I also tried the in-line black 10 micron filter when KTM first introduced it. On the second day of use it got hot and reduced fuel flow, causing my bike to run lean and hot. That was not a fun day. KTM later switched to the gray 20 micron filter to avoid this problem. But I quit using that filter on the Husaberg because it installed in the fuel rail at the injector, which was just too difficult to service. KTM later introduced a quick disconnect that accepted the in-line filter, making it very easy to use. But now I use the Zip-Ty Racing filter on both of my KTMs and my Husaberg.
The moral of the story is to keep your filters clean and use good quality gas and appropriate fuel additives. If you do, you should have years of trouble free riding on your fuel injected bike!