Tuning + optimization of Buell

FUEL SYSTEM

FEED THE BEAST!

It goes without saying that proper fuel delivery is critical for all engines.  Making sure your engine is being fed properly should be part of a routine maintenance check, before any form of tuning is done and when diagnosing an EFI related issue.  Buell motorcycles are notorious for having fuel system problems, which are often undetected or misdiagnosed.  As these bikes age the fuel pump assemblies can develop leaks that cause a loss of fuel pressure.  More often than not, the owner is unaware of a problem because by default, the ECM will try to compensate for this issue by raising the Adaptive Fuel Value (AFV) by as much as 150% which increases the duration of the injector pulse.  With a high AFV, the injectors are capable of delivering enough fuel at lower RPMs and cruising speeds, but at higher RPMs the injectors are eventually "maxed out".  The result is a very dangerous lean condition that goes undetected by the O2 sensor since high RPMs and throttle angles are outside of the closed loop range of the fuel mapping.  Instead of getting a Check Engine Light at an early stage of the problem, the owner may not be aware of the situation until something catastrophic happens.  

SIMPLE CHECKS TO PREVENT BIG HEADACHES

Even if your bike seems to be running well it's a good idea to look at what the current AFV setting is.  A tutorial for this is found HERE.  An AFV above about 108 near sea level could be caused by low fuel pressure, intake leak, sensor issue, etc.  If you see an AFV of 120 or more, it's almost guaranteed to be a fuel delivery problem.

 

If you suspect a fuel system problem you should measure your fuel pressure. For XB models we now offer a Fuel Pressure Tester.  This plugs in to the quick disconnect fitting of your fuel line once it is disconnected from the throttle body.  You can then perform a Fuel Pump Test using the Ecmdroid application.  On X1 and S3 models the pressure is measured at the Schrader valve located under the tank at the fuel outlet fitting.  The measured pressure should be ~49 PSI. This pressure should also bleed off slowly after the pump turns off.  

FUEL SYSTEM SOLUTIONS

Diagnosing a fuel system problem is easy, but finding the parts to solve the problem has been challenging.  New fuel pump assemblies are very expensive, if you can find one, and buying a used one that could have the same problem as yours (or worse) is not a good idea.  OEM fuel system parts are becoming increasingly obsolete, while replacement pump kits that can be found online are incomplete and usually contain cheap parts of questionable origin and quality, including fuel lines that aren't meant to be submersed in gasoline.  If you do manage to get a good seal during assembly, it probably won't last for long.

 

Revision Moto now offers fuel pump assembly rebuild kits for XB, X1 and S3 models made up of OEM quality components including genuine Walbro pumps that are made in USA.  All of the parts you need for a complete rebuild are included, for a fraction of the price of a new pump assembly.

 

We also offer a fuel pump assembly exchange service.  Send us an email for more information including pricing and availability.

Complete your fuel system refresh with our Fuel Injector Cleaning and Testing Service.