blowit

www.mullengineering.com You can also clink "link" above my signature. Not sure why I cannot make the signature itself hot, never looked into it. Let us know if you have any issues navigating.

We are the manufacturer of the billet drive gear. We designed it due to concerns from our customers and our experiences with customer engines. In testing, we determined that at operating engine temps, the plastic gear can get rather weak and something as simple as a tight bearing can cause excessive torsion and cause it to fail. While the plastic gear has proved to get the job done most of the time, it only takes one failure to cost a guy an engine and when many here are spending thousands on high HP builds, it just puts the mind a little more at ease that though even our billet gear can fail, the seal and bearing are very likely to fail first and give warning for repair before total failure. As well, it is a known problem with many plastics subject to heat and oil submersion. The oil works to break down the chemical bonds in the plastics, making them brittle. All in all, the gear was designed and released as a preventative measure. That being said, we have not had one call of a billet gear ever failing in an engine to date. Brandon Mull Engineering

I am not convinced that you have an air leak. More like carb tuning, cable issues, lean pilot jetting, or poor carb balance.

If you can't rebuild them, you need to return your tools and man card. They are very simple other than setting the float level which just takes understanding and usually not required. These carbs really don't have many parts to justify calling it a "rebuild". Jets never wear out but they do plug up and require cleaning. Your kit will likely include jets and needle/seat which commonly leak on the Mikunis. Don't sweat fixing them, just make sure you understand how to sync or balance them before you ride. that is critical for good performance and engine life. Brandon Mull Engineering

Start by swapping the plug wires side to side and see if the dead cylinder moves to the left. This will determine if you have a fuel or ignition related issue. Most likely a plugged pilot circuit in a carb. Brandon Mull Engineering

Hard to say where your problem lies just yet but if you have electrical issues, you need to sort that out first. The CDI usually fails due to failure of internal capacitors that fail to retain energy for a spark event so the spark energy gets less and less as well as produce sporadic spark. HOWEVER, if you are firing on one cylinder, the CDI is NOT the issue. The CDI creates spark energy twice per crank revolution with only two wires to the coil. In short, the ignition coil acts as a spark splitter. There is no way for the CDI to fire only one cylinder. I highly recommend you remove the ignition coil and bench test it, as well as the wires and caps separately. the caps and wires are very known for failure in which most people will misdiagnose this as a bad coil and replace it. Once you know things are firing right you can move on. I also think you might be fighting a carb balance or sync issue in which one side gets more fuel/air than the other at idle. This will be proven by swapping the spark plug wires. if the weak cylinder stays on the same side it was, you are likely fighting carb issues, not ignition issues. Brandon Mull Engineering

Guys, please just shoot me a PM or email with what you are wanting for your cases and we can go from there. Probably easiest to just include a shipped price for simplicity. Thanks

The seizure we found is most common from "fretting". This is familiar to us in the machine tool world. Basically the tapers do not mate correctly and there is movement at that junction and that causing heating and eventually welding. We just repaired a member's bike where this happened and ruined the brand new crank and flywheel. We typically put a film of oil on the taper to help it come apart. There is enough pressure in that taper to hold it from moving if assembled correctly. It is also HIGHLY recommended to test the runout or TIR of the flywheel each time it is remounted to ensure it does not wobble excessively which will cause this fretting issue.

We need a couple sets of Banshee engine cases for mock up and chop up for a couple of projects. Cases can be broke somewhat. They will never be ran or have oil in them but prefer something that is structurally sound for the most part. Let me know what you have.

Most likely a lean condition on the bottom or the carbs need synced. Remove the air filter and look into the back of the carbs while hitting the throttle (not running). The slides should come up exactly the same. If this is in check, check the idle air screws. Screw one in until it seats and count the turns you screwed it in. If they are 1.5-2.5 turns, take them down to .5 turns and see if the problem gets better. A bog like you are describing is most likely a lean condition and may require slightly larger pilots but usually adjusting the air screws gets it done. Brandon Mull Engineering

I am a little concerned with the "secret amount" since that that amount varies drastically with engine setup. That is like trying to hide a secret gasket thickness that comes with every piston kit. We don't really hide much in our head mods. We have been doing them for 15 yrs. Mull Engineering

I already have ported heads on my Banshee and put roost boost in the gas but still getting beat, by a 300EX. I took out all the muffler packing since a friend told me that a louder bike is a faster bike. I also took off the air filters. Just curious, I found some Terpentine at the hardware store that says "highly flammable" and wondering if this would make my bike faster? When I race, I hold the throttle down and wait until the engine stops rpm'ing any more before I shift. When I shift, I push down on the pedal on the right while pulling up on the pedal on the left. I can never remember which is which so sometimes I go the wrong way... A really good frend and sooper sharp mekanic told me to spray eethr in the engine to go faster. I tryd that and it made it really loud and I figured it was making more power but I have not figured out a way to hold the spray can to the engine while racing. Any help would be aprisheeated.

Refrained from posted before. The flames are from a lean condition on that cylinder either from: A, small main jet, increase size B, clogged main or pilot, simple fix problem with carb clean C, carb balance got off and one slide is open way before the other, clear to see with the eye. Highly unlikely to be timing or anything else. Brandon Mull Engineering

I am curious about the deficiencies of the Cheetah heads and how they are remedied? We don't really do squat with those motors because of the bad wrap they get. I just did not understand the explanation from the OP regarding "centered burn" or something. Maybe a pic or two would make that more clear. From the sounds of things, head velocities might be a little high. Possibly a minor adjustment can get them working right. What CR are they setup for? displacement? Fuel? Regarding topend pull, it is important to make sure the PVs are opening fully under load. If you are using a dyno, the easy way is just to compare a standard pull to one where you have purposely pinned the PVs WFO. You would obviously have some issues on the bottom end but those top numbers are what you are looking for. I remember doing some custom springs for one locally a couple years ago that was doing something similar.

I think one thing worth noting in this rant is when comparing heads, are we talking A, billet head with off the shelf domes B, billet head with custom cut domes for the specific engine setup C, Decked stock head where the mating surface is simply milled down D, Decked/rechambered stock head where the mating surface AND the chamber are machining for a specific engine setup. I think there is still some confusion in all the posts as to "what is what". We claim that our stock modded heads are better than any off the shelf billet head simply because we custom tailor the head for each engine. Obviously when comparing to custom machined domes, there would not be too much difference other than we have some limitations with the stock heads. Regarding stock head decking only, that should be reserved for people with a"very restrictive anal port". Reason is you are leaving HP on the table as well as inviting detonation and excessive heat due to a STILL inefficient flame front... We will not do or or recommend it but will admit that it will improve performance to a degree. This should, however, NOT be put in the same ball field as a proper decked/rechambered stock head. Regarding engine operating temps, there is just not bit of real proof that a billet head truly makes an engine much cooler. It does not take too much thermodynamic math to prove that adding a small amount of coolant volume (water) to the cooling system will indeed take longer to heat thus heating up SLOWER, BUT, once equilibrium temps are achieved, there would not be much of a difference because you are still governed by the heat exchanging properties of the radiator. NOW, if you compare a stock decked head to an "off the shelf" coolhead as many run, the coolhead dome is already refined for better combustion where as the decked stocker would still have a shit design which would lead to "slower" flame front propagation and increased head heating. Simply improving the chamber can actually "reduce" perceived operating temps due to the faster burn rate. In short, if you compared two engines that make 50HP and one is 30% eff and the other is 50% eff, which do you think makes more heat as a by product??? Now I am not going to defend stock heads tooth and nail because there simply are some things you cannot do with them BUT I think comparing apples to apples is important. Matter of fact, we have applied our thermal barrier coatings to the stock heads making them run noticeably cooler than ANY billet head without a coating, increase in eff because we are reflecting the heat back into the combustion charge, all while still costing less than a billet head. Cooler, faster, cheaper.... Just saying that there are ways around the issues discussed in the previous 50 pages...... Brandon

Can we PLEASE cut the drama cord already and let this sucker drop to the bottom??????????????

I am not sure I fully understand your statement but in most cases, forced convection as used in an engine cooling system far out weighs a comparison to nature convection as I think you are noting above. Due to the forced nature of the cooling system, natural convection really has no place in the cooling system. Just to clarify and defend stock heads, the owner usually already has a stock head so that just leaves machining which is 85.00 from us plus a gasket. A properly machined head is NOT a compromise in power at all. Many people swap heads just as they would swap domes and it is actually a faster swap not dealing with orings and such. So you can usually have 2 flavors on the shelf for 200 bucks or so. As for adding/subtracting gasket thickness to adjust for fuel use, that simply is NOT something we would ever advise for several reasons. In comparing displacement in a 350 engine, it will take approx 4cc difference between a good pump and race fuel setup. This would be a delta of .050" of gasket thickness. This means if you buy a racecut head from us set up for .040 squish, you would then have .090" squish clearance which is more than a stock Banshee has off the showroom. That will equate to, well, a slug dragging a bowling ball. We work hard here to tune efficiency into the burn cycle because head heating can be caused by poor burn rate. Please take a moment to hold a lighter to your hand for 1 sec then 5 sec and let me know which hurts worse.... In a nut shell, combust faster, and you can reduce head temps. This is also why many stock head jobs get a bad rap because they are simply decked and not rechambered. It is important to improve every aspect of the head while you are there. It is VERY important that we reduce head heating a focus that energy out the tail pipe where it can build a stronger and faster return wave to build power. Did anyone realize that spark timing is actually a work around to the volumetric problems of heads? Actually in design, it would be best to have a head that has variable volume on the fly. This is because we are constantly trying to control the burn speed and event timing precisely. As RPM increases, so does the rate of compression which has a dominating affect on charge heating and burn rate. This is curbed by reducing timing advance with rpm since the event will happen faster. I guess all I am saying is all the jargen about MSV, CR, fuel, etc, all just boils down to burn speed. The faster you compress air, the more heat that is generated, the more heat, the more volatile the mixture is, which in turn increases burn speed. OK, I am mumbling again. I guess all I was getting at is I do not think there is near enough work done to "tune" the target head volume or enough work done with ignition timing and they are so closely linked, they should be in every sentence together. Like how much volume and advance do you have at a certain RPM?? B

No, I would generally not recommend adding or subtracting gasket thickness in order to adjust the compression ratio for use of different fuels. Brandon

Just thought I would stop in and stir the pot... We machine stock heads for a variety of applications in the Banshee. In some circumstances, a cut stock head will run warmer than a comparable billet head. I will admit that an increase in coolant volume as well as internal surface area does help in the heat transfer efficiency. However, something to consider is many billet heads are able to move coolant straight across the head without going into the water jackets which can drastically affect sensor readings. It is very important to extract heat from the engine in the water jackets as well. This "short circuiting" effect can certain affect the perceived outlet temps while creating hot spots in the cylinder walls. It it important to also note that you need to retain a certain amount of heat in the head for proper combustion. I am not at all knocking billet heads. They work and have for 20+ years. It is important however to compare apples to apples. Actual cylinder temps are important data in comparisons like these. Considering that a Banshee engine can create 60kw of heat on demand, a few oz of water mathematically would not be a fix all because you still need to dissipate that amount of heat through thermal exchange. It is actually a total "fail" in design that the Banshee does not have good flowing water jackets and insufficient cooling around where a lot of the heat actually is - The exhaust ports... As far as HP is concerned, it really comes down to the matter of optimal design vs design limits in the stock head. There are certain things we cannot do with the stock head like create a 16:1 UCCR for a 350 stock stroke engine. Just not enough meat in the head for that. However, there are many apps such as a 4mm stroker stock cyl, 68mm cubs, etc that we can build a very good performing head for. Many of our customers prefer the stock head cuts to retain the use of proven stock type head gaskets as well as retain a stealth appearance. When you go to alky, most any of your heat issues just become moot due the drastic vaporization properties of alky.. Brandon Mull Engineering

IMO, if the threads are only "buggered", the "only" way to fix them is the thread file. Once you give them a shot, you will love them. I would not try to force a chase on there but I have seen some slick to piece chases that clamp down and work well but are too pricey for the home shop. Also watch the end of the crank. Many people will smack the end or they get damaged in shipping and it mushrooms the end and increases the diameter at the end. It can all be fixed though. Just don't make it worse. Brandon

You will find in true flattrack, attention to gearing is VERY important. When you shift, if you shift, holeshot, straight speed, etc. It sounds like some minor changes could really help but keep in mind that it is all about getting around the circle faster. Cannot tell you how many times I thought I was faster and turned out slower. Traction and gearing make a difference. B

I think in your situation, it would be advisable to test the accuracy of your gauge with a pot of boiling water. We have seen sensors read as much as 20% off. Your temps are certainly high enough to pay attention. Your mods should be just fine without extra cooling. Also, if your rad cap is failing, this can cause localized vaporization (steam) around the exhaust port area and that vapor raises the read temp of the sensor. Maintaining pressure in the system is very important for many reason. EDIT- To properly analyze a cooling system, you would need to get inlet temps as well from the other side (outlet) of the radiator. By comparing the deltaT of those two, you can determine if you have a radiator issue or a pump/pressure/cap issue. Brandon

Usually a loss of prime would indicate seal wear in the master cylinder as long as their are no visible signs of leakage. It is normal to see very tiny air bubbles in the master cylinder during cycling but they will form more or less foam at the top, not like an air bubble in the system. It does not take much seal damage to cause problems with the brake system. Brandon

Keep in mind that most high dollar operations really should be running a G code verification system like Vericut or Preditor. Problem is for simple operations, you can waste more time setting that up than actually testing at a machine on air. Mastercam, at the very least, should have a Gcode simulator that don;t suck so you can compare your program simulation to your gcode simulation side by side. Just makes toooo much sense... It is one thing to program things in MC, it is another to generate quality code that suits the machine. I still think there should be a better post editing tool or platform... If you have EVER modded a post, you will know what I am saying... I can spend days trying to edit a post...

NOPE.... Just simple things that can REALLY screw you... I also have never liked their ops tree format. It is messy and confusing IMO. In some situations, ops have taken a new file name for some unknown reason and they will simulate just fine but will not post out. That right there is what crashes machines.... It is buggy and combine that with the fact that I cannot fix ANY model in a reasonable amount of time and the paths sure as hell will not update and I would say SUCK IT.... If you move some minor geometry, it will want rechained. That sucks. I realize X4 has some new stuff to help with chaining but surfacing and such still take a 4yr degree just to operate. I keep hoping that Catia is just biting it's tongue and will comeone with a BA platform but that is probably 10yrs down the road....