Adjusting your fuel injection system
From time to time, even maintenance-free fuel injection systems need a little attention and resynchronising to ensure your engine runs smoothly.
Step by step: How to adjust your fuel injection system
Unlike carburettors, which often need re-adjustment, fuel injection systems require minimal maintenance as long as all the electronic components are in working order and the system is kept clean. To prevent soiling, a fuel system cleaner should be used in the fuel tank when the motorcycle is not in use to prevent resinous deposits. Also, you should always adhere to the air filter service intervals.
Just like multiple carburettor setups, the fuel injection system in multi-cylinder engines has multiple throttle valves, the synchronisation of which is crucial to smooth engine running. The throttle valves are opened and closed by the throttle twistgrip, thereby regulating the quantity of air and fuel supplied to the engine at a given moment. Due to mechanical stress, the basic setting of the throttle valves changes slightly over time and, as a result, the engine becomes noticeably out of sync when idling. You can tell from the sound of the exhaust system, and also from a fluctuating engine idle speed – put simply, the engine no longer runs smoothly. It's time to resynchronise the fuel injection system.
To adjust the fuel injection system, you need a synchroniser, such as the ones from Rothewald for 2- or 4-cylinder engines. Also the adjustment tools are very useful for some models. Before you start adjustment, warm up the engine so that the cold-start device does not falsify the readings. Then place the motorcycle securely on the stand – ideally in the open air but, if inside in a garage, always so that the exhaust fumes can escape directly to the outside without you breathing them in while you work.
Connect the tubes of the vacuum gauges to the connection points on the fuel injection system after first removing the rubber plugs or tubes from the connections.
Gaining access to the fuel injection system
If the tank covers the fuel injection system, it must be raised and supported on something, like a plank of wood. Often the tank cannot be removed entirely because it contains the integrated fuel pump. The pump is actuated by the control electronics and is required for the engine to run.
When "propping up" the tank, make sure that it cannot slip and cause injury or annoying damage to your motorcycle!
In addition, on our demonstration bike, the airbox must be removed to get at the fuel injection system.
Synchronising the throttle valves
Now you can start the engine and begin adjusting the throttle valves by screwing the bypass screws in or out until all gauges show the same readings.
The purpose of this is to adjust the small air gap opened up by the throttle valves when idling so that air is sucked into the combustion chambers on all cylinders at exactly the same vacuum and at the same rpm, which ensures the engine works evenly on all cylinders. To enable you to correctly read the gauges, they must first be calibrated to each other according to their instructions for use, and the damping must be adjusted so that the pointers flutter only slightly. When adjusting the throttle valves, generally the aim is not to set a specific vacuum – most motorcycle manufacturers do not specify one – but to achieve the same value on all the throttle valves. Then the system will work "in sync" for all cylinders. If one gauge shows a completely different reading from the others, this may indicate that the basic setting of that throttle valve is completely wrong, or it may mean there is a fault or damage such as loss of compression on one cylinder or a leaking intake manifold. If you cannot find and rectify the fault yourself, then you must go to a motorcycle workshop.
The throttle valves are adjusted using the so-called bypass screws (see Fig. 7). Never touch other sealed or colour-coded adjusting screws! All bypass screws should be open at least half a revolution.
Download this tip
For the garage: Simply download, print out and take it with you.
The Louis Technical Centre
Problems getting spare parts? Or maybe you've got a technical question about your motorcycle or an accessory The Louis Technical Centre can help! Remember to quote all the necessary details of your vehicle – better still, send us a copy of your registration document.
We will get back to you as quickly as possible!
So: send us your technical problem!
- by e-mail to firstname.lastname@example.org
- or by letter to Louis Technical Centre, 21027 Hamburg
These tips for DIY mechanics contain general recommendations that may not apply to all vehicles or all individual components. As local conditions may vary considerably, we are unable to guarantee the correctness of information in these tips for DIY mechanics.
Thank you for your understanding.
Louis DIY Mechanic Manual
The printed version
The big Louis DIY mechanic manual available in a printed version: in color and practical A4 format at cost price.