New Project: YFZ/Banshee Hybrid

[jcs003]

Is the no power problem new problem since the rebuild or was the rebuild suppose to fix the no power problem?

Jerry, it was supposed to fix the no power issue.  engine has new piston/rings, crank and all new bearings and seals/gaskets.  passes a leak down test and has 135 psi compression.  timing is 2 degrees advanced.  it has a shearer 2 into 1 exhaust and I have several carb options to choose from.

do you have any suggestions?

Thank you,

John

[Jerry Hall]

Jerry, it was supposed to fix the no power issue.  engine has new piston/rings, crank and all new bearings and seals/gaskets.  passes a leak down test and has 135 psi compression.  timing is 2 degrees advanced.  it has a shearer 2 into 1 exhaust and I have several carb options to choose from.

do you have any suggestions?

Thank you,

John

Borrow a set of Toomey T-5 pipes and silencers and see if that helps the problem.  My experience with 2 into 1 pipes on engines that have transmissions has been disappointing.  The exhaust port timings that makes good power on a Banshee is out of the range where a 2 into 1 design can function optimally.  Do not use the Toomey T-6 "Low end" pipes and silencers.  I have not been able to make the Toomey T-6 pipes work on any engine package I have tested.  

I have had a few customers that say that their 2 into 1 system works good.  When I ride their bikes, I am not impressed.  My expectations versus what I read in the advertisement of their systems was not met.  Advertisements that use terms like " low end"  "mid-range"  "top end" power are terms used by manufactures whose intent is to portray one shoe size will fit everyone.  These terms are vague and have different definitions to every reader and manufacturer.

[JohnTabata1]

Why not use a legit Banshee builder to start with?

[jcs003]

Why not use a legit Banshee builder to start with?

not sure what you mean.  the engine was originally built by Brandon of wildcard racing.  all i did was put in a new crank, pistons and rings.  mat shearer built the pipe.

[Jerry Hall]

not sure what you mean.  the engine was originally built by Brandon of wildcard racing.  all i did was put in a new crank, pistons and rings.  mat shearer built the pipe.

Do you know what type of engine package you have?  Does it have stock or ported OEM cylinders?   I have a lot of experience with Banshees and have made thousands of dyno runs during the development of different engine packages.  Do you have any dyno curves on your engine?  Do you have any dyno curves on your engine with different pipes?  Do you have any dyno curves with different carbs?........ Some dyno curves could tell me a lot as to what has been done to the ports and head.  Are you still running the 1 into 2 carb set up?  What does your intake/air filter system look like?  Are you running an OEM CDI box or are you running a programmable system?

[jcs003]

Do you know what type of engine package you have?  Does it have stock or ported OEM cylinders?   I have a lot of experience with Banshees and have made thousands of dyno runs during the development of different engine packages.  Do you have any dyno curves on your engine?  Do you have any dyno curves on your engine with different pipes?  Do you have any dyno curves with different carbs?........ Some dyno curves could tell me a lot as to what has been done to the ports and head.  Are you still running the 1 into 2 carb set up?  What does your intake/air filter system look like?  Are you running an OEM CDI box or are you running a programmable system?

Jerry,  it is mildly built trail port; stock cylinders. (I bought the engine used)  It was originally set-up with 28mm pwk.  it also has OEM ignition.  I have no dyno runs of this engine.  I am still running the 1 into 2 carb set up.  it is a chariot racing head with pump gas domes.  the timing is at +2 degrees.  the current carb is a 35mm pwk, I had a 38 mm pwk on yesterday.

This afternoon I leaned out the carb a bit and felt a small improvement in power.  however, the plugs is still rather wet.  I will go out on a limb and say my biggest issues is getting the carb tuned accurately.

I appreciate all your help.

[jcs003]

the intake roughed out:


new carb boot, which will take the angle out of the carb:

[Jerry Hall]

the intake roughed out:


new carb boot, which will take the angle out of the carb:

The foot long small diameter orange intake tube caught my eye.  I have not tested that long of an intake on a Banshee but I have done a lot of testing on the 125cc shifter kart engines, 250R Hondas and the 500 single cylinder two strokes that need to run air filters.  None of the aforementioned engines would have liked that long small diameter connector between the carb and air filter.  On the twin carbed Banshee with the stock air box, the development that I did on the Banshees did not like the air filter flanges that  had the 2.5 to 3 inch opening to the air filter.  They wanted a large opening from the plenum to the air filter just like what the engineers at Yamaha gave us on the stock Banshee air box.

There is a tuned length on the intake side of the engine just like there are tuned lengths on the exhaust side of the engine.  Many guys ruin a good engine package by neglecting to incorporate development and testing to the intake side of the engine.  

On a small displacement cylinder like on the Banshee I think that the engine would like to see about 2 to 4 inches of about 2.5" to 2.75" ID tubing and then dump into a larger diameter tube that is at least 4 to 5 inches in diameter all of the way to the air filter.  The flange on the air filter should never be smaller than the largest ID of the carb to air filter tube.  

An intake system like pictured above will  have 2 to 3 resonating systems.  Well developed engines will usually have only one resonating system on the intake side of the engine.  There is always one primary resonating system from the reed tips to the bellmouth of the carb on any engine.  If the distance from the reed to carb bellmouth is too short (where its tuned length is for a RPM that is out of range of the engine), the length of the primary system can be lengthened by adding some length of parallel or shallow angled tubing to the bell mouth side of the carb.  The system needs to dump into the atmosphere at this point or an air filter with a lot of surface area.  When the space confines of the bike does not allow us to place a large air filter at this dump point, sometimes we can connect the dump point to the air filter with a large diameter connector tube.  

Sometimes the large diameter tube that connects the air filter to the dump point of the primary system can still resonate with undesirable effects and can be fooled by strategically placing a Helmholtz resonator to bring the total system into the desired resonating frequency.  Helmholtz resonators (the little white plastic tank that is about halfway between the carb and air filter) are used by the stock TRX250R,  TRX450R and a large number of intake systems in the automobile industry.

[jcs003]

The foot long small diameter orange intake tube caught my eye.  I have not tested that long of an intake on a Banshee but I have done a lot of testing on the 125cc shifter kart engines, 250R Hondas and the 500 single cylinder two strokes that need to run air filters.  None of the aforementioned engines would have liked that long small diameter connector between the carb and air filter.  On the twin carbed Banshee with the stock air box, the development that I did on the Banshees did not like the air filter flanges that  had the 2.5 to 3 inch opening to the air filter.  They wanted a large opening from the plenum to the air filter just like what the engineers at Yamaha gave us on the stock Banshee air box.

There is a tuned length on the intake side of the engine just like there are tuned lengths on the exhaust side of the engine.  Many guys ruin a good engine package by neglecting to incorporate development and testing to the intake side of the engine.  

On a small displacement cylinder like on the Banshee I think that the engine would like to see about 2 to 4 inches of about 2.5" to 2.75" ID tubing and then dump into a larger diameter tube that is at least 4 to 5 inches in diameter all of the way to the air filter.  The flange on the air filter should never be smaller than the largest ID of the carb to air filter tube.  

An intake system like pictured above will  have 2 to 3 resonating systems.  Well developed engines will usually have only one resonating system on the intake side of the engine.  There is always one primary resonating system from the reed tips to the bellmouth of the carb on any engine.  If the distance from the reed to carb bellmouth is too short (where its tuned length is for a RPM that is out of range of the engine), the length of the primary system can be lengthened by adding some length of parallel or shallow angled tubing to the bell mouth side of the carb.  The system needs to dump into the atmosphere at this point or an air filter with a lot of surface area.  When the space confines of the bike does not allow us to place a large air filter at this dump point, sometimes we can connect the dump point to the air filter with a large diameter connector tube.  

Sometimes the large diameter tube that connects the air filter to the dump point of the primary system can still resonate with undesirable effects and can be fooled by strategically placing a Helmholtz resonator to bring the total system into the desired resonating frequency.  Helmholtz resonators (the little white plastic tank that is about halfway between the carb and air filter) are used by the stock TRX250R,  TRX450R and a large number of intake systems in the automobile industry.

jerry, so what you are saying is; sound waves play an important role in two stroke intakes as it does in the exhaust?

this tube I am using does have a resonating effect as far as it has a small amount of expansion and contacting when the RPMs vary.  Increased intake volume and such.  does this make sense?

also, the adapter that comes from the airbox tapers down, so it will not stifle the intake airflow.  I can get a picture to better show what I am speaking of.

I was considering having a custom intake fabricated, but i don't have the time to design and run the analysis.  I used my most basic engineering approach and hope it will work as desired.

what are your thoughts?

[jcs003]

Jerry, Here is the reducer I used:

[Jerry Hall]

Jerry, Here is the reducer I used:

What are the approximate diameters for your reducer?

[jcs003]

What are the approximate diameters for your reducer?

4" ---> 2-1/2".  the length of the taper (45*) is, 1-1/2" long.

[Jerry Hall]

That type of flange design will show an improvement on a flow bench over a sharp edge entry, which is a plus on any intake system.  Resonance optimization cannot be tested on a flow bench. I think that your system in the picture may have a resonance problem.  The late professor Gordon Blair from the Queens University of Northern Ireland devoted over 40 years of his life studying gas dynamics, pressure wave activity, and developing computer models to simulate the gas flow into, thru and out of engines.  His graduate students are working around the world using his knowledge to develop engines and further develop engine simulation software.  

The intake wave reverses sign when it gets a little past the large diameter of the flange and into the opening of the air filter, not when it reaches the bell mouth of the carburetor where the diameter of connector tube is too small to get a strong sign reversal.  My gut tells me that your orange tube is to long and probably wants to resonate a a frequency that would make a 4000 RPM engine happy not a Banshee that is happy in the 7500 to 10,000 RPM range.  

The wave activity in the exhaust and intake of an engine is complex and does not always follow basic acoustic wave theory because of the gas dynamics involved.  An engine is a system comprised of many small resonating systems that all have to work together. If one of these systems is not cooperating it can have adverse effects on the whole engine.  The adverse side effects can be a loss of power, dips and spikes in the power curve, an engine that cannot be tuned, or symptoms of an erratic behaving carburetor.

[jcs003]

That type of flange design will show an improvement on a flow bench over a sharp edge entry, which is a plus on any intake system.  Resonance optimization cannot be tested on a flow bench. I think that your system in the picture may have a resonance problem.  The late professor Gordon Blair from the Queens University of Northern Ireland devoted over 40 years of his life studying gas dynamics, pressure wave activity, and developing computer models to simulate the gas flow into, thru and out of engines.  His graduate students are working around the world using his knowledge to develop engines and further develop engine simulation software.  

The intake wave reverses sign when it gets a little past the large diameter of the flange and into the opening of the air filter, not when it reaches the bell mouth of the carburetor where the diameter of connector tube is too small to get a strong sign reversal.  My gut tells me that your orange tube is to long and probably wants to resonate a a frequency that would make a 4000 RPM engine happy not a Banshee that is happy in the 7500 to 10,000 RPM range.  

The wave activity in the exhaust and intake of an engine is complex and does not always follow basic acoustic wave theory because of the gas dynamics involved.  An engine is a system comprised of many small resonating systems that all have to work together. If one of these systems is not cooperating it can have adverse effects on the whole engine.  The adverse side effects can be a loss of power, dips and spikes in the power curve, an engine that cannot be tuned, or symptoms of an erratic behaving carburetor.

that is discouraging.  do you have any suggestions to improve this?

Thank you for the continued help.

John

[Jerry Hall]

1.  Define the problem by a process of elimination.  Does this bike run as good as a stock Banshee?

a. Does it have an aftermarket high current stator and flywheel for "big lights"?  If if does borrow a stock stator and flywheel and try it.  
We have had nothing but problems with the aftermarket flywheels, stators and CDI boxes.  Still no power, step B.

b.   Eliminate the long orange hose.  Can you install the YFZ450 intake hose on that carb and attach an air filter to it for strictly testing purposes? The YFZ 450 intake hose ID may be too small for the first few inches because Yamaha used the intake tube to compliment / extend the length of the carburetor to get the intake tract length right.  If the YFZ450 intake hose will not fit or the ID is too small, try to use a clamp on foam filter directly onto the back of the carburetor.  (use as large of a filter as space will permit)   After eliminating the orange hose run the engine and tune the carb.  Did the power improve?  if not step c.

c. Remove the 2 into one pipe and install a good set of Banshee pipes.  I prefer the Toomey T5 pipes.  All the pipes have to do is plug onto the cylinders and can be bailing-wired on so that you can ride it up and down a smooth road for testing or use someones dyno.  did the power improve?  If not I will continue based upon the engines response to the above changes.