Many manufacturers has built in fault codes to alert of any problems with the EFI sensors that tell the ECU how much fuel to inject at different rpm and load. Most engine sensors emit some noise in their signals and the problem is this value tolerance that the fault code looks for has to be large enough not to trip a false fault code due to noise but also small enough to know when the sensor is causing a problem. To avoid customer complaints generally this tolerance is on the large side so some performance problems can go unnoticed.
We see a fair number of off road bikes with premature engine wear from dirt ingestion. One often overlooked problem is the air filter cage. Many times these cheap plastic cages warp which causes the air filter to not seal tight against the air box. A good solution is to replace it with an aluminum aftermarket unit. Twin Air is one brand that offers this solution.
Most quality cast pistons have a silicon content of 18% or so versus a forged pistons max of aprox 12%. This higher silicon content results in less piston expansion and better high heat thermal properties which is desirable and critical in a 2 Stroke engine. The forged piston is stronger due to its grain structure which is desirable for a 4 stroke application.
Carburetor Flooding Problem
Have run across this a couple of times lately on older bikes and thought I would share this as it may help someone suffering from a similar problem. I you have a problem with a drip out one of one of the overflow hoses and your floats and float valves & height were all good check this. You may find you might have an invisible small split in the overflow tube. We do offer a repair for this.
Determining the Health of your Fuel Pump
Case Study on a Suzuki SV650S.
We can check the health of the fuel pump and filter by using a technique with our scope called "Current Ramping" What is is essentially is looking at a currrent draw waveform when the fuel pump is activated. Looking at the first waveform you can see the irregular pattern. This is an indicator that the pump is worn ( bushings, brushes, commutator etc.) We can also determine the pump rpm and average current draw which can also indicate a partially restricted filter element or a pump that is on its way out.
We replaced the in tank fuel pump and in the next picture you can see the obvious difference in the waveform. Regular pattern, average of 5 amp draw and aprox 6,000 rpm. Finding this probably saved a customer from being stranded somewhere.
Below is a picture of the fuel pump disassembled. The commutator is badly worn and there is hardly anything left of the brushes. This pump was certainly on the way out.
We call this a relative compression check as it does not give you an actual compression number in PSI but lets you quickly compare cylinders. In this example a 5 minute test told us this customer has a mechanical compression problem which required further investigation. As it turns out the valve clearance on Cyl 2 was tight. The other information we can gather from this is starter and battery condition. Peak starter draw should be under 400 amps and battery voltahe should not drop lower than 8 volts. This test costs only $27.50 and is a great way for you to get a quick check on your motor, battery and starter health !
Came across this interesting tidbit when working on a Suzuki RMZ450 while looking at a ignition waveform pattern. It appears that Suzuki is actually firing the spark plug twice at rpm's all the way up to 4,500. They are obviously doing this to improve low speed running. At over 4,500 rpm when the engine is running more efficiently they revert back to firing the spark plug only once. All engines misfire off and on especially at lower rpm's when volumetric efficiency is low. The longer spark duration that occurs when firing the coil twice helps improve the chance that ignition will occur at these lower rpm's.
Just added this Variable Speed Belt Sander to help with both the quality and speed of fabricating one off parts.
Damaged and /or ripped Carburetor Slide Diaphragms that have deteriorated from use is becoming a more common occurrence on older bikes. We are able to repair many of the carburetor slides by changing the damaged rubber only. Below is an example of damaged slides from a VT1100 Honda Shadow. These slides were no longer usable and are no longer available from Honda rendering the carbs useless.
This is an example of what we do here that a lot of shops can't and won't get involved in. This is a non rebuildable stock shock from a vintage 1984 Yamaha RZ350. The customer was looking for an upgrade in suspension so we gutted the rear shock and using a KYB 40mm valve body, some machining and ingenuity we were able to dramatically improve the action while saving the customer a good bit of money over buying a complete aftermarket shock. The nice part is the bike still looks stock. If you have a project and a realistic budget give us a call!
I have been involved in mechanics and motorcycling from a young age. I formed Cycle Improvements in 1981 and still have the same passion to learn today as when I started. Hope you find this blog interesting and educational.