blowit

You should not need anything special for this. standard 6-8" calipers have a tail that sticks off the end when you open them. That little tail is calibrated to measure depths. If you want something special, there are lots of measuring devices out there that might make life easier for you. Something that works well for us is clay. Push it into an area to get an impression, then measure the clay. This is not dead accurate but pretty close.

I am sure there are plenty of engines making power without that port adjustment and I don't mean to start any hot debate about it because there are lots of factors that go into ports. Factors just as turbulence in the port tube, velocity, pressure delta, etc. All things which I have learned that porters don't care about learning. Just move material around until it goes faster. No doubt even at the engineering level with OEMs, they have played around with countless theories of design. Lowering the transfer port makes the window bigger. This will reduce flow velocity on top of the piston. General physics principal indicates as we decrease velocity, pressure will increase so we will have a more dense charge. As well, depending on the actual velocity of the port flow, there will be a wedge shaped eddy of turbulent charge at the edge of the piston that likely does not get fully charged up with fuel. There are 4 transfer ports! That is a lot of volume. If there is one thing to learn with subsonic airflow, it is to keep all edges smooth, rounded, and no abrupt obstructions or cavities. When I see people knife edge the intake bridge, I realize someone did not do enough reading before grabbing a porting tool....

On a 4mil stock cylinder, the piston will travel 2mm further down thus the need to lower the ports as well. Not doing this can result in an eddy current setting up at the bottom of the port causing turbulence. In general, it helps the port flow. I mention this because of the disappointing dyno numbers. There might be something lacking in the porting.

If you swapped plugs and wires and problem stays on the left side, you don't have an electrical problem, you have an air leak or carb issue. I would check air screw setting on both carbs and pull pilot jet and check it. Seen it many times where a tiny ass hair is stuck in the jet causing a slight lean condition. Brandon Mull Engineering

I will try not to apply "deep thought" on this but possibly offer something to consider. The key word here is "potential". I think I remember trying to explain this before but basically the word potential describes what you would see on a multimeter when testing voltage. When two leads are connected or connected to a common buss, they would have "zero potential" in reference to each other. I suspect the reason Madd does not run into issues is because he does not run a lighting coil? On the factory Banshee, one side of the lighting coil is grounded to the engine AND chasses, and that should hold the same (zero) potential through the entire bike. If something does not stay connected well, you can end up with potential or stray voltage on the black wire. This will either piss off the CDI and it won't fire or put noise on the line that will damp the peak voltage amplitude to the ignition coil. I should note that you do NOT need a big, massive 4/0 cable for a ground. There is next to no power going through it. Technically speaking, 18ga wire would do it but I recommend bigger only for reliability purposes. 10ga stranded wire is just fine. Brandon Mull Engineering

Not sure if you got your question answered but there is no such thing as a DC stator. All stators will produce AC and will test out the same in regards to meter testing. The only difference in ones being used for DC conversions is the ground wire for the lighting is not grounded to the mount plate, but rather carried back to a rectifier box. Your lighting side test would just be the yellow and black wires IIRC. Brandon Mull Engineering

While the head is off, I would take the opportunity to take a few pics with the pistons down AND use a digital caliper to determine the height of all the ports. With that information, I might be able to point you in the right direction. I am not convinced domes are going to get you the missing 15hp, but you might have a combination of factors....mainly the ports don't match the pipes. That is what is looks like to me so far. Also, make damn sure when your pistons are at BDC, the piston timing edge is flush with the bottom of the ports. It's important. Also, once you have all this figured out and get your jetting right, you may want to start pushing on the timing. Many people get stuck using canned values you find on the Inet. Every engine is a little different and we have some wanting about +10*. If the engine responds favorably and the plug is looking good, keep pushing it. Brandon Mull Engineering

Sleeper, the lapping I refer to may be misunderstood as I don't advocate for any real metal removal because you can make the problem worse. This is by using only FINE paste with approx 600-800grit. The way we have chased the problem is by using Hi Spot blue marking paste to see the contact made between parts. In most cases, some sort of installation error has occurred around the key or the key was not set properly. The runout or TIR is the main thing to check. A flywheel that is running correctly will show TIR of less than .001". We have seen TIR of .010" which is WAY too much to operate safely.

I can agree with this to an extent but I will offer a few things here while trying not to make this into a novel. There must exist two sides to a circuit, if you will, an "in" and an "out". the ignition coil produces 5-7KV through a single lead and the ground strap side on the spark plug provides a path for the current. If you will notice, if you hold a spark plug lead out in air, it will not arc because it has no path to discharge. Now, it gets deep fast in this stuff but the terms are "ground reference" and "floating ground". All a ground is, is the "out" side of the circuit. We decide what that out side references to. We use the term "earth ground" when we couple the out side to the earth thus keeping all things touching the earth at the same potential, which is zero. I guess what I am saying is you can certainly get spark from the "in" side to the ground strap or "out" side of the plug when there is a path for current to flow, but it becomes a really good idea to keep all things referenced to the same ground to keep people from being shocked or things getting damaged. When an engine is accepting the current from the plug but the chassis is not coupled, we don't know what the potential is of the chassis, this is when people get shocked, or things get zapped. I will try an example, the low voltage transformer for a home because it is almost identical to an ignition coil. It has current flowing on the primary and nothing even cares where it gets its current flow or references, the secondary is isolated, but we take the center tap of that secondary which is the "ground" and we "reference" it to earth because we most certainly do not want a floating condition where there is potential (potential voltage discharge) between ground and neutral. We want those to be the same for safety of people and devices. The potential can be understood by grabbing say the POS lead of a 50VDC battery. No shock! Only when you touch both do you get current through your girly arms. This same thing can happen when you touch a floated ground vs some other chassis that has a different ground reference. I am probably rambling. Brandon Mull Engineering

Figured I would pop my head in to try to explain some of our findings on flywheel/crankshaft interface issues. What we determined is a condition called "fretting" which is common with tapered shaft interfaces if there is not consistent and uniform contact between the two mated parts. During high speed operation and function, the mated parts tend to vibrate locally causing localized heating, galling, welding, etc. Depending on the severity, this can appear as strange lines or colors in the interface, all the way to welding of the components. In a severe case that we analyzed where the crank had to be chopped off due to welding, we determined a large amount of runout from either improper installation of the flywheel, or improper contact of the tapered components. We recommend using lapping compound if the taper quality is in question and lightly rotate the flwheel without the key to set in consistent contact. It is also always a good and prudent idea to test the TIR of the flywheel with a dial indicator to verify it is running true. Runout or TIR will cause vibration, heat, and excessive radial forces on the crank bearings. Brandon Mull Engineering

As sort of a tangent to some work we were doing for a commercial customer, I decided the Yamaha community needed some really kick beer....I mean drink coasters!! We machined a gear design (which is a little more tricky) and engraved the Yamaha tuning fork logo. You won't find these at Wally! We machined both sides and installed a cork base. The bottom is machined to lift the gear feature up off the table for a floating appearance. For the guy that needs a conversation piece..... I just don't see how any Banshee nut can have a man cave bar and not have billet coasters. I am sure someone will ask "can you engrave my mom's name on it??? How about a picture of me doing a wheeeelie on my moped???" We are not really a custom design shop but if enough here thinks we need to do a big order of BHQ coasters, if we have enough numbers and interest, I am sure we can figure something out. If you have other ideas for the engraving portion, feel free to kick that over. If there is enough interest, we will do it. I am not sure how limited these will be. We had some extra material. Unless they go over real well, this might be a pretty limited item. Brandon Mull Engineering

Hello, I ran into this thread and figured I would pop in. Edgehanger, you might PM me with who you are are I can look more into it but just a couple things to note. 1. Cranking or kicking compression should never be the sole value used to determine fuel octane. It has no bearing. It might scare some but that 175psi with STOCK ports is about right! 2. Always let your engine tell you how much timing it wants, don't just go with an Inet value. Creep up on timing making observations and plug checks. What you will notice is most here say "ah, you need that compression down around 140-150". What you don't realize is most have at least mid level porting which drops the "cranking" compression and does drop the CCR, but does not drop the UCCR. We look only at the CCR and UCCR when doing head volume targets. If you take that same setup pumping up 175psi and apply an aggressive dune port, you are likely to see numbers in the 150s. Brandon Mull Engineering

I did confirm with someone that emailed us that this is not our Mull impeller product. I did not post to create any conflict or dispute matter, only to clarify as I figured it might be a situation of the seller not being certain. This may be a simple oversight. I wish both parties the best and I am sure something can be resolved civilly.

Good day, in the sake of accuracy, I do not believe this is one our Mull engineering impellers. Ours have specific features that separate them from the others. Thank you! Brandon Mull Engineering

You can always swap parts around enough that the problem will eventually reveal itself.

You may search some of my previous posts on electrical tests. There is no reason to go swapping parts around without knowing they are good or bad. The stator coils and flywheel can be easily tested with a basic 5w nightlight lightbulb. 9/10 times, if the resistance checks at the stator pass, the stator is fine. However, the flywheel magnets can break causing a loss in magnetic flux which induces the AC voltage from the stator. Lightbulb test will confirm everything at once. Brandon Mull Engineering

First off, the Banshee has pretty weak spark in general. The pickup gap affects only timing and pickup intensity to trip the triggers in the CDI. It will not affect spark energy. As well, rust on the flywheel will generally not affect spark energy. The magnets in the flywheel are what generate inductive energy through the ignition coil. If the magnets are damaged, that will affect voltage output. The easiest way to troubleshoot these issues is with an oscilloscope. You would be looking for AC voltage from the ignition coil around 50-100V and approx 1V from the pickup coil. The wave frequency is dependent on RPM so most basic meters will not detect it accurately as they are tuned for 60hz AC. Once you have that established, you can examine the wave forms on the primary side of the coil which will again be around 50-100V. DO NOT connect any meter to the secondary or you will fry it. The secondary should be checked with a ohm meter. Common issues are plug caps, and wire lead terminations. Another common issue is the use of resistor plugs WITH the resistor plug caps. These two resistors will work to reduce spark energy so use a non-resistor plug if you use factory spec resistor caps. Brandon Mull Engineering

Agree with above, I would select a less harsh media. Soda, Walnut, or dry ice. Sand will actually open up pores in the Aluminum and it will stain rather easy. Glass seals the pores but still is a little aggressive IMO. You may also consider clear coating the cases if you sand blast to seal them.

Must unplug the TORS black box or it will still be active.

These small batteries are well known for having a high discharge rate. They don't have much power to start with. To stay out of the no-go zone, I recommend adding a battery tender to the battery. You would hard wire a pigtail to the battery with a two pin plug off of that so you can easily just plug it in after a ride. These trickle juice in the mA range and will just maintain the surface charge.

So did the batt fix your issues? 12.5V is NOT full charge on a 12V battery. 12.7V is standard but with surface charge (just after charging), they are typically over 13V. A rectifier issue can certainly have a draw as the diode pack can leak to ground. That is easily found with a meter though and there are usually other symptoms. Make sure your charging system is getting that battery to full charge. I commonly charge a battery, then let it sit over night unplugged and see if it holds voltage. Bad batteries have either sulfated plates (reduced amps) or shorted plates (voltage leaks down). Just curious.

Not really accurate to say "forged is lighter than casted". About the only way to make any assumptions is to compare the densities of the different alloys used for both forgings and castings. As mentioned, you typically will use a hypereutectic high silica alloy for castings which is a trade off between elasticity and surface hardness or wear resistance. Believe me, a lot goes into that alloy blend to ensure a good compromise. Based on the structural characteristics of each alloy and the intended structural design, you then add or subtract material to meet the requirement. As commonly done in aerospace, we closely look at the structural need and remove extra material that is not needed to reduce weight. Even within forgings, you will see some pistons much heavier than others. Lighter is NOT always better. Lighter means you are taking away material that you might actually need. However, in a piston requirement, inertia is a bitch.... ie, that piston has to accelerate and decelerate a LOT and that can wear on the wrist pin locations as well as rods/bearings. There are tradeoffs in both cast and forged. The reason forged pistons need more room is they thermally expand all funny due to the natural grain being stretched in funny directions. Grain is sort of like rubber bands. With an annealed alloy, the rubber bands are all relaxed but as we add heat treatments or semi-solid forming (forging), you are stretching the rubber bands which improves structural performance. So no, you cannot blanketly say forged is lighter because it is heavily determined by the features and dimensions of the part. Then I guess you get into the elasticity of the pistons. there is a small amount of deformation of the piston during use. This deformation gets nasty with bad conditions such as pre ignition and detonation. Forged pistons handle these stresses better due to their alloy composition and elastic properties. Thus why you typically see race engines with forged pistons. Cast will last longer thus their extensive use in OEM engine applications.

Swap the plug wires side to side to determine if this is electrical or fuel related. Electrical will mean the problem moves to the right side but my gut says this is fuel related. When you hit the kill switch you are allowing it to load up a bit. Try turning in the air screw on that side to .25 turns out but note where it was. You also need to make sure slides are sync'd correctly. This sounds more like a sync or idle setting issue but may be a partially blocked pilot jet on that side. Just because you did a carb clean does not mean they did not clog again. The in tank filter sucks monkey balls. Use an inline high flow. Brandon Mull Engineering

You will be shooting blanks unless you learn what the bore size really is, via measuring it. If there is out-of-round (eccentricity) or taper out of spec, it will need bored but you won't know that without measuring. As far as cast vs forged, I could go at it all day but cast is just fine for mild engines. The higher silica makes them harder and less prone to wear. ie, they last longer. Brandon Mull Engineering

This sounds like you are tripping the TORS system. Are you sure it is deleted? If you touch the throttle and it runs fine but acts like you hit the kill switch when you let off, that sounds more electrical. Brandon Mull Engineering